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ANIMAL PARASITES

AND

HUMAN DISEASE

BY
ASA GC. CHANDLER, M.S., Pu.D.
INSTRUCTOR IN ZOOLOGY, OREGON AGRICULTURAL COLLEGE,

CORVALLIS, OREGON

FIRST THOUSAND

| NEW YORK
- JOHN WILEY & SONS, Ine.
Lonpon: CHAPMAN & HALL, Limrrep
1918

CoryrricHT, 1918
BY
Asa C, CHANDLER

MAY -7 1918

Stanbope [Press

F. H.GILSON COMPANY
BOSTON, U.S.A.

©c1.4494919

ky te |

To
MY MOTHER

WHOSE SELF-DENYING LOVE AND UNFAILING
DEVOTION MADE MY SCIENTIFIC
EDUCATION POSSIBLE

PREFACE

IT is the belief of the writer that one of the most pressing needs
of the present time is the education of the people as a whole in
the subjects of vital importance with which this book deals,
and an increased interest in this field of scientific work. Scien-
tists are the leaders of the world, and should constantly endeavor
to keep a little ahead of the lay population who follow them.
It is, however, important that the leaders should not only
blaze the trail, but should make it sufficiently easy to find so
that the followers may not fall too far behind. In the intense
fascination of exploring the trail, and the eager impulse to press
on to newer and ever newer fields, the scientist is in danger of
forgetting the handicaps of his followers, and of leaving them
hopelessly in the rear. Popular ignorance of many important
facts of parasitology and preventive medicine, even facts which
have been common bases of operation for scientists for many
years, is deplorable. To a large extent, however, the scientists
themselves are to blame, for in their enthusiasm for discovery
they have forgotten to make it possible for the laity to reap the
benefits of their investigations. There is even a tendency to
belittle the efforts of those workers who devote their energies
toward assisting the general public to keep in touch with scientific
progress. A book or paper which collects the work of others,
models it into a connected whole, and makes readily available
what before was widely scattered and accessible only to a skilled
“library-prowler,” is stigmatized by the term ‘‘ mere com-
pilation.” It is the firm belief of the writer that this is not
only unjust but unwise. No less mental and physical energy,
if not perhaps even more, is necessary for efficient ‘‘ mere com- .
pilation ”’ than for the addition of new facts to scientific knowl-
edge, and the value to civilization, which must be the ultimate
criterion by which all scientific work is judged, must be equally
as great, if not greater. The value of connecting related facts
is twofold: it helps to keep the world in general somewhere
nearly abreast of the times, and it is a distinct aid to further

Vv

vl PREFACE

progress. Having the courage of his convictions along these
lines, the writer has spent much time which he might other-
wise have spent on original research in the compilation and popu-
larization of the subject matter of this book.

It is the aim of this volume to present the important facts of
parasitology, as related to human disease, in such a manner as
to make it readable and useful not primarily to the parasi-
tologist, but to the public health and immigration service officers;
to the physicians who are concerned with something more than
their local practice; to teachers of hygiene, domestic science or
other subjects in which health and preventive medicine are im-
portant; to college and high school students; to the traveler;
and to the farmer or merchant who is interested in the progress
of science and civilization. It is the hope of the author that
this book may not only be a means of making available for the
laity facts which may and probably will be of direct importance
to them at one time or another, but that it may also be instru-
mental in arousing the interest of more students in this branch
of science, to the ultimate end of enlisting a larger number in
the ranks of its workers.

No attempt has been made in the following pages to give
detailed descriptions of parasites, or to go further into their
classification than seemed necessary to give a correct conception
of them. Likewise discussions of correct scientific names and
synonymy have been entirely omitted, since, important and
interesting as they may be to a parasitologist, they are of no
interest to the lay reader. An attempt has been made to use
scientific names which are most generally accepted as correct,
except that in cases of disagreement between American and
European usage, the American name has been used. In cases
where some other name than that adopted in this book has been
or is still in common use, it is given in parenthesis to afford a
clue to the literature associated with it.

The endeavor to avoid repetition in the discussion of certain
parasites in one chapter, and of their transmitting agents in
another, has often presented difficulties, since some facts might
equally well be included in either place. As far as possible
these facts have been given in the place where the author has
felt that they would most often be sought, but mistakes have
undoubtedly been made, and furthermore what one reader would

PREFACE | vii

search for under ‘“‘ malaria,’’ for instance, another would seek
under ‘‘ mosquitoes,” and vice versa. For this reason frequent
cross-references are given.

As far as has seemed advisable, without too greatly encumber-
ing the text with round-about phrases, scientific terms have been
omitted or if used have been explained. It is difficult to keep
constantly before one the unfamiliarity with even everyday
scientific terms of many readers for whom this book is intended,
but an earnest attempt to do so has been made.

In the text the author has purposely refrained from citing
references and from mentioning more than a few names of in-
vestigators. It obviously would be impossible to give refer-
ences, or even to mention more than a small per cent of the thou-
sands of contributors to the material here assembled without
making the text cumbersome and unreadable, especially for the
readers for whom the book is especially prepared. Only a few
of the leading figures in the history of each group of parasites
have been mentioned; other citations would have meant a
more or less arbitrary selection of a few from among many,
which must inevitably result in injustice.

For similar reasons no bibliography is given. Instead, the
author has prepared a list of ‘‘ Sources of Information ”’ which
includes the names of all the leading periodicals in which im-
portant articles on parasitology have appeared or are likely to
appear, and a list of books which cover all or a portion of the field
of parasitology in a comprehensive manner. In these books
will be found bibliographies; most of the references cited in
these bibliographies will be found in the magazines or papers
listed in “‘ Sources of Information ”’ and this list will aid any-
one interested in pursuing the subject farther to keep in touch
with the new work which is constantly appearing. The author
has felt that more real value would attach to such a list than to
a list perhaps 50 times as long and yet inevitably incomplete,
containing exact references to particular articles.

The illustrations, with two or three exceptions, have been
drawn by the author either from specimens or from illustrations
of other authors. Pen and ink drawings have been used con-
sistently in place of photographs since it is believed that such
drawings, if carefully done, are far more valuable for scientific
purposes than are photographs. The trained eye is able by

vill PREFACE

voluntary concentration on certain parts, and inattention to
others, to see much more than can a camera, which has no such
power of adjustment. A pen and ink drawing can, therefore,
represent more accurately what can be seen by the eye than can
a photograph. The author has received valuable advice re-
garding the illustrations from Mr. A. J. Stover, scientific il-
lustrator at the Oregon Agricultural College, and wishes to take
this opportunity to express appreciation for it.

Deep appreciation is felt for the invariable willingness with
which authors, editors and publishers of scientific papers and
books have given permission to copy illustrations. Special
mention should be made, however, of the generosity of Sir
Patrick Manson and of the American publishers of his ‘‘ Tropical
Diseases,’ Wm. Wood and Co.; of Dr. A. Alcock, author of
“Entomology for Medical Officers’’; of Professor Wm. A. Riley
and Dr. Johannsen, authors of ‘‘ A Manual of Medical Ento-
mology,’ and of Dr. A. W. Sellards, who, in the absence of Dr.
Strong, lent photographs taken in Peru by the Harvard School
of Tropical Medicine. The illustrations taken from the journal
Parasitology have been especially numerous, and mention should,
therefore, be made of the unreserved permission to use them
given by the editor, Professor G. H. F. Nuttall. Many illus-
trations of worms have been taken from the work of two of the
real pioneers in the study of helminthology, Professor Karl
Leuckart of the University of Leipzig, under whom many of
the present parasitologists were trained, and Professor Arthur
Looss of the University of Cairo in Egypt. It is a high tribute
to the work of Professor Leuckart that many illustrations
published by him in the first comprehensive work on the animal
parasites of man, in 1863, are still the best available ones and
will be found reproduced in the majority of modern works on
the subject.

Particular appreciation is felt for the assistance received from
three publications which contain reviews of current literature
in particular phases of medical zoédlogy, namely, the Tropical
Diseases Bulletin, which reviews practically all current work
on protozoan parasites and helminthology, the Review of Applied
Entomology, Series B, containing abstracts of nearly all work
on medical and veterinary entomology, and the Journal of the
American Medical Association, which gives references to all

PREFACE ix

articles in the leading medical journals of all countries, and
reviews many of them. Any of these periodicals will be lent
by the Association library, at the average cost of postage, to
any member of the Association. These three publications, on
account of their scope and thoroughness, are of inestimable
value to anyone who attempts to keep pace with the progress
of the medical sciences. There are, however, few if any of the
journals or books listed under “ Sources of Information ”’ which

have not been drawn upon either for illustrations or infor-

mation or both. All of these, collectively, have made this book
possible, and to them, and to the workers who contribute to
them, are due, therefore, not only the thanks of the author but
also the thanks of everyone who may profit in any way by this
book.

The writer is very deeply indebted to the authorities who have
been kind enough to read the manuscript, and who have freely
given the benefit of helpful suggestions and criticisms. Pro-
fessor Gary N. Calkins, Professor of Protozodlogy at Columbia
University, Dr. B. H. Ransom, Zodlogist of the U.S. Bureau of
Animal Industry, and Dr. L. O. Howard, Chief of the U. S.
Bureau of Entomology, have helped materially to round off
the rough corners, and fill in the chinks, of the sections on Pro-
tozoa, ‘‘ worms,” and arthropods, respectively.

Hearty thanks is also due my wife, Belle Clarke Chandler,
for the invaluable assistance she has given by her constant and
efficient codperation in the editorial part of the work.

TABLE OF CONTENTS

CHAP. PAGES
MPMPEE TRG NPEONEN! of ee te ee oe oO) ee oe dc oc en wba rs 1-11
eee Aenea in GENBRAL. <4 22). 6. 2k Sc dwee wale eee ees 12-25

PART I. PROTOZOA

RODE CHON, TO.FROTOZOA. ... 0.66 kav ee cia hee 26-37
ee SE MEGED ABI le LE oe wisn shia wend SE dw do Os ala Yo as 38-73
pete GT res a wee eS Se gk e oo tv lew Bs we ted « 42-48
IRS ee. Pe a eS ena hea) 48-62

Pr he eee: oS ten a aE Lae oN 63-65
PUHCeMOUS JAUMOIEE.. Gis. ils oe 'ee be b a dew ce we oe ) 65-69
fee Herero ak ttt hehe ticiuheee eee pee. | 69-70

Other Spwachzete Diseases... 2... bi elew Dee es 70-73

VY. L&rISHMAN Bopres AND LEISHMANIASIS................ 74-92
en ey Oe ee ca Pea ei ew e's Mek oe kae 77-82
satmuiler KWemeamar Aisa sa ltkesaiece el trie es 82-84
LOSES OPS 022, Sale Sahm i hla ete ea ee Meee ger 84-88

ia mL OMRI AR eID ia ose 5 ay k's RES OOS Oe, 89-92

VI. TrypANOSOMES AND SLEEPING SICKNESS.............. 93-114
ee Seen i ce. Re ee ee, 98-108
Pinay SPMPASe rac. see eee 2 0 OL ee 108-114

VII. INTESTINAL FLAGELLATES AND CILIATES.............. 115-127
Biemapelate Protezon:. wo. sii est Ee. 117-118
Multi-flacellate Protozoa... . . 6. ees 118-125
irae a; een Pnee Re I eT SS. | 126-127
ORINDA CEU gets as, Nl OS Oils 6s! « ok PI 128-146
eRe DG MON SEMLCRY oF o> om di Se SS o's eee Anes 130-137

So PETES SA Sey RGSS gh le aire oO a eran renee Sit ne 137-139

(NEL SUE Tg SUVS Ces RR RR a Re 139-146

[SL IST ATRL (8 AE et iS ee ee ened ea 147-167
X. OTHER SPOROZOA, AND OBSCURE OR INVISIBLE Parasites 168-195
Rare ammenier s Oe red alates i es he vale was Ps 170-173
Meee OS ROLOALIENE il tea a. 8 ae eee ce ot whe P, 173-174

SDE U DS POG CRN adh Ae tet ga ae 174-176

“LIPDLVD DESL ye 176-181

Xl

CuHapP.

XI.
XII.

XIII.

XIV.
XV.
XVI.
XVII.

XVIII.

XIX.
XX.

XXI.

CONTENTS

Yellow Fever Group. ..... .. ic dx, ores sh se ee
Yellow Fever. .... << 4.05 os balsa e's tee

Spotted Fever Group... .. 25.0. 5.42240.)
Rocky Mountain Spotted Fever..........:.......
Kedah... . . 0 hcgtesn orn uke eebaear ease yee aan

Chlamydozoa. .......s.ieursus esate sen en

PART Il “WORMS” =.-
INTRODUCTION TO THE ““WORMSB”’.....6..0eec+ss)euum

Tem FLUEDS.. . .'¢s.c cde eae ees a

Blood Fhukes ... . <. «53 dade ¢ Geese scm Sue ee
Lung Plukes. ... 0: id csddslve ts otvsk bee ces
Liver Plukes.... is 3 5/0 9 ade <> os chee oe ee
Intestinal Flues: ... 21.04.4535 te idee wae ee

THe TAPHWORMS... i ..6..dsawudencms oor oe

Family Trentide... .: .. 1 ...Ja 00505. ie
Family Dibothriocephalidsw... ... .4.....:4+..+ eee
Larval Tapeworms in Man. [...........1....5eneee

HoOOKWORMS . 06:2 cca dod oye Wace ov bite es
OTHER INTESTINAL ROUNDWORMS.................-.-
Trichina Wontea. . 920 Ser. soe ee

FILARIZA AND THEIR ALIN: . .. i. os iveesell

Filarta baneroptt «a0 2 PFs oe wee al
Other Species of Milarise.<... 2.21.3 so. o.55 eee

LERBCHES... . «ioe iw cceeloe vo 5s bs bees © ak ee

PART III. ARTHROPODS
INTRODUCTION TO ARTHROPODS... ....-+...+.-.-)00me

Tan Mrres. 2722 ee a cc Aibtbsce de ep oe Ae ie

Harvest Mites). 2 3... his.on tive x nes aia i ee
Other Occasionally Parasitic Species................
Itch Mites

Tieks and. Disease. ..: . +... «8 eee
Other ‘Troublesome Ticks. .< “sj32e cn ease eee

186-187

188
189-192
189-191
191-192
192-195

224-228
228-230

231-253

239-245
245-247
247-253

254-269
270-285
286-297

298-314

299-307
307-314

315-321

322-330

331-351

333-337
337-341
342-346
346-348
348-351

352-369

359-363
364-369

pi te he i a a. ae

CONTENTS XH

CHAP. PAGES
eer: MaepEuGs AND. THEIR ALLIES.” .....0.0-0 cues cess eee 370-386
CRE! OLDE 2 2 ale eS aga ee 371-379
Mpierdseasine ise ts ck hea ee Be ees 379-383

Remeser ane Prevention... oo... eo. kw eee ae ee - 383

RARER HMMM Re tenn Se hg Aare aa See ag a ba Baybee ed 3s 383-386
NENG 0 Me rey oN Se Pe late wae fe Wa eles Hs 387-403
ery. HGRAS: 2... ee ie a eee ara ce Psd dsm 404-423
MACE ETORS (5. > sche soe oe cnc ohare obs wd wna viedole 424-462
Mosquitoes and Malaria cco eho ve pee eR Se we 438-443
Mosquitoes and Yellow Fever... 2... 00)... 6 oi ea 443-448
Mosqmitdes ANG Denewe. 2. a ee ecw ones 448-449
Missannnece ate Oar he oS ee ce pe le 449-451
Mosqmtocsand Dermatobia. . . . 2 i oe ce we ee 451-453

Mosquito Bites and Remedies for Them............. 453-455

Comical anier Parbernvination.. owe. vs ea eee ee ee 455-462

fee, Oraer BLoop-SuckIne Pus... ....2...00 6.0.0 600008- 463-508
Poicwmematuetiied sy ois. Ao Se Sob ye ened 466-473

crue Widees- (Chirondmids),:.o. i. bes dee dela 2 473-477

Hisekives ar utialo Gnas: 00 oko seen ee wee nes 478-484

OS Seg DS SS) | rr a lke eo aa 484-490

WSS BASGVD 53 7 AO Ra Baar cleo, 5 Sta ot) Sear a 490-504
Stable-Flies, Stomorys, and Their Allies.............. 504-508

Seer fax MAGGcotS AND IMYTASIS.......:.......080 000 +000 509-528
Binad-sucane Morrots. co... ok ace ok he oe es 511-513

Rioeeoie une@er ane Skin... io... oka Pees eee 513-519

Myiasis of Wounds and of Natural Cavities of the Body 519-523

Minacis of thecbtestine.-. . 2.90... A Meee 523-528

emi MGC UNRORINATION 20 cit .o sos av bee's hb as odatek olla yale ce 529-533

ANIMAL PARASITES AND
HUMAN DISEASE

CHAPTER I
INTRODUCTION

One of the most appalling realizations with which every student
of nature is brought face to face is the universal and unceasing
struggle for existence which goes on during the life of every
living organism, from the time of its conception until death.
We like to think of nature’s beauties; to admire her outward
appearance of peacefulness; to set her up as an example for
human emulation. Yet under her seeming calm there is going
on everywhere —in every pool, in every meadow, in every
forest — murder, pillage, starvation and suffering.

Man often considers himself exempt from this interminable
struggle for existence. His superior intelligence has given him
an insuperable advantage over the wild beasts which might
otherwise prey upon him; his inventive genius defies the attacks
of climate and the elements; his altruism, which is perhaps his
greatest attribute, protects, to a great extent, the weak and
poorly endowed individuals from the quick elimination which is
the inevitable lot of the unfit in every other species of animal on
the earth. Exempt as we are, to a certain extent, from these
phases of the struggle for existence, we have not yet freed our-
selves from two other phases of it, war and disease. We have
some reason for hoping that after the present world-wide con-
flagration of war has burned itself out and its ashes, the flesh and
bones of its countless victims, have disintegrated and disappeared
from view, we may be able to free ourselves from the probability
of ever again taking part in or witnessing such a spectacle.
That the helpless bondage in which we were once held by disease
will never again be our lot, we can say with more assurance.

1

2 | INTRODUCTION

One by one the diseases which formerly held the world in terror,
or made parts of it practically uninhabitable, are falling before
the onslaught of modern science. The vast majority of human
and animal diseases are now known to be caused by organisms
which live as parasites within the body. In all but a few cases
these organisms are now definitely known, their habits under-
stood, their means of transmission and multiplication worked
out. What such knowledge means to the human race can hardly
be overestimated. In the 14th century Europe was swept by an
epidemic of plague which destroyed probably one-fourth of her
entire population — something like 25,000,000 people. That
a similar epidemic would have swept over the United States
in the present century had it not been for modern scientific
knowledge of the cause and means of transmission of plague,

which made it possible to nip the epidemic in the bud in San —

Francisco and New Orleans, is reasonable to believe. In the

latter part of the 19th century the French attempt to build a~

canal at Panama failed dismally after a stupendous loss of life
from yellow fever and malaria. Shipload after shipload of
laborers, engineers, nurses and doctors were sent to the great
‘“ white-man’s graveyard,” the majority to succumb in a few
weeks or months to these diseases, at that time uncontrollable.
In the early part of the 20th century, by exterminating malaria
and yellow fever on the Canal Zone, through the application of
the knowledge which had been gained in the intervening years,
the Americans made possible the building of the Panama Canal.
In an incredibly short time this zone was transformed from a
veritable pest hole to one of the healthiest places in the world,
and incidentally the “‘ conquest of the tropics,’ previously looked
upon as a more or less hopeless task, was shown to be not only
possible but profitable. To quote another example, through-
out the history of the world typhus fever has hovered like a
death dragon over nearly every army camp ever assembled,
and has followed in the wake of war to add the last touch of
horror and desperation to the inhabitants of the countries involved.
In the present unprecedented war only those countries which have
not kept abreast of the times in the application of scientific knowl-
edge have suffered seriously from this terrible scourge. Were it
not for the application of modern knowledge the horrors of the
present war would have been even more awful than they are now.

IMPORTANCE OF PARASITIC DISEASES 3

A decade or two ago a child’s reader contained the following -
lines:
‘““ Baby Bye,
Here’s a fly;
We will catch him, you and I.
How he crawls
Up the walls,
Yet he never falls!
I believe with six such legs
You and I could walk on eggs.
There he goes
On his toes,
Tickling Baby’s nose.”’

What a contrast to this attitude toward the housefly are our
present-day fly-swatting campaigns, our crusades against possible
breeding places of flies, and our education of the public by slogans,
placards, lectures, magazine articles and books regarding the
filthy habits and disease-carrying propensities of this selfsame
housefly! -

But let us not think for a moment that the battle is won. Not
only are there some diseases which still baffle our attempts to
cure them or to control them, or even to understand their nature,
but those which we already know how to control are by no
means subdued. Plague continues to take a toll of life in India
amounting to at least several hundreds of thousands a year;
malaria even today destroys directly or indirectly millions of
people every year and more or less completely incapacitates
many millions more; syphilis is yet one of the principal causes
of insanity, paralysis, still-births and barrenness in the civilized
world, and ‘is estimated to exist in 10 per cent of the population
of the United States, 7.e., in about 10,000,000 people; hook-
worms still infect and render more or less imperfect over half a
billion people in the world;—and these are all diseases the causes
of which are known, the means of transmission recognized,
methods of prevention understood, and the cure of which, with
the exception of plague, is entirely possible.

It is evident that the crying need of the present time is not
so much additions to our knowledge of the cause, control and
prevention of diseases, much as this is to be hoped for, as it is

4 INTRODUCTION

the efficient application of what we already know. Popular
ignorance of diseases, even such common ones as malaria and
syphilis, is nothing short of appalling. This ignorance is by
no means confined to the poorly educated masses; it is wide-
spread among educated, college-bred people, and, piteous as it
may seem, is characteristic of many professional men, among
them even physicians bearing good reputation. There are a
number of causes for this unfortunate condition. Many physi-
cians of the old school have been so busy or so unprogressive
that they have never attempted to add to or modify the knowl-
edge they had when they first took up the medical profession 20 —
or 30 years ago; people with erroneous or distorted views of
things publish their ideas in newspapers or magazines as authori-
tative statements, and thus unmeaningly mislead the enormous
number of people who swallow such newspaper articles without
even a flicker of hesitation; quack doctors, those hellish buz-
zards who prey upon the innate gullibility of the greater part
of the human race, willfully mislead and scatter at random the
seeds of misinformation which have held back the progress of
sanitation and health to a pitiful extent and have borne as their
fruit sorrow, misery and suffering; and, finally, such is the
conservativeness, or rather imperviousness, of our species that
a new idea requires, often, not decades but centuries to penetrate
thoroughly the popular mind. It is nearly 60 years since Darwin
brought the theory of evolution into serious consideration and
showed the folly of belief in special creation, yet it is no exag-
geration to say that a very large majority of people at the present
time do not believe in evolution. It is 250 years since the idea
that living organisms do not spontaneously spring into exis-
tence from non-living matter was first promulgated, and nearly
60 years since the last vestige of possibility was torn from the
theory of spontaneous generation, yet even today the prev-
alence of such beliefs as that ‘‘ horse-hair snakes” develop
out of horse hairs in water is nothing short of astonishing. It
is 120 years since Jenner proved the efficacy of vaccination
against smallpox, yet there exist at the present time numerous
anti-vaccination societies whose sole purpose is to denounce
vaccination as an impractical and illogical proceeding. How
can we expect popular belief in the mosquito transmission of
malaria which was demonstrated only 20 years ago!

EXOTIC DISEASES 5

The importance of the study of parasites in connection with
human disease to every community in the world is becoming
more and more obvious, even to those relatively free from para-
sitic diseases. There are those who think that such diseases
as kala-azar, sleeping sickness, Oriental fluke infections and
many other local or “ tropical” diseases are of no vital im-
portance except to inhabitants of the countries directly influ-
enced or to travelers through these countries. That the im-
portance of such parasitic diseases is far greater than this is
obvious from the fact that, with modern facilities for com-
munication and with the extent of foreign immigration at the
present time, there is no part of the world so remote that the
things which affect it may not also affect any other part of
the world if conditions are suitable.

There is probably no common exotic infection which is not
repeatedly brought into the United States through immigration
ports, especially in ports where the most thorough medical in-
spection of immigrants is not made. In the port of San Fran-
cisco alone over 50 per cent of 6428 Orientals whose feces were
examined in the course of a little over two years were infected
with hookworms, each one capable of starting a new center of
infection in a previously free community. According to Dr.
Billings of the U. S. Immigration Service, during the ‘“ Hindu
Invasion” of the Pacific Coast of the United States in 1911,
about 90 per cent of all arriving Hindus were found to be in-
fected with hookworms. It is unfortunate that even at the
present time a considerable proportion of arriving Orientals
cannot, under the immigration law, be subjected to medical
examination.

The possibility or probability of other diseases becoming
established in places not before troubled by them is a subject
of vital importance to any community or nation. Some of them
have already become established in places which were formerly
free. The fact that acquaintance with these exotic diseases is
lacking in the new territory, their nature not understood, means
of curing them unfamiliar, and means of prevention of spread
unknown, often results in much needless suffering and loss of
‘life. Furthermore, many infections are much wider in distri-
bution than has formerly been supposed. To cite one example,
amebic dysentery, and liver abscess which is often the sequel to

6 INTRODUCTION

it, occurs over the greater part of the United States, yet not
only are the people unfamiliar with the disease and its cause,
but most physicians are unacquainted with it and do not know
how to diagnose or treat it.

The history of modern medicine, so far as infectious diseases
are concerned, is nothing more nor less than the history of para-
sitology in its broad sense, including bacterial and fungous para-
sites as well as animal parasites. Previous to the beginnings of
our knowledge of the existence of microscopic parasites, and of
the effects produced by them, nearly all diseases were interpreted
as visitations from angry deities, as the work of demons or as
the effect of supernatural causes. Such ideas are still prevalent
in those parts of the world where bacteriology and parasitology
have not yet penetrated.

With the exception of the superficial acquaintance which the
ancients had with external parasites and a few parasitic worms,
parasitology began about the middle of the 16th century when
Fracastorio, an Italian, published his belief that disease was due
to invisible organisms multiplying within the body. With the
invention of the microscope by the Dutch lens-grinder, Leeu-
wenhoek, actual observation of microscopic organisms became
possible, and this famous pioneer in science observed, in 1675,
‘“animalcule ” in rain-water, putrid infusions, saliva, and
diarrheal excretions, and made illustrations of them. Based
on these scanty observations, the idea that all diseases were
caused by these ‘“‘ animalcule’”’ became rampant: during the
succeeding century. In 1762 Plenciz, a physician of Vienna,
apparently with the tongue of a prophet, expressed the idea
that all infectious diseases were caused by living organisms,
that there was a special ‘‘ germ” for each disease, that the
incubation period of diseases was due to the time necessary for
the infecting organisms to multiply, and that the organisms
might be conveyed through the air as well as by direct or indirect
contact. In the 18th and 19th centuries there was much con-
troversy as to the origin of “‘ germs ”’ and the possibility of their
spontaneous generation from putrefying matter. A belief in the
origin of living organisms only from pre-existing organisms was
first expressed by the Italian Redi, in 1668, but scientific proof
of it came much later. Experiments by Spallanzani in 1769,
Schulze in 1836, Schwann in 1839, Schroeder and von Dusch in

HISTORY _ 7

1854, and finally Pasteur in 1860 removed one by one the last
straws to which the sinking theory of spontaneous generation
was still clinging.

With the exception of tapeworms and some intestinal round-
worms, one of the first worm parasites to be discovered in man
was Trichinella, in its larval stage in the muscles, this discovery
being made by Peacock in 1828. The hookworm was discovered
by Dubini in Italy in 1838; the blood fluke and the dwarf tape-
worm by Bilharz in Egypt in 1851; Filaria (larve) by Demar-
quay in 1863; the Chinese human liver fluke by MacConnell
in India and MacGregor in Mauritius in 1874; the adult Filaria
by Bancroft in 1876. The first parasitic protozoan to be dis-
covered and recognized as such was the ciliate, Balantidiwm
coli, a cause of dysentery, discovered by Malinsten in 1856.
The spirochete of relapsing fever was discovered by Obermeier
in 1873; the dysentery ameba by Lésch in 1875; the malaria
parasite by Laveran in 1880; the sleeping sickness trypanosome
by Forde and Dutton in 1901; the Leishman bodies of kala-azar
by Leishman, and independently by Donovan, in 1903; the
spirochete of syphilis by Schaudinn in 1905.

Knowledge of the complicated life histories characteristic of
many parasites practically began with Zenker’s demonstration
of the life cycle of Trichinella in 1860 and Leuckart’s experimental
proof of the strange life cycle of the beef tapeworm in 1861.
In 1874 Weinland discovered the snail in which the liver fluke
develops, though the relation of flukes to molluscs had ‘been
previously suspected. In 1879 the epoch-making discovery of
the réle of the mosquito in the development of filarial worms was
made by Manson and the science of Medical Entomology was
born. This discovery has been so far reaching in its results and
it has revolutionized preventive medicine to such an extent that
it may justly be looked upon as marking the beginning of a new
era in the history of preventive medicine, comparable with the
discovery of the germ causation of disease. One of the first
and certainly the greatest outcome of the discovery was the
discovery by Ross in 1898 of the relation between mosquitoes and
malaria. Other important discoveries concerning life histories
and modes of infection quickly followed. The transmission of
trypanosome diseases by tsetse flies was discovered by Bruce in
1893; the relation of mosquitoes to yellow fever by the American

8 INTRODUCTION

Yellow Fever Commission in 1900, and to dengue by Graham
in 1902; the relation of ticks to African relapsing fever by Dutton
and Todd, and independently by Koch, in 1905; the relation
of ticks to spotted fever by Ricketts in 1906; the relation of
lice to typhus by Nicolle and his fellow workers in Algeria in 1909,
and independently by Ricketts and Wilder and by Anderson and
Goldberger in Mexico in the same year (published in 1910);
the relation of cone-noses to a South American trypanosome
disease by Chagas in 1909; the life history of blood flukes by
Leiper in 1914 and 1915; and the rdle of crabs as second inter-
mediate hosts of lung flukes by Nakagawa in 1916.

The evolution of knowledge concerning the treatment of para-
sitic diseases has proceeded along two distinct lines, one, de-
struction of the parasites by drugs which are more or less
specifically poisonous to them, the other by vaccination or immu-
nization. One of the first specific drugs known was quinine for
malaria. The use of cinchona bark from which quinine in its
various forms is manufactured is said to have originated with the
Indians of Ecuador, and to have been introduced into Europe
by’ Spaniards in 1642. The sulphate of quinine, which is the
form of the drug in commonest use now, was first used in 1840.
In 1880 Bozzolo, an Italian, first introduced thymol as a remedy
for intestinal worms, especially hookworm, and this has been
considered a standard and almost specific cure for hookworm
until within the last two years, when oil of Chenopodium has
been substituted for it to a large extent. The next specific drug
of great importance to be discovered was salvarsan for spiro-
chetes, discovered by Ehrlich in 1905. In the same year
atoxyl, one of the most efficient remedies yet discovered for
trypanosome diseases, was discovered by Thomas. Emetin was
discovered to be a specific remedy for amebic dysentery by
Rogers in 1913 as the result of Vedder’s work with ipecac, from
which emetin is manufactured. In 1914 tartar emetic, pre-
viously used as an alternative for arsenic compounds (chiefly
atoxyl) against trypanosomes, was discovered by Vianna to be
a wonderfully efficient specific remedy for the severe South
American leishmaniasis, and was subsequently found to be spe-
cific for all Leishmania diseases.

Treatment and prevention of disease by immunization has
experienced a wonderful development in the past 35 or 40 years.

IMMUNOLOGY : 9

Some of the phenomena of natural acquired immunity were of
course familiar even to the ancients, and people have practiced
for centuries exposing themselves to diseases at convenient times
in order to acquire subsequent immunity. Jenner in 1797
devised vaccination with cowpox to give immunity to smallpox.
It was not until 1880 and 1881 that Pasteur discovered the
possibility of producing immunity by inoculation of germs arti-
ficially rendered harmless or relatively harmless, or by the inocu-
lation of the strained excretions of the bacteria as they exist in
pure cultures.

From Pasteur’s epoch-making discoveries has arisen in the
last 25 years the science of immunology. Although up to the
present time the successful use of vaccinations or inoculations
for cure of, or protection from, disease germs has been applied
chiefly to bacterial diseases, the same principles of immunity
apply to diseases caused by animal parasites and we may con-
fidently expect in the not distant future a great extension of this
relatively new field of medicine to diseases caused by animal
parasites. It has already been applied successfully to some
spirochete diseases, and to some trypanosome diseases. The
difficulty of growing many animal parasites in cultures has largely
held back progress along this line, and it is only recently that
much advancement has been made. Only a few years ago
eulturability and non-culturability were believed to be dis-
tinguishing characteristics between bacteria and Protozoa.
Although methods for growing pure cultures of bacteria arti-
ficially were devised and used by Pasteur in 1858, and greatly
improved by Robert Koch 15 or 20 years later, it was not until
1903 that the artificial cultivation of trypanosomes was ac-
complished by two American workers, Novy and MacNeal.
In 1905 Rogers in India succeeded in cultivating the Leishman
bodies of kala-azar, and thus established their relationship to
certain flagellated parasites of invertebrate animals. Since then
other investigators have succeeded in the cultivation of other
parasitic protozoans, the latest important accomplishment along
this line being the successful cultivation of spirochetes by
Noguchi in 1910-12, and of malarial parasites by Bass and Johns
in 1913. As yet no pathogenic amebe have been successfully
cultured, probably due to their dependence on the presence and
action of certain kinds of bacteria.

10 INTRODUCTION

Even more important, if anything, than ability to grow para-
sites on artificial cultures in order to experiment with them, is
ability to transplant them into animals which can be experi-
mented on. Only by wholesale animal experimentation, car-
ried on patiently and persistently, for years sometimes, could
many of the great medical victories of the past 25 years have
been won. To quote from MacNeal, ‘‘ The importance of ex-
perimentation upon animals in the development of our knowledge
concerning disease-producing microérganisms can hardly be
over-estimated. . . . Only in this way (by the use of animals
in considerable numbers) has it been possible to discover the
causal relation of bacteria to disease, and the way in which
diseases are transmitted. . . . The inoculation of animals also
provides accurately controlled material for studying the course
and termination of the disease as well as the gross or microscopic
lesions produced by it.’ One can hardly help feeling bitter
against those well-meaning but misguided individuals who
publicly denounce and endeavor to minimize the unselfish and
tireless labors of scientists who have made possible the allevi-
ation and prevention of so much human misery and suffering.
To quote from Dr. W. W. Keen in speaking of the results of
Dr. Flexner’s experiments on monkeys and guinea-pigs with one
of the most deadly human diseases, cerebrospinal meningitis:
_ “ which was the more cruel, Dr. Flexner and his assistants who
operated on 25 monkeys and 100 guinea-pigs with the pure and
holy purpose of finding an antidote to a deadly disease and with
the result of saving hundreds, and in the future thousands on
thousands of human lives; or the women who were ‘ fanned
into fury ’ in their opposition to all experiments on living animals
at the Rockefeller Institute ‘no matter how great the antici-
pated benefit? ’ 3

“Tf these misguided women had had their way, they would have
nailed up the doors of the Rockefeller Institute, would have pre-
vented these experiments on one hundred and twenty-five animals,
and by doing so would have ruthlessly condemned to death for
all future time five hundred human beings in every one thousand
attacked by cerebrospinal meningitis!

“Tf your son or daughter falls ill with the disease, to whom
will you turn for help—to Flexner or to the anti-vivisec-
tionists?”’ 7

SCIENTIFIC PROGRESS 11

It is inconceivable that any anti-vivisectionist, if bitten by a
rabid dog, would not hasten to be given a Pasteur treatment to
prevent the horrible death from hydrophobia which would
otherwise almost inevitably result, or if stricken with syphilis
would not submit to treatment with salvarsan in order to pre-
vent the probable ruin not only of his own life, but also of: the
lives of his life-mate and of his unborn children. There is little
thought then of the blood of the monkeys, guinea-pigs, or other
animals with which the God of Knowledge was paid to make
such treatments possible!

The discoveries mentioned in this brief résumé of the history
of parasitic diseases are but a few of the more conspicuous mile-
stones on the path of progress of modern medicine as related to
animal parasites. They may be likened to the posts of a fence,
while the hundreds of other discoveries, less striking in them-
selves, perhaps, but nevertheless necessary, correspond to the
pickets. The posts are useless without the pickets as are the
pickets without the posts. There is not one of the great out-
standing discoveries in the field of parasitology and preventive
medicine which could have been made without the aid of the
less illustrious accomplishments of many other scientists. Our
present ability to cope with and control disease is due not alone
to the great work of such men as Manson, Laveran, Ross, Pasteur,
Koch, Reed, Schaudinn and Ricketts, but also to the careful,
pains-taking work of thousands of other investigators, who, often
without‘any semblance of the honor and recognition which they
deserve, and perhaps even under the stigma of public denuncia-
tion, work for the joy of the working and feel amply repaid if they

add a few pickets to the fence of scientific progress.

CHAPTER II
PARASITES IN GENERAL

Definition. — According to the Standard Dictionary, a parasite
is a living organism, either animal or plant, that lives on or in
some other organism from which it derives its nourishment for
the whole or part of its existence. In the following pages only
those parasites which belong to the animal kingdom are taken
into consideration. The vegetable parasites, chiefly bacteria and
fungi, are dealt with only incidentally.

It is often difficult to draw a sharp line between parasites and
predatory animals; a panther is unquestionably a predatory
animal, and a tapeworm is unquestionably a parasite, but a
mosquito or horsefly might well belong in either category. It is
usual to look upon an organism as a parasite when it habitually
preys upon other organisms which are superior to it in size and
strength. In accordance with this view all animals which
habitually prey upon man, other than a few which occasionally
attack and overcome him by superior physical prowess, may be
considered as parasites and are so treated here.

The state of dependence of an inferior on a superior organism
probably arose very soon after life began to differentiate in the
world. It would be difficult, if not impossible, to explain step
by step the details of the process of evolution by which some of
the highly specialized parasites reached their present condition.
In some cases parasitism has probably grown out of a harmless
association of different kinds of organisms, one of the members
of the association, by virtue, perhaps, of characteristics already
possessed, developing the power of living at the expense of the
other, and ultimately becoming more and more dependent upon it.

Kinds of Parasites. — There are all kinds and degrees of para-
sitism. There are facultative parasites which may be para-
sitic or free-living at will, and obligatory parasites which must
live on or in some other organism during all or part of their lives,

and which perish if prevented from doing so. There are inter-
12

KINDS OF PARASITES 13

mittent parasites which visit and leave their hosts at intervals.
Some, as mosquitoes, visit their hosts only long enough to get a
meal, others, as certain lice, leave their hosts only for the purpose
of moulting and laying eggs, and still others, as the cattle tick,
Margaropus annulatus, never leave except to lay eggs. There
are parasites which pass only part of their life cycles as para-
sites; botflies, for instance, are parasitic only as larve, hook-
* worms only as adults. Some organisms live parasitically in two
or more different animals, often of widely different species, in
the course of their life histories. Such, for instance, are the
filarial worms and numerous protozoan parasites, which begin
life in a vertebrate animal, continue it in an insect, and finish it
in a vertebrate again; the tapeworms, which begin life in cer-
tain vertebrates and finish it in other individuals of the same or
different species; the flukes, which begin life as free-living em-
bryos, continue it through two or more asexual generations in
particular species of snails, become again free-living or else
parasitize second intermediate hosts such as crabs or fishes, and
finally gain admittance to their ultimate vertebrate hosts.
There are permanent parasites which live their whole lives, from
the time of hatching to death, in a single host, but in which the
eggs, or the corresponding cysts in the case of Protozoa, must be
transferred to a new host before a second generation can develop.
Such are many intestinal protozoans and round worms. The
final degree of parasitism is reached, perhaps, in those parasites
which live not only their whole lives, but generation after gener-
ation on a single host, becoming transferred from host to host
only by direct contact. Such are the scab mites and many
species of lice. There is every gradation among all the types of
parasites mentioned above, and a complete classification of para-
sites according to mode of life would contain almost as many types
as there are kinds of parasites.

It is sometimes convenient to classify parasites according to
whether they are external or internal. External parasites, as
the name implies, are those which live on the surface of the body
of their hosts, sucking blood or feeding upon hair, feathers, skin
or secretions of the skin. Internal parasites live inside the body,
in the digestive tract or other cavities of the body, in the organs,
in the blood, in the tissues, or even within the cells. No sharp
line of demarcation can be drawn between external and internal

14 | PARASITES IN GENERAL

parasites since inhabitants of the mouth and nasal cavities and
such worms and mites as burrow just under the surface of the
skin might be placed in either category.

Effects of Parasitism on Parasites. — The effect of parasit-
ism is felt by both parasite and host. There is a sort of mutual
adaptation between the two which is developed in proportion
to the time that the relationship of host and parasite has existed. :
It is obviously to the disadvantage of internal parasites to cause
the death of their host, for in so doing they destroy themselves.
It is likewise to the disadvantage of external parasites, not so
much to cause the death of their host, as to produce such pain
or irritation as to lead to their own destruction at the hands of
the irritated host. It is interesting to note, for instance, that
insects which depend to a large extent on man for food have
less painful bites than do insects which only occasionally or ac-
cidentally bite human beings. Together with a softening down
of the effects of the parasite on the host, there is a concomitant
increase in the tolerance of the host to the parasite. It is a well-
established fact that a disease introduced into a place where it
is not endemic, 7.e., does not normally exist, is more destructive
than in places where it is endemic. The variations in suscepti-
bility to parasites are directly connected with the subject of
immunity, which will be discussed later. An organism and the
parasites which are particularly adapted to live with it may, in
a way, be looked upon as a sort of compound organism. Those
parasites which live part of their life in vertebrate animals and
part in other parasites of these animals, as lice, ticks and biting
flies, are absolutely dependent for their existence on the relation-
ships of the vertebrates and their parasites, and form a sort of
third party to the association.

Aside from the toning down of their effects on the host, para-
sites are often very highly modified in structure to meet the de-
mands of their particular environment. As a group, parasites
have little need for sense organs and seldom have them as highly
developed as do related free-living animals. Fixed parasites do
not need, and do not have, well-developed organs of locomotion,
if, indeed, they possess any at all. Intestinal parasites do not need
highly organized digestive tracts, and the tapeworms and spiny-
headed worms have lost this portion of their anatomy completely.
On the other hand, parasites must be specialized, often to a very

_ SPECIALIZATIONS 15

high degree, to adhere to or to make their way about in their
particular host, or the particular part of the host, in which they
find suitable conditions for existence. Examples of speciali-
zations of external parasites are the compressed bodies of fleas,
permitting them to glide readily between the hairs of their hosts;
the backward-projecting spines of fleas, which are of much assist-
ance in forcing a path through dense hair by preventing any
back-sliding; the clasping talons on the claws of lice; the barbed
probosces of ticks; and the tactile hairs of mites. In these same
parasites can be observed marked degenerations in the loss of
eyes and other sense organs, absence of wings, and, in some
cases, reduction of legs. Internal parasites are even more pe-
culiar combinations of degeneration and specialization. They
possess all sorts of hooks, barbs, suckers and boring apparatus,
yet they have practically no sense organs or special organs of
locomotion, a very simple nervous system, and sometimes, as
said before, a complete absence of the digestive tube.

Still more remarkable are the specializations of parasites, in
their reproduction and life history, to insure, as far as possible,
a safe transfer to new hosts for the succeeding generations.
Every structure, every function, every instinct of many of these
parasites is modified, to a certain extent, for the sole purpose of
reproduction. A fluke does not eat to live, it eats only to re-
produce. The complexity to which the development of the re-
productive systems may go is almost incredible. In some adult
tapeworms not only does every segment bear complete male
and female reproductive systems, but it bears two sets of each.
The number of eggs produced by many parasitic worms may run
well into the hundreds of thousands. The complexity of the
life history is no less remarkable. Not only are free-living stages
interposed, and intermediate hosts made to serve as transmitting
agents, but often asexual multiplications, sometimes to the ex-
tent of several generations, are passed through during the course
of these remarkable experiences.

Effects of Parasites on Hosts. — The effects of parasites on
their hosts are almost as numerous and as varied as are the kinds
of parasites, and vary besides with the susceptibility of the in-
dividual concerned, his physical condition, and complication with
other infections. In general it may be said that a parasite damages
its host in one or more of three ways: (1) by robbing it of food

16 PARASITES IN GENERAL

which has not yet been assimilated and utilized, (2) by mechani-
cally injuring its tissues or organs, (3) by the formation of ex-
cretions or “‘ toxins,’’ which act as poisons.

The first method of damage is of least importance, though it
is obvious that the amount of food abstracted by some parasites,
e.g., large tapeworms which may reach a length of several yards
and grow at the rate of several feet a month, must be considerable.

Much more serious are the various kinds of mechanical injury
to tissues or organs. This damage is done by the blood-sucking
parasites, such as hookworms, flukes, leeches and blood-sucking
arthropods and the tissue-devouring forms, such as dysenteric
amebe, malaria parasites, lung flukes, and fly maggots, which
may not only devour the cells of the body, but may also cause
hemorrhages, give portals of entry for other infections, and per-
forate the intestine. Here also belong the obstructing parasites,
which by their presence block bloodvessels, as do subtertian
malaria parasites or blood flukes; stop up lymph vessels, as do
adult filarial worms; or partially or completely close up such
ducts as the bile duct and pancreatic duct, as do liver flukes.
There are also parasites which damage and inflame the tissues by
boring through them, as does Trichinella, the guinea-worm, itch
mites and fly maggots.

The third type of injury, by excretion of toxic substances, is
done to some extent by practically all parasites. In external
parasites the damage is usually done by an excretion, usually
of the salivary glands, which prevents the coagulation of blood,
and tends to inflame the tissues with which it comes in contact.
In the case of internal parasites the toxic substances are prob-
ably in most cases the waste products of the parasites, voided
into or absorbed by the blood or neighboring tissues. In many
cases these toxins have specific actions on particular tissues or
organs, so that parasites in one part of the body may do their
chief damage to an entirely different part. Intestinal worms,
for instance, may produce considerably greater derangements
of the blood or of the nervous system than of the intestine; the
trypanosome of Chagas’ disease produces, by means of toxins,
specific effects on the thyroid gland and gives rise to the symp-
toms which result from interference with the gland, even though
the parasites may not be located in the gland itself; the bite of
certain ticks along the line of the spinal cord or on the middle

INFECTION AND TRANSMISSION 17

line of the cranium produces a specific effect on the motor nerves,
causing paralysis, presumably through the action of salivary
secretions or of the excretion from the coxal glands; the amebe
of pyorrhea, or the bacteria associated with them, which infect
the teeth and gums give rise to such symptoms as rheumatic
pains in the joints, anemia and a disturbance of digestion. In
fact it may be said that a very large number of diseases or ab-
normal conditions which were once attributed to purely physical
causes, such as imperfections in the organization of the body,
or which have been accepted merely as common derangements
of the human machine for which no direct cause could be found,
have been traced to the effect of particular parasites located,
perhaps, in some unsuspected part of the body. We are daily
widening the scope of this phase of pathology, and this is one of
the main reasons for the present important position of parasi-
tology among the medical sciences.

Modes of Infection and Transmission. — The portals of entry
and means of transmission of parasites is a question of the most
vital importance from the standpoint of preventive medicine.
In the past few decades wonderful strides in our knowledge along
these lines have been made, but there is much yet to be found
out. ,

With a very few exceptions animal parasites do not exist in
air and dust as do many vegetable parasites, although some
spirochetes, coughed from the lungs or throat, may infect other
individuals by being breathed in, and the granules formed by
some of these spirochetes may be blown about with dust and
thus infect in the manner of many bacteria.

Many parasites may be spread by direct or indirect ponies
with infected parts, e.g., the spirochetes of syphilis and yaws,
the mouth amebe, the parasites of Oriental sore, itch mites and,
of course, free-moving external parasites. The parasites of the
digestive system and of other internal organs gain entrance in
one of two ways. They may bore directly through the skin as
larve, e.g., hookworm. More commonly they enter the mouth
as cysts or eggs, e.g., dysentery amebe and Ascaris; as larve,
e.g., pinworm; or as adults, e.g., leeches. Access to the mouth
is gained in many different ways, but chiefly with impure water,
with unwashed vegetables fertilized with “ night soil,” or with
food contaminated by dust, flies or unclean hands. The para-

18 PARASITES IN GENERAL

sites of the blood or lymphatic systems usually rely on biting
arthropods (insects, ticks and mites) to transmit them from host
to host, and it is in this capacity, 7.e., as transmitters and inter-
mediate hosts of blood parasites, that parasitic arthropods are
of such vast importance (see p. 322).

Geographic Distribution. — The geographic distribution and
dispersal of parasites is another subject which has received
much fruitful attention in recent years. Parasites, like other
organisms, are dependent upon certain physical conditions of
their environment in order to thrive. One of the most important
limitations on the dispersal of a parasitic disease is the distri-
bution of suitable hosts. Some parasites can live with ap-
parently equal vigor in a large number of hosts, others are
confined to a few or to one only. A double limitation is placed
on parasites which require two hosts in order to complete their
life history; they obviously cannot exist beyond the territory
where both hosts exist together. The local as well as geographic
distribution of the hosts is, of course, effective in limiting the dis-
tribution of the parasites. In the case of human parasites, the
alternate host is practically the only limiting factor. The geo-
graphic distribution of human sleeping sickness is coincident
with the distribution of certain species of tsetse flies; the distri-
bution of yellow fever nowhere extends beyond the range of a
certain species of mosquito; Rocky Mountain spotted fever is
‘geographically limited by the distribution of a certain species of
tick. The accidental or gradual extension of the range of one of
these intermediate hosts is likely to be followed by an extension
of the disease carried by it. It sometimes happens that a strain
of a certain parasite establishes itself in a new host, thus often
greatly extending the territory which it affects, and this is a
possibility which must always be remembered and watched
for. The trypanosome of Rhodesian sleeping sickness, for in-
stance, is very possibly a race of Trypanosoma brucei, which is
common in domesticated and wild game animals in a large
portion of Africa. Some slight alteration in the nature of the
parasite has made it possible for it to affect human beings and
thus give rise to a new disease. A somewhat different situation
is presented in the case of Rocky Mountain spotted fever, the
parasite of which has not yet been discovered. In nature ap-
parently only one species of tick acts as an intermediate host,

NATURAL IMMUNITY 19

though experimentally other ticks may become infective. There
is obviously a constant possibility of the establishment of the
disease in other species of ticks and thus of greatly widening the
area affected.

Temperature is an important limiting factor for those parasites
which can be directly influenced by it, as external parasites and
those which are free-living during a part of their existence.
In Mexico, for instance, human lice are entirely absent from the
hot coastal plains, though abundant on the high central plateau.
Hookworms, which are free-living in their young stages, are con-
fined to a broad strip around the tropical and warm temperate
portions of the world, and occur outside these limits only in
short-lived epidemics during the warm part of the year. Such
parasites as bots and screw-worms are equally exposed to the
influence of climate, since they are free-living in the adult stage.

Some parasites are limited by other environmental conditions.
In the case of such intermittent external parasites as mosquitoes,
biting flies and cone-noses it is obvious that not only tempera-
ture and humidity, but also the presence of suitable breeding
places and of suitable haunts during resting times must be neces-
sary for their continued existence. Again, the local distribution
of hookworms is determined, to a large degree, at least, by the
nature of the soil. These worms abound where sandy soil occurs,
but are rare or absent where there is only limey or clayey soil.

Natural Immunity. — As has already been pointed out, when
a parasite is introduced into a region where it was previously
unknown, or, what amounts to the same thing, new hosts are
introduced into its territory, its ravages are usually worse than
in places where it has been endemic for a long time. The hosts
and parasites of a given region come to a point of equilibrium.
The host becomes largely immune to the effects of the parasite,
and yet harbors it in sufficient numbers to form a reservoir for
it, and thereby acts as a “‘carrier.’”’ In some cases a total or
partial immunity is built up in youth, when the power of resist-
ance to parasitic invasion is usually high; in other cases it is the
result of a long struggle extending through many generations.
A good example of immunity acquired in youth is found in the
case of yellow fever, and of partial immunity, gained through
many generations of adaptation, in the case of hookworms in
negroes. The terrible destruction wrought by sleeping sickness

20 PARASITES IN GENERAL

when introduced into virgin territory in Uganda is a good ex-
ample of the results which may come from such an introduction:
in districts where sleeping sickness has existed for a long time
the death rate from it is often only two or three per thousand,
whereas in one district in Uganda the population was reduced
from 300,000 to 100,000 in about seven years. It is not im-
probable that the extinction of many of the striking types of
animals which dominated the earth in past geologic ages may have
been brought about by the sudden appearance of or exposure to
new and deadly parasites; only those forms of life which were
able to resist the onslaught of the parasites remained to continue
the course of evolution.

This leads us to a consideration of the remarkable facts of
immunity. The power of the blood of vertebrate animals to —
react against invading organisms or poisons by producing sub- |
stances which will destroy them is one of the most wonderful
adaptations in all the realm of nature. Though the details of
the reaction are still unknown, the chemical substances concerned
still undetermined, and many of the influencing factors not yet
understood, yet the progress in our knowledge of the mechanism
of acquired immunity has taken great strides since Pasteur
first placed the development of immunity on a scientific basis
not quite 40 years ago. There are several ways in which the
body may react against parasites. One method is by the ac-
tivity of the large free-moving white blood corpuscles, which
actually capture and devour the parasites after the manner of
predaceous protozoans. This, of course, can be done only in case
of very small parasites, such as bacteria and Leishman bodies.
Apparently the parasites first must be rendered digestible to the
white blood corpuscles by the presence of an accessory substance
in the blood, known as an opsonin. This substance may be
thought of as acting like a sugar coating on a bitter pill, though its
effect is more analogous to that of cooking on starch, 1.e. increased
digestibility. Opsonins are normally present in the blood but
increase as a reaction to the presence of parasites. The degree
of development of opsonins in the blood, and consequent power
of the white blood cells to capture and digest parasites, is known
as the opsonic index.

Sometimes a number of cells work together to form a capsule
around larger parasites, thus walling them in and limiting the

IMMUNITY REACTIONS 21

sphere of their activity; this occurs in the case of T'richinella,
filarial worms, larval tapeworms, fly maggots, etc. It occa-
sionally happens that enzymes are developed which enable
the surrounding cells slowly to digest the parasites thus im-
prisoned. 7

More important than these physical methods by which the

“body is able to combat parasites are the biological or chemical

methods. One of the most wonderful adaptations in the animal
kingdom is the ability of tissues, chiefly the blood and lymph of
vertebrate animals, to react against invading cells, whether they
be bacteria, Protozoa, blood corpuscles of unrelated animals, or
other foreign cells, by producing substances known as anti-
bodies which dissolve these cells, or cause them to agglutinate,
i.e., clump together and lose any motile power they may have.
The living body is also able to destroy the poisonous action of the
excretions or toxins of parasites by the development of protective
substances known as anti-toxins which form some sort of a chemi-
cal union with the toxins. Other poisonous products are ren-
dered harmless by the formation of “ precipitins’’ which have
the special property of uniting with the toxic substances to pro-
duce insoluble and consequently harmless precipitates. Pre-
cipitins are found to react against any foreign protein, of para-
sitic origin or otherwise, introduced into the body. There is
some question as to whether immunity reactions against animal
parasites are exactly comparable with those against bacteria,
but the difference is probably a matter of degree and not of
fundamental nature. The higher organization of Protozoa and
of other animal parasites enables some of them to react against
the destructive influence of the serum by encysting, or by form-
ing spores, and thus they are able to continue their existence in
spite of the development of immunity, though in very limited

numbers and with limited activity. The result is immunity

without sterilization; in other words, although the body becomes
more or less completely immune as far as suffering from the
effects of the parasite is concerned, yet the parasites, limited in
number and activity, still exist within it, and such a host becomes
an ‘‘immune carrier.” With few exceptions protozoan diseases
are contrasted with bacterial diseases in this respect. The
gradual development of anti-toxins, precipitins, etc., probably
accounts to a large extent for the relative immunity which is

22 PARASITES IN GENERAL

developed against the effects of intestinal worms as well as against
blood and tissue parasites.

Artificial Immunity. — In every case the reaction of the body
against parasites invading it is due to the presence of some
particular substance in the parasite which stimulates the body
to react against it. This substance, whatever it may be, is .
called an antigen. The possibility of acquiring immunity with-
out being subjected to the disease lies in the fact that the antigen
is also present in parasites which have been weakened, by one of
several methods, to such an extent as to be powerless to cause
the usual symptoms. It may also be present in the dead para-
sites or even in the strained excretions from parasites, as obtained
from pure cultures. Vaccinations, in the broad sense, are inoc-
ulations into the system of weakened or dead parasites or of
their products. The body reacts against the harmless antigen
thus injected and antibodies are built up just as if the disease had
been actually passed through. Antibodies persist throughout
life in the case of some parasites, for several years in others, and
for only a short time in still others. When the efficacy of the
naturally or artificially acquired immunity is gone, as determined
by experimentation, a new vaccination must be submitted to in
order to obtain protection. Thus yellow fever immunity, which,
however, cannot be artificially produced, normally persists
through life; smallpox immunity, as acquired by vaccination,
for a number of years; and artificially acquired typhoid immunity
for about three years.

Still another method of inducing immunity is possible. By
rendering some susceptible animal very highly immune to a
particular parasite by repeated inoculations of virulent germs,
its serum becomes so charged with antibodies and so powerful
in its action against the particular parasite involved, that a very
small quantity of such serum injected into another animal or
man is sufficient to give a ‘‘ passive’’ immunity — passive be-
cause the second animal has taken no active part in the for-
mation of antibodies. Such immune serum has been found of
value in the prevention and cure of certain spirochete dis- -
eases as well as a number of bacterial diseases. It has the
advantage of causing no discomfort during the development of
the immunity, but usually is of shorter duration than “ active ”
immunity.

ANAPHYLAXIS 23

The principles of artificial immunity, as remarked before, have
only recently become understood, but the science of immunology
is yearly becoming extended. As this paper is being written,
experiments with preventive and curative inoculations against
typhus fever and against infantile paralysis are being worked
out and there is reason to hope that before another year dawns
these two terrible diseases may be added to the already consid-
erable list of diseases which can be prevented by artificially
produced immunity. Smallpox, rabies, cholera and diphtheria
are some of the more important diseases whose guns have been
unloaded by this means. While, as remarked before, compara-
tively little advance has been made in the application of the
principles of immunity to animal parasites, yet there seems to be
hope that in the coming years many diseases caused by Protozoa
and worms may be conquered by further knowledge of immu-
nology.

Anaphylaxis. — Mention should be made of the phenomenon
of anaphylaxis, commonly defined as an exaggerated suscepti-
bility to the poisonous effect of foreign substances in the blood,
and to account for which many different explanations have been
proposed. Based on extensive experimental work, Novy and
De Kruif have recently (1917) offered a new and revolutionary
explanation which is bound to be of far-reaching significance.
According to these workers, normal circulating blood must be
presumed to contain a substance, termed the ‘‘ poison matrix,”’
comparable in a general way with the substance in the blood
known as fibrinogen. The latter substance, under certain condi-
tions or in the presence of certain reagents, is transformed into
fibrin, which forms a network of fibers in the meshes of which the
blood corpuscles are caught, and by means of which the clotting of
blood is effected. The same reaction which leads to the coagu-
lation of blood also transforms the poison matrix into an actively
poisonous substance or ‘ anaphylatoxin,’ which produces the
symptoms commonly known as anaphylaxis. Furthermore, it
is shown that the transformation of the poison matrix into
anaphylatoxin is induced or accelerated by the addition of al-—
most any foreign substance to the blood, e.g., bacteria, trypano-
somes, tissue cells, agar, peptone, starch, various salts, and even
distilled water. In other words “ the circulating blood, through
a variety of agents, may be changed from a beneficial and harm-

24 PARASITES IN GENERAL

less to an injurious and poisonous state. The foreign substance
is merely the trigger which, so to speak, ignites or explodes the
charge contained within the blood vessels.’ In the case of so-
called ‘specific anaphylaxis,” in which anaphylactic poison-
ing results from the injection of particular kinds of organisms
or toxins, as, for instance, the shock that results from typhoid
vaccination of a person already immune to typhoid, the specific
action is due to the production of ordinary anaphylatoxin by the
interaction of an antibody, already developed, with the antigen
which produced it. To cite another example, it has been shown
that injection of the ground bodies of ox warbles into cattle
which have been infested by even small numbers of these mag-
gots produces an anaphylactic shock. According to the theory
of Novy and De Kruif this would be explained as follows: the
presence of warbles in the cattle causes the production of anti-
bodies in the blood. Injection of warbles places large quantities
of the antigen in the blood. Interaction of antibody and antigen
produces a substance which transforms the poison matrix al-
ways present in the blood into anaphylatoxin, and the latter
' produces the symptoms of poisoning. The theory has recently
been advanced that the severe effects of the bites of some blood-
sucking arthropods, such as ticks, mites and blackflies, in which
the first attacks are much milder than the later ones, may be
in the nature of anaphylactic reactions. According to the
theory of Novy and De Kruif, these effects would be produced
by the formation of anaphylatoxin as the result of an interaction
of an antigen in the arthropod’s salivary secretions with an anti-
body already formed in the bitten individual.

Novy and De Kruif point out the possibility that substances
inducing the formation of anaphylatoxin may be produced in a
normal individual by some peculiarity of diet, exposure, obscure
infections, etc., and while the amount of poison thus produced
may not be sufficient to cause an acute anaphylactic shock, it
may be sufficient to cause a subacute or chronic form of poison-
ing, leading to anemia, cachexia, etc. The significant state-
ment is also made, and is apparently well supported, that a con-
siderable part of the toxic effects of infectious diseases is in all
probability due to the formation of anaphylatoxin. The so-
called ‘‘ endotoxins ”’ supposed to be liberated in the blood by
the disintegration of bacteria and other parasites possibly do

TREATMENT OF ANAPHYLAXIS 25

not exist as specifically toxic substances. They may be sub-
stances which induce the formation of anaphylatoxin.

Should further investigation indicate that much of the toxic
effects in various infectious diseases are really produced by a
single substance, anaphylatoxin, the treatment of such diseases
will be revolutionized. In addition to the giving of drugs to de-
stroy the infecting organisms, an attempt must be made to find
an agent to destroy anaphylatoxin in the blood and to pre-
vent its further formation. Novy and De Kruif have shown
that, in test tubes at least, alkali not only destroys but also pre-
vents the further formation of this poison, and they suggest the
use of alkalis in the treatment of conditions in which anaphylaxis
may be playing a part. Already striking results have been
obtained in severe cases in which anaphylactic poisoning was
believed to exist, by the simple administration of sodium bi-
carbonate or sodium acetate in doses of from three to five grams
dissolved in about a half a glass of water, given at intervals of
half an hour to an hour. The object of this is to raise the alka-
linity of the blood to a maximum level and to keep it there during
the time anaphylatoxin is being formed. If confirmed by further
investigation, these facts must be looked upon as among the most
important discoveries in the entire history of medicine, and how
far reaching their effects may be cannot now be even guessed.

PART I— PROTOZOA

CHAPTER Il
INTRODUCTION TO PROTOZOA

Place of Protozoa in the Animal Kingdom. — It is usual for
zodlogists at the present time to divide the entire Animal King-
dom into two great sub-kingdoms, the Protozoa and the Metazoa.
These groups are very unequal as regards number of species.
The Metazoa include all the animals with which the majority
of people are familiar, from the simple sponges and jellyfishes,
through the worms, molluses, and the vast horde of insects and
their allies, to the highly organized vertebrate animals, including
man himself. The Protozoa, on the other hand, include only
microscopic or almost microscopic animals, the very existence of
which is absolutely unknown to the average lay person. Al-
though some Protozoa are readily visible to the naked eye there
are others, such as the yellow fever organism, which are too small
to be seen even under the highest power of the microscope. There
is no question but that in point of numbers of individuals the
Protozoa exceed the other animals, millions to one; a pint jar
of stagnant water may contain many billions of these minute
animals. About 10,000 species of Protozoa have been described,
but it is probable that there are thousands more which are not
yet known to science.

The distinction between the Protozoa and Metazoa is based
on a characteristic which is of the most fundamental nature.
The Protozoa are animals which perform all the essential func-
tions of life within the compass of a single cell. The Metazoa,
on the other hand, are many-celled animals, with specialized
cells set apart to perform particular functions. A protozoan
cell, even though sometimes living in a colony of individuals
which are all bound together, can live its life and reproduce its
kind quite independently of any other cells, having in itself the

powers of digestion, respiration, excretion and secretion, sensi-
26

PROTOZOA AND BACTERIA 27

bility, motility and reproduction. Most metazoan cells, on
the other hand, are so specialized for particular functions that,
if separated from the other cells with which they are associated
in the body, they die almost immediately.

The very fact of evolution makes it difficult to draw a sharp
and fast line between two groups of organisms, even between
such fundamentally different groups as the Protozoa and Meta-
zoa. There are always border line exceptions which make the
work of the systematic zodélogist at once difficult and interesting.
In the case in hand there are colonial Protozoa in which all of the
cells are not exactly alike, but have at least the beginnings of
specialization. Some protozoans, such as the intestinal flagel-
late Giardia (or Lamblia), are composed, as adults, of essentially
two cells instead of one. Such animals have been placed by
some authors in a distinct order to which the name Diplozoa
(double animals) has been applied. On the other hand, in the
lowest metazoans, the sponges, there is only very limited speciali-
zation of the cells, while in the little-known animals which are
designated as ‘‘ Mesozoa”’ there is even less differentiation.

‘The distinction between Protozoa and Bacteria, though in-
volving the distinction between animals and plants, is much
more difficult. As we descend the evolutionary scale of plants
and animals the usual distinctions between them disappear and
it becomes difficult if not impossible definitely to place certain
species in either the plant or animal kingdom. The possession
of a distinct nucleus of some kind and some type of sexual re-
production are the characteristics which usually distinguish the
Protozoa from the less highly organized Bacteria. Often, how-
ever, it is difficult to discover sexual phenomena, or to interpret
them with safety, and the presence or absence of a nucleus is
sometimes equally difficult to determine. In such cases pe-
culiarities in life cycle, chemical reactions, staining properties
and the like are resorted to as distinguishing characteristics.
Most biologists are now inclined to group all of the single-celled
animals and plants, including Bacteria, into one great group
known as the Protista, a suggestion first made by Ernest Haeckel.
The existence of such groups of organisms as the Spirochetes
and the Piroplasmata, occupying intermediate positions between
Protozoa and Bacteria, and of such groups as the chlorophyll-
bearing flagellates, occupying an intermediate position between

28 INTRODUCTION TO PROTOZOA

protozoans and green alge, makes such a group as the Protista

appear both natural and convenient.

Structure. — A protozoan, in its simplest form, conforms to
the usual definition of a cell—a bit of protoplasm containing

Est===--myon.
(str. rete oes.)

—
a ttie.- “es eee

C.V, --~--h ----~ Sk. lam:
Ns
mac.n. ~--
bah
CB 8:
sat N
ng B
mic.n. ---- 1
he
Yall --- --end
ect. ------
-----cut.
H-=-- Cae
?
--- cyTop.

Fic. 1. A complex ciliate, Diplodinium ecaudatum,
showing highly developed organelles; czec., cecum or
rectal canal; cut., cuticle; c.v., contractile vacuole;
cytop., cytopyge or cell anus; cytost., cytostome or cell
mouth; d.m., dorsal membranelle; ect., ectoplasm;
end., endoplasm; mac. n., macronucleus; mic. n., mi-
cronucleus; myon. (str. retr. ces.), myonemes, strands
for retracting cesophagus; ces., cesophagus; or. cil.,
oral cilia; sk. lam., skeletal laminew. x 750. (After
_ Sharpe.)

a nucleus. Some-
times there are two
or more similar nuclei
and in the majority
of ciliates there are
two nuclei which dif-
fer from each other
bothinform and func-
tion, a large “‘ macro-
nucleus’? which is
associated with the
ordinary vegetative
processes of the cell,
and a small ‘ micro-
nucleus”? which ap-
parently is concerned
only with sexual re-
production. In some
protozoans nuclear
material is extruded
from the nucleusitself
into the protoplasm
outside where it floats
about in the form of
minute particles or
granules known as
chromidia, the latter
sometimes having the
power, under certain
circumstances, of
forming new nuclei.

In some _ Protozoa

there is no nucleus as such, though the essential substance of
the nucleus, chromatin, is always present, but in scattered par- —

ticles.

The protoplasm of a protozoan is usually more or less clearly

ORGANELLES 29

divisible into an outer and inner zone, the ectoplasm and endo-
plasm, respectively (Fig. 1). There is no fundamental difference
between these two layers of protoplasm, merely a difference in
density. The ectoplasm is the less fluid and comparatively clear,
while the endoplasm is more fluid and somewhat granular. The
clearness of the differentiation between ectoplasm and endo-
plasm is sometimes useful in distinguishing species of protozoans,
especially amebe. The ectoplasm differs from the endoplasm

Fic. 2. Types of organs of locomotion in Protozoa; A, Ameba with pseudo-
podia; B, a heliozoan with ‘‘axopodia’’; C, Bodo with free flagella; D, Trypanosoma
with flagellum attached to undulating membrane; E, Choanoflagellate with flagel-
lum and ‘‘collar’’; F, Pleuronema with cilia and undulating membrane formed of
fused cilia; G, modes of insertion of cilia; H, Aspidisca with cirri. (Figs. F to H
from Calkins.)

in function as well as in appearance. The ectoplasm may be
likened to the body wall and appendages of higher animals while
the endoplasm may be compared with the viscera or inter-
nal organs. The endoplasm digests food and has the power of
secretion and excretion, while the ectoplasm produces the vari-
ous organelles for locomotion, food getting, oxygen absorption
and special senses. The term “ organelle”’ is used in place of
“ organ ”’ for structures which are only parts of a single cell.
Organelles. — The organelles contained in a protozoan’s body
may be many and varied. Those connected with movement or
locomotion differ in different groups and form the chief -charac-
teristic on which the usual classification into Sarcodina, Flagellata,

30 INTRODUCTION TO PROTOZOA

Ciliata and Sporozoa has been based. The simplest type of
movement is by means of simple outflowings of the body proto-
plasm known as pseudopodia (Fig. 2A). This is the common
type of movement in one of the four great classes of Protozoa,
the Sarcodina. In the Flagellata the organelles for locomotion
are long lashlike outgrowths known as flagella (Fig. 2C), from
one to eight or more in number. These originate from a parti-
cle of deep-staining material which is called the blepharoplast or
‘centrosome.”’ In many parasitic flagellates there is another
deep-staining body, of very variable size and form, known as the
parabasal body (also
called by some au-
thors the kineto-nu-
cleus or blepharo-
plast). Various types |
of parabasal bodies
are shown in Fig. 3.
This body usually
arises from the basal
granule and often
remains connected
with it, apparently
being associated with

Fic. 3. Types of parabasal bodies (p). A, Leish- the function of loco-
mania; B, Herpetomonas; C, Trypanosoma; D, Prowa- .
zekia cruzi; E, Prowazekia lacerte; F, Polymas; G, motion. From the
Trichomonas augusta. fact that it seldom

occurs except in
parasitic forms it is possibly a special adaptation to the peculiar
environment encountered by such animals. By some protozo-
ologists the parabasal body has been looked upon as a second
nucleus with the special function of control over the locomotor
activities of the animal, and it has been thought to originate by
direct division from the main nucleus, but there is no conclusive
evidence for this view. As aresult of the idea that the parabasal
body is of nuclear nature some workers have separated those
protozoans which possess a distinct “ kineto-nucleus ”’ from those
which lack it, creating the order “‘ Binucleata ”’ for them.
In the Ciliata the organs of locomotion are in the form of cilia
(Fig. 2F), hairlike outgrowths which are shorter and more
numerous than flagella and different from them in motion.

STRUCTURE 31

Each cilium arises from a tiny deep-staining dot or basal granule
(Fig. 2G), which, however, is probably not homologous with the
blepharoplast of the flagellates.

Various modifications of the organelles of locomotion occur,
e.g., the undulating membrane of many flagellates (Fig. 2D),
formed by a delicate membrane connecting a flagellum with the
body; the “‘collar”’ of the choanoflagellates (Fig. 2E); the mem-
branelles and cirri of ciliates (Fig. 2F and H), formed by the
’ fusion of rows or groups of cilia; and the axopodia (Fig. 2B) of
some Sarcodina formed by the development of supporting rods
in pseudopodia, thus making a permanent structure. Of quite
a different nature, but none the less organelles of movement, are
the myonemes (Fig. 1, myo.), found in many Protozoa, and cor-
responding to the muscle fibers of Metazoa. They enable the
animals to twist and bend their bodies. The myonemes are
extremely delicate contractile fibers which run in various direc-
tions in the ectoplasm of the animal; they occur most commonly
in flagellates and ciliates. In some protozoans structures have
been described which show every evidence of being highly or-
ganized neuromotor apparatus, 7.e., a definitely arranged and
organized substance having a nervous control over the contrac-
tile fibers or myonemes (Fig. 1, mot.).

Organelles for food-taking occur chiefly in the flagellates and
ciliates. Such protozoans may have a “cytostome” or cell
mouth for the ingestion of food (Fig. 1), and a “ cytopyge”’ or
cell anus for the elimination of waste matter. They may also
have a delicate membranous pharynx (Fig. 1, ph.) for leading
the food material into the endoplasm, and food vacuoles (Fig.
1, f.v.) into which the food is accumulated and in which it is
circulated inside the body. In some protozoans, namely the
Suctoria, a much modified group of ciliates, there are developed
sucking tentacles’ for the absorption of food. In others there
are tiny capsules in the ectoplasm containing minute threads
which can be shot forth when stimulated, and used either to
overpower prey or for protection from enemies. For the ex-
cretion of waste products of the body there is often present one
or more contractile vacuoles (Fig. 1, c.v.), little cavities in the
protoplasm of the body which expand with water containing
urea and other waste matters conducted to them by tiny radiating
canals, and which periodically contract, forcing their contents

a2 INTRODUCTION TO PROTOZOA

outside of the cell, sometimes through a definite excretory pore.
Sense organs in the form of pigment spots sensitive to light,
and outgrowths sensitive to chemical substances, giving, perhaps,
a sensation comparable with taste, are present in some species,
especially in free-living ones. Various organelles serving the
function of a skeleton may be developed in the form of a tough
cuticle, a chitinous, calcareous or siliceous shell, a chitinous sup-
porting rod or “‘ axostyle’’ (Fig. 30, axo), or even a complicated
internal skeleton of calcareous material. While no protozoan
possesses all of these organelles, many possess a considerable
number of them and exhibit a degree of complexity and or-
ganization almost incredible in a single-celled animal which is
barely, if at all, visible to the naked eye.

Physiology and Reproduction.—In their physiology and

manner of life the Protozoa differ among themselves almost as —

much as do the Metazoa. Some ingest solid food through a
cytostome or by wrapping themselves around it, others possess
chlorophyll and are nourished in a typical plant manner, and
still others absorb nutriment by osmosis from the fluids or
tissues in which they live. Acid substances corresponding to
the gastric juice and alkaline substances simulating the intesti-
nal juices may be present in the protozoan body, often localized

in definite regions, and acting upon the food as it circulates in

the food vacuoles. The waste material either is voided through
a cytopyge or is left behind by a simple flowing away of the
protoplasm. Body excretions are collected by the contractile
vacuoles and voided by them, or they are simply passed through
the body wall by osmosis.

The multiplication or reproduction of protozoans is of two
quite distinct types, an asexual multiplication, more or less
comparable with the multiplication of cells in a metazoan body,
and sexual reproduction, comparable with a similar phenomenon
in the higher animals. Several common asexual methods of
multiplication occur amongst protozoans, namely, simple fission,
or division into two more or less equal parts; budding, or separa-
tion of one or more small parts from the parent cell; and multiple
fission or sporulation, a breaking up into a number of individuals
orspores. Multiplication by one of these asexual methods may go

on with great rapidity for a long time, but sooner or later some.

process at least remotely resembling sexual reproduction usually

REPRODUCTION -~ 33

occurs. While such a process has not been observed in many
protozoans, it presumably occurs in all under certain conditions.

The analogy between a protozoan life cycle and a metazoan
life cycle has become understood only in recent years. As a
result of the painstaking experiments of Calkins and other pro-
tozodlogists, it is now usual to compare the entire life cycle of a
protozoan animal from one sexual reproduction to the next,
including all the intervening asexual generations, resulting per-
haps in millions of individuals, with the life cycle of a single
metazoan. According to this view the asexual reproduction,
as remarked above, is comparable with the multiplication of
cells in a metazoan body, except that, instead of all the cells
resulting from such multiplication remaining together and be-
coming specialized for particular functions, they separate and
live as independent individuals. Just as the cells of a meta-
zoan body grow old after a variable length of time and lose their
youthful vitality and reproductive power, so the protozoan
cells, after a variable number of multiplications, gradually lose
their vitality and reproductive power. In the metazoan certain
cells have the power of renewing their waning vitality by union
with a cell of the opposite sex (sexual reproduction), thus be-
ginning the cycle again. In the protozoan the sexual phenomena
which have been observed are believed to have the same signifi-
cance, and there is evidence that at least in some Protozoa the
sexual power may be confined to certain individuals which would
then be comparable with the sex cells of the metazoans. Calkins’
experiments led him to believe that in Paramecium, a common
ciliated protozoan on which he experimented particularly, old
age and death were inevitable after a variable number of asexual
generations without. sexual reproduction. It has recently been
shown, however, that when conditions of life are perfect, Para-
mecium may continue to multiply asexually for an indefinite
time. Periodically, however, a complete reorganization of the
cells occurs which apparently has an effect similar to that pro-
duced by sexual reproduction, the animals having renewed vi-
tality for many generations. This remarkable process, named
“endomixis,” is strikingly analogous to parthenogenesis (de-
velopment of unfertilized eggs) in higher animals. Another
analogy is that under unfavorable or adverse conditions sexual
reproduction replaces endomixis, just as in such animals as

34 INTRODUCTION TO PROTOZOA

rotifers and small crustaceans it replaces parthenogenesis,
though either endomixis or parthenogenesis apparently may con-
tinue indefinitely with conditions favorable.

Another phenomenon which is often, though not alsrasi
associated with sexual reproduction is encystment, 1.e., the de-
velopment of an impervious enclosing capsule in which the
delicate protozoan cell is able to resist extremely adverse en-
vironmental conditions, such as very high or low temperatures,
drouth, presence of injurious substances, lack of oxygen, ete.
The degree of protection afforded by encystment can be judged
from the fact that encysted amebe exist in considerable numbers
on the sun-baked sands of Egypt. Encystment may take place
whenever environmental conditions become unfavorable, or as a
normal stage of existence following sexual reproduction, thus
being comparable with the impervious shelled eggs of many |
higher animals, or sometimes as a step preliminary to some form
of asexual reproduction. Nearly or quite all parasitic protozoans
which are not transmitted by an intermediate host adapt them- -
selves for passive transfer from one host to another by encystment.

A full understanding of the significance and limitations of the
sexual and asexual phases of the life histories of parasitic Proto-
zoa is of great importance, since means of control and prevention
often hinge on these points. In many species of protozoan para-
sites a different host is required for the sexual portion of the
life history than that utilized for asexual reproduction, though
this is not true, in general, of the intestinal parasites. Some
species, although normally utilizing a second host for the
sexual reproduction, are apparently able at times to pass from
host to host without the intervention of an intermediate host of
different species. This is true, for instance, of the sleeping
sickness trypanosome, 7’. gambiense, which is normally trans-
mitted by a tsetse fly, Glossina palpalis, as an intermediate host,
but which is thought to be capable of direct transmission by
sexual intercourse as well. It is interesting to note also that,
according to observations made by Gonder on trypanosomes
(quoted by Nuttall), characters such as immunity to certain
drugs, acquired by protozoans and maintained through thousands
of asexual generations in vertebrate hosts, may be blotted out at
a stroke in the invertebrate host by the sexual process which
presumably occurs there. The great significance of this is

CLASSIFICATION 30

evident: one of the difficulties connected with drug treatment of
some protozoan diseases is the power of the protozoans to be-
come immune to the drug when given in doses which are not
destructive to the host; if such immunity is lost during trans-
mission by an intermediate host there is no danger of an immune
race of the parasite becoming permanently established.
Classification. — It is little wonder that such a varied assem-
blage of single-celled animals as constitutes the group Protozoa
should be difficult to classify. It is obvious that these simple
animals may be profoundly modified by their environment and
such modifications can actually be seen in the course of the life
history of many. The changes in form undergone by a trypano-
some, for instance, under different environmental conditions and
at different periods in the life history are represented in Fig. 18.
It has been the custom among zod6logists to divide the Protozoa
into four classes, based principally upon the nature of the organs
of locomotion. These classes in brief are as follows: Sarcodina,
including forms with pseudopodia; Flagellata, including forms
with flagella; Ciliata, including forms with cilia; and Sporozoa,
a heterogeneous assemblage of parasitic protozoans which as
adults have no organs of locomotion, and which reproduce by
breaking up into spores. Though other classifications have
been attempted, the above system is the one generally used.
It is probable that it is not in all respects a natural classifica-
tion, and that changes in it will be made with increasing
knowledge of Protozoa. A few examples of the difficulties con-
nected with this classification may be pointed out. There are
protozoans, as Craigia, which are typical Sarcodina during
part of their life cycle and typical flagellates during another
part, and some, such as certain soil amebe, which readily
change from one phase to another under the influence of varying
environmental conditions; there are others, as Mastigameba,
which exhibit at once typical pseudopodia and a whip-like organ
which can only be regarded as a flagellum; there are species
having organs in every way intermediate between flagella and
cilia; the Sporozoa contain some species, such as the malaria
parasites, Plasmodium, which during a part of their life have
typical pseudopodia and suggest relationship with the Sarcodina,
others which show striking affinities to the Flagellata, and still
others which possess coiled projectile threads in polar capsules,

36 INTRODUCTION TO PROTOZOA

resembling the nematocysts of jellyfishes. Some of the latter
have recently been elevated to the rank of a separate class,
Cnidosporidia, by the German parasitologist, Braun. Many
other difficulties in connection with the classification of the
Protozoa as outlined above could be cited, but since no more
acceptable classification has yet been proposed this classification
is followed here.

The class Sarcodina consists in the main of free-living forms
occurring in the ocean, fresh water and soil. Many of the marine
forms are furnished with calcareous shells which are largely in-
strumental in building up chalk deposits. The majority of the
parasitic species belong to the genus Endameba.

The class Flagellata contains some of the most primitive as
well as some very highly specialized kinds of animals. Manly of
the free-living forms possess chlorophyll and are included by
botanists in the Plant Kingdom. There could be little question
about their vegetable nature were it not for the fact that there is
every gradation between those which are typical plants in form
and function and those which are equally typical animals in
every respect. The parasitic species are all of distinctly animal
nature, some ingesting and devouring solid food, others absorb-
ing food by osmosis. With the flagellates were once included,
also, the spirochetes on account of a supposed relationship with
the trypanosomes, but this theory has long since been exploded,
and the spirochetes are now usually looked upon as only dis-
tantly related to the flagellates.

The class Ciliata is least important of the four classes of Pro-
tozoa from the parasitologist’s point of view. There is only
one species of ciliate, Balantidiwm coli, which is common and
widespread enough and pathogenic enough in its effects to deserve
serious consideration as a human parasite. A few other intestinal
ciliates have been discovered in man but they are of little im-
portance.

The class Sporozoa contains parasitic forms exclusively, but
fortunately man is peculiarly exempt from the attacks of all but ©
a few species. Among the few, however, are included the ma-
larial parasites, which rank among the first of pathogenic organ-
isms as regards significance to the human race as a whole. It is
possible that the undiscovered parasites of such diseases as
Rocky Mountain spotted fever, yellow fever and dengue, and

IMPORTANCE 37

the parasites of obscure nature associated with smallpox, rabies
and other important diseases may prove to be members of this
group.

Importance. — Taken as a whole the Protozoa must be looked
upon as a group of organisms of prime importance as human para-
sites. Although Leeuwenhoek discovered the existence of Pro-
tozoa nearly 250 years ago, the first parasitic species, Balantidium
colt, was discovered by Malmsten in 1856, only 61 years ago.
At the present time a large proportion of medical practice and
disease prevention in tropical countries, and a considerable pro-
portion in all countries, depends on our knowledge of the habits
and life history of parasitic Protozoa, nearly all of which has been
gained in the last 35 years, and much of it in the last 15 years.
Almost daily new discoveries in connection with disease-causing
Protozoa are being made; there are few branches of scientific
research which offer a brighter or more promising field of endeavor
for students at the present time than the investigation of patho-
genic Protozoa.

CHAPTER IV
SPIROCHATES

General Account.— On the vague unsettled borderline be-
tween Bacteria and Protozoa there is a group of organisms which
are waging a frightful war against human life and health. These
organisms, commonly known as spirochetes, when first discovered
were supposed to be of bacterial nature. Later, for many ap-
parently valid reasons, they were thought to belong to the Pro-
tozoa, but one by one these reasons for looking on them as animals
rather than bacteria are falling away and many biologists at the
present time relegate them to their old place among the Bacteria.
They still serve as a bone of contention, however, between bac-
teriologists and protozoélogists, and at present we can only look
upon them as occupying an intermediate position between the
Bacteria on one hand and the Protozoa on the other.

Like Bacteria the spirochetes lack any distinct nucleus; their
multiplication is commonly by transverse division, although the
more typically protozoan longitudinal division has also been
claimed for them by some investigators; and no unquestionable
conjugation or other sexual process has been observed. Like
Protozoa, on the other hand, some of the spirochetes have a
membrane, the “ crista,’’ which reminds one somewhat of the
undulating membranes of trypanosomes; they react to certain
stains and chemicals in a protozoan manner; and they multiply
in a specific intermediate host which serves as a means of trans-
mission to a new host. Until recently it was believed that some
spirochetes passed through a distinct phase of development in
such intermediate hosts as ticks or bedbugs, but some doubt has
been cast on this, and it is now the commonly accepted belief
that the organisms live and multiply in the body of a tick or
insect just as bacteria do in artificial cultures, without going
through any phase of their life history which does not at least
occasionally occur in the vertebrate host.

Spirocheetes are excessively slender threadlike animals, spirally
38

REPRODUCTION 39

twisted like corkscrews. ‘They are very active in movement,
and dart back and forth across the field of a microscope so
swiftly that they can hardly be followed by the eye. The move-
ment is apparently by wave motions passing through the body,
often accompanied by a rotation of the body in corkscrew fashion.
Swiftly moving spirochetes show many small waves in their
bodies, while the more slowly moving ones have larger and more
graceful curls. They also have the power of bending their
bodies to and fro, and of oscillating while attached to some object
by one end. Spirochetes ordinarily divide by a transverse
division of a single thread into two; a spirochete in the act of
such division can be seen in Fig. 6. The result of growth in
length and transverse division is that the spirochetes of any
given species are very variable in size. Often individuals can
be found which have incompletely divided and which hang to-
gether in long chains. Another interesting method of repro-
duction in spirochetes, the details of which have been worked out
largely by Fantham and his students, is by “ granule-shedding,”’
i.e., the production of tiny granules by a breaking ‘up of the
body substance inside the delicate enclosing membrane into a
chain of round “ coccoid bodies,” resembling coccus forms of
bacteria (Fig. 4). These minute bodies are set
free either by a disintegration of the enclosing
membrane or by a rupture of the latter at
one end. The elongation of the granules, the
taking on of the sinuous form and the ultimate
development of diminutive spirochetes are said
by several investigators to have been observed
by them in living cultures of these organisms.
It is probable that the granule-shedding occurs o°
at regular periods in the life of spirochetes, act
and that it is comparable to the process of Fic.4. Spirocheta
sporulation in malarial parasites. It appears to duitoni, showing
be particularly associated with the existence in Process of granule
the intermediate host if there is one, but it gon and shed:
: ding. (After Fan-
also occurs in the blood of the vertebrate host, tnanry) ~
sometimes apparently in preparation for the
transfer to the intermediate host, sometimes as a protection
against adverse conditions. It is quite likely that some spiro-
chetes may be able to resist atmospheric drying up while in

40 SPIROCHATES

the granule stage and may thus be transmitted in dust or on the
bodies of flies. Spitrocheta bronchialis, causing a form of bron-
chitis, is probably transmitted in this way.

There is a wonderful variation in the size and form of spi-
rochetes and also in their mode of life. A few species are free-
living and of very large size, in fact almost visible to the naked
eye (} mm. in length), and there are many large species which
live as harmless commensals with various mollusks. The
disease-causing species (some examples of which are shown in

|

AO OR EO pee F 6@4

Fig. 5. Types of parasitic spirochetes. <A, Sp. dutton; B, Sp. novyi; C, Sp.
pallida; D, Sp. refringens; E, Sp. balanitidis; F, Sp. vincenti; G, Sp. icterohemor-
rhagie. X about 1500. (After various authors.)

Fig. 5) are very much smaller, often being so delicate and slender
as to be hardly visible under the highest powers of the micro-
scope. Not all the small spirochetes of vertebrates are patho-
genic however; two species occur almost invariably in the
human mouth, living on the tartar of the teeth and about the
roots of the teeth, and yet, normally at least, cause no ill effects.
One of these inhabitants of our mouths, Sp. buccalts, is a relatively
short blunt species, but the other, Sp. dentiwm, is excessively
slender, and practically indistinguishable when living from the
spirochete of syphilis. Other harmless spirochetes occur in
various stagnating secretions or excretions of the body, — the
tonsils, and in the intestinal mucus.

Spirochetes and Disease. — There is some question about
how many distinct human diseases are caused by spirochetes.
The mere presence of spirochetes in sores or diseased tissue is
not sufficient reason for believing that they are the direct cause
of the diseased condition, for, like many bacteria, they are often
found in exposed sores which are known to be due to other
causes. Spirochetes are often found associated in sores or ulcers
with certain kinds of bacteria, and both bacteria and spirochetes

PATHOGENIC SPECIES At

have been thought by some workers to be different stages in the
life history of a single organism.

Spirochetes living in animal bodies have a strong feadeake to
localize in definite parts of the body or in special tissues. The
spirochetes which choose the mouth, the teeth or the digestive
tract as a habitat have already been mentioned. Spirocheta
bronchialis confines itself to the respiratory tract, causing a cer-
tain type of bronchitis. Sp. schaudinni localizes in skin tissue,
causing ulcers, in certain tropical countries; Sp. icterohemorrhagie,
although probably invading many parts of the body, especially
affects the liver and kidneys; the spirochetes of the various types
of relapsing fever confine themselves to the blood; Sp. pertenuis,
the cause of yaws, produces a local sore followed by a general in-
vasion of the body, but it returns to the skin tissues and settles
there; Sp. pallida, of syphilis, is able to produce lesions almost
anywhere in the body, but in any given case usually attacks
some special organ or tissue, such as the central nervous system,
skin, bones, reproductive system, arteries, etc. Other spiro-
chzetes have been found in connection with many different
maladies, for instance, Sp. orientalis in “ ulcerating granuloma
of the pudenda,” an ulceration which spreads over the skin
and mucous membranes of the external genital organs; Sp.
vincentt in Vincent’s angina, a diphtheria-like affection of the
tonsils and throat; Sp. bronchialis in certain types of bron-
chitis; and Sp. balanitidis in balanitis, an erosion or ulceration
of the glans of the penis. There seems to be more or less
evidence that the spirochetes found in connection with these
diseases, often associated with bacteria of various kinds, may
be at least partially responsible for them, but to prove this is a
very difficult matter. |

In general the diseases caused by spirochetes may be divided
into three groups. The first of these is the type in which the
organisms live in the blood and cause general symptoms, such as
fever, spleen enlargement, and anemia, and have a tendency to
cause relapses. Of such a nature is rat-bite fever and the vari-
ous forms of relapsing fever. Second, there is the type in which
there are general constitutional symptoms often preceded by a
local lesion of some kind, followed later by .a localization of the
organisms in special organs or tissues. This type, characterized
by continued or remittent attacks rather than by short relapses,

a SPIROCHATES

includes such diseases as syphilis, yaws, and infectious jaundice.
The third type is that in which occur only local ulcerating sores
of skin or mucous membrane; of such a nature are the other
diseases named above.

Relapsing Fever

In every continent in the world, with the possible exception of
Australia, there occurs a form of relapsing fever caused by spiro-
cheetes in the blood. In Africa it ranks next to malaria and
sleeping sickness as a scourge of that disease-cursed country.
In India it is hardly less severe, while in Eastern Europe and
America it is a mild disease. The clinical effects of these various
strains of the disease vary, especially in the number and duration
of the relapses. The mode of transmission also varies and the
parasites are apparently distinguishable and are therefore given
different scientific names. The African spirochete, Spirocheta
duttoni (Fig. 6), is the largest,
being about 16m (qs5q of an
inch) in length; it has only two
or three complete spiral turns
and is quite generally admitted
to constitute a distinct species.
The other forms, Sp.recurrentis
of Europe, Sp. novy: (Fig. 5B)
of America, Sp. carteri of ori-
ental countries, and perhaps
still others in other regions,
are often looked upon as mere

a —_ strains or varieties of Sp. re-

Fie. 6. Spirocheta duttoni in blood of cyrrentis, which was the one
experimentally infected rat. Upper indi- first described. ~These so-
vidual shows transverse fission. X 1000. - i
CG NGS saa ieee called species differ among

themselves chiefly in size, and
in the closeness and regularity of the coils. Each type, however,
is quite variable within itself, and one is likely to be misled as
to size by the hanging together of several individual or partially
divided spirochetes in a chain. The varying symptoms of the
different types of the disease and the fact that immunity to one
does not give immunity to another are reasons for considering the
relapsing fever spirochetes as constituting several species.

RELAPSING FEVER 43

Although relapsing fever was known to physicians over a
century ago, it was not until 1873 that Obermeier discovered
the hitherto unseen agitator which causes it; he made his dis-
covery during one of the epidemics which spread from Russia
over Poland and Prussia. .

Many great epidemics have swept Russian, Austrian and
Balkan cities. Early in the present European war Serbia was
held in the grip of an epidemic of relapsing fever of unusual
severity and of high fatality. In Bombay and other Indian
cities the oriental type of the disease is nearly always present,
and it sporadically appears in various parts of North Africa,
China and Japan. In tropical Africa it occurs over a large
part of the continent occupied by the tick which transmits it.
It is also probably widely distributed throughout Mexico and
Central and South America. In the United States it occurs
chiefly as irregular epidemics among immigrants. Just recently
a small epidemic occurred in Colorado.

Transmission. —In Africa, where the disease is commonly
known as ‘“ tick fever,” it was thought for a long time to be the
result of the poisonous nature of the bite of a common house-
infesting tick, Ornithodorus moubata (see p. 360, and Fig. 155).
This tick, which inhabits the huts of natives throughout Central
Africa, is the chief if not the only transmitter of the Central
African relapsing fever spirochete, Spirocheta duttoni. It can
infect both man and monkeys by its bite.

It has been shown that the spirochetes can live for a long time
in the ticks though they apparently disappear from the digestive
tract after nine or ten days, many of them penetrating to the
blood-filled body cavity while still in the spirochzte form. Leish-
man found that the spirochetes break up into a series of tiny
granules which penetrate many of the organs of the tick, in-
cluding the ovaries and eggs. When the ticks are exposed to a
temperature of 95° F. for a few days the spirochetes reappear.
The ticks may remain infective a year and a half after feeding
on an infected person though frequently fed on clean blood in
the meantime, and a single tick may, therefore, infect a number
of people. By means of the granules the spirochetes may- be
passed on to a second, or even to a third, generation of ticks
through the eggs. Young ticks reared in the laboratory from
infected parents have been found capable of transmitting the

44 SPIROCHATES

disease. Indeed, the tiny unfed nymphs are very infective, and
on account of their small size are particularly dangerous since
they are not easily detected. The ticks do not usually transmit
the parasites by means of the beak but deposit a bit of infected
excrement beside the wound they make; from here the spiro-
chetes make their way into the blood, aided by the scratching
which follows the tick bite. However, when the tick is kept
for a few days at a temperature of 95° F. the salivary glands. as
well as nearly all other organs become infective, and the disease
may then be transmitted in the usual insect manner, by injection
with saliva. The relapsing fever of Abyssinia and Somaliland
is transmitted by a closely allied tick, Ornithodorus savignyt.
African tick fever is said to have been imported into Persia,
-where it is transmitted by O. tholosani. The complete life cycle
of Spirocheta duttoni is shown diagrammatically in Fig. 7.

The other types of relapsing fever spirochetes do not appear
to have such definite and invariable transmitters. Nicolle and
his fellow workers have shown that in Algeria the head and
body lice are undoubtedly the means of spreading the disease.
In experimental work they have shown that there is a rapid tem-
porary disappearance of the spirochetes from the body of the
louse after they have been sucked with blood from an infected per-
son; during this time they are presumably in the granular stage.
After about eight days the spirochetes reappear and are abundant
in the body cavity of the louse for some 12 days before they
finally disappear for good. The lice are infective while spiro-
chetes are present in their usual form, and also just before they
reappear at the end of eight days. It is by crushing the louse
and allowing the juices from its body cavity to contaminate the —
wound that infection is obtained.

In experimental work in Algeria a man experimented upon
was bitten several thousand times by infected lice without con-
tracting the disease, but one louse crushed, and the body fluids
placed on the conjunctiva, caused the disease to develop. The
same result would undoubtedly have occurred if the crushed
louse had come in contact with a wound of the skin.

In some cases the spirochetes are transmitted through the
eggs to the next generation of lice, just as in the case of ticks and
the African disease. The louse has been shown to be the trans-
mitter of relapsing fever in India also.

RELAPSING FEVER — TRANSMISSION 45

In Europe several different pests are probably implicated in
the transmission of relapsing fever. In Persia and neighboring
countries the miana tick, Argas persicus (see p. 364, and Fig. 159),
is probably the chief offender, while in Russia, Serbia and the

Fic. 7. Life cycle of Spirocheta gallinarum, applicable also to Sp. duttoni of
relapsing fever. A, multiplication by transverse division in vertebrate blood: B,
formation of coccoid bodies in vertebrate blood: C, infection of cells of tick and
formation of coccoid bodies; D, multiplication of coccoid bodies in tick; E, de-
velopment of spirochete forms from coccoid bodies after reéntering vertebrate
blood. x 1500. (After Hindle.)

Balkan States lice and probably also bedbugs are the trans-
mitters (see p. 378). It is noteworthy that relapsing fever al-
ways thrives best in those countries where body cleanliness is
neglected, and where vermin are in consequence abundant. In
fact, the prevalence of relapsing fever in any country, as of typhus,

46 SPIROCHAZTES

is in inverse proportion to the prevalence of the use of soap and
water. Relapsing fever, in countries where it is transmitted by
lice, always spreads most rapidly in cold weather when people
are huddled together in stuffy, filthy houses, thus giving the lice
ideal opportunities for doing their evil work.

In Mexico and Central America it is believed that certain ticks,
Ornithodorus talaje and O. turicata, which in form and habits
closely resemble the African relapsing fever tick, transmit the
disease, but this has not been proved. O. turicata is said to be
the transmitter in Colombia, but the bedbug and other ticks are
also suspected.

Relapsing fever is not a contagious disease as was formerly
supposed. A typical case in the Bellevue Hospital in New York
failed to spread the infection to anyone else during the 89 days’
stay of the patient, although no special precautions were taken.
to prevent it from spreading.

The Disease. — In the human body the spirochetes appear to
live exclusively in the blood, where they become fairly common,
though never abundant, at regular intervals. In the meantime
they apparently disappear though they are undoubtedly present
either in the granular form, or else in such limited numbers as
to be practically impossible to find. The repeated increase and
decrease of the spirochetes in the blood goes hand in hand with a
recurring fever broken by periods of apparently almost normal
health. The time of incubation of the disease varies from two
days to two weeks, but in most cases the initial attack comes on
the third or fourth day. It usually begins with severe chilly
sensations, headache and shooting pains in the limbs. The
ensuing fever lasts intermittently for several days, being accom-
panied by such symptoms as rapid pulse, enlarged spleen, con-
stipation, nausea and mental disturbances. After several days
the temperature suddenly drops below normal and remains so
for a period of seven or eight days, during which time the patient
recovers rapidly, feels perfectly well and thinks it unnecessary to
remain at home or in the hospital any longer. Then comes the
first relapse, repeating all the symptoms of the first attack, some-
times in somewhat milder form. Following this there is a second
period of apparently normal health, usually followed by a second
relapse, this time much milder. The number of relapses varies:
in the European and allied types the second relapse is mild, and

RELAPSING FEVER — TREATMENT A7

is the last one felt; in the African type, on the other hand, there
are usually four or five relapses, of shorter duration and more
irregular in occurrence. In a Gibraltar case Manson observed
eight distinct relapses, but this is very unusual. Hemorrhages
under the skin and in various organs of the body often occur,
and cases have occurred recently in Hungary in which the men-
inges (tissues covering the brain and spinal cord) were severely
affected, causing various. nervous disorders. Spleen, liver and
other organs are frequently affected.

Even the African type of the disease does not ordinarily have
a high mortality, though some epidemics are more serious than
others. In an epidemic in Tonkin in 1912, 48 per cent of 703
cases were fatal. In India the fatality is often high on account
of the well-meant but pernicious habit of depriving fever-stricken
people of food, thus often increasing the exhaustion caused by
the disease. Abortion is a common result in pregnant women.
A single attack gives permanent immunity to any one particular
type of the disease but not to others. |

Treatment and Prevention. — Ehrlich’s famous spirochete
poison, “‘ No. 606,” or salvarsan, destroys the spirochetes of
relapsing fever more readily, if anything, than it does other
species of spirochetes, since the parasites live in the blood stream
into which the drug is directly injected. A single injection
nearly always causes the disappearance of the parasites from the
blood and prompt recovery from all symptoms of the disease.
Preventive and curative inoculations of the serum of highly im-
mune animals has been found to be effective in rats and monkeys.
The power of the immune serum can be so increased by repeatedly
inoculating an animal that very small injections of it are sufficient
not only to cut short the course of the disease in these animals
but also to give an immunity of considerable duration. It is
probable that the same serum would immunize. human beings
as well.

Eradication of vermin from person and home and avoidance
of places where infected parasites might be acquired are the
most important protective measures in places where an epidemic
is raging. Methods for the control of ticks are discussed on page
369, of lice on page 400 and of bugs on page 383. Since the
parasites are not ordinarily introduced directly into the blood
by the beak of the transmitter, but are simply voided with the

48 SPIROCHATES

excrement in the vicinity of the wound, careful disinfection, with
alcohol or carbolic acid, of the wound before the removal of the
parasite is a good means of prevention if the suspected trans-
mitter be caught in the act of biting.

Syphilis

History. — There are few diseases which mean more to the
human race as a whole than syphilis, due in part to its almost
universal distribution, and in part to its insidious and deceiving
course, thereby leading to untold misery and disaster. Rosenau
says “‘ civilization and syphilization have been close companions ”’
the one has followed in the wake of the other like the gueril-
las behind an army. Unlike most diseases, syphilis is one of

whose origin among civilized nations we have strong evidence..

There are many reasons for believing that syphilis was acquired
by the members of Columbus’ crew when they discovered the
island of Haiti, and that it was carried back to Spain by them on
their return. These adventurers promptly joined the army of
Charles VIII of France in its invasion of Italy in 1494. Soon
after the army had triumphantly set up a court in Naples it
became weakened through the ravages of a terrible venereal
disease of unusual intensity, hitherto apparently unknown in
Europe. The following year the army retreated almost in a
rout and was broken up, the miscellaneous troops scattering all
over Europe to their respective home countries, and carrying the
new disease with them. In the next four years the disease had
spread to practically every country in Europe, and was soon car-
ried by the Portuguese to Africa and the Orient. The venereal
nature of the disease was fully recognized, and its foreign origin
was well known, each nation trying to shift the responsibility to
another by name, many peoples calling it the ‘‘ French disease,’
others the “‘ Spanish disease,”’ etc., while the Spanish alone seemed
aware of its real origin in America and called it ‘ espafiola ”
which then meant Haiti. The absence of any reference to a
disease resembling syphilis in the historical records before the
discovery of America; the absence of any bones showing evidence
of syphilitic attack in the abundant pre-Columbian remains in
Europe, and abundance of such bones in American remains,
many of which must certainly be pre-Columbian; the positive

ie

Ae
SYPHILIS — RECENT HISTORY | 49

evidence of Spanish physicians and historians at the time of the
return of Columbus; and the severity of the great epidemic
in the latter part of the 15th century, —it being almost in-
variable for an infectious disease, when first introduced among a
new people, to rage with unwonted severity; all these facts
point strongly to the American origin of syphilis.

Interesting as is the early history of the disease, the recent
history is infinitely more so. By the beginning of the twentieth
century medical men had come to the end of their rope in knowl-

edge and treatment of the disease, and found themselves at a

standstill. But in 1902 the disease was successfully transmitted
to animals where it could be conveniently studied; in 1905
Schaudinn discovered the spirochete, Spirocheta (or Treponema)
pallida (Fig. 5C), which is believed to cause the disease. In
1906 Wassermann demonstrated the possibility of detecting
latent syphilis by the reaction which bears his name; in 1910
Ehrlich made the epoch-making discovery of his famous drug,
“No. 606,” or salvarsan, a deadly poison for spirochetes of all
kinds, and a cure for syphilis in nearly all stages; in 1913 the
direct relation of syphilis to insanity, paralysis and other diseased
conditions of the central nervous system was demonstrated by
the discovery of the organisms in the cerebrospinal fluid, and in
the same year a method of destroying the parasites in the central
nervous system was discovered. There is no other instance in
the history of medical science where such wonderful strides
have been made in such a short time in the knowledge and control
of a disease. At the beginning of the twentieth century syphilis
was one of the most horrible, hopeless and tragic diseases known
to ravage the human body; it is now a disease which can be
readily recognized even in latent stages; it can be cured in its

early stages; and the terrible tragedies resulting from apparent

but imperfect cure can be avoided. Its eradication, however,

will not soon, if ever, be accomplished, since in this are involved

some of the most intricate moral and social questions with which
we have to deal.

Prevalence. — The prevalence of syphilis is difficult to de-
termine for at present the recording of syphilitic cases is prac-
ticed to a very slight extent, and accurate data can be obtained
only in military organizations and certain public and private
institutions. Sir William Osler places syphilis as third or fourth

50 SPIROCHATES

of the killing diseases. The use of the Wassermann reaction for
the detection of syphilis has greatly extended the possibility of
arriving at an estimate of the prevalence of the disease, and has
shown that it is far more common than was formerly believed.
Yet even the Wassermann test fails in about 10 per cent of cases.
It is now known that the disease may be present in latent but
nevertheless infective form for many years after all active symp-
toms have disappeared. The recently published report of the
British Royal Commission on Venereal Diseases concluded that
the number of people infected with syphilis cannot fall below
ten per cent in large cities, and that at least one-half the regis-
tered still-births are due to this disease. They found that in
Britain this as well as other venereal diseases is most prevalent
in the unskilled labor class, and least among miners and agri-

cultural laborers. Fournier estimated that in Paris 15 per cent -

were infected. In China syphilis is, next to tuberculosis, the
most common disease. In the United States conditions are
no better than elsewhere; some cities, notably San Francisco,
are much moye heavily infected than others. Of 111 cases ad-
mitted to the Children’s Hospital in Boston 31 per cent were
infected with syphilis. Of 102 children admitted to a Chicago
hospital, none of them for syphilis, 30 were syphilitic. In the

“red light” districts of cities, which undoubtedly serve as the

centers of distribution for the disease, the per cent of syphilitic
prostitutes is very high. Dr. Browning found every one of
104 prostitutes in Glasgow infected, and a like condition among
109 men, women and children classed as “‘ vagrants”’.

According to Capt. E. B. Vedder of the U. 8. Army, the sta-
tistics compiled from over 1000 new recruits in two widely sepa-
rated camps (in New York and Ohio respectively) showed that
over 19 per cent of all applicants for enlistment, approximately
one in five, are probably syphilitic, although only a trifle over 2
per cent showed any symptoms of the disease which would ex-
clude them from the army as the result of a rigid physical exam-
ination. From this Vedder concludes that there is a good reason
for believing the percentaye of syphilis among the young men in
civil life, between the ages of 20 and 30, to be fully 20 per cent.
“It means that when a man’s daughter marries, the chances are
just one to five that she will become the victim of ‘ damaged

Pe)

goods’.”” Vedder shows further that in the relatively select class

Se

TRANSMISSION OF SYPHILIS 51

of young men at West Point from two to five per cent are prob-
ably syphilitic. In the U. 8. Army, as a whole, Vedder believes
an estimate of 16 per cent of syphilis among the whites is con-
servative, and his statistics show that the per cent increases
steadily with the ages of the enlisted men, and as the years of
service increase. Among enlisted negroes, who are notoriously
more syphilitic in civil life than are whites, syphilis is two or
three times as prevalent as among white enlisted men. “ This
study confirms observations that have already been : published
indicating that syphilis is so prevalent among negroes that it is
possibly the greatest single factor in the production of disability
and high mortality rates among the race.’ The figures obtained
from an examination of 531 Porto Rican enlisted men are most
startling of all — over 50 per cent show evidence of being probably
syphilitic.
Transmission. — Syphilis is fundamentally a venereal disease,
transmitted by sexual intercourse, and over 90 per cent of cases
are undoubtedly of such origin. It is a common belief that this
is the only way in which the disease can be acquired, and some-
times an unjust stigma of shame and disgrace is attached to a
perfectly innocent case of syphilis. As already remarked, in
the vast majority of cases the parasites are directly acquired
from their usual habitat in the underworld, but over 20,000
cases of innocent syphilis have been reported, and five per cent
of infections occurring in the army are of innocent origin. <A
horrible case is on record where seven young women at a church
social in Philadelphia acquired syphilis from kissing a young
man who had a syphilitic sore on his lip. A case recently oc-
curred in one of our western cities which was ultimately traced to
the eating of apples sold by an Italian who was in the habit of
spitting on his fruits and rubbing them on his sleeve to shine them.
Public drinking cups, public towels and soiled bed-linen serve
admirably as temporary abodes for the spirochztes of syphilis,
-but fortunately these curses of civilization are in most places
abolished by law. Unsanitary barbers and dentists can easily
spread infection, and dentists and physicians often themselves
contract the disease from handling. syphilitic patients, the
spirochetes readily entering the smallest cut or abrasion of the
skin. Midwives and wet nurses are likewise exposed to infection
from diseased babies, as are the babies from diseased nurses.

52 SPIROCHATES

Indeed, when we think of the many ways in which syphilis
spirochetes may be transmitted from person to person it is sur-
prising that the number of innocent cases is not much greater.
The Spirochetes. — The spirochetes of syphilis, Spirocheta
pallida (Fig. 5C), vary in length from four to 14 yu (gy'o0 to taro Of
an inch) and are immeasurably slender. They are more closely
curled than the spirochetes of relapsing fever, having usually
from six to 14 very regular, short, sharp curls, quite different from
the long graceful curves of a relapsing fever parasite. The
living organisms are very active and dart with great speed
across a slide, threading their way between blood corpuscles or
cells. The spiral turning of the body reminds one of the undulat-
ing movements of a swimming snake. Another spirochete, Sp.
refringens (Fig. 5D), is often found associated with Sp. pallida.

During the early stages .

of their sojourn in the body ~
the spirochetes can always

secondary lesions, and in the
neighboring lymph glands.
During the second phase~
of the disease and also
toward the end of the
first phase the spirochetes
occur in variable numbers
in the blood, and very
early make their way into
the cerebrospinal fluid in
Fia. 8. Spirocheta nee in liver tissue the brain and ee inal cord.
of a congenital syphilitic. After it was found that
the spirochetes actually
invade the central nervous system, and cause diseases of it, it was
supposed that this occurred only occasionally in late stages of
the disease. During the last year or two it has been shown,
however, that the great majority (80 per cent) of syphilitics show
distinct pathological changes in the spinal fluid, due to spiro-
cheetes in it, from the date of the primary sore, and are therefore
possible candidates for syphilis of the nervous system. During
the second phase the spirochetes make a general invasion of
the entire body, later showing some special predilection for

be found in the primary and /

¢

_

COURSE OF SYPHILIS 5B

¢

certain tissues or organs. The gummy sores or “ gummas”
which often break out during the third stage of the disease have
usually been considered non-infective, and spirochetes could not
be found in them. Recently, however, the parasites have been
found in some of these lesions, also. In congenital syphilis
the parasites often multiply in enormous numbers in the unborn
child, penetrating practically every organ and tissue of the body.
The liver especially is often found literally teeming with spiro-
chetes (Fig. 8).

The Disease. — Syphilis is a disease which has no equal in its
deceptive nature. It is largely due to this fact that so many
tragedies result from its ravages. Its effects on the individual
are often horrible enough, leading to disease of almost any tissue
or organ in the body, but it is only when judged in the light of
the additional damage that is done to the innocent wife or
husband, as the case may be, and to the next generation, that
the true meaning of syphilis can be measured. Syphilis may
remain latent and unsuspected for twenty years or more, and the
earrier still be infective. Meanwhile, perhaps in ignorance of
his condition, he may infect a hitherto sound person whom he
has taken for a life companion, and cause her, or him, to be
ravaged and slowly destroyed by this horrible disease. Worse
than this his chances of having healthy children are small. It
has been shown that about 45 per cent of those who later become
victims of general paralysis from syphilis never can have any
children, either on account of sterility or of repeated abortions.
The author of the statement in the Bible that “‘ the sins of the
fathers shall be visited upon the heads of the children unto
the third and fourth generations’? may well have had in mind
the hereditary effects of venereal diseases, but he might have
stated further that often there is no third or fourth generation.
The only pity of it is that this is not always the case, for those
who are brought into the world are in the majority of cases
hopelessly handicapped either mentally or physically. Feeble-
‘mindedness is five times as common in syphilitic families as in
normal ones. There is some reason for believing that the hideous
mentally deficient children known as mongols are the result of
syphilis in parents. And finally, as if all this were not enough,
the carrier of latent syphilis may later develop general paralysis,
or some other disease of the nervous system or other organs, which

| ~=»5B4 SPIROCHATES

will render him an ineffectual social unit, and make him and his
- family a burden to the community.

In the majority of cases the disease begins with a hard sore
on the skin or mucous membrane known as the “ primary
chancre.” This usually appears at the point of infection in from
ten days to three weeks after the infection occurs. In some cases
such a chancre never develops. The chancre gradually heals
up and the second stage begins, in which general constitutional
symptoms appear, as fever, anemia and a general run-down
condition during which the patient is very susceptible to other
diseases, such as tuberculosis. Often there is an extensive
breaking out on the body, production of scaly patches of skin,
and inflammation of the mucous membranes of the mouth and
throat.

From this point on the course of the disease depends on what .
particular tissues or organs the spirochetes especially attack,
for although the parasites, as said before, may produce disease
almost; anywhere in the body, in any given case there is usually a
localization. It seems that certain strains of the parasites have
special preference for certain tissues. The differences in this
respect have been shown by Nichols to hold good through many
transfers from animal to animal, and visible differences in the
parasites can be observed. In about 40 per cent of cases syphilis
settles in the nervous system, causing a great variety of evil
effects, such as feeble-mindedness, tabes, or locomotor ataxia,
general paralysis, epilepsy, insanity and moral defectiveness.
Often it settles in the skin and mucous membranes, producing
the gummy sores or ‘‘ gummas ”’ which were formerly supposed to
be the usual tertiary stage of syphilis. It may select the bones,
muscles, arteries, heart, reproductive system, or any other part
of the body, in each case producing a different set of symptoms,
but in every case weakening the vitality and leading ultimately
_to an early grave.

An active attack on one tissue or organ of the body seems to
have an inhibiting effect on other attacks. It is well known that
an infected person presumably with an active attack of the
spirochetes on some organ in his body will not develop new
lesions when re-infected. Possibly this explains why there is
often a relapse of the nervous system after incomplete treatment
of skin syphilis. The spirochetes in the nervous system which

DIAGNOSIS OF SYPHILIS 55

are not reached by the drugs may flare up and produce a serious
attack after the spirochetes in other parts of the body have
been killed and the skin lesions healed. On the other hand
paralytics with an active attack on the central nervous system
seldom show any other symptoms. Unborn babies seem not
to be subject to such specialized attacks, but, as already pointed
out, are often found with every organ and tissue in the body full
of spirochetes. There is a form of the disease occurring in
adults known as “ malignant syphilis ” in which ulcerating sores
appear early and gradually eat away large portions of the skin.
It is marked by extreme anemia and great weakness, and usually
causes an early death.

Diagnosis. — The modern methods of diagnosing syphilitic
infection have revolutionized our knowledge of the disease, and
have done much toward placing its treatment and control on a
scientific basis. In at least 50 per cent of syphilitic cases there
are no symptoms which can be attributed positively to syphilis,
but we now have several tests for the disease, two of which are
of wide application, and, together with the characteristic lesions
in certain stages of the disease, make it possible to detect syphi-
lis in practically any phase.

The simplest of these indicators for syphilis is the ‘ luetin
test.”” This consists of the injection under the skin of a sterile
emulsion of the dead bodies of the spirochetes from a culture.
If the test is positive, 7.e., if syphilis is present, the inoculation
results in a solid or a pus-filled pimple, usually appearing in a
few hours but sometimes not for several days. This test is ap-
plicable to latent syphilis only, and never gives positive results
during the active primary and secondary stages of the disease.
Its value lies in the fact that it is sometimes sensitive to latent
infections which the Wassermann reaction, now to be described,
does not demonstrate.

The Wassermann reaction, although it fails to reveal syphilis
in rare cases, 1s one of the most valuable and dependable means
of diagnosis known in medicine. It is now almost universally
_ used in well-equipped laboratories. The reaction is also positive
to some other diseases, such as yaws (also a spirochete disease),
leprosy, malaria, scarlet fever and other diseases, but all of
these can be diagnosed beyond doubt by other means and thus
prevent a false diagnosis of syphilis. The reaction in brief is as

56 SPIROCHZTES

follows: A little serum from the suspected person is mixed with
an extract of liver and some guinea-pig serum, and added to a
solution of blood corpuscles from a sheep or ox. If the person
from whom the serum was drawn is syphilitie,
the blood corpuscles are dissolved by this
mixture and the red color is lost, whereas
if the serum is not syphilitic no change in
the blood corpuscles takes place, and the
red color is retained. The greater the num- ©
ber of spirochetes in the body the more

Fic. 9. Wassermann OPVious is the discoloration produced. As
Reaction. Neg.,nega- stated before there are possible sources of
live; Fos. boner eo aermoneinthis test, but if properly, made with
standard reagents, and with sufficient control tests, it can be con-
fidently relied upon.

Treatment. — There are many quack doctors who are still
practicing the same inefficient methods of curing syphilis that were
in vogue several centuries ago. Syphilitic sores are powdered
and cauterized and cured, and the patient is given to believe
that his disease is cured. Unfortunately, as we have seen, the
course of the disease is of such a nature that the doctor’s claim of
having cured may be borne out for months or years before the
insidious disease appears again, this time in a much more de-
structive and perhaps incurable state. Superficial treatment of
syphilis sores, accompanied perhaps by a few “ tonic ”’ pills, in
no way destroys the virulence of the parasites or alters the future
course of the disease. It merely makes the chance of correctly
diagnosing the disease more difficult, and it frequently results in an
unsuspecting victim carrying the disease untreated to a stage
where it has wrought irreparable damage to himself, his life-mate
and his children.

Treatment of the disease formerly consisted in the adminis-
tration of mercuric chloride. While this sometimes effected an
apparently complete cure, over 80 per cent of syphilitics suffered
relapses in spite of the most persistent treatment. In 1910
Ehrlich, after years of experimentation, offered humanity his
famous preparation, ‘‘ No. 606,’ known as salvarsan, an arsenic
compound which is deadly to spirochetes. When this drug is
injected into the veins of a syphilitic, it almost immediately
kills all the spirochetes except a few which have stowed away in

SWIFT-ELLIS TREATMENT 57

inaccessible parts of the body, and these must be caught by con-
tinued administration of the drug, or by special methods. The
most successful method of treatment is an alternate use of
mercury and salvarsan, this apparently being more effective
than salvarsan alone. There is now on the market a modified
form of salvarsan, known as neosalvarsan, which is milder in
its effects on the body but usually considered less powerful in

destroying the spirochetes. Several other more or less valuable
- substitutes for salvarsan are now prepared. On account of the
war, salvarsan itself, a German product, is at present difficult to
obtain.

Salvarsan injected into the veins does not reach the spiro-
cheetes in the central nervous system, and since it is too injurious
to be injected directly into the spinal fluid, the usual treatment
of syphilis is inapplicable to syphilitic infections of the nervous
system. An injection of salvarsan into the lymph spaces under
the fibrous coverings of the brain is sometimes used, but is not
always successful. Swift and Ellis, of the Rockefeller Institute,
discovered in 1913 that the blood serum of a syphilitic who had re-
cently been given salvarsan was destructive to spirochetes and
could be injected into the spinal fluid without injurious results.
Out of this grew the so-called Swift-Ellis treatment of syphilis
of the nervous system by the use of “‘ auto-salvarsanized serum,”
i.e., the serum of the patient himself after having been given
salvarsan an hour before. This serum is heated for half an hour
to make the salvarsan in it more active, then diluted and injected
into the spinal canal. While complete cures in late cases of
paralysis and other nervous diseases could hardly be expected
from this or any other method, the results which have been ob-
tained are very encouraging. It has been suggested that in all
eases of syphilis the Swift-Ellis treatment be made routine as a
protective measure since, in the majority of cases, the spiro-
chetes invade the nervous system in the early stages of the
disease and the consequences of their establishment there are so
terrible as to warrant every possible preventive measure.

The modern methods of diagnosing syphilitic infection have
given a definite standard of cure, and the success or failure of
treatment can be positively demonstrated. A uniform negative
Wassermann reaction given several times during a year, and ab-
sence of any symptoms, can be looked upon as an indication of

58 SPIROCHZTES

cure, though some doctors consider a negative Wassermann reac-
tion for two years necessary to indicate a certain cure on account
of rare cases of relapse, even after a year of apparent absence of
the spirochetes. In contrast to the 85 per cent of relapses which
occurred when mercury alone was used to treat.syphilis, less than
four per cent of relapses occur after treatment with both mercury
and salvarsan. Certainly salvarsan may justifiably be con-
sidered “‘ one of the mightiest weapons in medicine.”’

Prevention. — The control and ultimate eradication of syphilis
is, in spite of our present methods of diagnosis and treatment, a
dream of the distant future. In its prevention are involved so
many social and moral problems upon which people will not
agree that the task is beset with great difficulties.

According to Dr. Snow of the American Social Hygiene Asso-

ciation, the means of controlling and preventing syphilis fall —

into three groups: (1) care and treatment of existing cases with
a view to preventing their spreading the infection, (2) protection
of the uninfected by education and administrative measures, (3)
the development of social defenses against the disease.

As regards the first type of preventive measures, practically
all medical men and public health workers are agreed. Adequate
means for the diagnosis and treatment of syphilis should be pro-
vided in all cases. At present not only are there no laboratories
for diagnosis or free hospitals or clinics for treatment provided at
public expense, but most of our private physicians and hospitals
shun syphilitics, and refuse to care for them. Many physicians
at the present time have little knowledge of venereal diseases.
The suggestion of the British Royal Commission on Venereal
Diseases urging that this subject be given a prominent place in
all medical schools is certainly worthy of being put into practice
immediately. In many of our large cities and in most of the
small ones there is not a single hospital which will admit a patient
for a venereal disease. Of 30 general hospitals in New York

City, only ten receive patients with recognized syphilis in the

infective stages. Theoretically a syphilitic in the infective stages
should be as carefully watched and cared for as a leper or small-
pox patient, yet the syphilitic, the victim of immorality usually,
but sometimes only of the carelessness of some other culprit,

is turned loose without treatment, but with full power to infect |

all with whom he comes in contact directly or indirectly. We

PREVENTION OF SYPHILIS 09

seem to have made little advance since 1496, when the Parlia-
ment of Paris decreed that all persons found infected with syphilis
should leave the city within 24 hours.

The British Royal Commission urged the provision of ample
facilities for free diagnosis of these diseases and for free treat-
ment when necessary. Such measures have already been at-
tempted in a few instances in our own country and their ultimate
success on a large scale is insured. The New York City Health
Department in a single year examined 59,614 specimens of serum
for the presence of syphilis and three-fourths of these were re-
ceived from private physicians. A few public health institutions
are doing splendid work in the operation of a department for the
diagnosis of venereal diseases and the giving of personal advice.
The Oregon State Board of Health is undertaking an extensive
correspondence with persons in all parts of the state who write
for information in response to venereal disease placards posted in
appropriate places. The provision of ample facilities for the
free treatment of syphilis in the way of hospital service when
necessary, of proper medication, and of the extension of Social
Service hospital work is something which we have only begun to
touch upon, but which will undoubtedly come in time. The
fact that no facilities have hitherto been provided for the care
of syphilitics either at public expense, or in the private practice
of physicians and hospitals, is a disgrace to our civilization and a
menace to our health. The medical prevention of syphilitic in-
fection after exposure to it is possible and succeeds in the great
majority of instances if attended to within a few hours after ex-
posure. The use of self-applied medical treatments has been
fairly successful in military life, but as shown by Dr. Snow it is
of doubtful value in civil life, since the intelligence required to
apply medical preparations properly is lacking in those who need
it most — immature boys, drink-befuddled men, defective girls,
and the average prostitutes. These classes constitute the bulk
of the citizens who become exposed to infection and since the
personal supervision of a physician is necessary in most cases,
‘it might best be required in all. Private physicians, dispensary
officers and the health department staff are the persons qualified
to employ medical treatment designed to prevent infection after
exposure to it. Avoidance of exposure constitutes the best and
only safe preventive measure before exposure.

60 SPIROCHATES

As to the second type of prevention, the protection of the unin-
fected by education and administrative measures, great advances
are being made. One of the most important measures, and one
to which we are slowly coming, is the compulsory notification of
the Public Health Department of all cases of venereal diseases so
that whatever action seems best may be taken to safeguard the
public health. There can be no question but that such a record-
ing of venereal diseases would work for the best good of all con-
cerned, both the patient and the public. Laws compelling the
notification of health departments of venereal diseases now exist
in eleven states and a number of cities in the United States,
but only in rare instances are they enforced. Such a law in
modified form has been passed and is being enforced in Western
Australia.

With the notification of venereal diseases, many other prac- —
tical measures could be inaugurated, such: as the exclusion of
infectious syphilitics from occupations connected with the
preparation and serving of food; the careful instruction of
syphilitics concerning various phases of their disease, and possible
means of transmission, thus in many cases securing their active
codperation; and the effective prevention of the marriage of
syphilitics. The last is one of the most important measures
that could be adopted. Many states at present prohibit the mar-
riage of persons with venereal diseases but without enforcement
of notification these laws are worse than useless, since they may
give a false sense of security. Knowing the awful consequences
of inherited syphilis it is the duty of society to prevent the
marriage of syphilitics even with the full knowledge and consent
of both parties. The Royal Commission urged only the full
information of the undiseased party in marriage, allowing the
union to be made if then consented to. In this they seem not
to have given due consideration to the rights of the next genera-
tion. With compulsory notification of venereal diseases, and a
law refusing a marriage license to any person who has or has had
syphilis and cannot pass the accepted laboratory tests for the
disease, the pitiful results of hereditary syphilis could be largely
prevented. Even the remote possibility of the spectacle of a
diseased wife and of stillborn, insane, or physically imperfect
children should be enough to induce any man worthy of the
name to take every precaution to avoid such a tragedy, but if

SYPHILIS AND PROSTITUTION 61

he is unwilling to do this for himself and his posterity, social laws
should do it for him.

Sanitary laws are in effect in many places which help to pre-
vent infection from such sources as public drinking cups, towels,
bed-linen, and other articles, but such laws, excellent as far as they
go, are inadequate, since no law can cover all the articles which

may be rendered infective by contact with a syphilis sore. One
common source of infection, though more for gonorrhea than for
syphilis, is the improperly constructed toilets in public schools.
These are usually built so high, and of such a type that school
children, little girls especially, are exposed to infection every
time they use them. Many cases of venereal diseases in school
children, particularly in larger cities, have been traced to this
source.

No preventive measure which does not strike directly at the
primary source of infection can be adequate in coping with any
disease. Just as we fight malaria through the mosquito, sleep-
ing sickness through tsetse flies and typhoid through contami-
nated water and houseflies, so we must fight syphilis and other
venereal diseases through prostitution. The abolishment of this
vice would unquestionably mean the abolishment of venereal
diseases. At present, at least in many places, this is certainly
not possible. The abolition of ‘“ red light ”’ districts is invariably
followed by a parallel increase in clandestine prostitution, luring
many who would abstain from unmasked brothels; to say nothing
of the increase in seduction and rape of innocent girls. The
most feasible plan at present, as successfully tried in many
European cities, especially Germany, is the municipal supervision
of restricted ‘‘red light” districts. By continuous medical
attendance, and the enforcement of strict sanitary measures, the
normal spread of disease from this source has been reduced to a
great extent. It may be argued that municipal control of prosti-
tution implies public sanction of it, and is therefore morally
wrong. This perhaps is true but there can be no question about
the futility of attempting, at the present state of our civilization,
to abolish prostitution or even to lessen it materially by passing
laws against it. In view of this it is merely a question of a greater
or lesser evil, and there can be no moral crime in lessening the
dangers from an evil which we are powerless to destroy. It may
be said that the lessening of danger from disease in houses of

62 : SPIROCHETES

prostitution will increase their popularity. The same argument
might be used, and has been used by the ultramoralists, to show
that it is morally wrong to attempt to cure venereal diseases,
since this lessens the terror of them. Such arguments might have

more force if syphilis were a disease which affects only the indi-
vidual, and was not a source of danger and burden to the com-

munity. Moreover it seems doubtful whether the person whose
character is such a combination of moral weakness and cowardice
that he shuns houses of prostitution only from dread of disease,
will not spend his time in seducing innocent girls, or in other
hardly less despicable crimes. It may further be pointed out
that disease and immorality go hand in hand. A healthy body
is conducive to a healthy mind, so by eliminating disease we

would be doing at least as much toward giving a death stab to

immorality as toward extending it.

The medical supervision of prostitution, adopted as a tempo-
rary measure, should be accompanied by efforts toward its
ultimate reduction. The abolition of alcoholic drinks, the im-
provement of conditions in slums, the furnishing of decent
surroundings and wholesome sports and exercises, and the en-
forcement of minimum wage laws for women are all measures
which tend toward the reduction of prostitution, but foremost
of all such measures should be education; in this lies our most
powerful weapon against immorality and venereal disease. Hos-
pitals, public schools, churches, libraries and the lecture plat-
form all have the power of spreading the gospel of sex hygiene,
each in its own way, each in a way especially suited to its listeners.
Even the theatre can enter the field of education and it has done
so. The play, and the motion picture patterned after it, entitled
‘“ Damaged Goods,” in the estimation of the author, has done a
great deal of practical good. Yet many ministers, teachers and
newspapers, often in total ignorance of-the real nature of the
play, and in absolute neglect of their own opportunities for
educating, have severely criticized the play as “immoral.” Such
men and women, who should know better, are nothing short of
a disgrace to the institutions they represent and are largely
responsible for the present popular ignorance concerning one of
the matters of most vital interest to humanity — sex hygiene.

SPIROCHZTA PERTENUIS 63

Yaws

A common feature of nearly all tropical countries is the disease
known as yaws or frambesia. In the Fiji Islands all healthy
children are expected to pass through an attack of yaws and are
sometimes inoculated with it by their parents. It is common in
many parts of equatorial Africa, particularly on the West Coast.
In the West Indies it is also a very common disease, especially in
the islands which are largely inhabited by negroes. There is
some evidence that yaws was imported to America from Africa
with the slaves as were some others of the most troublesome Amer-
ican diseases. In Brazil the disease is called ‘‘ buba brasiliensis ”’
and is often confused with Leishmanian diseases.

The parasite which is the cause of this loathsome disease is a
spirochete, Sp. pertenuis, which is hardly distinguishable from
the spirochete of syphilis, and was for a long time thought to be
identical with it. Recent investigations, however, have shown
that there are some slight differences in the two parasites, though
not enough to be recognizable by anyone but an expert. Like
the spirochete of syphilis, Sp. pertenwis inhabits many different
organs and tissues of the body, being found especially in the
spleen and lymph glands and in the tumor-like “ yaws.”’ It is
not yet conclusively proved that yaws and syphilis are not slightly
different types of the same disease, though most workers believe
in their distinctness, and for practical purposes, at least, it is best
to consider them as distinct. One of the arguments in favor of
the unity of the two diseases is that typical syphilis seldom occurs
where yaws is prevalent, and vice versa, but this may be due to
a reciprocal immunity, 7.e., yaws giving immunity to syphilis, and
syphilis to yaws.

The Disease. — In from 12 to 20 days and occasionally longer
after infection constitutional symptoms appear, such as fever,
rheumatic pains, and general illness. These symptoms are some-
times very severe, but usually they are slight and often hardly
noticeable. After several days of such symptoms there appears a
peculiar powdery scaling-off of the skin, sometimes almost invisible
but at other times making white marks, especially conspicuous
on the dark skin of negroes. After several days little pimples
appear over the hair follicles in the patches of powdery skin.
As these grow the raw flesh from beneath pushes the horny

64 SPIROCHATES

epidermis up, causing it to crack over the surface in such a way
as to give the little tumor the appearance of a raspberry. Little
yellow summits soon develop on the tumors, composed not of
pus but of a cheesy material. Some of the pimples grow no
further, but most of them become capped
over with the yellow cheesy substance
which catches and holds particles of dust,
and thus become very dirty. These are
the ‘“‘ yaws”’ from which the disease takes
its name. During their formation they
cause some itching, but are not painful.
They reach the height of their develop-
ment in 12 or 14 days and then usually
begin to shrink, the dirty yellow cap, now
dark colored, falling off and leaving a
sound patch of pale skin. Sometimes,
Fig. nae cand a aws. however, though in less than ten per cent
of cases, ulceration of the yaws takes
place, but this is probably due to complicating infections. The
time that the disease lasts varies greatly according to the general
health and constitution of the patient. In normal mild cases it
may be all over in less than two months, while in weak or sickly
individuals crop after crop of yaws may appear for months or
years, recurring at irregular intervals. There is some evidence also
that there may be a rare tertiary stage of yaws corresponding to
a similar stage in syphilis, characterized by a diseased condition
of the bones of the arms and legs, ulcers, etc., though this may
often be due to mixed infections with syphilis or other diseases.
The disease known as gangosa, prevalent in Guam and other East
- Indian Islands, is thought by some to be a consequence of yaws.
Yaws is very seldom a fatal disease except in young children.
Like syphilis it is very contagious, but the parasites are not
transmitted from mother to baby before birth or by nursing.
Treatment and Prevention. — Care of the general health of
yaws patients and conditions leading to the free eruption of
the yaws aid much in shortening and alleviating the course of
the disease. Salvarsan is poisonous for the parasites of yaws
as it is for other spirochetes, and is an almost sure cure at any
stage of the disease when injected either into the veins or muscles.
In experimental animals the parasites disappear within 24 hours

INFECTIOUS JAUNDICE 65

after the injection of salvarsan. Galyl and other arsenical sub-
stitutes for salvarsan are also effective against the disease.

The suppression of yaws in communities where it is common
consists largely in affording isolated hospitals or houses for
yaws patients and in preventing the patients by proper care and
treatment from spreading the disease by contagion. Personal -
care on the part of the patient is often more than could be
expected, considering that yaws is most common among half-
civilized and ignorant tropical races. However, the lure of a
comfortable and congenial ward where he could get good treat-
ment would undoubtedly induce many a native to submit to the
practice of being sanitary, however it might grate upon his nerves
at first. His accounts of the good treatment received would
help in luring others, and what few ideas of sanitation he might
have retained would help in spreading the gospel of sanitation.
In this way the prevalence of the disease, at least in local areas,
could be greatly reduced, and public money used for such pur-
poses could be considered well spent.

Infectious Jaundice or Weil’s Disease

In parts of Europe and in Japan, and also reported from various
parts of North America, there occurs a disease characterized
especially by fever and jaundice (7.e., affection of the liver causing
a marked sallow color due to bile pigments in the blood), the cause
of which has long been a puzzle to medical men. It has often
been confused with yellow fever and with bilious typhoid, and it
is not certain even now that the latter is not a very severe type of
Weil’s disease. Early in 1915 the connection of a new species
of spirochete, Sp. icterohemorrhagie, with the disease was dis-
covered by two Japanese investigators, Inada and Ido. Later
in the same year, and independent of the Japanese work, the same
organism was discovered in Germany in connection with Weil’s
Disease, the German investigators suggesting the name Sp.
nodosa. One could almost wish that the German name had been
given first!

The Disease. — A week or more after infection the first symp-
toms appear rather suddenly in the form of headache, high
fever, and a feeling of leaden fatigue in the legs which soon
changes to intense pains. The muscles become so tender that

66 SPIROCHATES

even a slight touch is unbearable. Usually the spirochetes are
abundant in the liver, suprarenals, blood and other organs and
tissues during this initial “febrile” stage of the disease, but they
are destroyed in the liver and suprarenals by antibodies usually
by the seventh day. During the second week of the disease,
termed the ‘‘icteric’’ stage, the fever subsides and marked jaundice,
accompanied by swelling and pain in the liver, usually appears,
though this symptom is sometimes evident as early as the third
day. In some cases, in Europe at least, jaundice may not appear
at all. The fever usually reappears in milder form about the
end of the second week, but it is of short duration. Such symp-
toms as vomiting, nose bleed, upsetting of the digestive system,
swollen spleen, weak but rapid pulse, and meningitis are usually
associated with the disease, and kidney trouble is nearly always

present, and is sometimes more severe than the jaundice. A>

tendency for the mucous
membranes and _ various
organs to bleed is a common
and dangerous symptom.
During the icteric stage of
the disease the spirochetes
disappear from the blood,
and are gradually destroyed
in other parts of the body;
they persist longest in the
kidneys, since the antibodies
which destroy them else-
where are apparently ineffec-
Fig. 11 Re is me who died from inal agence those:
Weil's disease on cea day, showing Spiro- in the kidney tubules. They

_cheta icterohemorrhagie in ,tissue. ~X 200. eontinue to be excreted with
(Sketched from figure by Inada et al.)

weeks, though nearly all symptoms usually disappear much earlier.
If death occurs, it nearly always comes between the eighth and
sixteenth days of illness. The disease is said to be not as severe
in Europe as in Japan, the mortality among infected soldiers i in
Flanders being less than six per cent.

The spirochetes are found in the blood, the cerebrospinal fluid,
and in many of the tissues of the body, oxpscialle the liver and the
kidneys. They vary in length from only four or five p to 20 yp

the urine for six or seven

TRANSMISSION OF INFECTIOUS JAUNDICE — 67

(ssoo tO reso Of an inch) and are characterized by pointed and .
usually hooked ends (Fig. 5G). According to the workers in
Japan the undulations are irregular and more like those of the
relapsing fever spirochetes than like those of the spirochete of
syphilis. Noguchi, however, states that the number of coils in
a given length is greater than that in any spirochete hitherto
known, there being ten or twelve coils in five uw (sa/59 of an inch).
The figure (Fig. 5G) shows only the gross undulations of the
organism and not the individual coils. From their descriptions
it would seem that the Japanese workers have mistaken these
eross undulations for the true coils. Noguchi believes this
spirochete to have characteristics sufficiently distinctive to war-
rant its being placed in a new genus, Leptospira. The spiro-
cheetes become most numerous from the 13th to the 15th day of
illness, and begin to diminish and degenerate by the 24th or
25th days, though they may continue to be excreted with the
urine for six or seven weeks.

It is probable that the spirochetes gain access to the body
either by way of the alimentary canal or directly through the
skin. The disease can be experimentally transmitted to guinea-
pigs by applying an emulsion of diseased liver to the shaved but
uninjured skin, infection taking place in as short a time as five
minutes. Infection is more certain if any abrasion of the skin
exists.

It has been shown that both the urine and the feces of infected
people contain living spirochetes and that these excretions are
infective. Since infection can occur directly through the skin
contact with contaminated ground is dangerous and probably
accounts for the prevalence of the disease in certain mines in
Japan. Rats have been shown by Japanese investigators to
serve as a reservoir for infectious Jaundice. The spirochetes are
very common in rats, especially in the kidneys, being con-
stantly excreted with the urine. Examination of 86 rats in
cities and coal mines in Japan where infective jaundice occurs
showed that nearly 40 per cent carried virulent spirochetes in their
kidneys, in most cases demonstrable by microscopic examination
of kidney tissue or urine as well as by experimental inoculations.
In America the parasites have been demonstrated in wild rats
caught in the vicinity of New York City and in Nashville, Tenn.
The ease with which rats may contaminate food with their ex-

68 SPIROCHATES

-eretions makes it appear probable that these animals are an im-
portant means of spreading the disease, and this most readily
explains the common occurrence of epidemics in families. Two
cases have been reported as having resulted from the bites of
rats. That rats serve to spread Weil’s disease in Europe also
appears evident from its common occurrence where rats are
abundant. In Europe butchers are especially prone to it, and
severe epidemics of it have broken out in the rat-infested war
trenches.

Treatment and Prevention. — The Japanese investigators find
evidence that salvarsan is destructive to Sp. icterohemorrhagie,
but their results are far from convincing and the German inves-
tigators say that salvarsan does not destroy the parasites. More
investigation and experimentation needs to be done before this
question can be settled.

Investigators of both countries have had greater success in
treating the disease by injection of the serum of a convalescent or
of an animal which has become immune. The Germans found
the convalescent serum effectual, either as a preventive or for
cure, when diluted 100 times. Japanese workers, on the other
hand, put far more faith in active immunization. They inject
spirochetes which have been weakened by subjection to very
dilute carbolic acid and left on ice for a week. Guinea-pigs can
be immunized by such injections, or even by injections of foe
parasites or the products of their disintegration.

Prevention of this disease, as of plague, evidently resolves itself
largely into rat destruction by poisoning, trapping and rat-proof-
ing. Some reduction should be obtained by keeping food where
rats cannot get access to it, and, of course, where it cannot be-
come infected, directly or indirectly, by the excretions of human
patients. However, since the parasites are able to penetrate
directly through thin skin, especially if there are any abrasions,
care should be taken to prevent contamination with urine of
objects or surfaces which are likely to come in contact with the
hands or other parts of the body of other people. As remarked
before, epidemics in mines are largely due to insanitary habits
and contamination of the ground. In mines or other places
where sanitary conditions are difficult to enforce, wholesale im-
munization would probably be effective, but good results can
also be obtained by disinfecting the ground. According to

RAT-BITE FEVER 69

Japanese authors, two epidemics in coal mines have already been
prevented by the latter method, combined with removal of inun-
dated water.

Rat-bite Fever

In many parts of the world, especially in Japan, there occurs a
disease which follows a rat bite, and is therefore known as “‘ rat-
bite fever.”’ It has been reported from various localities in the
United States. Some inflammation occurs at the place of the
bite and the neighboring lymph glands swell up. After several
weeks a high fever ensues, preceded by chills and headache.
The apparently healed rat bites become inflamed and there is
usually a red rash which spreads all over the body. In from
three to seven days the fever subsides but it recurs, usually
within a week, with similar symptoms, and the rash is more
constantly present than in the first attack. In some cases there
are still more relapses.

The similarity of the disease to such spirochzte diseases as the
relapsing fevers is obvious, and its spirochete nature was long
suspected by Japanese physicians, especially when they found
salvarsan to be effective in its treatment. Within the past few
months some Japanese physicians (Futaki, Takaki, Taniguchi
and Osumi) discovered in seven out of eight
patients numerous actively moving spirochetes
in the broken-out skin and in swollen lymph ,
glands. Animals were successfully inoculated $8
with the disease by means of bits of skin tissue
and blood containing spirochetes. The organ-
ism, which has been named Spirocheta morsus
muris, is described as being an actively moving yy. 12. Spiro
animal, larger than Sp. pallida of syphilis, but cheta morsus muris,
smaller than the relapsing fever spirochetes. aoe ea
It is rather short and thick with an attenuated human and animal
portion or flagellum at each end (Fig. 12). Long pe oa
spirochetes, at first thought to be specifically dis- taki, Takaki, Tani-
tinct from the short thick forms, also are found ae a aaa
in human infections. According to Kaneko and Okuda these are
probably degenerate forms resulting from the action of anti-
bodies. :

The Japanese investigators have been unable to find the spiro-

70 SPIROCHATES

cheete in the saliva of infected rats or of other rodents, but only
in their blood. From this the conclusion has been drawn that
the source of infection in a rat bite is blood from hemorrhages
of the gums or tongue which contaminates the teeth.

Both mercury and salvarsan are effective in the treatment of
this disease as of most other spirochete diseases.

Attention should be called to the fact that rat bites may often
give rise to diseases which may be of quite different nature from
the ‘‘rat-bite fever’ described above. It is well known that
many different infective organisms live in the mouth and around
the teeth of such animals as rats, and it is not surprising that
infections of divers kinds may result from rat bites, and that
these infections should have been confused with typical rat-bite
fever. Several investigators have described a vegetable organ-
ism, Streptothrix, as the cause of rat-bite fever. Recently Ruth
Tunnicliff has shown that a form of pneumonia in rats is pro-
duced by a Streptothrix very similar to, if not identical with, that
described in some cases of rat-bite fever. It is very probable
that these cases were really infections with the pneumonia-caus-
ing organism, and quite distinct from the Japanese disease.

Other Spirochzte Diseases

Spirochetes, often in association with bacteria of various kinds,
have been found in a number of other human diseases, and are
in all probability at least partially the cause of them. —

The common spirochete, Sp. buccalis, which lives about the
gums and roots of the teeth in almost all human mouths is
thought by some investigators to be entirely harmless, living
only on waste matter. By others it is thought to become
pathogenic under some circumstances, and, in partnership with
certain cigar-shaped bacteria, to be the cause of Vincent’s angina,
a diphtheria-like ulceration of the tonsils and throat; of noma,
an ulceration of the mouth cavity and cheeks; of ulcerations of
the nose, teeth and lungs; and of balanitis, an ulceration of the
genital organs which may occur after unnatural sexual relations.
In central America there is a common disease ‘‘ mal de boca”
(disease of the mouth) which is marked by swollen, spongy and
tender gums over which a whitish pellicle forms. It is infectious
and is probably caused by a delicate spirochete found on the

DISEASES OF MUCOUS MEMBRANES 71

lesions. Some workers believe that some or all of these afflictions
are due to different species of spirochetes and bacteria, but the
fact that both organisms are found together in all these diseases,
and that they show only such slight differences from the organ-
isms in the mouth as would be expected under altered conditions,
makes it seem quite possible that Spirocheta buccalis and its con-
stant companion, a cigar-shaped bacterium, are the causes of
all of them. The conditions which seem to favor the growth and
disease-producing propensities of these organisms are heat,
moisture, filth and absence of air. Wherever these conditions
prevail, and these ordinarily harmless organisms can get a foot-
hold, sores and ulceration are likely to result, accompanied by
more or less fever and digestive disturbance due to absorption
of poisonous substances from the decaying tissues.

The treatment of these affections must vary with their location.
‘For the sores on the tonsils or mouth cavity in Vincent’s angina or
noma either salvarsan or silver nitrate is effective. It should be
daubed on the injured tissue with a piece of cotton. The silver
nitrate is less dangerous than salvarsan and equally effective for
these superficial ulcers. Treatment of the infected parts with
a two per cent solution of silver nitrate for a few days results in
a rapid healing. In case of balanitis, ordinary cleanliness and
exposure to air is sufficient to cause a spontaneous healing in
four or five days. Washing with hydrogen peroxide, which
liberates oxygen in the presence of organic matter, is very de-
structive to such organisms as these, which thrive best in the
absence of air.

In the Sudan region of Africa, and also in Colombia, South
America, there is found a certain type of bronchitis, marked by
fever and often by hemorrhages along the respiratory tubes,
which is accompanied by the spirochete, Sp. bronchialis. This
parasite has very slender pointed ends, and averages eight to.
nine p (spp Of an inch) in length, but its most marked charac-
teristic is its variability. These spirochetes reproduce by the
peculiar method of “ granule shedding,” breaking up into tiny
round bodies which later develop into new spirochetes. It is
probable that these little particles of living matter can resist
drying up in air, especially in humid atmospheres, and may there-
fore be transmitted with dust or with little droplets of moisture
propelled by coughing.

ie, SPIROCHETES

Tropical Ulcer. — Still another human disease that has been
attributed to spirochetes is tropical ulcer, also known by the
more impressive name, “ tropical sloughing phagedena.” This
is a type of sore on the skin, most commonly of the leg, which

_ originates either in some slight abrasion of
the skin or in some preéxisting wound or
sore, especially in persons debilitated by
some other disease or by alcohol. It begins
in a tiny blister which soon bursts, and the
sore thus exposed spreads very rapidly, con-
stantly sloughing a yellowish, moist and

exceedingly fetid matter. After a few days,
pee Gee Bey ta while the sore is still spreading, the center
Halberstadter in Kolle of the slough begins to. liquefy and is grad-
seg eC abate ually sloughed off and heals. Usually the
ulceration confines itself to the skin but sometimes it goes deep
into the muscles, nerves and bloodvessels, even injuring the
bones and joints. Sometimes permanent deformity or even
death results from these extensive excavations, death resulting
especially from the opening of some large bloodvessel.

Tropical ulcer occurs in nearly all hot damp tropical countries.
Although not definitely proved, it is usually accepted that the
spirochetes, Spirocheta schaudinni, which can almost always be
found in the ulcers, together with cigar-shaped bacteria found in
association with them, are the ringleaders in producing it. The
treatment usually recommended is a thorough cauterization of
the sore, followed by antiseptic washes and applications. Sal-
varsan and other arsenic compounds have been found beneficial
in many cases. Finocchiaro and Migliano in Brazil claim to
have found a specific cure for this loathsome disease in an appli-
cation of powdered permanganate of potash or in a compress of a
one to ten solution of this substance. They achieved a complete
cure in from ten to thirty days in every one of seven cases.

Ulcerating Granuloma.— Of a somewhat similar nature to
tropical ulcer, and of wide distribution in the tropics, is “‘ ulcerating
granuloma of the pudenda,” a sore which spreads, very slowly
however, over the external genitals and along the moist folds
of skin in neighboring regions. Both spirochetes and bacteria
have been found deeply situated in the tissues at the bases of
these sores, but to what extent either or both are responsible for

PATHOGENICITY 73

the condition is not known. The disease is peculiar in being
very refractory to treatment by any of the usual methods of
cauterization or application of drugs. Recently, however, it
has been found to succumb to X-ray treatment, and this method
is now extensively employed. Aragao and Vianna in Brazil
and Breinl and Priestley in Australia have obtained excellent
results from intravenous injections of tartar emetic.

Spirochetes have been found in connection with still other
human afflictions, and it is possible that they may be the cause
of them. In most cases, however, it is more probable that spiro-
cheetes which are normally harmless and live only on dead matter
find congenial surroundings in tissues diseased by some other
cause, and that this accounts for their presence. Often, however,
such ordinarily harmless spirochetes may change their habits
under suitable conditions and become pathogenic, thus aggra-
vating the diseased condition. The pathogenic propensities of
spirochetes have been demonstrated in so many cases, however,
that they may rightly be looked upon as one of the most destruc-
tive groups of human parasites.

Since this book has gone to press Futaki has found a spirochete, which he
has named spirocheta exanthemotyphi, in the kidneys of seven out of eight
typhus victims in Japan, and in the urine of six out of seven other typhus
patients. The spirochete was also found in a monkey inoculated with blood
from a typhus patient. It is possible that the minute coccoid bodies found in
typhus-infected lice by Rocha-Lima, and named by him Rickettsia prowazeki
(see p. 169), are really the granule stage of this spirochete.

CHAPTER V
LEISHMAN BODIES AND LEISHMANIASIS

Leishman Bodies in General. — While investigating the cause
of a deadly disease of tropical India known to the natives as
kala-azar or dumdum fever, Leishman, in 1903, and at about the
same time, Donovan, discovered in the spleen of victims numerous
little round parasites. These looked to Leishman exactly like the
non-flagellated stage of a trypanosome (see Chapter VI), and he

naturally took them to be developmental stages of trypanosomes, |

and added another terrible disease to the credit of those murder-
ous animals. Later, however, it was found that while these little
round organisms resemble a certain stage in the life history of a
trypanosome, yet they never reach this fully developed form.
Nevertheless it was discovered that when transferred to the in-
testine of certain insects, or when grown on artificial cultures,
they undergo a wonderful transformation. They become elon-
gate in form and develop a waving flagellum, assuming what is
known as a ‘“‘ Herpetomonas”’ form (see Fig. 14L), and they move
about so actively that it is difficult to believe that they are really
transformed from the un-animal-like round bodies found in
diseased human bodies. Such flagellates, under the name “ Lep-
tomonas’’ or ‘‘ Herpetomonas,”’ had been known before, and- were
recognized as common parasites of insects, belonging to a primi-
tive group of the class Flagellata. They were also known to
present, during their development, this unflagellated round
condition, but always in the bodies of insects. Here was a
vicious form of the parasite which was not content with life in an
insect, but must adapt itself to live in the bodies of warm-blooded
animals. There is reason to believe that some of the flagellates
which normally live exclusively in the intestines of blood-sucking
insects have the power, if injected into warm-blooded animals,
to adapt themselves to the conditions they find there, causing
more or less local inflammation and sores. In Panama, for
instance, sporadic cases of sores occur in which are found Leish-
74

=

HAMOFLAGELLATA 15

man bodies in small numbers, resulting from the bite of horse-
flies (Tabanidee) of various species. There is every reason to
believe that the parasites in these sores are normally parasitic
in the insects only, but are able to adapt themselves to their new
environment in human flesh and to multiply there for a time.
They are permanently sidetracked, however, and have no further
chance of completing their life history or of reaching new hosts,
unless a suitable fly should, by some infinitesimally small chance,
suck blood from the sore in which they were developing, and thus
rescue them.

Several investigators have recently shown that a number of
typical insect flagellates, if injected into mice and rats or other
mammals, or even birds, may become pathogenic and even
cause the death of the animal. That the well-established Leish-
mania diseases of man and other animals originated from insect
flagellates can hardly be doubted, but it is possible that in some
eases the parasites may have adapted themselves to their new
- type of host to such an extent as to have become quite independ-
ent of the insects from which they originated. Fantham suggests
that all forms of Lesshmania and Herpetomonas may be mere
physiological races of a single species which is variously adapted
to live in a variety of different hosts, and perhaps able to adapt
itself anew to unaccustomed hosts under certain conditions.

Leishmania and Herpetomonas belong to a group of the class
Flagellata known as the Hemoflagellata. This group presents
a series of forms from the simple Leishmania, which at times is
a non-motile, unflagellated organism, through the increasingly
highly developed Herpetomonas and Crithidia to the trypano-
somes (see Fig. 18). Some reach only the Herpetomonas stage as
adults, others only the Crithidia stage, while others pass through
the entire series of developmental stages and reach the final
trypanosome stage. All of them are probably primarily parasites
of the guts of insects or other invertebrates, and only compara-
tively few of them have adapted themselves to spending part
of their existence in the blood or tissues of vertebrates. Ap-
parently only the Leishmania and trypanosome forms are
adapted for existence in vertebrates, since the other forms are
not found in them, except in rare instances when Herpetomonas
forms are found in the blood of Leishmania-infected individuals.
A number of species have become thoroughly adapted to life in

76 LEISHMAN BODIES AND LEISHMANIASIS

vertebrates and are now normal parasites of them, and others,
as already shown, if accidentally introduced may be able to
multiply sufficiently to cause local or temporary sores, or even a
fatal infection.

All the species of hemoflagellates which normally live in warm-
blooded animals in the form of Leishman bodies are grouped
together in the genus Leishmania. A number of human diseases
are known to be caused by them. Kala-azar of southern Asia,
already mentioned, is the most severe one. A similar disease,
infantile kala-azar, occurs around the Mediterranean, especially
in children. There are also a number of Leishmanian diseases
which, instead of causing constitutional disturbances, cause sores
or ulcers on the skin or mucous membrane. One type, oriental
sore, also called by various local names, is widespread throughout
many tropical countries, especially southern Asia and around the
eastern end of the Mediterranean, and possibly in tropical South
America. It causes temporary sores on the skin, chiefly of the
exposed parts of the body; the sores may or may not ulcerate. -
In South America there occurs a much more vicious type of
the disease in which the skin sores are followed by ulcers spreading
over extensive areas of the mucous membranes of nose and mouth,
often resulting fatally. A parasite, Aphthomonas infestans, be-
lieved to be allied to Leishmania, has recently been described by
Stauffacher as the cause of foot-and-mouth disease.

The clinical manifestations of these ulcers and sores on the skin
or mucous membranes are extremely variable and indicate the
possibility of there being a number of different species or at least
varieties of Leishmania causing them. There are some parasi-
tologists who believe that all the different kinds of Leishmani-
asis — internal, cutaneous or mucosal — are caused by different
strains of the same species, while others believe in the existence
of several species. Usually four species are recognized, as fol-
lows: Leishmania donovani, causing kala-azar; L. infantum,
causing infantile leishmaniasis; JL. tropica, causing cutaneous
sores; and L. americana (brasiliensis), causing sores or ulcers of
long duration on the skin and mucous membranes. However,
until we are familiar with the adult forms of all the various types
of Leishmania, and know more about their life histories, we can
only guess at their classification.

KALA-AZAR rif

Kala-azar

About 1870 there began a great epidemic of a strange and
deadly disease in Assam, India, which spread up through the
Brahmaputra Valley. It was believed to have been imported
by the British from Rangpur, where a similar epidemic had been
raging for some time before. Whole villages and settlements
were depopulated and the country was terrorized by the “ black
sickness.”’ It is said that victims of the disease were driven out
of the villages, sometimes being made unconscious with drink,
taken into the jungle, and burnt to death. Some villages com-
pletely isolated themselves from the outside world, and still
others were entirely deserted for new and uninfected districts.
The natives were most severely affected, no doubt due both to
their filthiness and unsanitary habits and to their weak con-
dition as the result of almost universal malaria and hookworm.
Before the true nature of the disease was discovered it was usu-
ally diagnosed as ‘‘ severe malaria’”’; one physician concluded
that it was excessive hookworm infection, since he found hook-
worms almost universally present in kala-azar sufferers.

This Assam epidemic, which lasted for many years, is the only
recent case of a great epidemic of kala-azar, although the disease
now occurs endemically in many parts of India and Southern
China, and is spreading in the Sudan region of North Africa.
It has been pointed out that the endemic parts of China, chiefly
along the north bank of the Yangtse River and its tributaries,
correspond closely in latitude and climate to a considerable part
of southern United States, and since kala-azar is believed by some
to be spread by bedbugs and perhaps other vermin, there is danger
that once introduced it might become endemic in America.
A single case has been found in Brazil, contracted in a region
where another form of Leishmaniasis is prevalent. How this
case should be explained is difficult to know. :

Transmission. — In spite of numerous experimental investiga-
tions to discover the mode of transmission of the kala-azar para-
site, Leishmania donovani, the question is still obscure. Captain
Patton, of the British Medical Service in India, adduced some
evidence that the common Indian bedbug, Cimex hemipterus
(rotundatus), is the normal intermediate host and transmitter
of kala-azar. Using laboratory-bred bugs, Patton succeeded in

78 LEISHMAN BODIES AND LEISHMANIASIS

getting abundant growths of the parasites in the intestines of
the bugs after they had been fed on infected blood. When
sucked up by the bugs, the Lezshmania-laden cells in the blood are
digested and the parasites set at liberty in the stomach. Here
after several days they begin to go through their remarkable
transformations and active flagellated Herpetomonas forms de-
velop similar to those which occur in artificial cultures (Fig. 14,
F to O). After several days of free active life the parasites
round up again, lose their flagella, and are then presumably
ready for inoculation into a new host. All these changes occur
during a period of 12 days. Patton has not, however, shown
that the bedbug is capable of transmitting the parasites to other
victims by means of its bites, though it is possible that scratching
of the bites and crushing of the bugs might cause infection.
Developmental stages have also been traced in the mosquito, |
Anopheles punctipennis, but here again there is no proof of the
insect’s method or power of transmitting the parasites to new
hosts. The facts connected with the spread of the disease in
India seem to favor the theory of transmission by a household
insect. Rarity of the parasites in the circulating blood has been
claimed as an argument against the insect transmission theory,
but Patton has shown that almost every smear of blood from an
infected person contains white blood corpuscles with the Leish-
man bodies in them. On the other hand the manner of spreading
of the disease in Sudan is rather opposed to a theory of insect
transmission, and it has been suggested that infection may take
place through the medium of contaminated water or food, since
experimental animals occasionally become infected when fed on
infected material. The suggestion is also made that an intestinal
wound of some kind may be necessary to allow the entrance of
parasites into the blood and organs of the body. Bodies re-
sembling Leishman bodies have been found in the feces of in-
fected persons, so that faeces may in some way have to do with
the transmission of the parasites. The difficulty experienced in
inoculating the disease into experimental animals makes the
investigation of its transmission very difficult. The parasites
develop readily in artificial cultures at relatively low tempera-
tures, presenting the series of changes shown in Fig. 14. These
forms are practically identical with those found by Patton in the
-intestine of the bedbug and undoubtedly represent part, at least,

PARASITE OF KALA-AZAR 79

of a possible cycle in an insect host. That this phase of the
life history of the parasite may normally be omitted is never-
theless quite possible.

Human Cycle. — After entering the human body, the para-
sites probably utilize the blood and lymph streams to obtain
transportation to all parts of the body, but do not live free in

Fic. 14. Parasites of kala-azar, Leishmania donovani; A, isolated parasites
from spleen; B, dividing forms from liver and bone marrow; C, spleen cell with
parasites; D, group of cells with parasites; EH, parasite ingested by leucocyte; F-O,
from cultures; F and G, early stages after ingestion; H, large dividing forms; J,
development of flagellum; J, small flagellated form; K and L, flagellated Herpe-
tomonas forms; M and N, unequal division; O, parasites resulting from unequal
division shown in M and N. xX about 1500. (After Leishman.)

80 LEISHMAN BODIES AND LEISHMANIASIS

the body fluids. They enter the delicate endothelial cells which
line the blood and lymph vessels, and also the cells of the spleen,
liver and lymph glands. Within the cell they have entered
they grow and multiply rapidly (Fig. 14C and D). The indi-
vidual parasites (Fig. 14A) are exceedingly small, about two u
(less than ;,.,; of an inch) to four w in diameter. They are
round or oval in form with a large nucleus and a smaller para-
basal body shaped like a little rod and set more or less at a tan-
gent to the nucleus.

In a short time, by dividing and re-dividing, the Leishman
bodies completely fill the cell they inhabit, causing it to enlarge to
many times its normal size (Fig. 14C). There may be as many
as several hundred parasites in a single enlarged cell. The
parasitized endothelial cells often seem to ‘‘ run amuck,” breaking
loose from their normal position on the lining of bloodvessels.
and becoming free-living carnivorous cells like the white blood
corpuscles. When these parasite-filled cells finally burst, the
liberated parasites enter new cells, or are gobbled up by the
white blood corpuscles (Fig. 14E). It is probable that the para-
sites are ingested by bedbugs while inside free endothelial cells
or white corpuscles in the blood.

The Disease. — The incubation period of kala-azar after in-
fection is not definitely known, but Manson cites one case where
an Englishman was attacked by a fever, which terminated in
kala-azar, within ten days after arriving in an endemic locality.

A high fever usually marks the onset of the disease, and this
persists more or less irregularly for several weeks. Meanwhile
the spleen and liver enlarge enormously, increasing and decreas-
ing with the fluctuations of the fever. After several weeks the
fever drops and the patient becomes almost normal for some
time, only to be attacked by the fever again, with an enlargement
of spleen and liver. These remittent attacks gradually dwindle
to the steady low fever, accompanied by sweating spells, rheu-
matism-like aches, high pulse rate, anemia and a general wasting
away, with the skin often a dark earthen color. Dysenterie
symptoms, with discharges of blood and mucus, are common,
especially in the late stages of the disease, and frequently after
death the intestine is found to be extensively ulcerated, with
numerous parasites in the walls of the ulcers. Parasites are
usually found most abundantly in the spleen, liver capillaries,

TREATMENT OF KALA-AZAR 81

bone marrow and lymph glands. When the chronic condition
is reached the patient presents an appearance not unlike that
resulting from chronic malaria, and it is little wonder that the
diseases were long confused. Usually complication by some
other disease, especially dysentery, which gets a severe hold on
account of the low vitality of the victim, causes death (accord-
ing-to Rogers in 96 per cent of cases), but in a relatively small
per cent of cases there is recovery. A steady gain in weight,
however slight, is said by Mackie to be a fairly accurate sign of
recovery.

Treatment. — Within the past three years (1914-1917) the
remarkable destructive effect of antimony, especially in the form
of tartar emetic, on Leishman bodies has been thoroughly es-
tablished. Tartar emetic as a cure for Leishmanian diseases
was first tried out in 1912 with astonishing success by Vianna,
a Brazilian investigator, on the Leishmanian ulcers of the face
and nasal mucosa. Similar treatment has been applied with
equal success to oriental sores and to infantile kala-azar. Its
application to the more severe Indian kala-azar has been attended
with great success, and even advanced stages of the disease can
sometimes be cured by its use. Rogers and Hume have used
it extensively in India. Injections of metallic antimony have
_also been found of great benefit in treatment of this disease.

The usual method of giving tartar emetic is by injections into
the veins, as in trypanosome diseases. From one to ten ce. of.a
one per cent solution is given, the dose being gradually increased
in accordance with the age and tolerance of the patient. The
drug is a powerful one, and if given in over-doses may cause
severe disturbances of the digestive tract and of the kidneys, but
if it is given in small quantities to begin with, and its effects
carefully watched as the doses are increased, it can be used with-
out danger and constitutes a treatment as specific in its’ effects
as 1S quinine on malarial parasites, or salvarsan on spirochetes.

Prevention. — On account of the uncertainty which exists con-
cerning the mode of transmission of kala-azar, victims of the
disease and those who have closely associated with them should
be quarantined and their houses thoroughly disinfected to kill
any bedbugs or other vermin, as well as any Leishman bodies
which might exist in any body excretions. The safest method
in the case of the native huts which are hopelessly filthy and

82 LEISHMAN BODIES AND LEISHMANIASIS

unsanitary is to burn them with all ther junk. This method of
stamping out the disease before it has had time to spread has
been successfully used on some of the tea estates in Assam.
For the successful prevention of the spread of the disease, an
isolation of 300 to 400 yards has been found sufficient, a fact
which exonerates most flying insects as transmitters. Houses in
endemic regions should be kept scrupulously free from bedbugs,
and any place where bugs might be acquired should be care-
fully avoided.

Since the parasites have been shown to exist in the feces of
infected persons, careful and thorough disposal of the feces

should be attended to. The possibility exists that non-blood-

sucking flies which frequent human feces may be instrumental
in spreading infection. Until proved otherwise, precautions
against this should be taken in endemic places.

Infantile Kala-azar

In many of the countries bordering the Mediterranean—Algeria,
Tunis, Malta, Crete, Greece, southern Italy, Sicily, Spain and
other regions — there occurs a disease which in many respects
closely resembles true kala-azar, but differs from it very strikingly
in other ways. While true kala-azar attacks young and old
alike, the Mediterranean disease attacks infants and children
almost if not quite exclusively. Children between one and two
years old are most frequently subject to it, whilé children over
six years old are practically exempt. While true kala-azar is
not readily communicable to other animals than man, the Medi-
terranean disease occurs naturally in the dogs of endemic regions
and in some places where the disease is not known to occur in

children. It can be experimentally transmitted not only to

dogs but also to rats, mice and, with more difficulty, to monkeys.
Cats cannot be successfully inoculated. It is believed by some
that the disease in dogs is different from that in children, but the
similarity in symptoms, and geographic distribution, as well as
the fact that dogs can be infected by parasites from human
beings, and other dogs from these dogs, all point to the identity
of the diseases.

Transmission. — A remarkable fact connected with artificial
inoculation of the disease is the great quantity of infective ma-

? oie
oe See e

aD OT ees

TRANSMISSION OF INFANTILE KALA-AZAR 83

terial which is necessary to produce infection. Injection of
infected material under the skin does not transmit the disease,
although in nature this is probably the mode of transmission.
Evidently, then, the natural means of transmission must be by
more powerful or virulent parasites than can be obtained from
already infected animals. The common opinion is that the dog
flea, Ctenocephalus canis (see p. 416), is the usual transmitting
agent, and that this insect serves as an intermediate host for the
parasites. This opinion is based on the fact that parasites ap-
parently identical with those in infected children have been
found in the tissues and feces of fleas. Brumpt, however, be-
lieves that there has been confusion with an apparently harmless
flagellate which is frequent in fleas even where infantile kala-azar
does not occur. Patton suggests that the kala-azar of dogs may
really be an infection quite distinct from the infantile disease and
caused by infection with the common intestinal flagellate of fleas,
Herpetomonas ctenocephali. ‘The possibility that the human dis-
ease may also be caused by this flagellate seems to have been
overlooked; the fact that the fleas do not readily become in-
fected from sucking an infected child does not necessarily argue
against the origin of the human parasites from fleas. Recent
work by da Silva and Spagnolio in attempting to infect fleas by —
allowing them to feed on a naturally infected child has been un-
successful. They fed 25 fleas on an advanced case of the disease
and secured no infection of the fleas in 484 feeds. These authors
do not believe in the relation of fleas to infantile kala-azar, and
point out that the disease is at its height in the spring before
fleas have become very abundant.

Infection of bedbugs with Leishmania infantum is not suc-
cessful. If fleas do serve as the usual transmitting agents, it is
probable that after development in the flea the Leishman bodies,
as suggested above, become more resistant and are able to establish
themselves in situations where they would otherwise be destroyed
before they had a chance to multiply and adapt themselves.

Since so many dogs around the Mediterranean are infected,
although only a small number give any indication of it, they
probably serve as a reservoir for the disease. Not infrequently
children attacked by kala-azar have been known to have played
with diseased dogs, and it is easy to see how the fleas which
almost always infest dogs in these regions could infect children.

84 LEISHMAN BODIES AND LEISHMANIASIS

The Disease. — The disease is much like true kala-azar in
most of its clinical manifestations, though differing in details.
It is characterized by fever, aches and anemia, and by excessive
enlargement of the spleen, the liver also enlarging somewhat.
Though in some places comparatively mild, in others it is ex-
tremely fatal. Recovery is rarer the younger the patient; in 130
cases reported from Palermo and Naples, 93 per cent of the chil-
dren under two years old succumbed to it, while 87 per cent of
the older children died. Similar high mortality has been re-
ported in other parts of Italy.

Usually after recovery from a single attack immunity is given,
almost always lasting until the susceptible age is passed.

Treatment and Prevention. — Wonderfully successful results
have been obtained in the treatment of infantile kala-azar with
tartar emetic as described on page 81. Of eight children treated
with tartar emetic in Italy, all of whom were between five and
27 months old, except one boy of six years, seven recovered com-
pletely. - In the last stages of the disease the vitality is so weak-
ened that recovery is impossible even with the destruction of all
the parasites. ;
_ Prevention obviously les in keeping infected dogs away from |

children. In endemic regions dogs should be kept scrupulously
free from fleas, and all dogs showing the slightest symptoms of
feverishness, enlarged spleen or emaciation should be killed, and
their bodies burned to destroy fleas. Even if this were done it
would not be sufficient to stamp out the disease completely, since
so many dogs carry the infection in latent condition, serving as
a reservoir for it without showing any appreciable symptoms.
Basile showed the value of attacking the disease in dogs by de-
stroying all obviously infected dogs in a certain township in
Italy. In the year the dogs were destroyed there were seven
new cases of the disease in children in a population of 2000, but
in the following year not a single new case appeared, and in the
year after only one.

Oriental Sore

One of the commonest sights in many tropical cities, particu-
larly in the cities of the eastern Mediterranean region and south-
western Asia, is the great number of children, usually under three
years of age, who have on the exposed parts of their bodies un-

OCCURRENCE OF ORIENTAL SORE 85

sightly ulcerating sores, upon which swarms of flies are constantly
feeding. The exudations from such sores are teeming with Leish-
man bodies, Leishmania tropica (Fig. 15A and B), which very
closely resemble those of kala-azar. In some cities infection by
these parasites 1s so com-
mon and so _ inevitable
that normal children are
expected to have the dis-
ease and visitors to the
cities seldom escape a
sore aS a souvenir, even
if present for only a short
time. In Bagdad, Wenyon
has shown that almost as
soon as the children are
relieved of the wrappings
in which they are covered
as babies, and allowed to
run free and play in the
streets, they are almost
certain of infection. Since
one attack gives immu-
nity, oriental sores ap- fic.15. Parasites of oriental sore (Leishmania
pearing on an adult person Worst): A. Band C, parasitss from sore th
in Bagdad brands him as the cells, the others (B and C) within the cells;
a new arrival, and the 2 Herpetomonas form taken from bedbug 48

: hours after feeding on sore; EH, the same, dividing
same 1S undoubtedly true form. x 4000. (After Wenyon.)

in many other tropical
cities. The disease is prevalent from India through Persia, Syria
and Arabia and along the south shore of the Mediterranean as
far as Morocco. True oriental sore probably occurs commonly
in many cities of tropical South America, though here it is ob-
viously difficult to distinguish it from the skin sores of espundia.
Transmission. — Though oriental sores may appear at any time
of the year, they are particularly abundant in the autumn months
in most cities of the Old World. Since the usual time of the
appearance of the sore, as nearly as can be judged, is about two
months after infection, though sometimes much less and often
much longer than this, infection must usually occur during the
hot mid-summer months. This fact suggests the probability of

86 LEISHMAN BODIES AND LEISHMANIASIS

the parasites being transmitted by some biting insect which
appears during this season. There can be no doubt that the
myriads of flies which collect on the sores must mechanically
‘carry the parasites in many cases from infected individuals and
deposit them on wounds or cuts of others where they gain access
to the body. It may be that one or more kinds of insects act as
intermediate hosts; in fact, it has been claimed that in India the
bedbug is an intermediate host for this as well as for the kala-azar
parasite. In Teheran, where a large proportion of the dogs (in
one case 15 out of 21 street dogs) show Leishmanian sores, the
parasites have been found in the gut of a fly, Hippobosca canina,
common on the dogs. Camels and horses are also subject to
infection in some places. A number of French workers in North
Africa have suggested that the sandfly, Phlebotomus minutus,
which is very abundant there, is the transmitter of the disease
and that the common Algerian gecko, Tarentola mauritanica,
may play the réle of a reservoir for the disease. The sandflies
swarm about the lizards in large numbers, and also bite man
readily. Leishman bodies have been found in the blood of a
number of geckos near Tunis. On the western face of the Andes
in Peru there occurs a similar disease known as uta, which has been
shown by Townsend, of the U. 8. Bureau of Entomology, to
develop in the intestine of two little gnats, Forcipomyia ute and
Forcipomyia townsendi, very closely allied to the American
“ »punkies.”” Inoculation of the gut contents of these insects into
guinea-pigs produces sores believed to be identical with uta, and
Townsend believes the insects transmit the disease in nature by
voiding the Leishman bodies from the anus while sucking blood,
the puncture being contaminated in this way. Whether this dis-
ease is a very mild form of espundia, described below, or is more
closely allied to true oriental sore, is difficult to say. According
to the description given by Dr. Strong and his colleagues of the
Harvard expedition to Peru, uta is not so mild, and may attack
the mucous membranes as does espundia. Possibly both diseases
occur there. Dr. Strong has pointed out that the flagellated
stage of the uta parasite differs from that of other Leishmania
in possessing a basal granule in addition to the nucleus and para-
basal body.

The Disease. — Although oriental sore often has a long incu-
bation period, and produces such profound constitutional changes

COURSE OF ORIENTAL SORE 87

as to build up an immunity which is usually effective for life,
the general symptoms are so mild as to be usually unnoticed.
Slight fevers and general malaise are frequent at all times in
tropical countries, and it would be extremely difficult to connect
such non-characteristic symptoms with a sore appearing perhaps
months afterward. There is some evidence, however, that at
least in some cases fevers do occur which are attributable to the
parasites of oriental sore.

The nature and course of the sores vary to some extent in
different localities. The sore usually begins as a small dark pimple
which causes very slight itching and little if any inflammation of
the surrounding skin. The pimple grows slowly and develops in
one of two ways, forming either an ulcerating or a non-ulcerating
sore, more popularly known as female and male sores respectively.
In the former type, under a flaky scab which soon falls away or is
scratched off, there develops a shallow ulcer exuding a foul-smell-
ing yellow fluid. Usually the sore covers an area about the size
of a dollar, the older portion often healing while the ulcer is still
extending in another direction. The surface of the ulcer is
covered by red granulations which bleed readily. In most lo-
calities these ulcers are not painful, but those occurring along
the eastern slope of the Andes in Peru and Bolivia are said to be
very painful.

The non-ulcerating or male sores grow slowly and develop a
covering of white flaky scales over a thin red skin, below which is
a mass of red granulations where the parasites may be found in
large numbers. The non-ulcerating sores sometimes break down
and ulcerate, but usually grow to about the same size as do the
“female” sores, and then gradually shrink, finally healing as
do the others.

The sores, of either kind, nearly always occur on exposed parts
of the body, as the face, neck, arms or legs. Occasionally they
occur on the lips or edges of the nose and spread to the mucous
membranes, but this must not be confused with the mucous
membrane ulcerations of American leishmaniasis. A single sore
is the most common condition, but secondary sores sometimes
develop in its vicinity, and sometimes a great many sores may
occur on an individual. In the Peruvian uta several sores seem
to be the rule, these occurring at the sites of the bites of gnats
and possibly other insects.

88 | LEISHMAN BODIES AND LEISHMANIASIS

The sores usually last for a year, more or less, gradually healing
over, but leaving permanent scars. The uta sores of the Peru-
vian Andes, which have a much shorter incubation period, may
run their course and heal in much less time, according to Town-
send in as short a time as 15 days. Except in rare cases, after
an oriental sore has once run its course and healed a person is
permanently immune to any further attacks.

Treatment and Prevention. — The use of tartar emetic as a
cure for oriental sores is as productive of good results as it is in
the case of other Leishmanian infections. With the usual one per
cent or two per cent solutions of this drug injected into the veins
the sores yield promptly and, if treated at an early stage, can be
prevented from leaving scars.

In badly infected places there might be some advantage in
allowing the sore to run its course, inoculating it on an inexposed
part of the body where it could cause no visible disfigurement,
since in this way a permanent immunity to further infection
could be prevented. It is better to keep the sores open than to
allow a scab to form over them, since the scab shuts in the pus
and results in more extensive ulceration and inflammation. Ap-
plications of various kinds which will soothe the inflammation
and keep the sores as dry and clean as possible are beneficial.
The use of hypodermic injections of dead cultures of the parasite,
as in anti-typhoid vaccinations, has been found to hasten the
healing. The inoculation of the active disease germs on inex- |
posed parts of the body, especially in young children in whom —
the sores are never very extensive, is easily accomplished, and has
been practiced in Bagdad and other cities where the disease is so
prevalent as to make avoidance of it almost impossible. Such
a procedure tends to lessen the number of exposed sores, to
which flies or other insects might get access. Unless the disease
should be found to be transmitted by insects which suck the
parasites from the circulating blood, which seems very unlikely,
the protection of the sores will greatly reduce the prevalence of
this unpleasant feature of tropical cities.

It is possible that an immunity may be established by the
inoculation of dead parasites as in the case of typhoid fever, but
this has not yet been demonstrated.

SKIN SORES OF ESPUNDIA 89

Espundia or American Leishmaniasis

In many parts of Brazil, Paraguay, Bolivia, Venezuela, French
Guiana and other countries of tropical South America there
occurs a horrible form of Leishmanian ulcers which attack both
the skin and the mucous membranes of the nose and mouth
cavity. These ulcers do not grow to a limited size and then heal,
but slowly and constantly spread further and further, lasting
for a period of five, ten, fifteen or more years. The disease goes
by a great variety of local names of which espundia is the most
common. The best name of all is probably ‘“‘ American Leish-
maniasis.”” The name “ buba braziliensis ’’ has been given it by
some writers, but erroneously, since this name properly belongs
to another tropical disease, yaws. A few cases of Leishmania
ulcers have been observed in dogs in South America. Monkeys
can be experimentally inoculated. The organism causing these
intractable ulcers has been named Leishmania americana (bra-
ziliensis). It is a very minute animal, and is found usually in
rather scanty numbers in the sores; it can be distinguished
from the parasite of oriental sore, L. tropica, of which many
authors believe it is a mere variety, rather by its pathogenic effects
than by any peculiarity of form. Flagellated forms of the para-
site are occasionally found in the sores.

Skin Sores. — The sores on the skin, which do not always
_ulcerate, usually begin as one or two itching spots that seem to
be produced by the bites of insects. If the sores are of the non-
ulcerating type there is produced a great deal of red granular
tissue, raised slightly above the surrounding skin, and bleeding ~
easily. The surface, which is rosy in color, is rough, resembling,
according to one author,.a cauliflower. An intolerably’ foul-
smelling fluid is constantly emitted which sometimes dries over
the sore to form a crust of varying thickness. The fluid given

- _ off is infectious and starts new sores if it comes in contact with

any broken skin on the same or another individual.

In the ulcerating type of the disease in the skin the same fetid
fluid is emitted, but instead of the sore being elevated, it is ex-
tensively excavated and has raised borders. Often an enclosing
crust forms over it and it is improperly called a “‘ dry sore.’”’ In
this case the fluid is shut in between the crust and the sore and
causes even more intensive destruction of the tissues. Some-

90 LEISHMAN BODIES AND LEISHMANIASIS

times nearby lymph glands also become infected. Such general
symptoms as evening fever, pains in the joints, headache, etc.,
sometimes accompany the ulceration, probably due to the ab-
sorption of toxins.

As remarked before, the exudations from the sores are extremely
infectious for either the same individual or another one. Con-
sequently it is not infrequent to find on a single individual a
great many sores, up to 50 or more, in all stages of development,
though more often there are only a few. In one case recorded
from Brazil there were 35 active sores and 29 extinct ones, and
these were arranged in a more or less symmetrical manner, sug-
gesting the influence of the nervous system on their location.
The sores become secondarily infected with bacteria and spiro-
chetes and are sometimes attacked by screw-worms and other
fly maggots. The rarity of Leishman bodies in the late stages of |
the sores suggests that the secondary infections may then play
an important réle, though the prompt cure which follows treat-
ment destructive to the protozoans shows that the latter still play
a leading part.

Mucous Membrane Ulceration. — A far more vicious mani-
festation of the disease and one which follows the cutaneous sores
is the ulceration of the mucous membranes of the nose and mouth
(Fig. 16). It.may be several months or over a year after the
skin sores develop and often after they have healed that the
mucous ulcerations appear. In rare cases ulcers have been
known to occur in the vagina also. Ordinarily the infection
commences as a tiny itching hardness or swelling of the mucous
membrane, usually in the nose, the infected membrane becoming
inflamed, and marked either with small granular sores or with
blister-like swellings. The lymph glands in the infected regions
become swollen and turgid. A granular ulceration begins in a
short time, invading all the mucous membranes of the nose and
spreading, by means of infective fluid which flows down over the
upper lip, into the mouth cavity, attacking the membranes of
the hard and soft palate. Its advance is obstinate and slow, and
gives rise to serious complications. The nostrils become too
clogged to admit the passage of sufficient air and the patient
has to keep his mouth constantly open to breathe. His repul-
sive appearance and fetid breath help to make his life miserable.
Affections of the organs of smell and hearing, and even sight,

TREATMENT OF ESPUNDIA 91

often supervene, and the voice is weakened or even temporarily
lost. The digestive tract becomes upset from the constant escape
down the throat of the exudations from the ulceration, mixed with
saliva or food. A spreading of the nose due to the eating away
of the septum is a characteristic feature. Although in late stages
of the disease the entire surface of the palate and nasal cavities
is attacked, and the septum between the nostrils destroyed, the
bones are left intact, a feature which readily distinguishes a
Leishmanian ulcer from a syphilitic one. Usually the victim of
espundia, after long suffering, sometimes for 20 or 30 years,
succumbs to the disease from pure exhaustion and from poison-
ing by exuded liquids which are swallowed.

Fig. 16. A case of espundia before and after treatment with tartar emetic.
(After d’Utra e Silva.)

Treatment and Prevention. — It was in connection with ulcers
caused by Leishmania americana that the curative action of
tartar emetic was first worked out by Vianna in the Instituto
Oswaldo Cruz at Rio de Janeiro. The treatment of espundia
with this drug, injected into the veins, has been thoroughly tried
out in the past two years with great success. Although the
mucous membrane ulcers do not yield to the treatment as readily
as do skin sores, yet they can be cured with persistent treatment,
even in cases in which the nose and throat had been infected for
several years. The tartar emetic is injected as a one to two per
cent solution, as for other Leishmanian diseases, five to ten cc.

92 LEISHMAN BODIES AND LEISHMANIASIS

being injected daily for from five to 40 days. As remarked else-
where, it must be administered very carefully and slowly since
it is ikely to produce much irritation.

Practically nothing can be said about the prevention of the
disease, since its method of transmission is unknown. The
natives of South America believe that it results from the bite of
some jungle insect, probably a horsefly (tabanid), but nothing
definite is known about it. Blackflies, mosquitoes and ticks
have been suggested as transmitters also. Since the disease is
contracted in forests in the daytime, and the sores usually de-
velop on exposed parts of the body, tabanids seem to be in-
_ eriminated by circumstantial evidence. However, it is possible
that houseflies or other non-biting insects may carry the infection, -
the punctures of biting insects serving merely to open a door of
entrance for the parasites. Natives of Paraguay believe that
rattlesnakes harbor the parasites and that the latter are trans-
mitted to man either by blackflies or ticks, both of which attack
the snakes. Although only a popular belief, this is interesting in
view of the incrimination of geckos as reservoirs of oriental sore
parasites in. Algeria.

It would seem obvious that in case a skin sore of the espundia
type develops, great care should be taken not to allow the mu-
cous membranes to become infected by contact. Yet a case is
cited by da Matta where an ignorant wood-cutter who had been
tormented by espundia of the skin for five years and who persist-
ently cleaned his nose with infected fingers, never developed the
slightest affection of the mucous membranes. In other cases,
simultaneous affection of the mucous membranes and skin is
common.

CHAPTER VI
TRYPANOSOMES AND SLEEPING SICKNESS

Importance of Trypanosome Diseases. — One of the blackest
clouds overhanging the civilization of tropical Africa is the
terrible scourge of sleeping sickness, a disease caused by protozoan
parasites known as trypanosomes. ‘The destiny of the equatorial
parts of Africa depends largely on the issue of the struggle of
medical science against this haunting malady. The ravages of
the disease were well known to the old slave traders, and the
presence of “lazy niggers’ lying prostrate on wharves and
decks with saliva drooling from their mouths, insensible to emo-
tions or pain, was a familiar sight. It did not take these astute
merchants long to find that death was the inevitable outcome of
the disease, and they very soon recognized swollen glands in the
neck as an early symptom and refused to accept as slaves negroes
with swollen glands (see Fig. 24). Nevertheless sleeping sick-
ness must often have been introduced with its parasites into
various parts of North and South America, as it frequently is even
at the present time, and only the absence of a suitable means of
transmission has saved the Western Hemisphere from being
swept by it.

Up to about thirty years ago sleeping sickness was confined to
a limited part of tropical West Africa, but with the opening up of
Central Africa by whites and the consequent movements of
disease-carrying inhabitants to new portions of the continent,
the afflicted country was greatly extended. The great explorer
Stanley, in his expedition to reach Emin Pasha, was almost un-
questionably responsible for the introduction of the scourge into
Uganda and the lake regions of Central Africa in 1888, where it
had hitherto been unknown. In one district of Central Africa
the population was reduced from 300,000 to 100,000 in the course
of seven years, from 1901 to 1908, and there are records of whole
villages and islands being depopulated.

In 1909 there occurred a case of sleeping sickness contracted in

93

94 TRYPANOSOMES AND SLEEPING SICKNESS

Rhodesia in southeastern Africa occasioned by a distinct and ap-
parently newly originated type of trypanosome, as indicated
by its sudden appearance and startlingly rapid spread. This
type of sleeping sickness is more deadly than the older type and
there is reason to fear that unless efficient methods of control-
ling it and stamping it out are discovered it will spread over a
large part of tropical Africa. The disease has already spread
over a great part of Rhodesia, Nyasaland and Portugese Hast
Africa, and has been reported from German East Africa. There
is apparently a rather high natural immunity to the disease, which
alone is responsible for the small number of the victims.

In the same year, 1909, a fever
caused by a trypanosome was dis-
covered by Chagas in tropical
Brazil, and has since been found
to be widely distributed there, and
to be the cause of much of the
non-malarial ‘“‘ fever”’ for which
the jungles of tropical South
America are famous.

The Parasites. — The trypano-
somes, next only to the malarial
parasites, may be considered man’s
most deadly enemies among the
Protozoa. Like the Leishman
bodies described in the preceding
chapter, they are members of a
primitive group of the class Flagel-

lata, but of somewhat higher or-

adie, Fz, Tumowne genbion ganization, and probably higher in
b. gr., basal granule; und. m., undu- the scale of evolution. Trypano-
7 a n., nucleus; fl., fla somes are very active, wriggling
| little creatures somewhat suggest-

ing diminutive “‘ artistic dolphins” (Fig. 17). They are about 25 yu
(about yo'55 of an inch) or even less in length, spindle-shaped, and
somewhat flattened from side to side like an eel. Along the “back”
runs a flagellum connected with the body by an undulating mem-
brane, like a long fin or crest. This terminates at what is really
the anterior end in a free tail-like flagellum. It is by means of
the wave motions of the membrane and the lashing of the flagel-

DEVELOPMENTAL STAGES 95

lum that the animal moves through the blood or other fluids of
the body, either forward or backwards, so rapidly that it is difficult
to observe under the high power of a microscope as it wends its
way between the blood corpuscles on a slide. .The body of the
animal contains, in addition to the large round nucleus near the
middle, another deeply-staining structure, the parabasal body
(see p. 31) at the posterior end near where the flagellum origi-
nates. The body also contains other granules of various sizes.
+ There are a great many kinds of trypanosomes inhabiting many
different animals. Those living in cold-blooded animals have
no apparent effect on their hosts but the species infesting mammals
almost always cause disease. In man their effect is particularly
deadly and the African species usually cause death if allowed to
run to the sleeping sickness stage. Unlike many kinds of para-
sites most trypanosomes can live in a great many different hosts.
The common sleeping sickness trypanosome, for instance, can
live not only in man but also in monkeys, dogs, rodents, domestic
_ animals and a large number of the wild game animals of Africa.

Se Most kinds of trypanosomes, like the malarial parasites, live
only part of their life histories in the blood or other fluids of
their vertebrate hosts, undergo-

ing another phase of it in the
digestive tracts of insects or other /
invertebrates. In their interme-
diate hosts they undergo remark-

A

able transformations; the whole
series of forms through which
trypanosomes may pass in their
development, and which may
represent a phylogenetic as well
as an ontogenetic series, is shown
in Fig. 18. The first or Levsh- ‘ 3
mania form, which stands at the ,,/,/8,Diseram of developmental
foot of the series, is a rounded form; B, Crithidial form; C, Herpeto-
bod eh 1 el monas form; D, Leishmania form. (After
ody with a large central nu- Wenyon.)

cleus and small rod-shaped para-

basal body usually set at a tangent to the nucleus (Fig. 18D).
Next in development comes the Herpetomonas form which differs
in having a long slender body and in having a flagellum produced
from the parabasal body (Fig. 18C). Next comes the Crithidia

96 TRYPANOSOMES AND SLEEPING SICKNESS

form, differing from the preceding in that the parabasal body
has moved back to near the middle of the body, and the flagellum
is connected with the body for half its length by an undulating
membrane (Fig. 18B). This type is a very common develop-
mental phase in nearly all trypanosomes, but it is also the adult
condition of many insect parasites. Finally there occurs the
fully-developed trypanosome form (Fig. 18A), apparently es-
pecially adapted in form and structure for life in vertebrate
bodies. The method of develop-
ment of this form from a crithidial
type can easily be seen from Fig. 18.
Only the first or Leishmania form
and the last or trypanosome form
normally occur in vertebrate bodies,
though all of the four types are
found in the digestive tracts of in-
vertebrates. The fact that some
flagellates never develop further
than the Herpetomonas form, and
others never further than the Crith-
idia form, makes a study of this
group of Flagellates very confusing,
since when a Herpetomonas or crith-
idial type is found in an insect gut
‘ it is very difficult if not impossible
Fic. 19. Trypanosoma rhodesi. to Say whether it is an adult animal
ense, from blood of monkey inocu- which never undergoes any further
‘ated from case of human sleeping development or is only a develop-
sickness. Note posterior position of
nucleus in short blunt forms, espe- mental phase of a trypanosome of
cially in lower figure. x 2000. .
(After Kinghorn and Yorke.) a vertebrate animal.

It is often very difficult to dis-
tinguish different species of trypanosomes; of over 70 known
species only a few can be distinguished on morphological grounds.
Average size, position of nucleus and parabasal body, length of
snout, and presence or absence of a free flagellum are sometimes
useful in identifying them. More reliable, however, are their so-
called ‘ biological characteristics,” such as pathologic effects on
different animals, susceptibility of different hosts, the effect of
serum immune to certain species, and the ‘ cross-immunity re-
actions.” The last is the most certain method. Thus, if an

PATHOGENIC SPECIES | 97

animal has recovered from an attack by one strain of trypano-
some it is rendered immune and will not succumb to second
attacks of the same strain, though it is still susceptible to others.

As remarked before there are at least three species of trypano-
somes which are known to cause disease in man, two in Africa
and one in South America. The African species, causing sleep-
ing sickness, are the most deadly but the South American species
is frequently fatal, especially to children, and often renders a life
worse than useless. The Gambian trypanosome, Trypanosoma

Fic. 20. Trypanosoma gambiense in rat blood, showing long, intermediate and
short forms all in one microscopic field. x about 1200. “Drawn from microphoto-
graph by Minchin.

gambiense, is the cause of the commoner and more widespread
form of sleeping sickness, while the Rhodesian species, JT. rho-
destense, 1s the cause of the recently established East African
form of the disease. The most salient distinguishing character-
istic between these two species of trypanosomes is the posterior
situation of the nucleus of the Rhodesian parasite in a certain
per cent of individuals when they are developed in rats and some
other animals (Fig. 19). This is a feature never observed in the
Gambian trypanosome. Both species vary a great deal in form,

+ ed
‘igs
uy

and three distinct types may be observed at once in the blood of
an infected animal, a long slender form with a long free flagellum,
a short stumpy form with a short flagellum and a form interme-
diate between these (Fig. 20). Some investigators regard the
trypanosome causing the mild sleeping sickness of Nigeria as a
distinct species, named 7’. nageriense.

98 TRYPANOSOMES AND SLEEPING SICKNESS

Sleeping Sickness

Transmission. — Sleeping sickness of either type, and also
many trypanosome diseases of lower animals, is transmitted
primarily by certain species of tsetse flies which act as inter-
mediate hosts for the trypanosomes. The Gambian parasite, as
first shown by Sir David Bruce, is normally transmitted by the
tsetse fly, Glossina palpalis, and its distribution is now almost |
coincident with the range-.of this species. It occurs on the
west coast of Africa from the Senegal River to the State of
Mossamedes in Portuguese West Africa, including nearly all
the tributaries of the Niger and Congo Rivers. Eastward it
extends to the valley of the Upper Nile and Lake Victoria Nyanza |
in Uganda and along the east shore of Lake Tanganyika. |

The Rhodesian trypanosome depends on the more widespread
and less easily controlled Glossina morsitans. 'This species of
tsetse fly occurs all the way from northeastern Transvaal to
northern Nigeria in West Africa and to southern Sudan in the
basin of the Nile in’ East Africa. So far, the disease caused by
the Rhodesian parasite is limited to a small portion of East
Central Africa but it is spreading both north and south.

Experimentally other species of tsetses are able to transmit
the Gambian disease, but it is doubtful whether any except
G. palpalis are important transmitting insects in nature. As in-
timated above it is only the absence of tsetse flies in other parts :
of the world that we have to thank for the fact that sleeping :
sickness when introduced is not propagated. Experiments show
that it is also possible for the Gambian trypanosome to be trans-
mitted mechanically by the stable-flies, Stomoxys, though this
probably seldom happens in nature. Macfie has shown that in
Nigeria the human trypanosomes undergo developmental stages
in a stable-fly, S. nigra, but circumstances did not allow him to
determine whether the salivary glands become infective as in

oe

DEVELOPMENT IN TSETSE FLY 99

tsetse flies. There is evidence that sleeping sickness, like surra,
a trypanosome disease of horses, may also be transmitted sexu-
ally or through abrasions of the skin, but this is certainly not
the usual method of transmission.

The tsetses are blood-sucking flies resembling stable-flies,
which inhabit the brushy borders of lakes, streams or swamps,
— the so-called “‘ fly-belts.”” The distinguishing characteristics
of the tsetse flies and of the various disease-carrying species are
discussed in the chapter on biting flies, p. 490.

For a long time it was thought that the tsetse flies could trans-
mit trypanosomes only in a simple mechanical way, the para-
sites adhering to the proboscis, and being subsequently injected
into the blood of another person. It is now known that the
trypanosomes of sleeping sickness can be transferred in this
manner only for a few minutes after an infective feed, but that the
fly again becomes infective after a period of three or four weeks.
Meanwhile the parasites have undergone a series of changes in
the gut of the insect and finally become stored in the salivary
glands from which they are poured with the salivary juices into
the blood of a new victim.

Life Cycle in Fly.—According to observations on Trypanosoma
gambiense in Glossina palpalis by Miss Robertson the critical
time for the. trypanosomes after they are sucked up by the fly
is when the fly feeds the next time, since in many cases they are
swept out of the body with the new influx of blood, or digested.
Having stood their ground until they have become established in
the new influx of blood they multiply so rapidly that permanent
infection of the fly is almost certain. The difficulty experienced
by the parasites in establishing themselves in the gut of their
insect hosts largely accounts for the relatively low percentage
(usually less than five per cent) of infections which result from feed-
ing of tsetse flies on infected blood. - When conditions are favor-
able for development in the fly the parasites multiply first in
the middle intestine, producing long-snouted forms such as shown
in Fig. 21B. After the tenth to fifteenth day long slender forms
(Fig. 21C) are developed, and these move forward in the digestive
tract. These slender trypanosomes have long snouts and differ
most strikingly from the earlier forms in the appearance of the
nucleus (Fig. 21C). After several days more the trypanosomes
make their way to the fly’s salivary glands, to the walls of which

100 TRYPANOSOMES AND SLEEPING SICKNESS

they attach themselves by their flagella (Fig. 21D) and, rapidly
multiplying, undergo a crithidial stage. As multiplication con-
tinues free-swimming trypanosome forms are again produced

To cerebrospinal fluid causing sleeping
sickness and death.

Transmission by =
bite of tsetse

yf Forms in salivary glands
ready for re-infection.
(20-30% day)

Crithidiol forms in
salivary glands
(2 or 3 days later)

Forms in mid gut 48h
after infective meal).

newly arrived form in
. Salivary signe
(12% to 20" days.) _

Long slender forms tn proventriculus.
= ( bout lotta | 5t*days)

Fie. 21. Life History of Trypanosoma gambiense. x 1500. (Constructed
from figures by Miss Robertson.)

which very closely resemble the parasites in vertebrate blood
(Fig. 21E) and which are now capable of infecting a vertebrate
host. The whole cycle in the fly usually occupies from 20 to 30
days. According to Kinghorn and Yorke the time required for

DEVELOPMENT IN MAN 101

Glossina morsitans to become infective varies from 11 to 25 days,
but under unfavorable conditions the parasites may remain in
the fly in an incomplete stage of development for at least two
months. A temperature between 75° F. and 85° F. is necessary
for the full development of the parasite n the fly, ending in
invasion of the salivary glands. For two days after the trypa-
nosomes have been swallowed by the fly they remain infective if
injected into a vertebrate, but after this time they must pass
through the crithidial stage before they are again infective.

The reader will note that
no sexual reproduction,
such as is so conspicuous in
the mosquito cycle of the
malarial parasites, has been
described in this fly cycle
of the trypanosome, though
the general features of the
cycle are so parallel. It
can hardly be doubted that
sexual reproduction of some
kind, or at least something
which takes the place of it,
does occur in the tsetse fly,
but it has not yet been

recognized by scientific ob- Fic. 22. Method of division in trypano-
somes. A, elongated form ready for division;

servers. B, form with divided parabasal body and par-
Life Cycle in Man.—The tially split undulating membrane; C, form with

7 hy ieered double parabasal body, double undulating
parasites, when injecte membrane, and double nucleus; D, almost

into man or other suscepti- completely divided forms, adhering by poste-
ble animals by a tsetse fly, ™* "4

live and multiply in the blood, swimming free in the serum with-
out entering the corpuscles (Fig. 21A). They obtain nourishment
bysimply absorbing food material through the delicate cuticle which
coversthem. The method of division is the usual protozoan type of
simple fission. When about to divide the trypanosome elongates
(Fig. 22A) and the parabasal body at the posterior end divides
first (Fig. 22B). Then the flagellum and undulating membrane
begin to split from the posterior end forward, the central nucleus
divides (Fig. 22C), and the animal splits into two parts which hang
together longest by the “‘snouts” or posterior ends (Fig. 22D).

102 TRYPANOSOMES AND SLEEPING SICKNESS

The fast-multiplying parasites do not remain in the blood of
their victim but penetrate many of the tissues and organs of
the body, especially the liver, spleen, lungs and lymph vessels
and glands. The last mentioned are probably one of the main
strongholds of the parasite in the body and the swelling of
lymph glands, especially in the neck, has already been men-
tioned as one of the characteristic symptoms of sleeping sickness.
The parasites are not present in constant numbers in the blood,
but periodically appear in large numbers and then apparently
disappear at fairly regular intervals. Often the trypanosomes
are so few in the blood that their presence can be proved only by
causing disease through the injection of some of the blood into a
susceptible animal or by causing the parasites to multiply, as
they will quite readily do, in a
suitable artificial culture me- .
dium. In Nigeria the parasites
are hardly ever seen in the blood
of infected persons, but they can
be found by puncturing a lymph
gland. According to recent
investigations by Fantham the
trypanosomes, probably as a re-
action against antibodies which

¢ : tend to destroy them, shrink into

Fic. 23. Agglutination of trypano- roynded sporelike bodies with-
somes, 7’. lewist, in blood of immunized ;
rat. (After Laveran and Mesnil.) out locomotory organs but with

a protective shell. In this
condition they remain until conditions again become favorable
for them when they once more elongate, develop a flagellum and
undulating membrane, multiply and reappear in the circulating
blood. After several months or years the parasites penetrate
the cavity of the brain and spinal cord and live in the cerebro-
spinal fluid which fills it; this invasion of the central nervous
system is the direct cause of the dread sleeping sickness stage of
the disease.

While under normal and favorable conditions the trypanosomes
merely live and multiply in the way described above, they are
capable of reacting in a very peculiar manner when exposed to
unfavorable conditions, such as the presence of drugs, low tem-
perature or administration of serum from an immune animal.

X\

COURSE OF SLEEPING SICKNESS 103

Under such circumstances they have a tendency to mass together
in large numbers, up to a hundred or more, like sheep in a storm,
all with their flagellated ends projecting from a common center
(Fig. 23). Such ‘‘ primary agglomerations ”’ may adhere to form
“secondary agglomerations ’’ comprising altogether many hun-
dreds of parasites. When the unfavorable conditions disappear,
the trypanosomes disentangle themselves without any apparent
ill effects, although a few of them remaining agglutinated may
die and disintegrate. Another peculiar habit described by some
investigators is the extrusion from their bodies of very minute
granules, really tiny buds from the nucleus, which ultimately
develop into new trypanosomes. ‘This is said to occur just be-
fore the temporary disappearance of the trypanosomes from the
blood.

The Disease. — The course of the disease caused by trypano-
some infection is insidious and irregular in the extreme. The
Gambian and Rhodesian diseases are essentially alike in their
symptoms and in the course they run, except that the latter is
usually more rapid in development and more virulent in effect,
as a rule causing death within three or four months after in-
fection. The variety of the
Gambian disease found in
Nigeria is comparatively mild
and of long duration.

The bite of an infected tsetse
fly is usually followed by itching
and irritation near the wound.
After a few days fever is felt
and a peculiar tenderness of the
muscles develops, so that strik-
ing against an object causes
undue pain. Usually the fever
comes and goes at irregular in-
tervals of days or weeks oreven ‘Fic. 24. Negro infected with trypano-
months, an infected person {ants having clarged cervical glands
sometimes carrying the para-
sites in his blood, as shown by its infectivity when injected into
susceptible animals, for months at a time without any appreciable
fever, and in insufficient numbers to be seen readily by microscopic
examination. When the attacks of typical trypanosome fever do

104 TRYPANOSOMES AND SLEEPING SICKNESS

come they generally are worse in the evening, unlike malarial fevers.
After a variable time the victim becomes weak and anemic, probably
due to toxins secreted by the parasites, his pulse becomes rapid,
and various lymph glands, especially those of the neck, tend to
swell up and become tender. Often an irritating rash breaks out
on the skin during the early stages of the disease. Loss of am-
bition and vitality usually figure prominently, and childbirth
is seriously interfered with. It is possible that after weeks or
months or years of irregular fever and debility the disease may
spontaneously disappear, and never become more than trypano-
some fever. Usually, however, the parasites ultimately succeed in
penetrating to the cerebrospinal fluid in the cavity of the brain
and spinal cord, and “ sleeping sickness ”’ results. In some cases
the onset of this horrible disease has been known to be delayed

for seven years after the beginning of the disease, but usually it

comes in the course of a few months.

Sleeping sickness is ushered in by an increase in the general
physical and mental depression, the symptoms being not unlike
those of hookworm disease but more pronounced. The victim
wants to sleep constantly and lies in a stupor; his mind works
very slowly, and even the slightest physical exertion is obnoxious.
Eventually the sleepiness gets such a hold on him that he is
likely to lose consciousness at any time and even neglects to swal-
low his food. After weeks of this increasing drowsiness, his
body becomes emaciated, a trembling of the hands and other
parts of the body develops, with occasional muscular convulsions
and sometimes maniacal attacks. He finally passes into a state
of total loss of consciousness ending in death, or death may end
the unhappy condition earlier during an unusually intense con-
vulsion or fever, or through the agency of some complicating
disease. Death, so far as is known at present, is the inevitable
outcome. A large per cent of infections occur among people
of middle age. Old people are significantly few in number in
sleeping sickness districts. The presence of these few may be
due to a natural or acquired immunity. In Nigeria the disease
predominates in young people, possibly because they are water-
carriers and are therefore more exposed to the bites of testse flies.

Treatment. — In the early stages of the Gambian disease, a
cure can sometimes be effected by the administration of certain
drugs. Various arsenic and antimony compounds act as spe-

, |

TREATMENT OF SLEEPING SICKNESS 105

cific poisons against the Gambian trypanosome, having a decided
effect in a few hours. The most effective method for the use of
arsenic is to inject it into the muscles in the form of salvarsan or
atoxyl, the latter being a compound which is more frequently and
effectively used to kill trypanosomes in the blood. It is injected
as a weak solution, the injection being repeated every few days
for a period of many months, even though all symptoms of the
disease may long since have disappeared. A serious objection
to the use of atoxyl is the slight degree of toleration which many
people have for it, and the serious effects which it frequently has
on the optic nerve, often causing blindness, and on the digestive
apparatus.

A. still more effective drug for destroying trypanosomes in
blood and lymph is tartar emetic, an antimony compound. It
is injected in very weak solutions directly into the veins, care being
taken not to allow any of it to escape into the muscles or con-
nective tissues since it is excessively irritating to these tissues.
Usually a high fever follows the administration of either this
drug or. atoxyl, probably due to the toxic substances liberated
in the blood from the dead bodies of the trypanosomes.

The chief difficulty in the use of either of these drugs is that the
trypanosomes tend to build up a tolerance for them, in much
the same way that a man may build up a tolerance for opium
or other drugs. This tolerance is hereditary and gives rise to
“‘ arsenic-fast ”’ or ‘“‘ antimony-fast”’ strains of trypanosomes.
In such cases the parasites cannot be destroyed. It is an inter-
esting fact that in at least one species of trypanosome, 7’. lewisi
of rats and mice, and probably others as well, when strains im-
mune to atoxyl are passed through their intermediate host, a
louse, where they presumably undergo sexual reproduction or
some process which takes its place, the tolerance is entirely lost.
Thus the sexual process at a stroke eliminates acquired charac-
ters which have been maintained through thousands of asexual
generations in passages from mouse to mouse or from rat to rat.
This fact, if invariably true, is of considerable importance in
the outlook for the treatment of sleeping sickness, since it would
prevent what would otherwise inevitably happen, the evolution
of a permanent strain of trypanosomes immune to both arsenic
and antimony. ‘The fact that parasites resistant to arsenic may
not be resistant to antimony, and vice versa, makes it advisable

106 TRYPANOSOMES AND SLEEPING SICKNESS

in treating trypanosome fever to give both drugs either to-
gether or alternately.

When the disease has reached the sleeping sickness stage
and the parasites have penetrated the cerebrospinal fluid, a
cure has so far never been accomplished. The arsenic and anti-
mony compounds which are so destructive to trypanosomes
will not permeate the nervous tissue and diffuse into the cerebro- |
spinal fluid, and they are too poisonous to be injected into the
spinal canal. The success that has been attained in the use of
salvarsanized serum (see p. 57) against spirochetes in the cere-
brospinal canal gives hope that a similar mode of treatment may
be used in the case of sleeping sickness. All that can be done
for sleeping sickness now is to alleviate the suffering and postpone
the inevitable end.

Although the use of immune serum from animals which have
recovered has been very successful in curing and immunizing
various lower animals against certain trypanosome diseases, this
has not yet been accomplished for man.

The Rhodesian trypanosome consistently resists both arsenic
and antimony treatment, and no successful drug has been found
for combating this parasite.

Prevention. — Since the tsetse flies, Classi palpalis and G.
morsitans, are by all odds the most important means of trans-
mitting the Gambian and Rhodesian trypanosomes respec-
tively, the prevention of the diseases resolves itself into the prob-
lem of avoiding or exterminating these insectsg Methods for
controlling and destroying tsetse flies are discussed in the chap-
ter on Biting Flies, p. 501.

In places where tsetse fly extermination has not or cannot be
accomplished the best safeguard is the avoidance of the “‘ fly-
- belts.”” In the case of G. palpalis these belts consist of narrow
strips along the brushy edges of water, but with G. morsitans
they are not so closely limited, the flies being sometimes found
at considerable distances from water. Villages or camps should
always be removed from fly-belts, and travel through the belts,
when absolutely necessary, should be done on dark nights when
the flies seldom bite. Occupations carried on in fly-infested
areas should be discouraged or prohibited. In Uganda fishing
along the fly-infested streams and lake shores is one of the chief
occupations indulged in by the natives, who go naked and are

PREVENTION OF SLEEPING SICKNESS 107

constantly bitten. The deadly epidemic of sleeping sickness in
Uganda was fostered by the fishing industry. It has been sug-
gested that by importing dried sea fish to trade for agricultural
products the natives might be induced to change their occu-
pation. In Congo the rubber industry is the one which is the
most deprecated. Personal protection against tsetse flies is dis-
cussed on page 501. |

Another method of protection is suggested by the researches
of Van den Branden who has found that a single injection into
the veins of salvarsan or neosalvarsan or some of their compounds
will sterilize the blood against trypanosomes for a period of several
months — in the case of salvarsan copper for 19 to 24 months.

Infected individuals should not only be kept away scrupulously
from places where flies can possibly get access to them, but should
also be prevented from traveling to new places. Some strains
of trypanosomes seem to be much more virulent than others,
and the introduction of a virulent strain to a region where a
mild strain previously existed has occasionally caused a con-
siderable increase in the disease. The strict quarantine of in-
fected persons, while unquestionably worth while, is not a meas-
ure sufficient to stamp out the disease, since many of the wild
animals of Africa serve as reservoirs for the disease, harboring
the parasites in their blood but not succumbing to them. Tsetse
flies on the shores and islands of Lake Victoria, after the entire
population had been stringently kept away for three years so
that the flies could not have fed on human blood during this time,
were found to be still infective. The situtunga antelope and
other wild game undoubtedly served as a reservoir. It has been
suggested that a war of extermination be made on the rich and
interesting wild game of. the countries infected with the Rho-
desian trypanosome in the hope of checking the rapid spread of
the disease (see p. 503). It has recently been shown by Taute,
however, that a large proportion of the wild game of Nyasa-
land is infected with a trypanosome indistinguishable from
Trypanosoma rhodesiense in all its general characters but non-
pathogenic to man. Taute evidently had the courage of his
convictions since he tried several times to infect himself with
this trypanosome without success. It is possible, however, that
a high natural immunity to the parasite may exist in many people,
and thus explain Taute’s negative results.

108 TRYPANOSOMES AND SLEEPING SICKNESS

Probably the deadly Trypanosoma rhodesiense is merely a strain
of this wild game trypanosome which has undergone some
physiologic change or mutation, making it possible for it to live
in the human body. Bruce and some others consider it identical,
in every respect except its ability to live in human bodies, with
the well-known and widespread 7’. bruce: which causes nagana in
wild and domesticated animals.

A concrete example of sleeping sickness extermination is to be
found in the fight against it on the Island of Principe by the
Portuguese Sleeping Sickness Commission. Sleeping sickness
had been a scourge on the island for years when the Commission
began its work in 1911. Its efforts were directed against the
tsetse fly, but this was accompanied by an active campaign
against pigs, dogs and other trypanosome carriers, and the
thorough care and treatment of human victims. The methods
used are discussed in Chapter XX VI. The Commission cleared the
island of sleeping sickness in a four years’ campaign, but the tsetse
flies are not yet totally exterminated, and the present condition
on the island can only be maintained by constant work in the
future, though at comparatively slight cost.

Chagas’ Disease

A very different but hardly less destructive disease is caused
by a trypanosome, Trypanosoma (or Schizotrypanum) cruzi, in
certain parts of South America.
Chagas, of the Oswaldo Cruz
Institute, first investigated the
disease in the state of Munas
Geraés in Brazil. He found that
nearly all children in the endemic
regions were stricken with the
disease, usually before they were

Fie. 25. Trypanosoma cruzi in blood .
of experimentally infected monkey. ON€ year old. “The mortality was

A, so-called male form; B, so-called found to be very high, and those

female form. (After Chagas. : «bee ae
( a) who survived the initial acute

attack usually passed over into a chronic diseased condition, very
often being left to live a worse than useless life as paralytics,
idiots or imbeciles. The disease has since been found in other
parts of Brazil and in neighboring countries. Large bloodthirsty

CHAGAS’ DISEASE — PARASITE IN MAN 109

bugs of the genus Triatoma serve as intermediate hosts; bugs of
a number of species infected with trypanosomes morphologically
indistinguishable from T’. cruzi have been found all the way from
Central America to Argentina, but the disease in man has been
recognized only in
a small part of
this extensive area,
though it is sus-
pected of existing
in northern Argen-
tina and may oc-
cur in many more
places than is now
known.

Human Cycle.—
The trypanosome
causing this disease
very closely resem-
bles the sleeping
sickness trypano-
somes in form but
it is quite different
in its life history.
In the human body,
Chagas recognized
two distinct types
which he believed
to be male and fe-
male forms, but
subsequent work

Fig. 26. Trypanosoma cruzi. A, cyst containing Leish-
Peg mania forms in muscle fiber of guinea-pig, cross section;
indicates that these n., nucleus of muscle fiber. B, older cyst, containing

trypanosome forms, in neuroglia cell in gray matter of
two t ypes are cerebrum; n.,’ nucleus of parasitized cell; bl. cap., blood
merely young and capillary; unpar. c., unparasitized cells. > 1000. (After

adult forms of the Vianna.)

parasite. Unlike other trypanosomes this species as found in
the blood never exhibits stages in division, and this fact led
Chagas to search for some other form of multiplication. He
found in the lungs of infected animals what he thought to be
a process of division of the trypanosomes into eight parts, but
this later was found to be a stage in the life history of an entirely

110 © TRYPANOSOMES AND SLEEPING SICKNESS

different parasite. The real method of multiplication was first
discovered by Vianna in the bodies of man and animals who had
died of the disease. Vianna found in various tissues, especially in
the walls of the heart, the striped muscles, the central nervous
system and various glands, greatly swollen cells which served as
cysts, enclosing a mass of rapidly dividing trypanosomes, varying
in number from just a few to many hundreds. In younger cysts
the parasites are round in form and exactly resemble Leishman
bodies (Fig. 26A), while in older cysts the flagellum can be seen
on many individuals and the trypanosome form becomes evident
(Fig. 26B). When the enclosing cell has swollen to the bursting
point, the swarming mass of trypanosomes is liberated. Each
parasite, unless destroyed, then penetrates a new cell somewhere
in the body, usually near where it originated, and begins the

process of reproduction again. Only in the early acute stage of .

the disease can the parasites live in the blood, since the blood
serum rapidly reacts by the formation of antibodies, and be-
comes deadly to trypanosomes. Chagas believed that the para-
sites could live within the corpuscles as well as in the serum, but
later work does not confirm this.
On account of the development of
antibodies in the blood serum, the
parasites are very seldom found in
the blood of chronic cases of the
disease, though their cysts may be
abundant in various tissues and
= glands in the body.

Fic. 27. Trypanosoma cruzi in Life Cycle in Bugs, and Trans-
blood of ape, said to be inside cor- mission. — The intermediate host
‘puscles. (After Chagas.) Bs»

of Trypanosoma cruzi is a large
black and red bug, Triatoma megista, known to the natives as
“Darbeiro.” It is related to the cone-nose, Triatoma sangusuga,
of our southern states. The barbeiro is a fierce blood-sucking
insect which infests the dirty thatched or mud houses of the
natives, coming out at night and skillfully secreting itself in the
daytime (see p. 379, and Fig. 168).

It was found that the bugs in the houses where Chagas’ disease
had been observed were invariably infected with trypanosomes
in their gut, and from this fact and from the habits of the bug
Chagas rightly deduced and later proved that the bug was the

|

CHAGAS’ DISEASE — PARASITE IN BUG 111

transmitting agent of the trypanosome. A few hours after a
bug has fed on infected blood the trypanosomes begin to change
form in the midgut, becoming round and Leishmania-like in form,
losing the flagellum and undulating membrane (Fig. 28A, B and
C.) Then comes a period of very rapid increase in number, the
parasites gradually pushing backward toward-the hindgut by
sheer multiplication. After about two days Crithidia forms
begin to develop and become numerous in the hindgut, being

Fic. 28. Development of Trypanosoma cruzi in digestive tract of bug (Tria-
toma megista). A, freshly ingested form; B, rounding up and loss of flagellum, 6
to 10 hrs. after ingestion; C, Leishmania-like form in midgut, 10 to 20 hrs. after
ingestion; D, redevelopment of flagellum and undulating membrane, 21 hrs. after
ingestion; EH and F, crithidial forms in hindgut, 25 hrs. after ingestion; G, trypa-
nosome form from salivary gland, 8 days or more after ingestion. (After Chagas.)

voided with the excrement from time to time (Fig. 28D, E and F).
It has been suggested that these crithidial forms do not play any
part in the transmission of the disease to man but that they rep-
resent a return to a primitive condition suited to existence in the
bugs, and that they may be transmitted from bug to bug in this
form, since the bugs are known to prey to some extent upon each
other and a'so upon their excrement. Torres, however, considers
transmission of the flagellates from bug to bug as very doubtful.

Chagas believes that there is a second cycle of development in

f12 TRYPANOSOMES AND SLEEPING SICKNESS

the bugs which he interprets as sexual reproduction. After about
ten days there occasionally occurs in the midgut of the bugs
round organisms with thick capsules, and in a few cases Chagas
has observed, after about six days, what seemed to be a division
of this body into eight individuals each presumably giving rise
to a trypanosome of a new generation. Whether or not the
infective trypanosomes arise in this way they appear in the mid-
gut from the eighth day onward. The occurrence of the infective
parasite in the salivary glands (Fig. 28G) is very irregular. The
fact that parasites have occasionally been found in the body
cavity of bugs suggests that the trypanosomes may make their
way through it to reach the salivary glands. As already re-
marked the trypanosomes in the bugs have never been found
infective before the eighth day, but once the infective forms have
developed they persist in the bugs for over a year.

The barbeiro is not the only insect capable of acting as an
intermediate host for Trypanosoma cruzi. Several other South
and Central American species of Triatoma have been found to |
be naturally infected with this trypanosome or with one mor-
phologically indistinguishable from it, and experimentally the
trypanosomes develop in the cosmopolitan species, 7. rubro-
fasciata.and other cone-noses and in bedbugs. Nor is man the
only vertebrate host. Experimentally apes, dogs and guinea-
pigs are subject to infection, and in nature the common Bra-
‘zilian armadillo, Dasypus novemcinctus, and various rodents have
been found infected, their infection undoubtedly being carried
by the common bug, Triatoma geniculata, which infests their
burrows. The fact that infected bugs occur in some places
where Chagas’ disease is not known to occur suggests that, as is
the case with Trypanosoma rhodesiense and the trypanosomes
undistinguishable from it except by their harmlessness to man,
not all strains of the parasite cause human disease. It is inter-
esting to note that a very similar trypanosome has recently been
discovered by Kofoid and McCulloch in Triatoma protracta of
southwestern United States. This bug is common in nests of
wood-rats and frequently attacks man also. This discovery
suggests one of two things: either the trypanosome described
as T’. triatome, and which is admitted by the discoverers to differ
from 7’. cruzi only in slight characteristics of questionable im-
portance, is really identical with or a mere variety of T. cruzi,

COURSE OF CHAGAS’ DISEASE 113

or else others of the trypanosomes observed in species of Triatoma
from Argentina to Central America may not be identical with
the trypanosome which is the cause of Chagas’ disease.

The Disease.—In endemic regions Chagas’ disease is so
prevalent that children are usually attacked within a few months
after birth, and at this tender age are often unable to withstand
its effects. If death does not result the disease passes over into
one or other of its various chronic forms. As a result it is very
rare to find acute cases in anyone but young children or new
arrivals. The latter, however, usually come from other infected
regions and show marks of the chronic disease, and so are not
susceptible to a new acute infection.

The acute infection is marked by a constant high fever, lasting
from ten to thirty days, often without remission, and by a charac-
teristic swollen face, noticeable from a considerable distance.
The skin has a peculiar feeling of ‘“ crepitation’’ due to the
mucous infiltration of the tissue under the skin. The lymph
glands especially in the neck and arm pits swell up, the liver and
spleen become enlarged, and the thyroid gland becomes swollen
as in goitre. In fact, most of the symptoms are connected with
interference with the thyroid gland which, while becoming
massive in size, becomes reduced in function, thereby causing a
number of nervous and constitutional symptoms. This inter-
ference is due, apparently, not so much to invasion by the para-
sites as to a specific effect of the toxins produced by them and
carried by the blood. These are the constant features of the
disease; the other symptoms vary according to the localization
of the parasites. Frequently they multiply in the heart muscles,
and the functions of the heart may be seriously interfered with.
Very often, and with the most dire results, the parasites invade
the brain and spinal cord. When this happens the mortality is
high, and it is only a pity that it is not higher, since it would
be better if death always eliminated these unfortunate trypano-
some victims who are spared only for an unproductive, piteously
mutilated life, doomed to grow up with the intellect of an infant,
or as paralytics, idiots or imbeciles.

The chronic forms of the disease follow the acute form by the
development of a substance in the blood which is deadly to the
trypanosomes, so that the latter are restricted to the protecting

tissue cells in which they multiply. The commonest chronic

114 TRYPANOSOMES AND SLEEPING SICKNESS

form is that in which the predominating symptoms result from
an enlarged but insufficient thyroid gland—goitre, cretinism, con-
vulsions, swollen skin and various functional disturbances, includ-
ing imperfect heart and intellectual defects. Another chronic form
is that in which the heart is especially affected. The fact that
the parasites have a special predilection for the heart muscles
makes this form of the disease very common. The results of locali-
zation of the parasites in the nervous system have already been
mentioned. The intensity of the motor disturbances, varying
from paralysis or spasmodic convulsions of a single muscle to
complete paralysis or convulsions of the whole body, has no rela-
tion to the degree of intellectual affection, which may vary from
a simple cretinoid condition to complete idiocy or infantilism.
It is doubtful whether the disease is ever recovered from entirely

if left to run its course. Sometimes the symptoms become:

gradually less intense, in other cases they become worse and new
ones develop, or recurrences of acute symptoms may develop,
due either to reinfection or to a loss of the trypanocidal power of
the blood.

Treatment and Prevention. — The treatment of Chagas’ dis-
sease is still in the experimental stage but there is some evidence

‘that tartar emetic may prove to be of great value in dealing with -

it, at least in early stages. In fact it was the success obtained by
Vianna in combating the disease with tartar emetic that first
suggested to him its use against Leishmanian diseases.

Prevention of the disease consists largely in avoiding and ex-
terminating the barbeiros. It is practically impossible to keep
the bugs out of mud or thatched houses. For this reason the re-
building of houses with other material is being urged everywhere
in Brazil and with good results. The town of Bello Herizonte,
for example, which was formerly termed “ a nest of cretins ” is
now nearly free from Chagas’ disease, due to the remodeling of
the houses. People traveling through infected districts can
readily protect themselves by sleeping under mosquito nets and
by avoiding the native houses. There is said to be no danger
of being bitten by the bugs in daytime or in the presence of arti-
ficial light, since they come forth only in the dark.

The extermination in the vicinity of villages of armadillos and of
the various rodents which harbor the trypanosomes would be a
valuable aid in the reduction of the disease.

Wegiioats

CHAPTER VII

INTESTINAL FLAGELLATES AND CILIATES

The human intestine furnishes a habitat for a considerable
number of animals belonging to all four classes of Protozoa,
though it is not so subject to such infections as are the digestive
tracts of many lower animals, especially the ruminants. By
far the most important intestinal protozoan of man is an ameba,
Endameba histolytica, discussed in connection with other para-
sitic amebze in a subsequent chapter. Probably next to the
amebe from a pathogenic point of view should stand the ciliate,
Balantidium coli, which is, however, not common in most parts
of the world. The various flagellates of the intestine, from the
simple bi-flagellate forms, such as Bodo, Cercomonas and Prowa-
zekia, some of which are probably only accidentally parasitic, to
the highly organized multi-flagellate forms, such as Trichomonas
and Giardia, which are very common human parasites, differ
‘ greatly as regards their pathogenic importance, and opinions
do not agree concerning the importance of particular ones.

General Characteristics of Intestinal Protozoa.—In some
respects nearly all the Protozoa which make their home in the
digestive tracts of animals resemble one another. Nearly all of
them secrete for themselves resistant transparent cysts which
protect them from drying up or from the presence of an unfa-
vorable medium. In the encysted state intestinal protozoans are
able to exist under the unfavorable conditions found outside the
body of the host, and are capable of remaining in this state in a
sort of torpid condition for long periods of time until they gain
access to a new host. The cysts of intestinal protozoans are
analogous to the resistant eggs of intestinal worms, and like
worm eggs their presence in the feces of infected persons serves as
a convenient means of diagnosis. The unencysted protozoans
which may be carried out of the intestine die quickly and
probably could not produce a new infection even if swallowed
immediately, since in some species at least they are unable to

115

116 INTESTINAL FLAGELLATES AND CILIATES

‘withstand the action of the acid juices of the stomach. None of
the human intestinal Protozoa require a second host to transmit
them as do the blood-dwelling parasites. While outside the
~ body they remain dormant in their cysts for weeks or months
until they can gain access to a host again through food or water.
There is still much doubt as to the extent to which intestinal
protozoans are confined to particular hosts. Some workers
believe that each animal has its own species peculiar to it, and
that these species are not capable of infecting different hosts.
Evidence is accumulating, however, to show that in some cases
at least this is not so, and that many intestinal protozoans of
man are able to live in such animals as rats, mice and hogs.
Most intestinal protozoans are of very wide geographic distri-
bution, their abundance in any given place being largely deter-

mined by the warmth of the climate and the sanitary, or rather -

unsanitary, conditions.

As remarked before there has been much discussion concerning
the effect produced by various species of flagellates in the in-
testine. Naturally these parasites are seldom discovered except
when there is some intestinal ailment, since in normal health
feces are seldom submitted for examination. Where routine
examinations have been made regardless of physical condition,
it has been found that a large per cent of people in unsanitary
places are infected. Stiles, in a town in one of our southern
states, found that from 50 to 100 per cent of the children were
infected, and it would probably be easily within the bounds of
truth to say that 75 per cent of all people in warm countries liv-
ing in places where unsanitary conditions prevail are subject
to infection with one or several species of intestinal Protozoa.
As Stiles has pointed out, such infection usually means that the
infected person has swallowed human excrement, since it would be
impossible for any natural agency to separate the microscopic
protozoan cysts from the feces in which they are found. This
fact, impressed upon the mothers of infected children, especially
when accompanied by the remark that one could not tell whether
the infection had come from the excrement of a white or a negro,
was found by Stiles to be one of the most powerful means of
improving sanitary conditions in the South.

Facts which support the view that intestinal flagellates are of
more importance pathogenically than has commonly been sup-

PATHOGENIC IMPORTANCE 117

posed have been furnished recently by the findings in returned
British soldiers, in whom uncomplicated infections with flagel-
lates have been found in many dysenteric cases, and also by the
investigations of Lynch, Barlow, Escomel and others in various
parts of the world. Still further evidence is furnished by the
fact that parasites very closely allied to species found in man
have recently been shown to be unquestionably of pathogenic
importance, at least under certain conditions, in lower animals.

Obviously, however, in view of the large number of infected
persons, the intestinal protozoans must often have little or no
pathogenic effect. There is, nevertheless, much individual dif-
ference in susceptibility, and different strains of the same para-
site seem to vary in the effects they produce. Moreover it is
highly probable that a great many slight and perhaps almost
unnoticed symptoms, resulting in a certain amount of interference
with the digestive tract and in a general lowering of the health,
may find their ultimate cause in intestinal parasites, either pro-
tozoans or worms or both. The health of people living in warm
and tropical countries, even aside from the effects of malaria and
other warm-climate diseases, is proverbially less perfect than that
of people in the usually more sanitary northern countries. It is
quite probable that intestinal Protozoa may play a part in this
lowering of the tone of health.

In the paragraphs below a brief account of the more important
intestinal flagellates and ciliates is given, with what is known of
their pathogenic effects, in the following order: (1) the bi-flagel-
late forms, Bodo, Cercomonas and Prowazekia; (2) the muliti-
flagellate forms, Trichomonas, Macrostoma and Giardia; and (8)
the ciliate, Balantidium.

Bi-flagellate Protozoa

Most primitive of the intestinal flagellates are the bi-flag-
ellated forms, several genera of which have been found in the
- human intestine. These are, namely, Bodo, Cercomonas and
Prowazekia (Fig. 29). The relation of these animals to the
still more primitive mono-flagellated trypanosomes and their
allies is shown by the parasites of the genus Trypanoplasma
found in the intestines of fishes and in a number of invertebrate
animals. The animals of this genus resemble trypanosomes in

a

me

118 INTESTINAL FLAGELLATES AND CILIATES »

the general form of the body and in the possession of a parabasal
body and an undulating membrane, but have an additional free
flagellum. In Cercomonas (Fig. 29C), according to Wenyon,
the trailing flagellum is attached to the side of the body as far
as the posterior end, usually being continued as a free flagellum.

Fie. 29. Bi-flagellated parasites. A, Bodo; note absence of parabasal body.
B, Prowazekia; note parabasal body (par. b.). C, Cercomonas; note trailing
flagellum attached to side of body. This is not recognized as a flagellum by some
workers. xX 2000. (After Wenyon.)

According to others Cercomonas has only a single flagellum, the
free one at the anterior end. Bodo and Prowazekia (Fig. 29A and
B) both have two flagella, one waving anteriorly, the other trail-
ing behind; Prowazekia differs from Bodo, and also from Cercomo-
nas, in having a parabasal body.

Of these parasites only Prowazekia, of which several poorly
defined species have been recorded from man, can be considered
a true human parasite; Bodo and Cercomonas, as found in freshly
passed feces, are probably free-living forms which have been
ingested accidentally as cysts with water or food. Wenyon
states that all three genera grow readily in cultures and form

small round cysts, two to eight u (,;,1,;5 to ssbo of, an inch) in
diameter. They probably all pass through an ameboid stage in
which they are indistinguishable from the small amebze of the

‘“limax ”’ group.

Multi-flagellate Intestinal Protozoa

Trichomonas intestinalis. — Of the several flagellates which
have been found in the human digestive tract and feeces, Tricho-
monas is the commonest. It makes its home in the upper

a ss Cae

TRICHOMONAS 119

part of the large intestine and ccecum, often multiplying in
prodigious numbers. Trichomonas also lives in the vagina and
in the urinary tract, being quite often found in vaginal discharges,
especially in cases of leucorrhea. It has been commonly believed
that the vaginal parasite, which is larger than that of the intestine,
is a distinct species, and it has been given the name T’. vaginalis,
but there is reason for believing that it is identical with the
intestinal parasite. Other intestinal parasites are sometimes
found in the urinary tract. This or a closely allied species is also
occasionally found in the mouth,
about the tartar of the teeth. Ac-
cording to Goodey the mouth form
differs from the intestinal form to
a sufficient extent to warrant its n.
being given a distinct name, at least _
provisionally, and he proposes the
name Trichomonas (Tetratrichomo-
nas) buccalis.

Trichomonas intestinalis (Fig. 30)
is a pear-shaped flagellate averaging y
about eight to 15 u (soa tO rs59 Of axo-7"\,j Pa) --und. m.
an inch) in length, the size being in- Wf
versely proportional to the rapidity
of multiplication. It has three vig-
orously moving flagella arising from
the blunt anterior end and a fourth |
wavy one which turns backward and | 16.30. Tr Ce ee
is attached to the side of the body by axostyle; par. b., parabasal body (?):
an undulating membrane. Along the ie ; Ape ea
line of attachment of the undulating
‘membrane to the body is a structure which takes a deep stain,
called the chromatic basal rod and believed by some workers to
be a modified parabasal body. Arising near the anterior end and
running through the body is a sort of supporting rod called the
-“ axostyle,” which, according to Kofoid and Swezy, is also used
as an organ of locomotion. At the anterior end at one side of
the point where the flagella originate is a slight depression or
“eytostome ’’ which serves as a mouth. The small round
nucleus lies in the body just behind the origin of the flagella.
Other forms of the parasite with four or five anterior flagella

"120 INTESTINAL FLAGELLATES AND CILIATES

instead of three have been described but they are not so common
and there seems to be room for doubt as to whether these may not
be abnormal forms or division stages of the one species. Goodey
describes the mouth form of the parasite as having four flagella.
Trichomonas swims by active lashing movements of the free
flagella and by wave motions of the undulating membrane.
The body revolves as the animal wends its way through the
semi-liquid substances in which it lives. Multiplication is by
longitudinal division of the body, the flagella and undulating
membranes and internal structures all being duplicated before
the animal splits into two. A process of multiple fission resulting
in the formation of eight individuals has also been described.
Encystment, such as occurs in other intestinal protozoans,
has definitely been observed only recently in Trichomonas.
Some of the flagellates, after escaping from the body with the
feeces, soon degenerate, gradually losing all their appendages
except the undulating membrane. With-
out their flagella, and with their ameboid
movements, these animals closely resemble
amebe but can usually be identified by the
undulating movement which persists at one
side of the body. Others, without losing
ON ane Papen their appendages, become round and mo-
ment stage; B, encysted tionless as if in a cyst, but with no cyst
oe x 2400. (After Wall around them. When warmed up
they stretch themselves out and resume
an active life. It is probable that these forms are preparing for
encystment, since they correspond with pre-encystment forms
(Fig. 31A) recently described by Lynch. Lynch, who found con-
siderable numbers of cysts in a heavily infected case in South
Carolina, describes the cysts (Fig. 31B) as thin-shelled, pear-
shaped bodies, about three-fourths the size of the active flagellates.
The oval body of the animal with its appendages can be seen
clearly through the cyst wall in properly prepared microscopic
slides. Apparently no multiplication takes place in the cysts,
and they are merely “ resistance cysts ” to enable the animal to
withstand unfavorable conditions. Lynch has succeeded in culti-
vating Trichomonas and in infecting rabbits with it, but he could
not keep specimens alive in water or feces for more than a few
days under the most favorable conditions.

PATHOGENICITY OF TRICHOMONAS 121

Trichomonas is generally regarded as a harmless parasite, but
there seems to be strong evidence that it often causes diarrhea,
sometimes very severe and of long duration. Dr. Philip Hadley
and others have recently shown that a species of Trichomonas
found in turkeys, and frequently the cause of very severe disease
in these birds, is, under ordinary circumstances, quite harmless.
When, however, the digestive tract of the bird becomes deranged
for any reason, and its vitality and natural defenses presumably
lowered, the parasites penetrate certain cells in the intestinal
glands, invade the deeper layers of the intestinal wall and begin
to attack the tissues themselves. As expressed by Dr. Hadley,
“Having experienced its first taste of blood its whole nature is
changed; it becomes another animal, raging through the tissues
impeded by no protective action that the host organism is able
to muster to the defense. Here then we must recognize T'richo-
monas as a cell parasite, an organism that has the power to
actively invade living cells and to bring about their destruction.”
Furthermore the parasites substitute, at least to a large extent,
absorption of liquid food by osmosis for the ingestion of solid
' particles, such as bacteria, through the cytostome. Whether
or not the Trichomonas of other animals are likewise capable of
altering their habits is unknown. They do not cause such severe
diseases in other animals as they do in turkeys, but that they
become more distinctly pathogenic at some times than at others
is a well-substantiated fact. Epidemics of diarrhea and mild
dysenteric symptoms in man apparently caused by Trichomonas
have been reported from Peru, Brazil, China, South Carolina
and Indiana, and it is probable that the parasite is at least mildly
pathogenic wherever it occurs, tending to aggravate other in-
testinal ailments if not causing them directly. A case has re-
cently been reported of an Oriental who was suffering from a
foul-smelling decay of the jaw, accompanied by pains in the
joints, in which numerous Trichomonas were found in the jaw
lesion. After treatment with emetin there was rapid improve-
ment, which suggests that Endameba may also have been present.

No specific drug for use against Trichomonas has yet been
found. Methylene blue in weak solutions is absorbed by the
parasites and causes them to become round and quiet. Castellani
recommends taking methylene blue both by mouth and by means
of an enema, 1.e., irrigation of the large intestine. With this

122 INTESTINAL FLAGELLATES AND CILIATES

treatment the flagellates are said to decrease rapidly and to disap-
pear usually within a few days. Escomel, who has found Tri-
chomonas an important factor in diarrhea in Peru, advises an
enema consisting of one grain of iodine in a liter of water, taken
in the evening on three successful days. Unless the parasites
have established themselves in the membranes high up in the
intestine they are said to disappear after this treatment. As
with other intestinal Protozoa infection occurs through polluted
food or water.

Macrostoma (or Tetramitus) mesnili.— A parasite which
closely resembles Trichomonas in many respects is Macrostoma
mesnili (Fig. 32). It is smaller than the former, averaging about

Fic. 32. Macrostoma (or Tetramitus) mesnili; A, adult parasite (n., nucleus,
cyt., cytostome, 4th fl., fourth flagellum); B, end view of adult parasite, showing
cytostome with flagellum in it; C, degenerating form, resembling an ameba; D,
cyst, showing nucleus and cytostome. x 2000. (After Wenyon.)

eight or ten uw (zo Of aninch) in length. It has three slender
anterior flagella like Trichomonas but has no conspicuous undulat-
ing membrane. It has a large and conspicuous slit or cytostome
along one side which corresponds to the very small mouth cavity
of Trichomonas. Within the cytostome is a fourth inconspicu-
ous flagellum which seems to be attached to a small undulating
membrane. The posterior end of the body is drawn out into a
long point. As in Trichomonas tne nucleus les just behind the
origin of the flagella. The rest of the body contains numerous
vacuoles filled with bacteria, the latter apparently serving as
the staple article of diet.

GIARDIA INTESTINALIS rma | |e

The ordinary multiplication of Macrostoma is no doubt similar —
to that of Trichomonas. When ready to leave the body oval
cysts are formed seven or eight w (33/55 of an inch) in length,
within which the animal with its nucleus and large cytostome can
be seen (Fig. 32D). Wenyon has found Macrostoma cysts with
four nuclei and thinks that some multiplication may occur
within the cysts as it does in Endameba. The methods of trans-
mission and means of prevention differ in no way from those
of Trichomonas.

Giardia (or Lamblia) intestinalis. — Next to Trichomonas,
Giardia is the most common flagellate in the human digestive
tract. Unlike most of the other intestinal protozoans it estab-
lishes itself in the upper part of the small intestine. It is one
of the oddest-shaped little animals known. Wenyon aptly
describes it as follows: ‘‘ In shape it resembles a pear split into
two parts along the longitudinal axis. There is a flat surface
on which there is a sucking disk with raised edge, and a convex
surface. The tapering extremity or tail can be turned over the
convex back, and it terminates in two flagella. There are three
other pairs of flagella, the arrangements of which are best seen
by referring to the plate.” (Fig. 33.)

Giardia is remarkable in being perfectly bilaterally eee
every organelle, including the nucleus, being accurately repro-
duced on each side of the middle line. Between the two small
nuclei are a pair of rodlike structures (Fig. 33, par. b.) thought by
some workers to be parabasal bodies, from which the flagella -
arise. As seen in face view the parasite has a comical owl-like
appearance. This fantastic little animal, 12 to 18 yu (gd55 torsos
of an inch) in length fastens itself to the convex surface of an
epithelial cell by means of its sucking disk, resting with its
flagella streaming like the barbels of a catfish (Fig. 33F). Some-
times long rows of them can be found resting on the surface of the
epithelial cells of digestive glands. Miss Porter, who has studied
Giardia infections in British soldiers from Gallipoli, estimated
recently that in one case the number of cysts, each having been
an active flagellate in the intestine, exceeded 14,000,000,000 in
a single stool. The number of cysts in an average stool in a
case of moderate infection she estimated at 324,000,000.

Evidently this flageliate multiplies very rapidly, but its method
of multiplication is not fully understood. Division of unen-

124 INTESTINAL FLAGELLATES AND CILIATES

cysted forms has very rarely been observed, and some writers
have even gone so far as to say that it does not occur. It is well
known that division into two individuals takes place after en-
cystment, and Wenyon has recently expressed the opinion that
if the division is completed before the cyst is expelled from the
body of the host, the cyst may burst and liberate the two animals,

Fic. 33. Giardia (or Lamblia) intestinalis; A, side view (s. sucker-like depres-
sion); B, ventral view (par. b., parabasal bodies, n., nucleus); C, young cyst with
four nuclei; D, mature cyst containing two parasites; H, end view of young cyst;
F, parasite resting on epithelial cell. Figs. A—E, x 2000, after Wenyon; Fig. F,
X 1000, after Grassi and Schewiakoff.

the cysts thus serving as a means of multiplication. Kofoid
and Christiansen have recently succeeded in finding numerous
individuals of an allied parasite of the mouse, Giardia muris,
in process of division into two and also into four and eight indi-
viduals, both in the free and in the encysted state. That a simi-
lar process really occurs in the human parasite can hardly be
doubted, both from its similarity to the mouse parasite and from
the enormous numbers which may occur in an infected person
at one time. | |

The free active parasites become motionless and die soon after
leaving the body of the host with the feces, but encysted forms
(Fig. 33C, D and E) may retain their vitality for a very long time.

GIARDIA INTESTINALIS 125

The cysts usually form around single animals which then proceed
to divide into two or more individuals. The commonest condi-
tion is that of two parasites lying with their anterior ends at
opposite ends of the cyst (Fig. 33D).

According to Wenyon, Giardia is a very persistent flagellate,
often keeping an individual infected for years. It is sometimes
noticeably pathogenic, causing intermittent diarrhea in which
blood and mucus is passed, swarming with parasites. Between
such attacks the infected person passes apparently normal stools,
with only the cysts of Giardia in them. An active increase of
parasites accompanied by attacks of diarrhea is likely to occur
after exposure to weather, irregular diet, or other weakening
conditions. Many cases of dysentery and diarrhea in British
soldiers invalided home from Gallipoli were found to be due to
Giardia infection. The acute symptoms last from one to six
months, after which the symptoms practically disappear for a
variable length of time. Strangely enough there is always
spontaneous improvement upon a change to a cooler climate.

Giardia infections are extremely difficult to get rid of, and
some infections seem to survive every attempt at treatment.
They do not respond to emetin, though they are sometimes
destroyed by beta-naphthol. The latter drug in combination
with bismuth salicylate has been found successful in some cases.
Escomel in Peru uses a method of dieting followed by calomel
and castor oil and claims to rid his patients of the parasite by the
third day. The difficulty experienced in expelling these para-
sites is probably due to their habit of lodging themselves in the
digestive glands outside the main passage of the intestine, where
it is difficult for drugs of any kind to reach them.

Like other intestinal protozoans, Giardia is transmitted in the
encysted state with polluted food and water. Stiles has shown
that flies play an important rdéle in the spread of the infection,
carrying the cysts on their feet from open privies and depositing
them on human food. By capturing flies known to have fed on
Giardia-infected material and shaking them up in distilled water,
Stiles was able to recover Giardia cysts from them, thus prov-
ing as a fact what had long been believed without definite
proof,

126 INTESTINAL FLAGELLATES AND CILIATES

Ciliates .

Balantidium coli. — Although several species of ciliates have
been recorded as human parasites, there is only one species,
Balantidium coli (Fig. 834A), normally parasitic in hogs, which is
common enough to be of any importance. This large ciliate
stands next to Endameba histolytica among the Protozoa as a

TES
sea),

=

siithin

Nee

ime

id

GEE

il

pe

Fic. 34. Balantidium coli; A, free ciliate from intestine; n., nucleus; ec. v.,
contractile vacuoles; f. v., food vacuole; cyt., cytostome. B, cyst, as passed in
feces, containing two parasites. x about 500. (After Wenyon.)

cause of human dysentery. It is a large animal for a protozoan,
averaging from 50 to 100 uw (535 to sf of an inch) in length, and
thus being visible to the naked eye. Its body is oval and en-
tirely covered with cilia, and at the anterior end there is a gash-
like slit leading to the mouth or ‘ cytostome” (Fig. 34, cyt.).
The large bean-shaped nucleus (Fig. 34, n.) lies near the middle of
the body and near each end is a pulsating cavity or contractile
vacuole (Fig. 34, ¢.v.) which excretes waste matter. These
parasites multiply by transverse division, often so rapidly that
the animals do not have time to grow to full size and so become
very small. When ready to leave the body they form an oval
cyst about themselves. Sometimes two occupy a single cyst
(Fig. 34B), and later fuse together. Since the ciliated bodies of
the protozoans can be seen, under a microscope, inside the large
transparent cysts, their identification is not difficult. The cysts
can exist outside the body for a long time, awaiting an opportunity
for reinfection.

oe ee

BALANTIDIUM COLI 27

Balantidium swims about in the contents of the large intestine
devouring particles of fecal material. As long as the animal
confines its activities to this, no ill effects result, but it also has
the power, like Endameba histolytica, of invading the tissues
and causing ulceration, perhaps after an injury from some other
cause has given an opening for invasion. Although many in-
fected persons do not show any dysenteric symptoms, these are
likely to appear at any time. When they do appear, they are
of a very serious nature, and cause a high mortality. On post
mortem examination the large intestine is often found in a hor-
rible condition, ulcerated from end to end, with shreds of muti-
lated or dead tissue hanging from the walls.

Unfortunately there is no specific treatment for balantidial
dysentery as there is for the amebic disease. In some cases
emetin and alcresta ipecac (see p. 135) have caused a disap-
pearance of the parasites, but these are not reliable remedies.
Salvarsan and methylene blue have also been recorded as suc-
cessful in some cases. Organic compounds of silver seem to
have some value in destroying Balantidiwm, and there are other
drugs and herbs of much local fame which are undoubtedly
sometimes effective. Rest and care of the general health are
always required.

Prevention of balantidial dysentery consists not only in the
sanitary disposal of human feces, as in the case of other human
intestinal protozoans, but also in the proper care of hogs, since’
Balantidium is a common parasite of these animals, and is
probably normally a hog parasite. A large proportion of hogs
are infected in almost all warm and temperate countries, and it is
nearly always in hog-raising countries, and in places where there
is too close association between hogs and man, that balantidial
dysentery occurs. Around Manila, where the disease is fairly
common, the majority of the hogs are infected and pass encysted
parasites in their feces almost constantly. In Colombia the
disease is found only in those altitudes where hogs are raised
and among those who raise them.

CHAPTER VIII
AMEBZ:

TuHose of us who have had an opportunity, in studying micro-
scopic life in water, to observe the restless movements of the
tiny bits of naked protoplasm which we call amebex, having
watched them slowly creep along the surface of a slide, extending
a portion of the body as a finger-like projection or ‘ pseudo-
podium ” and then allowing the rest of the body to flow up to

the new position; having seen them creep up on tiny protozoans —

or other single-celled organisms and devour them by merely
wrapping themselves around them, thus engulfing them in an
improvised stomach; and having seen them propagate their
kind by simply constricting in the middle and dividing in two;
— those of us who have observed these acts on the part of such
tiny and simple animals have come to be fascinated by them and
to like them, and find it hard to realize that certain species are
‘nstrumental in causing some important human diseases. Amebz
are found almost everywhere in water, soil and carrion. They
have even been found recently to exist in large numbers in the
sunbaked sands of the Egyptian deserts, lying dormant in their
cysts which protect them from evaporation, ready to emerge
and resume an active life when they become moistened. In
view of the wide adaptability of these animals it is not surprising
to discover some living as parasites, finding congenial surround-
ings in the bodies of higher animals.

Classification. — Amebz are protozoans belonging to the sub-
class Sarcodina, a group characterized by a body without a
cuticle, though sometimes protected by a shell or cyst wall, and
by their peculiar method of locomotion. In the adult form they
have neither flagella nor cilia, but simply outgrowths of proto-
plasm, called pseudopodia. In the amebe and their close rela-
tives the pseudopodia can be projected anywhere on the surface
of the body, now here, now there, though the number, form and
activity of the pseudopodia are quite different in different species.

128

a

PARASITIC SARCODINA 9

The life history also varies in the different species, many possess-
ing a flagellated stage. On the basis of life history and habits
the old genus Ameba has been broken into a number of genera,
seven according to Calkins. Of these only three occur as para-
sites of man.

The amebz which are especially adapted to live as parasites
in the bodies of animals belong to at least two distinct genera,
Endameba and Craigia (or Parameba). Endameba includes
amebe of large size which are not readily distinguishable from
the free-living genera except in their parasitic manner of life
and by the fact that they will not grow in pure cultures. Craigia
includes parasitic species of amebze which, like some free-living
forms, pass through a stage
in which they possess flagella
and resemble true flagellates.
In addition to these, the
genus Vahlkampfia includes
species which may tempo-
rarily live as parasites in man
if accidentally swallowed.
They are minute in size, nor-
mally free-living, and have
no flagellated stage of devel-

opment. A few species are frye. 35. Chlamydophrys stercorea, show-

true parasites of cold-blooded ing portion of protoplasm of body (prot.)
and slender anastomosing pseudopodia (ps.)

animals. Belonging to the protruding from transparent shell (sh.); n.,
Sarcodina also, but not nucleus. X 300. (After Schaudinn, from

closely related to the amebe, oor

is a peculiar parasite, Chlamydophrys stercorea (Fig. 35), found in
freshly passed feeces of a number of animals, including man. It
has a transparent glassy shell of pseudochitin, through the mouth
of which it protrudes its slender pseudopodia.

The number of distinct species of Endameba which live in the
human body is still a matter of dispute. Due largely to the work
of Darling in disentangling the species of amebz only two are
now usually recognized as habitually inhabiting the human
intestine. One of these, H..coli, is a very common but ap-
parently harmless resident, while the other, EL. histolytica, is a
bandit of the first order, and the cause of amebic dysentery and
liver abscess, diseases of great importance in tropical countries.

30": ~ AMEBAD

Possibly Endameba coli will prove to be a group of related species
instead of a single species. In Brazil, for instance, Aragao has
described an ameba very similar to EL. coli in some respects, but
with certain constant differences, which he named E. brazilien-
sis. A small ameba, Vahlkampfia lobospinosa (Fig. 36), usually
supposed to be identical with the free-living fresh water species, is
often found in the large intestine and in feces, probably having been
ingested in cyst form with food. It does no
damage whatever. In our mouths several
species find a congenial environment, and
one, E. gingivalis (buccalis), is very common
and is thought by most workers to be at
least indirectly connected with pyorrhea,

which, next to decaying teeth, is probably
‘Gun Petes ks the commonest human disease. LH. gingivalis
ce. v., contractile vacu- also attacks the tonsils, and is probably
ee oe indirectly the cause of certain kinds of goitre.

Another species of ameba, which has only
rarely been found, is HE. mortinatalium. It has been observed in
various organs such as the liver, kidneys and lungs of syphilitic
infants and in two cases in the parotid glands of non-syphilitic
infants. Syphilis seems to serve as a favoring circumstance for
this species. On account of its rarity this ameba is not of such
importance to the human race as E. histolytica or E. gingivalis,
though apparently very destructive when it does occur. Another
species, HL. urogenitalis, has occasionally been found in the urogenital
tract, being voided with the urine. Two species of Craigia live
as intestinal parasites of man, and cause a type of dysentery
closely resembling that caused by EH. histolytica.

Amebic Dysentery

Importance. — One of the most serious menaces in the tropics —

is dysentery; people who have always lived in temperate countries
have no conception of the severity of this ailment. In many
tropical countries dysen ery ranks next only to malaria as a cause
of death, and very often it finishes the work of such diseases as
malaria, kala azar, and other fevers. When the American troops
occupied Vera Cruz in 1914 they found dysentery one of the chief
causes of death among the Mexican population. The occu-

TYPES OF DYSENTERY 13!

pation of the Phillipine Islands was accompanied by a frightful
epidemic of dysentery among the American soldiers, and until
the city of Manila was cleaned up it was a veritable pest hole for
the disease.

There are many different types of dysentery, especially in the
_ tropics, each showing somewhat different symptoms and having
to be treated in different ways. Some cases of dysentery are
due merely to improper diet, some to disturbances of the digestive
tract due to other diseases, and the majority to intestinal para-
sites of some kind, either bacteria, protozoans, or worms. Ina
restricted sense the term “ dysentery ” is used for intestinal dis-
eases caused either by bacteria or protozoans. The diseases
caused by protozoans other than amebz are discussed in the
chapter preceding this. ‘‘ Bacillary Dysentery ” is a bacterial
disease and need not be discussed here except in comparison with
the other types of dysentery. It occurs in temperate as well as in
tropical countries and is very common in epidemic form in armies,
prisons and asylums. Amebic dysentery, on the other hand,
is uncommon outside of warm climates but is endemic in local
areas in almost all tropical and subtropical countries. In some
districts 85 per cent of all dysentery is caused by amebe. Amebic
dysentery is common on the Gulf Coast of the United §$tates,
and endemic.cases probably occur throughout the United States,
since numbers of cases are on record from such northern states
as Minnesota and Iowa, though apparently not introduced directly
or indirectly from more southern localities. Since the beginning
of the European war amebic dysentery has become fairly common
in France. The so-called ‘‘ trench diarrhea” is often amebic
dysentery. Unlike the bacterial disease it does not give rise to
extensive epidemics in places where it is not normally found.

The réle played by amebe in dysentery was in doubt for a
long time. The presence of amebe in perfectly healthy indivi-
duals, and the fact that amebe grown in artificial cultures would
never cause dysentery experimentally, confused the problem.
As said before there are species of ameba, especially Endameba
coli, which, though closely resembling the real villain, EF. histo-
lytica, live in the human intestine apparently without doing the
slightest damage. Neither HE. coli nor E. histolytica will grow
on cultures, the cultured amebe being distinct from either, and
quite incapable of damaging the intestine. Walker and Sellards

2 AMEBAl

carried on a long series of experimental feedings with amebe of
various species and largely as a result of their work the true facts
of the case have been unraveled. They proved the harmlessness
of Endameba coli and also showed that E. histolytica and E.
tetragena, long considered distinct species, are really two phases
of a single species.

The Dysentery Ameba. — The dysentery ameba, LH. histolytica
(Fig. 37), is large and active, 25 to 40 u (oon to sd Of an inch) in
diameter, with a rather trans-
parent appearance and blunt
pseudopodia. The distinct
clear outer layer of protoplasm
and very indistinct eccentri-
cally placed nucleus, together

of vacuoles and particles of red
blood corpuscles in process of
es | digestion, are its distinguishing

Fig. 37. Endameba histolytica, living characteristics. A comparison
specimen showing ectoplasm and endo- of the vegetative form with
plasm, and several ingested blood corpus- ;. fae :
eles Sc 1000. that of E. coli is shown in

Fig. 838A and B.

There are two stages in the life history of this ameba, the
vegetative and the cystic. As long as conditions in the intestine
are favorable for their growth and development, the amebe con-
tinue in their active vegetative condition, multiplying by simple
division of the body into two. When conditions have become
unfavorable for them, however, as in later stages of the disease,
they decrease in size down to seven or eight w (about se55 of an
inch) in diameter, become round in form, and begin to develop a
tough cyst wall around themselves. This is known as the pre-
cystic stage (Fig. 39). From this stage they pass rapidly into
the cystic stage by the completion of the cyst wall and the divi-
sion of the nucleus into four daughter nuclei, thus forming the
well-known ‘“ tetragena’”’ cysts (Fig. 38A’), long supposed to
belong to a distinct species. Examined under a microscope they
look like tiny globules with a mother-of-pearl reflection. These
cysts can readily be distinguished from those of Hndameba coli
in that the latter usually have eight nuclei instead of four (Fig.
38B’). The cysts may remain in the intestine for a long time,

with the presence in the body |

BO crate cet a

MODE OF INFECTION 133

but they are eventually passed out. with the feces. Unlike
amebee in the vegetative stage, the encysted amebe are resistant
to drying and may live for at least a month in dried or partially
dried feces if not exposed to direct sunlight. They are not, how-

Fie. 38. Comparison of Endameba histolytica and E. colt. 1500. A, EZ.
histolytica, vegetative stage; note small indistinct nucleus (n.), clear ectoplasm
(ec.), ingested red corpuscles (c.) and contracticle vacuole (c. v.). B, E. coli,
vegetative stage; note large distinct nucleus (n.), indistinctness of ectoplasm, com-
mon absence of ingested food materials and of contracticle vacuole. A’, E. histo-
lytica, cyst; note small size (10-14 yw), four nuclei (n.), and ‘‘chromidial body’”’
(chr.). 3B’, E. coli, cyst; note large size (15-20 w), and eight nuclei (n.).

ever, so resistant to drying as are the cysts of many free-living
amebee.

In this condition the amebse may be blown about by the wind,
may contaminate garden vegetables where “night-soil’’ is used
as fertilizer, or may be carried on the feet
of flies. If by any of these or other means :
they reach human food or water and thus Fic. Precystic
secure entrance to the digestive tract, the Seer ie cite ee
cyst wall is dissolved by the pancreatic juice, 2 distinct species and
and four little amebe, each containing one of ae ee ae
the daughter nuclei which were formed when Penfold.)
the cyst first developed, are set free in the intestine and begin
to grow and multiply. The active vegetative amebe from an
acute case of dysentery are destroyed in the stomach if swallowed,

and cannot reach their feeding grounds in the large intestine;

134 | AMEB A

only the parasites in the encysted stage, with an enclosing capsule
to protect them from being digested, can reach the intestine and
cause disease.

The Disease. —In the experiments made by Walker and
Sellards in feeding ameba-infected material to animals and human
volunteers, dysentery symptoms appeared in from 20 to 94 days,
averaging about two months. The most marked symptom is
an acute diarrhea in which the stools consist largely of blood and
mucus. In a typical case from Alabama a patient passed as
many as fifteen or twenty stools in an hour. This condition
had been going on for years, recurring about three or four times
a year, lasting a month at a time. In the intervals between
these attacks the symptoms were mild and the patient passed
only two or three stools a day. Sometimes the attacks are more

regularly chronic, or may recur at long intervals. Often the |

dysentery is accompanied by evening fever-and anemia from
loss of blood in the bowels.

Instead of producing ulcers on the mucous surface of the aoe
intestine such as occur in bacillary dysentery, the amebe work
deeper into the muscular linings of the intestines. Local swellings
first appear, followed by an ulceration of the mucous membrane.
This produces a portal for the entrance of the amebe to the
tissue underlying the mucous membrane, and here they make
extensive excavations. The lesions are most common in the
upper half of the large intestine but can be found from the lower
part of the small intestine to the rectum. The exposed ulcera-
tions vary from the size of a pinhead to that of a silver dollar,
their ragged edges tending to roll into the crater-like areas.
Often the tunnel-like excavations under the mucous membrane
connect with one other.

Liver abscess is a common result of infection with Endameba
histolytica. Often these abscesses are of large size, filled with
a slimy and somewhat bloody chocolate-colored pus. Over a
quart of such pus has been removed from an amebic liver abscess.
The parasites are found at the edges of the abscess, eroding more
tissue and enlarging the pus cavity. How they reach the liver
to do their damage is not certainly known, but it seems probable
that they bore into bloodvessels in the walls of the diseased large
intestine and are carried by the portal vein to the liver, where
they find a fertile feeding ground.

eis

TREATMENT OF AMEBIC DYSENTERY 135

Treatment and Prevention. — One of the greatest discoveries
in the field of medical treatment since the production of salvar-
san by Ehrlich is the discovery of emetin as a specific poison for
amebee. Emetin is an alkaloid substance prepared from ipecac,
the extract of the roots of a Brazilian herb. It was long known
that ipecac sometimes had a very marked effect on dysentery,
but since amebic dysentery has only recently been differentiated
from other forms very variable results were obtained from its
use. Ipecac has a decided disadvantage in that it causes violent
vomiting, but its alkaloid, emetin, in the form of emetin hydro-
chloride, while possessing all the amebicidal properties of ipecac,
can be used in the form of injections into the veins, and therefore
does not cause vomiting. Experiments with cultural species of
amebze showed that emetin (emetin hydrochloride) is destructive
to amebze when diluted 500,000 times, and the intestinal amebe
on a microscope slide become round and motionless and ap-
parently dead when subjected to this very dilute solution.
Emetin is given in hypodermic injections. Almost without
exception the effect of the drug on the disease is certain and rapid.
Severe cases which have been running on for years can be cured
in four or five days by this simple treatment. One of the chief
disadvantages is that the treatment is often discontinued too
soon. The dysenteric symptoms disappear as if by magic and
the patient is often not willing to be subjected to continued drug
injections until every trace of the amebze has disappeared.
Emetin is powerless against encysted amebe and an apparently
cured patient may continue to harbor and scatter these dangerous
microscopic particles of living matter for some time, thus en-
dangering other members of the community. It is probable that _
self-infection from the remaining cysts is the cause of the fre-
quent cases of recurrence of amebic dysentery after inadequate
treatment. Under continued treatment the cysts gradually dis-
appear from the intestine, but their exodus is hastened by purges.
_ Bismuth subnitrate has been used with good success in con-
junction with emetin, the bismuth acting as a sedative on the
intestine and aiding in the healing of the lesions, and also as an
amebicide. Another aid to the efficiency of emetin is a daily
enema of saline salt solution, since this tends to eliminate the bac-
teria which are apparently necessary for the welfare of the amebe.
Another preparation of emetin, alcresta ipecac, is effective

136 AMEBZi

against dysentery amebe, though not so certain in its action as
the hydrochloride. It has an advantage in that it can be taken
in the form of tablets when a physician is not available and the
apparatus for hypodermic injection is not at hand. Some doc-
tors in southern United States have advocated the use of extract
of a common southern plant, Chaparro amargosa, to destroy in-
testinal amebx. This extract is very cheap and entirely devoid
of danger in ordinary doses, but its use in place of emetin has
not yet been sufficiently justified.

Walker and Emrich have recently (1917) reported the success-

ful use of oil of chenopodium for treatment of mild cases of amebic

dysentery, and especially of “ carriers.” It is pointed out that
emetin in its various forms is often inefficient in treatment of
carriers on account of its powerlessness against encysted amebze

and its inability to eliminate them. These investigators em-

phasize the importance, before giving the oil, of a preliminary
purgation with Epsom salts (magnesium sulphate) sufficient to
produce fluid bowel movements, the purpose being both to re-
move excess fecal matter from the intestine and to bring the
amebe out of their protective cysts and subject them in the
unencysted condition to the action of the chenopodium. The
treatment found most effective by Walker and Emrich is as
follows: (1) magnesium sulphate, from one-half to one ounce,
at 6 A.M.; (2) oil of chenopodium, 16 minims in gelatine capsules
(to obviate disagreeable odor and taste), at 8 A.M., 10 a.m. and 12M.,
and (8) castor oil, one ounce, containing 50 minims chloroform,
at 2 p.m. This or any other treatment should be followed by
examination of the feeces at intervals for some weeks after treat-
ment, to make certain of the cure.

The keynote to the prevention of dysentery whether it be
caused by amebe or other protozoans or bacteria is sanitation.
The efficacy of sanitary measures was well illustrated by the
fact that during the first month of the occupancy of Vera Cruz
by the Americans in 1914 there were four times as many cases of
dysentery as during the second month when sanitary measures
had been taken and were enforced. The fact that only the en-
cysted parasites as found in the fresh or dried feces of infected
individuals can cause disease suggests a simple remedy in the
proper disposal of infected feces. In tropical countries, however,
such a preventive measure is not so simple as it sounds. In

ea oe

CRAIGEASIS 37

many districts where amebic dysentery is endemic the first
rudiments of sanitation are unknown and every possible method
of transmission of amebic dysentery is given full opportunity.
Polluted drinking water, uncleanliness, transmission by flies,
and the almost universal use of ‘“‘ night-soil’’ (human feces)
for fertilizer, all help the cause of dysentery and account for its
prevalence.

The segregation and cure of dysentery patients, and the care-
ful disposal of their feces, is not enough to eradicate the disease
entirely since there are many immune carriers of the disease who,
though apparently well, harbor the encysted amebe in their
feeces and thereby constitute a source of danger to the community.
It is estimated that in the tropics about ten per cent of infected
persons show no marked symptoms. Thorough sanitation
throughout the community is the only preventive measure which
is adequate. .

Still another factor in the distribution of dysentery amebze
is the rat. Dr. Lynch of Charleston, S. C., discovered that in
that city rats suffered from amebic dysentery as well as man.
The fact that rats became infected by eating infected human
feces, the frequent occurrence of the disease in rats in houses
where human amebic dysentery has occurred, and the ready
transmission of the disease from rat to rat indicate that the rat
infection is identical with that in man, and is not due to the ameba
peculiar to rats, H. muris, and that rats may play an important
role in the spread of the human infection. It may be that rat
destruction will prove to be an important preventive measure
against amebic dysentery.

Craigiasis

Closely related to amebic dysentery in cause, symptoms,
treatment and prevention is a form of dysentery caused by
amebe of the genus Craigia (or Parameba), and hence called
“craigiasis.”’ The parasite of this disease was discovered by
Captain C. F. Craig, of the United States Army, in the Philip-
pines a few years ago, and named by him Parameba hominis,
a name which was later changed to-Craigia hominis. A nearly
allied species, C. migrans, was discovered by Barlow in natives
of Honduras. Cases of infection with one or the other of these
parasites have also been reported from southern United States,

138 AMEBA:

and it is not improbable that they will prove to be of wide geo-
graphic distribution, and often mistaken for Endameba or flagel-
lates, according to the phase of existence in which they are observed.

The Parasites.— As already remarked, Craigia resembles
some of the free-living soil amebe in that it passes through a
flagellated stage, but it differs from them in having only a single
flagellum instead of two. Briefly the life history of Craigia
hominis (Fig. 40A to F) is as follows: the adult form (Fig. 40K),
resembling a typical ameba, is about half the size of the dysentery

Fig. 40. Life cycles of Craigia.

C. hominis (A to F). A, swarmer just escaped from cyst; B, young flagellated
form; C, mature flagellated form; D, same, dividing; H, amebic form before
encystment; F, cyst with swarmers.

C. migrans (G to L). G, swarmer just escaped from cyst; H, young flagellated
form; J, mature flagellated form; J, amebic form developed by transformation
from J, without any multiplication; K, mature amebic form, ready to encyst; L,
cyst with swarmers (note larger size and smaller number of swarmers than in C.
hominis). 1000. (After Barlow.)

ameba (10 to 25 (s255 to tobo Of an inch) in diameter), and
when moving exserts several blunt pseudopodia. In addition
to the nucleus it possesses a structure, possibly a parabasal body,
which appears as a bright glistening object in the living animal
and stains deeply with nuclear stains. The animal multiplies
by simple division for a time, but eventually encysts, rotating
on its axis during the process of forming the double-walled cyst.
When fully developed the cysts (Fig. 40F) are considerably
larger than those of the dysentery ameba (15 uw (zeso of an inch)
in diameter) and contain about 40 round refractive bodies, which

:
3
:
2
j

CRAIGIASIS 139

later escape from the cyst and develop into little flagellated or-
ganisms called ‘“‘swarmers”’ (Fig. 40A and B). These grow to
several times their original size (Fig. 40C), multiply a few times
by simple division (Fig. 40D), and finally lose their flagellum and
pass again into the ameboid stage. C. migrans (Fig. 40G to L),
as described by Barlow in Honduras, where C. hominis also exists,
differs in that each flagellate on attaining full development passes
directly into the ameboid form without first multiplying. The
swarmers (Fig. 40H) are larger and fewer in number than are
those of C. hominis, and the adults (Fig. 40K) average a slightly
larger size.

The Disease. — Barlow describes craigiasis as he found it in
Honduras as more insidious in its development than amebic
dysentery and not so distressing in its early stages, but ulti-
mately quite as dangerous a disease. The symptoms — diar-
rhea with bloody and mucous stools, loss of appetite, abdominal
pain, etc.,— are quite similar to those of amebic dysentery.
In Barlow’s experience liver abscess is even commoner in craigi-
asis than in amebic dysentery. The disease is looked upon as
more dangerous to the community than amebic dysentery because
of the larger per cent of healthy carriers, who, though showing no
marked symptoms for years, may be a constant means of spread-
ing the infection. The usual source of infection is believed to be
polluted water.

Treatment. — Although emetin is as ee to Gene
as it is to other amebz, injections of the hydrochloride are not so
effective as in amebic dysentery since only the tissue-dwelling
ameboid forms are reached by the emetin in the blood, while
the free-swimming flagellated forms escape. Complete and
rapid cure is best effected by combined treatment with emetin
injected into the blood and ipecac taken by mouth, accompanied
by occasional flushing of the bowels with saline laxatives or
enemas to remove the cysts. The same preventive measures
used against amebic dysentery are applicable to craigiasis.

The Mouth Amebe

The fact that our mouths are inhabited by amebez of several
species has been known for many years, but only recently has
much interest centered in them, this interest being due to the

140 AMEB

belief of a number of investigators that the common ameba of

the mouth, Endameba gingivalis (buccalis), has a pathogenic
effect, and is the cause of pyorrhea. Although amebe have not
yet proved to be the direct cause of any diseased condition of
the mouth, yet this direct relation has been shown recently to be
by no means impossible, and an indirect relation is very probable.

Pyorrhea, or Rigg’s disease, in some stage afflicts the majority
of all adult people, and over 50 per cent of all permanent teeth
which are lost are lost as the result of pyorrhea. The apparent
relation between this disease and the presence in the mouth of
the above-mentioned ameba, E. gingivalis (buccalis), was first
demonstrated in 1914 by Barrett, and since then the relation-
ship between the disease and the amebe has been so well estab-
lished that there can be little doubt of it, except as to whether the

amebee cause the disease directly by destroying the tissues or in- |

directly by injuring the tissues and facilitating the entrance of
bacteria. The prevalence of amebe in the mouth, even in young
children, is well shown by a recent investigation by Anna Wil-
liams of the mouths of over 1600 school children in New York
City. Of the children between five and seven years of age 35
per cent were found infected, while of those between five and 15
years 60 per cent were infected.

The ameba, EF. gingivalis, which does the damage can be
‘shown up”’ by placing a bit of the pus from a tooth pocket on
a microscope slide. Here the villains will be found in the midst
of their wreckage. They are from one to three times the diameter
of.the pus cells, usually from 12 to 20 yw (sob55 to ye450 Of an inch)
in diameter, and have a granular appearance; the nucleus is rela-
tively very small. Often when stained they show dark bodies
inside of them which are probably the nuclei of other organisms
or of semi-digested pus cells. When living the amebze prowl about
sluggishly, pushing out a blunt pseudopodium now on one side
of the body, now on the other, then drawing up the body, and
pushing out more pseudopodia, thus slowly working their way
about between the pus cells and fragments of tissue. The outer
layer of the body, or ectoplasm, which serves as a sort of protect-
ing envelope, like the rind on a melon, is clear and transparent
but is not readily distinguishable except when the animal is
moving. The pseudopodia are always formed first out of this

clear ectoplasm, the more granular, grayish inner substance or

AMEBAZ OF THE MOUTH 141

endoplasm pouring out into it later. The reproduction of these
little animals is by a simple division of the body into two when
they have grown large enough to feel cumbersome as single
individuals. Although cysts are formed for protection against

Fie. 41. Common shapes of Endameba gingivalis, from human mouth. x 650.
(After Bass and Johns.)

an unfavorable environment, no multiplication within the cysts
has been observed such as occurs in Endameba coli or E.
histolytica. The cysts, which are rarely found, usually measure
from eight to ten u (se0 tO gs5q Of an inch) in diameter, and are
perfectly spherical with a thin wall.

Some investigators have suggested the possible identity of
E. gingwalis and E. histolytica, but, as pointed out by Craig,
the sluggish movements, small nucleus, absence of certain changes
in form of the nucleus observed in the dysentery ameba, formation
of cysts with a single nucleus, inability to produce dysentery
when swallowed and other characteristics all indicate that
without doubt the mouth ameba is quite distinct from the in-
testinal amebe. j

Other species besides EH. gingivalis have been found in the
human mouth, but little is known about them. E. kartulisi is
large with very distinct ectoplasm; it is said to occur only
rarely. Recently Craig has described another ameba of small
size, which he has provisionally named E. confusa on account of
the likelihood of confusing it with small specimens of E. gingivalis.

142 AMEB

Endameeba gingivalis and Disease. — As intimated above,
although the presence of amebe in the mouth has been known
for many years, these parasites attracted little interest until
1914 when several investigators called attention to an apparent
relationship between the amebz and the presence of pus pockets
between the teeth and gums, a disease known to dentists and
physicians as “ pyorrhea alveolaris.”” The amebz do not thrive
on exposed surfaces in the mouth, but find a congenial environ-
ment in any little secluded pockets between the teeth and gums,
in crevices between close-fitting teeth, or where a bit of food forms
a protected spot for them. Stowed away
in such places, and invariably accompanied
by bacteria and often spirochetes, they
multiply rapidly. That they feed largely
on other organisms cannot be doubted, but
that they prey also on the living tissue
cells is practically certain. Eventually the
delicate peridental membrane surrounding
the roots of the teeth (Fig. 42), correspond-
ing in a general way to the periosteum of
bones, is eaten away and becomes ulcerated.

Fie. 42. Sketch of

tooth showing peridental
membrane, which is the
tissue attacked by Enda-
meba gingivalis and the
seat of pyorrhea, peri-
dent., peridental mem-

brane; periost., perios-
teum:;: Ch. - Crowne
root; p. pulp. (After

Bass and Johns.)

The eating away of the living membranes
of the teeth and gums is accompanied by
a constant formation of pus, and a marked
proneness for the gums to bleed, often with-
out provocation. The swallowing and ab-
sorption of the pus and of the poisonous
waste products generated by the parasitic

organisms are probably the cause of the
more or less noticeable constitutional symptoms which accom-
pany the disease. These may consist of feverishness, dis-
ordered digestion, nervous troubles, rheumatic pains in the
joints, anemia, or various combinations of these ailments. We
_ have long known that unhealthy mouths were the cause of gen-
eral bad health, but we never until recently had any definite clue
to the reason why.

As the ulceration of the membrane continues, the tooth is
gradually loosened from the gum. Just as meadow mice girdle
fruit trees, so these amebe, or the bacteria or spirochetes which
accompany them, eat away the living “ bark ” of the teeth and

AMEBA AND PYORRHEA 143

gums, eventually causing the teeth to fall out. As already stated,
over 50 per cent of all permanent teeth which are lost fall out as
the result of pyorrhea.

Whether the formation of the pus pockets is initiated by the
amebe or by other organisms is not known, but certain it is that
‘Endameba gingivalis is almost without exception found in the
lesions, and at the very bottom of them, often burrowing into the
inflamed tissues to a depth of several times its own diameter,
devouring cells and transporting bacteria. The belief in the rdéle
of the amebze is based on these facts and on the fact that often,
though not always, the disease is greatly improved by treatment
with emetin, which has a specific action on amebe. Some in-
vestigators, notably Craig, consider it, to quote from Craig,
“more than doubtful that Endameba gingivalis is the cause of
pyorrhea alveolaris, this conclusion being based upon the follow-
ing facts: the occurrence of the parasite in a large per cent of
healthy mouths and in the material that can be scraped from
healthy teeth and gums; the occurrence and persistence of the
parasite in patients treated with emetin, even when marked

-improvement in the clinical symptoms have occurred; the ab-
sence of the parasite in some typical cases of pyorrhea; the lack
of improvement with emetin shown in numerous instances of the
disease, although the endamebe may disappear; and the fact
that emetin acts upon other organisms as well as upon endamebee
and the possibility that the improvement that often follows its
administration may be due to such action or to a favorable action
on the tissue cells.’ That these facts argue against the causa-
tion of pyorrhea by amebe alone is unquestionable. These

-facts, however, are not only not opposed to the possibility of
amebze being partly or indirectly responsible for the disease,
but may be interpreted as being in support of such a view. It is
entirely in accord with the known facts about the disease to
suppose that the pus pockets may be initiated or enlarged by the
action of amebe, the damage being then continued by bacteria
which have been given a portal of entry. This would account for
the occasional absence of amebz in typical cases of pyorrhea and
for the occasional cases of the disease which are not improved by
emetin. It is further quite conceivable that the amebe may live
for a long time in crevices in the mouth without doing any
damage, and yet be capable of causing or aggravating pus pockets

144 AMEBZ

under suitable conditions. Perhaps some slight injury to the
membranes or the combined action of the amebe and certain
bacteria is necessary to start the process. Parallel cases of
parasites which may live for a long time as harmless messmates
and then, under favorable conditions, become pathogenic are
well known; one of the best examples is the intestinal ciliate, ©
Balantidium coli. This would account for the presence of
Endameba g’ngivalis in healthy mouths. It is significant that in
her investigation of school children in New York, Anna Williams
found only 30 per cent of apparently healthy mouths, and 94
per cent of mouths with spongy and bleeding gums, infected.
As to the statement that amebe still exist in pus pockets after
treatment with emetin, even when there is marked improvement
in clinical symptoms, there is no doubt but that the number of
amebe is greatly reduced, and those on the frontier where the
most damage is done are undoubtedly killed, since they are most
exposed to emetin in the blood. The ineffectiveness of emetin
against amebz which are not directly in the tissues has been
demonstrated in the case of the free-swimming stages of Craigia
(see p. 1389). Again, were the improvement following treatment .
with emetin due to favorable action on the tissue cells, such im-
provement would invariably follow. That emetin affects other
organisms besides amebe is true, but it is more active against
these protozoans than against any other organisms, as far as is
known. ‘The complete cure of pyorrhea which emetin sometimes
effects, the almost invariable improvement shown after its use,
and the occasional failure of it, all point to the instrumentality
of amebz in causing or aggravating the disease, but indicate
that they may be aided and abetted, or entirely replaced, by

bacteria or other organisms. .

There is some evidence that chronic tonsilitis also is often
caused by E. gingivalis, since this parasite is found in the ma-
jority of diseased tonsils, irritating the tissues and opening the
road for bacteria.

An indirect relation of this same mouth ameba to certain types
of goitre also has been shown to be very probable. Evans,
Middleton and Smith found that diseased tonsils and nasal
passages and enlarged thyroid glands (goitre) are frequent com-
panions in the goitre belt of Wisconsin. They believe that the
amebe injure the tissues sufficiently to give ample opportunity

PREVENTION AND TREATMENT OF PYORRHEA 145

for bacteria to enter and multiply in enormous numbers, and that
certain of these bacteria produce poisoqnous substances which
exert a stimulative effect on the thyroid glands, thus causing
goitre. The effect of the presence of amebe, indirect as it is,
ean be fully demonstrated by destroying them with emetin. In
18 out of 23 cases of goitre treated with emetin the size of the
thyroid mass was obviously reduced.

Prevention and Treatment.— Ordinary cleanliness of the
mouth by frequent brushing of the teeth, rinsing of the mouth,
and care of imperfect teeth is the most important factor in keep-
ing the gums healthy and free from an injurious degree of amebic
infection. In the investigation of school children in New York
already mentioned the number of ameba-infected mouths was
reduced one-half by ordinary cleanliness and care. Such
methods, however, are of little value if the amebe have estab-
lished themselves in a pus pocket, since in such situations they
cannot be reached by the usual methods of mouth cleansing. In
the New York investigation it was found that mouths could almost
always be freed of amebe by using a mouth wash with a weak
solution of emetin, the latter being a valuable preventive measure.
In older people, however, where the amebe have often already
succeeded in stowing themselves away in little crevices and
pockets where mouth washes cannot reach them, some other
method must be employed. The ideal method is to open up and
thoroughly clean out any pus pockets which can be found.
This should be followed by a hypodermic injection of emetin,
repeated on a few successive days to destroy all amebe, wherever
situated. All amebe disappear in 90 per cent of cases in from one
to three days, while after six days of treatment, amebe disappear
in at least 99 per cent of cases. Usually with the death of the
parasites the soreness ceases, the pus formation stops, the gums
stop bleeding and the general health rapidly improves. Of
course it takes time for the injured tissue to heal and the part
destroyed is never replaced. There is also constant danger of
reinfection and the already eroded pocket forms an excellent
place for fresh amebe to take up a claim and begin their destruc-
tive work. Furthermore there are cases of pyorrhea which do
not respond to treatment with emetin, probably because the
work begun by the amebz is continued by bacteria. Emetin,
diluted 200 to 400 times in alcohol and applied with a tooth brush,

146 AMEBZ&

is usually sufficient to kill recently implanted amebic infections.
A thorough mouth rinse with a drop or two of emetin in half a
glass of water is an excellent protective measure but even with
the use of these means of prevention some apparently cured
cases of pyorrhea get reinfections within a few months.

The form of emetin known as “ alcresta ipecac,”’ in tablet form,
is often useful. Two of these tablets taken three times a day for
from four to six days is fairly certain to destroy amebe and has
the advantage.of being easily taken without the aid of a physi-
cian. It sometimes causes a little abdominal discomfort and
looseness of the bowels, but usually has no marked bad effects.

As intimated before, the prevention of infection with EHn-
dameba gingivalis is largely a matter of ordinary mouth hygiene.
Infection can be avoided to a large extent by care in eating and
drinking. One should never eat or drink with the same articles
that have been used by other people. The practice of promis-
cuous kissing is, of course, a ready means of transmission for
these parasites as for many others.

Occasional infection with the parasites of pyorrhea is, however,
almost inevitable. If the mouth is kept scrupulously clean and
in as near perfect condition as possible, the amebze may find no
congenial place to settle down, but in the vast majority of mouths
there is an abundance of fertile ground for them. Once they are
established in a pocket or crevice the injection of emetin, or the
taking of ipecac tablets, is the only safe method of getting rid
of them.

The mouth wash described above, consisting of a drop or two
of extract of ipecac in half a glass of water every evening is a
fairly safe means of prevention. Tooth pastes containing emetin

are now upon the market, but few physiciaus place much con-
a in them.

CHAPTER IX
MALARIA

Importance. — Of all human diseases there is none which is of
more importance in the world today than malaria, and this in
spite of the fact that we have a very full knowledge of its cause,
the manner of its spread, its cure, and means of prevention. It
has been estimated to be the direct or indirect cause of over one-
half the entire mortality of the human race. Sir Ronald Ross
says that in India alone it is officially estimated that malaria kills
over one million persons a year, a greater number of deaths than
was caused by the great European war in the first two years of
its existence. When there is added to this the thousands from
the rest of Asia, Africa, Southern Europe, South and Central
America, and the southern part of our own country who are
annually sacrificed on the altar of the malarial parasite; the
millions of others who are broken in health, incapacitated for
work and made easy victims of other diseases; the valleys,
countries, and even continents which have been barred from full
civilization and development by this more than by any other
cause; then only can we get a glimpse of the real meaning of
malaria to man. Ross argues convincingly that the downfall
of the great Greek empire and the present poverty-stricken
blighted condition of many parts of Greece is probably due
primarily to the invasion of that country, not by burning and
devastating armies of men, but by the malaria parasite, an in-
finitely more terrible though unseen foe which destroyed the new-
born infants, undermined the health of the children or killed
them outright, rendered the richest agricultural lands uninhabi-
table, and, in a word, sapped the vitality of the people until the
boasted power and glory of Greece is but a mocking memory.

Though historians and economists have failed to recognize ‘it,
the réle of malaria and other endemic diseases must have played
an enormous part in the history of the world and in the progress

of nations. Malaria and its powerful accomplice, the hook-
147

148 MALARIA

worm, are largely responsible for the present deplorable condition
of some parts of our own South. Dr. Howard estimated in 1907
that there were nearly 12,000 deaths a year in the United States
from malaria. This, however, is probably almost inconsiderable
when the amount of damaged health and weakened resistance to
other diseases is taken into consideration. Dr. Von Ezdorf, of the
U. 8. Public Health Service, in a recent attempt to estimate the
prevalence of malaria in the United States, obtained data, based
on morbidity reports, which indicate that at least four per cent of
the population of eight southeastern states — 1,000,000 people
— is affected by the disease annually, and found by 13,526 blood
examinations that over 13 per cent harbored malarial parasites
in their blood, the percentage being much higher in negroes
than in whites. Dr. Howard thinks that an estimate of 3,000,000
cases of malaria a year in the United States would not be too ©
high. Millions of acres of fertile land in this country are rendered
useless or only imperfectly cultivable. Taking everything into
consideration, Dr. Howard makes the astounding but well-
founded statement that the annual financial loss to the United
States from malarial diseases is not less than $100,000,000.
This is the condition in the United States, a large portion of which
is relatively free from malaria, and in no part of which is the dis-
ease so prevalent or so destructive as in the tropical portions
of Asia, Africa and South and Central America. In a broad way
one-third of the population of highly malarial countries suffer from
the disease annually. According to Ross the number of deaths
from malaria in India must reach 1,300,000 every year. Obvi-—
ously the importance of this disease to mankind is not likely to
be overestimated.

History. — ‘“‘ Malaria’ means bad air, and was therefore ap-
plied to a number of fevers which were commonly associated
with the bad air of swampy regions. The idea that malaria is
caused by bad air, unwholesome odors, damp night winds, or ~
impure drinking water is even yet adhered to not only by some
of the populace but even by a few unenlightened medical men.
Ross says that it takes ten years for the world to grasp a new
idea, but his estimate is far too low; it is now (1917) 37 years
since the organism causing malaria was discovered and 19 years
since its transmission by mosquitoes was experimentally proved.
It was in 1880 that Laveran, a French army surgeon in Algeria,

MALARIAL PARASITES > 149

¢

discovered a parasitic ‘‘ germ ”’ which he proved to be the true
cause of malarial fevers. Dr. King, of Washington, in 1883
suggested the probability of malaria parasites being spread by
mosquitoes, adducing much circumstantial evidence in support
of his views. It was not until 1898, however, that Sir Ronald
Ross, an Englishman in the Indian Medical Service, experiment-
ally proved that the malaria parasite is absolutely dependent
upon certain species of mosquitoes for its transmission from man
to man. Only six years ago (1911) the parasites of malaria were
first successfully cultured outside the human body by Bass and
Johns at New Orleans, a feat which will eventually lead to new
and valuable discoveries. Other workers deserve no less credit,
perhaps, for suggestive ideas, or for additional facts concerning
the life and control of the malarial parasites. The ultimate
results of their discoveries have only begun to be felt, but al-
ready such enterprises as the building of the Panama Canal have
been rendered possible. The Canal could never have been built
under the old régime of medical ignorance. Statues of the
pioneers in the work of unraveling the truths about malaria
and yellow fever might well have occupied conspicuous places
at the Panama Pacific International Exposition at San Francisco.

Malarial Parasites. — Malarial fevers, of which there are
several different kinds, we now know to be caused by protozoan
parasites which live at the expense of the red blood corpuscles,
and are injected into the human body and transmitted from
person to person only by the bite of certain species of mosquitoes.

The malarial parasites belong to the protozoan class Sporozoa,
or spore animals, so called from their habit of reproducing by
breaking up into a number of small parts or spores, instead of
sumply dividing into two as do most of the Protozoa. All of the
Class Sporozoa are parasitic and have no organs of locomotion
when full grown. Although there are many different kinds
which live as parasites in other animals, very few normally attack
man and only the malarial parasites, belonging to the genus
Plasmodium, are of primary importance. There is still consider-
able disagreement as regards the classification of the human
malarial parasites. Nearly all workers on the subject agree
that there are at least three well-defined species of Plasmodium
causing human malaria, and there is some evidence that distinct
subspecies or varieties of some of these occur. The commonest

150 MALARIA

and most widely distributed species is Plasmodium vivax, which
causes tertian malaria. Of somewhat more limited geographic
range, being confined to tropical and subtropical countries, but
of infinitely more importance on account of the deadly nature of
its attacks, is Plasmodium falciparum, the cause of the estivo-
autumnal type of malaria, also called malignant tertian or subter-
tian fever. During the hot part of the year in the tropics 96 per
cent of malarial cases are of the estivo-autumnal type. The third
species, Plasmodium malarie, causing quartan malaria, is relatively
uncommon, though more frequent in temperate than in tropical
countries. These three species of malarial parasites differ from
each other in a number of important details of structure and
life history and in the diseases which they produce.

Life History of Plasmodium falciparum; Human Cycle. —
The life history of malarial parasites may well be exemplified.
by that of the malignant estivo-autumnal parasite, Plasmodium
falciparum, as diagrammatically shown on Fig. 43. When first
injected into the human blood by a mosquito the animal is
exceedingly minute (Fig. 438A). It immediately enters or at-
taches itself to a red blood corpuscle, where it grows until it
occupies one-half or two-thirds of the corpuscle, meanwhile un-
dergoing a number of different forms. It first goes through a
“sionet ring” stage (Fig. 43B), the ringlike appearance being
due to the presence of a transparent area occupying the middle |
of the parasite, while the tiny round nucleus occupies a position
at one side of the parasite, simulating the setting in a ring. As
the parasite grows larger it becomes irregular in shape (Fig. 43C)
and quite active, constantly changing its form, thrusting out _
little clublike processes or pseudopodia, now here and now
there. Although it has been taken for granted that malarial
parasites penetrate the blood corpuscles and live inside of them
recent investigations by Mary R. Lawson (Mrs. Johnson) indi-
cate that this may not be the case at all, but that the parasites
may attach themselves to the surface of the corpuscles, squeezing
up little mounds of the substance of the corpuscles and encircling
these mounds with their bodies, just as a bit of skin might be
squeezed up between the fingers. Sometimes several parasites
attach themselves on top of each other around a single mound.
A number of facts give support to Mrs. Johnson’s theory: it
affords a logical explanation for the ring forms of the parasite; it

151

LIFE HISTORY

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152 MALARIA

explains the occasional distinct projection of the parasites at
the periphery or edge of the corpuscles (Fig. 44); and it accounts
for the ease with which the parasites may be distorted in making
blood smears. Another argument in favor of
this theory as opposed to the intracorpuscular
theory is that the hemoglobin in the corpuscles
is believed to be in a more or less solid state,
and would therefore make it difficult for the
parasites, if situated inside, to indulge in such
active movements as they do. The majority
of protozodlogists, however, have not accepted
B- Mrs. Johnson’s conclusions.

As the parasite develops there is a distinct

Fig. 44. Blood tendency for the affected corpuscles to clump
corpuscles showing

malaria parasites together, thus clogging the tiny capillaries which

at periphery. 8 are large enough to allow the passage of only a
shows two para- . : :
sites resting one Single corpuscle at a time. In this way the
ee capillaries of such organs as brain, spleen, bone
crophotographs by Marrow and others may be obstructed to a
Mary Lawson fatal degree. Three-fourths of the life cycle of
[Mrs. Johnsonj.) é . g
the parasites is usually passed in the plugged

capillaries so that only during one-fourth of their cycle can they
be found readily in the circulating blood.

After about forty hours the nucleus of the parasite divides into
a variable number of fragments, usually from ten or 15 to as
many as 382, 2.e., under favorable conditions it may split five
times, into two, four, eight, 16, and 32 parts. The rest of the
body divides itself into portions, one surrounding each fragment
of the nucleus, thus forming a little heap of “‘ spores ” (Fig. 43E)
ready to burst apart and leave the corpuscle on which the
parent parasite had been feeding. In the center of the heap
can be found a little mass of coal-black pigment granules, the
waste products resulting from the digestion of the oxygen-
carrying red substance of the blood, hemoglobin. When the
parent parasite bursts the young parasites formed by this rapid
process of multiplication are set free (Fig. 43F) in the blood where

each enters a new corpuscle and repeats the process of growth

and reproduction. The pigment and other waste products
which are left behind when the parasite multiplies are released
into the blood stream where they are carried to all parts of the

————— ee ee ee

NUMBERS OF PARASITES 153

body and deposited in the spleen or other organs or under the
skin, causing the sallow color so characteristic of malarial patients.
It is at the time of the bursting of the corpuscles and release of
the waste matters which act as poisons that the characteristic
chills and fever of malaria are felt. Since the cycle from one
generation to the next is usually about 48 hours in the estivo-
autumnal parasite the attacks of ague are felt at these intervals.
In the malignant type of malaria the bursting of all the para-
sitized corpuscles and release of poisonous waste matter does not
occur so nearly simultaneously as it does in the other species,
the result being that the paroxysms of chill and fever are drawn
out over many hours.

A “quotidian ”’ type of malignant malarial fever in which
agues occur every 24 hours is occasionally met with, the parasites
of which are thought by some authors to constitute one, or even
two, distinct species. The majority of cases of malaria with
daily-recurring fevers are due to double or triple infections, the
different broods maturing on different days.

This rapid process of multiplication in the human blood re-
sults in a short time in an enormous number of parasites, some-
times many billions. The actual quantity of parasites in a
human body in a case of severe estivo-autumnal malaria has
been estimated at 600 cc., or over one pint. It may or may not
mean more to the reader to know that such a quantity of ma-
larial parasites would number 3,000,000,000,000. A better con-
ception of the real meaning of such a number may perhaps be
gained when it is realized that to count off this number at the
rate of 100 per minute day and night without cessation would
require 30 times the period of time that has elapsed since the
birth of Christ. Eventually, however, either the parasite kills
its host, which very commonly happens with this particular
species, or the host, by the development of a temporary immunity
in his body, kills or, as it more often happens, suppresses the
parasite. Such a course of events unaltered, would lead to a
very early and complete extermination of the parasite. There is
a second chapter in the life history of Plasmodiwm which saves
it from such an early death.

After the parasites have been developing in the blood for about
two weeks or more there are developed special sexual forms or
gametocytes, male and female, in the form of sausage-shaped

154 MALARIA

crescents (Fig. 43K and L). Just as in the case of other kinds
of animals and plants, nature has adapted these animals to cope
with their environment. As long as the blood of their host forms
a suitable environment they continue to multiply in the normal
manner, but when conditions due to the formation of antibodies
become unfavorable they produce these sexual crescents in large
numbers and patiently await rescue at the hands, or rather the
beak, of a mosquito. The crescents may persist in the blood for
several weeks, gradually disappearing after all other symptoms
of infection have_vanished. Only slight differences can be seen
between the male and female gametocytes, the female being more
granular in appearance, and with the pigment particles arranged
in a more regular triangular manner (Fig. 43K and L).
Mosquito Cycle. — When sucked into the digestive tract of the
mosquito these gametocytes begin a complex developmental
cycle, providing conditions of temperature are favorable. The
most favorable temperatures are between 75° and 85° F. The
digestive fluids dissolve the remnant of the blood corpuscles, but
the crescents resist digestion (Fig. 43M and N) and become more
obviously sexually differentiated. The male gametocyte de-
velops into a “ flagellated body ” (Fig. 43P), a little sphere from
which several long slender filaments project. These are very
active, constantly lashing to and fro, and ultimately break loose
and wriggle about in the stomach of the mosquito like little
spermatozoa, which, in effect, they are. The female gameto-
cyte develops into an inactive sphere or gamete (Fig. 480) and
one of the filaments from the flagellated male enters to fertilize
it (Fig. 48Q). How perfectly the process simulates the act of
fertilization of an egg by a spermatozoan in the higher animals!
The result of the union of the filament from the flagellated
body with the inactive female gamete is a body which corre-
sponds in every way to a fertilized egg of a higher animal. This
new individual, the beginning of a new generation, grows, elon-
gates, and becomes quite like a little worm (Fig. 48R). It now
wriggles and worms itself about in the stomach of the mosquito
and penetrates the wall, lodging itself between the inner and
outer linings of the stomach (Fig. 48S). Here more rapid growth
takes place and a heavy capsule develops, protruding on the outer
surface of the mosquito’s stomach like a wart (Fig. 45). Mean-
while the contents of the capsule undergo important changes,

DEVELOPMENT IN MOSQUITO 155

dividing into daughter cells (Fig. 43T) from each of which slender
spindle-shaped bodies project like the “ stickers ’’ on a chestnut
burr (Fig. 43U). Ultimately the cells lose their identity and
the entire capsule or cyst becomes crammed
full to the bursting point with myriads of
these spindle-shaped bodies which have now
developed into spores (Fig. 43V). Such a
capsule may contain over 10,000 spores, and
there may be as many as 500 capsules on a
single mosquito’s stomach (Fig. 46). About yi. 4s Cross sec-
12 days or more, according to temperature, tion of stomach of
after the infected blood was swallowed by the ete nae ie
mosquito, the capsule becomes mature and subtertian malaria.
bursts, releasing the spores into the body cavity Goan TS os
of the mosquito. From here the little parasites

make their way to the three-lobed salivary gland (Fig. 46, sal. gl.)
lying in the fore part of the thorax and connecting with the
sucking beak. They assemble in the cells lining the salivary

Fig. 46. View of digestive tract of Anopheles, showing spore-filled capsules of
malaria parasites on wall of stomach. pal., palpi; prob., proboscis; ant., antenne;
ph., pharynx; ces., oesophagus; sal. gl., salivary glands; f. res., ventral food
reservoir; d. f. res., dorsal food reservoirs; prov., proventriculus; st., stomach;
~ .malp. tub., malpighian tubules; int., intestine. KeLo:

_ glands (Fig. 43W) and remain there perhaps for weeks, until the
mosquito bites. When this happens the parasites flow with the
poisonous saliva into the puncture made by the mosquito and,
should the prey of the mosquito be a human being, the whole

156 MALARIA

process of asexual multiplication in the human blood corpuscles

begins over again. Since it takes ten or 12 days for the sexual

cycle to be completed in the case of estivo-autumnal malaria,
an infected mosquito is not dangerous for at least this length of
time after biting a malarial patient. However, once the new
generation of spores has been developed, the mosquito remains
dangerous for several weeks and may infect many persons, as not
all the parasites are poured out of. the salivary glands at one
biting.

It is commonly believed that malaria parasites not only do not
develop but cannot live in the mosquito at a temperature below
60° F. but Dr. King has recently shown that the tertian parasite,
Plasmodium vivax, can survive several days in Anopheles quadri-
maculatus at temperatures slightly below freezing, and can with-
stand a mean temperature of 46° F. for 17 days. The exstivo-

autumnal parasite, P. falciparum, though more closely confined —

to the tropics than the other species, was found to survive a
temperature of 35° F. for 24 hours. This clearly shows that the
malaria parasites can readily pass the winter in the mosquito
hosts even in places where the mean temperature may fall con-
siderably below 60° F. for some time.

Other Species. — The other species of malarial parasites dif-
fer only in minor details of their structure and development.
The tertian parasite, Plasmodium wmvax, during the early stages
of its development in the blood corpuscles is extremely active.
Its unceasing restless changing of shape is fascinating to watch
under the microscope and one feels that it was very appro-
priately named “ vivax.” Unlike the malignant parasites of
estivo-autumnal malaria, the tertian parasites do not tend to
clump together, and so do not become plugged in the capillaries
but remain constantly in the circulation. To this fact, as will
be shown later, is due the ‘ benign ” nature of this and also of
the quartan parasite. The tertian parasites have the peculiarity
of growing very large and of causing the corpuscles which they
parasitize to enlarge and become unhealthy in appearance.
The number of spores which result from the sporulation every
48 hours ranges from ten to 25. According to Ross the normal
number of splits of the nucleus is four, which would result in
16 spores. One of the most striking points of difference from
the “malignant” parasites is the fact that the gametocytes

SPECIES OF PLASMODIUM 157

are not in the form of crescents, but instead resemble mature
parasites ready to sporulate. A comparison of Fig. 47A, A’ and
A” with B, B’ and B” and C, C’ and C” brings out the prin-
cipal differences among the three species of parasites as regards
size at maturity (A, B, C), number of spores (A’, B’, C’) and form
of gametocytes (A”’, B’”’, C”’).

Fic. 47. Comparison of three species of malaria parasites xX 2000 (figures
selected largely from Manson). A, A’ and A’, Plasmodium vivax; B, B’ and B”,
Plasmodium malarie; C, C’ and C’’, Plasmodium falciparum.

A, B and C, mature parasites in red corpuscles.

A’, B’ and C’, segmented parasites ready to leave corpuscles.

A”, B” and C’ , mature gametocytes.

The quartan parasite more closely resembles the tertian para-
site in flexibility of body and form of gametocytes (Fig. 47C”’), but
it differs in that it does not cause the corpuscle to enlarge (Fig.
47C) and is never active in movements. It produces only from
five to ten spores, the nucleus normally undergoing three splits.
The spores form a very regular rosette or ‘ daisy-head,” ar-
ranging themselves petal-like around the dark mass of pigment
in the center (Fig. 47C’). Unlike either of the other parasites
this one causes ague by its sporulation once in 72 hours instead
of in 48 hours. A comparison of certain phases of this parasite
with the same phases of the others will be found in Fig. 47.

Propagation. — As remarked above infection with malaria is
now known to take place exclusively through the bites of certain
species of mosquitoes, all belonging to the genus Anopheles (in-
cluding its subgenera). While over a hundred species of Anoph-

158 MALARIA

eles have been described, less than one-third have been proved
to be carriers of malaria. Some species will carry certain types
of malaria and not others (see p. 489). A knowledge of the
malaria-transmitting ability of various species of mosquitoes
and their habits is of the utmost importance in any attempt to
exterminate malaria by exterminating mosquitoes. The knowl-
edge that A. malefactor of Panama, breeding in cavities of stumps
and trees, was not a malaria carrier saved several hundred thou-
sand dollars in the anti-malarial campaigns in the Canal Zone.
The distinguishing characteristics of Anopheles and a brief
account of a few of the more important malaria-carrying species
will be found on pp. 439-441.

Reports of malarial outbreaks have occurred which were said
to be due to some other cause than mosquito transmission, but
when completely investigated there has always been found to be
a “leak”? somewhere. Sometimes the presence of mosquitoes
was unsuspected, sometimes other fevers have been mistaken
for malaria, and sometimes the malarial parasites have been
harbored for weeks or months in “latent” form. This is a
phase of malaria which is little understood, but it is a well-known
fact that long after symptoms of the disease have disappeared,
and the parasites can no longer be found in the blood, a fresh
outbreak may occur, coincident with some loss of vitality, or
some physiological shock on the part of the host from some
other cause. Often a mere change of climate and environment is
sufficient to precipitate ‘‘ latent’ malaria. It is highly probable
that the ordinary blood parasites are carried in the meantime
in such small numbers as to be practically impossible to find.
Ross has pointed out that if 1000 parasites in the body were
able to withstand the unfavorable conditions and existed there
during the ‘‘latent”’ stages, a man working 12 hours a day
searching blood smears would have a chance of finding one
only once in five years. Some authors have advanced the theory
that the gametocytes, suddenly stimulated by some unknown
cause, develop by parthenogenesis, 7.e., without the ordinary sexual
mosquito cycle, and thus cause the relapse. This idea has been
widely accepted but there seems to be little ground for it and some
positive evidence against it. The parasites naturally thrive
best when their host is weakened by some other influence which
then acts as an accomplice for them. Such influences are ex-

COURSE OF DISEASE 159

posure to sudden changes in climate, fatigue, dissipation and
other sickness. Even educated people often come to believe
that malaria is directly caused by these conditions.

Suffice it to say that many experiments, carried out with the
utmost care and accuracy, and checked by numerous repetitions,
have proved beyond doubt that the mosquito is the necessary
transmitter and intermediate host of malarial parasites. A few
investigators think it possible that other animals besides man
may serve as hosts for the malarial parasites, so that malaria
may occur even in uninhabited regions. Although many para-
sites are able to live in a number of different kinds of animals,
this does not seem to be true with the malarial parasites, and
all attempts to infect even monkeys have so far failed. Until
some definite proof of the réle of some other animal as a host
for human malarial parasites has been brought forward we may
look upon this as very improbable. Possibly the alleged presence
of malaria in uninhabited regions may be explained by the
malarial parasites in the mosquito passing into the eggs of the
mosquito, and thus being carried on generation after generation.
Though the germs of some diseases are known to do this in their
insect hosts, experiments with hereditary transmission of ma-
larial parasites in mosquitoes have so far been unsuccessful.

The Disease. — Malaria as a disease is extremely variable.
A “ typical” case of malaria, in the tropics at least, is a rather
unusual thing. As we have seen, there are at least three different
kinds of malarial parasites, each of which produces a somewhat
different disease. While ordinarily all the parasites of a brood
mature at regular intervals, a person in a malarial district may
be infected with two or more broods maturing at different times,
and the case may be farther complicated by a “‘ mixed ”’ infec-
tion, that is, by more than one species of malaria at a time.
Varying degrees of immunity, the effects of insufficient quinine
or other drugs, the presence of complicating diseases and the
virulence of the particular strain of parasites all have a hand in
modeling the effects produced by “‘ malaria.” It is little wonder
that in some places practically every ailment or feeling of ‘“‘ ma-
laise” is attributed to malaria. In the tropics such a diagnosis
- would be correct in a great many cases. However, the habit
of attributing any indisposition which cannot be accounted for
otherwise to malaria has been transplanted into non-malarial

160 MALARIA

places, and it is not uncommon to hear of a person having a
‘touch of malaria’ when in reality he has only indigestion, a
cold or a light case of la Grippe. It is largely due to this fact
that malaria is looked upon in non-malarial districts as of such
small consequence.

The early stages of all types of malaria are similar except that
the quartan type produces the intermittent fevers on every third,
instead of every second, day. During the incubation period of
the disease there is a feeling of ennui with headache and perhaps
slight fever. After about a week, when the parasites have mul-
tiplied to 150,000,000 or more, the regular intermittent fevers
set in. Each attack begins with a shivering chill, sometimes
accompanied by convulsions, so severe that the teeth chatter
and goose-flesh stands out all over the body. Yet the tempera-
ture will be found to be several degrees above normal, and still
going up. In the wake of the chill comes a burning and weak-
ening fever, with violent headache and vomiting and a tempera-
ture from six to eight degrees above normal. The fever stage in
turn is followed by a period of sweating, so profuse that the
clothes or bedding may become wringing wet. The sweating
gradually subsides, the temperature drops rapidly, often below
normal, and the patient, after from six to ten hours in the case
of benign infections and about 20 hours in malignant infections,
rests fairly easy until the next attack. The fact that the attacks
most commonly occur between midnight and noon, instead of in
the evening, is often useful in distinguishing malaria from other
intermittent fevers.

‘In the case of “benign” (tertian and quartan) infections
after these agues have recurred for about ten days or two weeks,
the symptoms gradually subside and the patient experiences a
rally. From this point either he may recover completely (even if
untreated) or he may suffer a relapse with all the old symptoms of.
regular agues. Then comes another rally and a second relapse,
this continuing for months or years, aided, perhaps, by constant
reinfections. During all this time general symptoms of emaci-
ation, sallowness, anemia and enlarged spleen constantly in-
‘erease at a diminishing rate with each elapse, and decrease at
-a similarly diminishing rate with each rally, so that eventually a
fairly constant state of spleen-enlargement, emaciation, anemia,
sallowness and general run-down condition is arrived at — the

_ BLACKWATER FEVER 161

well-known condition of chronic malaria, or malarial cachexia,
common especially in children. The spleen enlargement is the
most readily recognizable symptom of chronic malaria and there-
fore the ‘‘ spleen rate,’ 7.e., the percentage of enlarged spleens
in a community, gives a fairly accurate measure of the prevalence
of malaria to which some degree of immunity has been developed.
Usually, unless the weakened condition has given some other
disease a chance to put an end to it all, a general improvement
ultimately begins. This is especially true in children, so that
by the time they reach adult life they are in fairly good health
and immune to malaria.

In the case of estivo-autumnal or malignant malaria the
course of the disease is often not so light, and early death is not
a rare occurrence. The fact that the bodies of the malignant
parasites clump together and plug the capillaries, thus preventing
the proper flow of blood in the vital organs, is probably the chief
cause of their malignant nature. One of the most certain symp-
toms of a malignant attack of malaria is a total loss of conscious-
ness or coma, due to a plugging of the capillaries in the brain.
Indeed, 50 per cent of the deaths from malaria are said to be
caused by a plugging of the brain capillaries. The type of brain
disease which may be caused is very variable but some mental
disturbance almost always occurs, and may take place at almost
any time during the course of the disease, though it never occurs
during the first fever fit, probably because the parasites are not
yet numerous enough to do any great damage.

In connection with malarial fevers there must be mentioned
a much dreaded and little understood condition known as ‘‘ black-
water fever.’ This is a disease in which something destroys
the red blood corpuscles in large numbers, causing the coloring
matter of the blood, hemoglobin, to be liberated, eventually to
be voided with the urine, giving the latter a very dark color.
_ At the same time there is a more or less irregular fever, bilious
vomiting and severe aches. In a great many cases it results in
death. This disease has usually been considered as an outcome
of severe malaria, since it always occurs in malarial countries
and usually follows or accompanies an attack of malaria. It
is not uncommon in southeastern United States, some parts of
tropical Africa, southern Europe and many parts of tropical
Asia and the East Indies. In many other malarial districts it

162 MALARIA

is entirely absent. It is suggested by Manson that the fever is
caused by a distinct organism, and that malaria is merely a
predisposing cause.

Immunity and Epidemics. — Absolute immunity to malaria
is rarely if ever acquired but, as already remarked, oft-repeated
infections especially in childhood tend to build up a high de-
gree of tolerance to the effects of the parasites and a diminution
in the number of parasites in the body. The protection afforded
by a single infection is very slight, and is retained for only a
short time in the absence of reinfections. Even the cumula-
tive effect of numerous infections disappears rapidly in the
course of a few years. Some authors divide malaria into two
types. There is a “tropical” form, occurring in places where
reinfections can occur practically throughout the year on

account of the continued warm temperature. The other, a —

‘“‘ subtropical” form, is found in regions where cold weather
causes an annual seasonal interruption of infection by a cessation
of breeding on the part of Anopheles, and by a discontinuance of
growth on the part of the parasites in the mosquitoes. In tropi-
cal malaria a fairly constant degree of immunity is maintained,
and epidemics are rare if they occur at all. In Java and other
tropical places, according to Robert Koch, nearly every native
child, under four years of age, has his blood teeming with ma-
laria parasites from which he suffers little inconvenience. These
parasites gradually become scarcer in older children and are
often practically absent in adults who, however, have been shown
to be passive ‘‘ carriers’ of small numbers of the parasites and
therefore a source of danger to the community. The “ carriers,”
though relatively immune to the more acute symptoms of the
disease, are left in the run-down condition of malarial cachexia.
As pointed out by Gill, there is a striking analogy between the
confirmed opium-eater and the malarial cachectic. Both have
purchased their immunity at a heavy price. In the former the
emaciated frame, sallow complexion and other signs of debility
proclaim the victim of a drug habit; in the latter the enlarged
spleen, the lack of physical and mental energy, and the shrunken
body bear witness to the havoc wrought by long-standing ma-
laria. In the case of neither does death often take place as the
direct effect of their respective poisons, but both readily fall
victims to intercurrent affections. In subtropical malaria, on

4

—T .. oe fe ee

TREATMENT 163

the other hand, the average tolerance of the community to the
disease suffers an annual relapse, and may constantly decrease
for a number of years. When the immunity of the community
as a whole becomes quite low, and there is a sudden increase in
the probability of infection by a great increase in number of
mosquitoes, accompanied possibly by an influx of infected people,
an epidemic of the disease may occur of such extraordinary se-
verity as to involve almost the entire population, and to cause a
mortality of several hundreds per thousand. Such devastating
epidemics, probably of the subtertian type of malaria, have been
termed ‘‘ fulminant malaria’’ and are believed to occur quite
extensively in malarial countries lying just outside the region of
“tropical”? malaria. Fulminant malaria in especially severe
form occurs periodically in parts of India and in Italy.

It was formerly thought that considerable racial immunity
protected the negro races, but it has been shown that in many
cases, at least, the immunity has been acquired by constant
exposure to the disease, and that it disappears upon removal from
infected regions. The whites in southern United States are said
to suffer markedly more from malaria than do the negroes though
the latter are more frequently parasitized, but this may be due,
in part at least, to the more permanent residence of the latter
in the malarial districts. As said before, individual resistance
to the effects of the disease is variable. Occasionally there is
found a fortunate individual who is naturally absolutely immune,
but this is a very rare occurrence.

Treatment. — It is one of the greatest blessings in the world
that we have for malaria a definite and specific cure as near to
being a “sure cure’”’ as has been discovered for any disease.
Quinine has been found absolutely destructive to malarial para-
sites. While a dose of quinine given during a fever attack will
not act quickly enought to cut it short, it will, if given immediately
after an attack, prevent the next one, or at least alleviate it.
Meanwhile the organisms disappear from the circulation. It is
usually supposed that they are directly killed by the quinine,
which acts as a virulent poison for them, though this is doubted
by some workers. The methods of administering quinine must,
of course, vary with the age and condition of the patient, and the
state of the disease. Sometimes very speedy action is needed,
and it is not safe to wait for quinine to be slowly absorbed from

164 MALARIA

the stomach. Many a patient has died from malaria with
enough quinine in his stomach to have saved his life had it been
properly given. In such cases injections into the muscles, or
still better, directly into the veins, is necessary. In malignant
malaria quinine does not reach the parasites plugged in the
capillaries and therefore can destroy them only as they sporulate
and get back into the circulation. Since the parasites of this
type often sporulate at irregular intervals a constant supply of
quinine at a killing concentration must be kept in the blood.
However, overdosing with quinine is not an uncommon fault
with physicians. Quinine poisoning in some respects resembles
malarial symptoms and the physician, thinking the latter are
not abating, gives still more quinine until the patient succumbs
to it. Not a few malarial deaths are really due to excessive
quinine. Malarial specialists, such as Professor Bass of New
Orleans, say that it is never necessary to give more than ten or
possibly fifteen grains of quinine at a time, if given as the case
requires it. Twenty grains of quinine sulphate a day taken by
mouth in several doses for a period of two weeks is said by Bass to
‘disinfect anyone. Quinine must be avoided during or immedi-
ately following an attack of blackwater fever, since the symptoms
of this malady are intensified by its use.

In case of severe malarial cachexia, the only safe course is for
the patient to leave the malaria-infected country in which he
has been living, and stay away for an extended period of time.
He should take regularly small doses of quinine to kill any lurk-
ing parasites which may remain in his body, and do everything
possible to build up his general health and to regain his lost
vitality.

Prevention. — The prevention of malaria is a problem that
should be solved not by individuals but by civic effort. Ross
says: ‘‘ It (malaria) is essentially a political disease — one which.
affects the welfare of whole countries; and the prevention of it
should therefore be an important branch of public administration.
For the state as for the individual health is the first postulate
of prosperity. And prosperity should be the first object of
scientific government.”’ |

Since the malarial parasites have two hosts, man and mosquito,
the possibility of exterminating them in either host presents itself.
- Stephensport, in New Guinea, was practically cleared of malaria

PREVENTION 165

in a few months by destroying the parasites in man by whole-
sale “‘ quininization.”’ In most places, however, the difficulties
connected with this method of extermination are even greater
than those associated with its alternative, the destruction of
malarial mosquitoes. The relation of partially or entirely im-
mune “ carriers”’ to the spread of malaria is of extreme impor-
tance and is usually greatly underestimated. The number of
such apparently healthy carriers in malarial districts is astonish-
ingly large. Eradication of malaria by attacking it in man would
entail the persistent and thorough quinine treatment of all these
carriers as well as of patients.

Undoubtedly in practically every case, if accompanied by as
extensive a use of quinine as is possible, eradication of malarial
mosquitoes is the most effective and most permanent preventive
measure. A discussion of methods of reducing and controlling
such mosquitoes will be found on pages 455-462.

Complete extermination of malarial mosquitoes is not necessary
to reduce or even to eradicate malaria entirely. Ross has shown
by mathematical computation that a relatively high number of
malarial mosquitoes per person is necessary in a community to
propagate malaria successfully. A small deviation above or
below a certain number of malarial mosquitoes, probably between
40 and 60 per person during a month, a deviation too small to
be detected readily, will mean the difference between an ulti-
mate extermination of the disease and its permanent establish-
ment. Ross also shows that the relation between the amount
of malaria in a given region and the number of malarial mosqui-
toes is so definite that it can be mathematically computed.
These facts are of importance in the fight against malaria since
they demonstrate to us that we do not have to exterminate
totally even the malaria-carrying species of Anopheles in order
to exterminate malaria, and our task becomes much less difficult.
By this partial extermination some of the most malarial districts
_in the world have been practically freed. Up to 1900 over 16,000

deaths a year from malaria occurred in Italy; now they may be
counted in hundreds. One of the first demonstrat ons of what
could be accomplished by mosquito extermination was made by
Major Ross in 1902 at Ismailia on the Suez Canal where from
1100 to 2500 cases of malaria occurred annually in a population
of less than 10,000. Four years later not a single new case

166 MALARIA

occurred there. The same thing on a much larger scale was
accomplished in the Canal Zone at Panama by Surgeon-General
Gorgas and his staff. On this relatively large malaria-infested
area the death rate for the total population of about 100,000 was
reduced 64 per cent in four years. The deaths from malaria
were reduced about 85 per cent in less than four years, and yellow
fever was totally eradicated. Similar feats have been accom-
plished at Havana, Staten Island, and other places. One of the
most recent examples of what can be done was furnished by the
American occupation of Vera Cruz in 1914. The American troops
were severely attacked by malaria of all three types, and an anti-
mosquito campaign was immediately inaugurated. It cost the
Sanitary Department $5000 a month to oil the pools, drain the
low parts of the city and its environs, and dispose of the standing
water in street gutters, refuse heaps, etc., but in a few months
Vera Cruz, one of the most deadly malarial districts in the world,
was practically freed from Anopheles, and danger of malaria
reduced to almost nothing.

Obviously the wholesale reduction or extermination of malarial
mosquitoes can be accomplished only by communities or by
government aid. San Antonio has freed itself of mosquitoes
and mosquito-borne diseases by enlisting the services of the
school children. In our southern states, where there are
65,000,000 acres of swamp land, and where the chief malarial
mosquitoes are swamp breeders, malaria can never be destroyed
until state and federal governments are willing to invest money
as readily to take water off the land in these parts of the country
as they now invest it to put water on the land in the arid western
parts.

Much can be done toward reduction of malaria in selecting
dry brushless sites for houses and in constructing them in mos-
quito-proof fashion. The houses one sees in the. American
Government settlements on the Canal Zone, built well up off
the ground and with open sleeping porches, wide verandas and
airy windows, all carefully screened, are ideal for tropical dis-
tricts where malaria and other insect-borne diseases are common.
They present a happy combination of airiness, sanitation, and
complete protection from insect pests. .

In well-known malarial districts it is a good personal safeguard
to use screens as much as possible and to take regular doses of

QUININIZATION 167

quinine at all times as a preventive measure. In the pine swamps
and along the coasts of Florida malaria is practically absent on
account of the effectiveness of screening .necessitated by the
abundance of non-malarial mosquitoes. Three to five grains of
quinine daily, or ten to fifteen grains once a week, is an almost
certain malaria preventive. Quinine, however, is apt to cause
abortion in pregnant women, though less so than is a severe
attack of malaria. Some people are naturally very susceptible
to quinine and cannot take it; such people should carefully
avoid malarial districts. Tea, coffee and other mild stimulants
are also said to be beneficial, but the safest course is always the
same — quinine,

CHAPTER X

OTHER SPOROZOA, AND OBSCURE OR INVISIBLE
PARASITES

ALTHOUGH the class Sporozoa includes a very large number of
species, all of which are parasitic, and many of them the cause of
fatal diseases in vertebrate as well as invertebrate animals, yet
very few other than the malaria parasites, already discussed,
are normally parasitic in man, and none of these can ‘be looked

upon as of prime importance in the causation of human disease.”
Of greatest importance, perhaps, are the Coccidiida or coccidians,

which in lower animals are frequently the cause of fatal diseases
and have been known to be fatal to man, though in some cases
causing very little inconvenience. Another sporozoan parasite
which is of importance where it occurs is Rhinosporidium, which
produces tumors in the nose. A group of muscle-dwelling
Sporozoa, the Sarcosporidia, occur accidentally or sporadically
in man. |

There is another group of Sporozoa, the Piroplasmata, related
to the malaria parasites, which are the cause of some of the most
fatal diseases of domestic animals, including Texas fever and Hast
Coast fever of cattle, biliary fever of horses, etc. These diseases
are invariably, as far as known, transmitted by ticks. There is
one human parasite, Bartonella bacilliformis, the cause of Oroya
fever of Peru, which is thought to belong to this group of organ-
isms. There is a possibility that Rocky Mountain spotted fever
and the related Japanese disease, kedani, may also be caused by
Piroplasmata, though the parasites have not yet been discovered.

There are a number of other diseases, some of them of great
importance, of which the “‘ germ ”’ either has never been seen or is
of obscure nature. It is not always possible to guess at the
nature of such undiscovered parasites but in Some cases we can
get a fairly accurate conception of them from a study of the course
of the diseases they cause, the conditions under which they thrive
and their means of dissemination. One by one the villains be-

168

re ee ~“e

OBSCURE AND INVISIBLE PARASITES 169

hind the screens are brought to light, experimented with, and
brought under control but there are still some which have defied
the most ardent researches of modern science and have never yet
been discovered. The fact that many of them are able to pass
through filters of certain kinds, as shown by the infectiveness of
fluids containing them after having been passed through the
filters, demonstrates that at least in some stages of their de-
velopment they are actually too small to be visible under the
highest power of the microscope.

However, in the case of some of these unseen parasites we have
sufficient knowledge of their habits and life histories to wage a
fairly intelligent war against them, at least as regards prevention.
The parasite of yellow fever, for instance, has never been seen
with certainty. Yet we know almost beyond question that it is
a protozoan, we know its full life history in a general way, and to
a large extent we know how to combat it, far better, in fact, than
we know how to combat some of the well-known parasites.
There are two other diseases, dengue and phlebotomus fever,
which are quite certainly caused by parasites related to that of
yellow fever, but which have not yet been discovered. Until
recently typhus fever was included in the list of possible proto-
zoan parasites but Plotz in 1914 discovered a bacillus which is
now quite generally believed to be at least partially the cause
of that disease. Rocha-Lima and others have found certain
minute bodies in typhus-infected lice which they suspected might
be of protozoan nature, and Rocha-Lima has named them
Rickettsia prowazeki.* American investigators are inclined to
look upon these bodies as forms of the bacillus discovered by
Piotz.

Several other diseases, some of them of prime importance, of
which the parasites are of obscure nature, are believed by some
workers to be caused by Protozoa: such are hydrophobia or
rabies, trachoma, smallpox, verruga peruviana (not Oroya fever),
foot-and-mouth disease, measles, scarlet fever and a few others.
The parasites or parasite-like bodies which are associated
with these diseases are in some cases minute, in other cases,
e.g.. hydrophobia, of relatively large size. In most of these
diseases the “ germ” or virus is capable of passing through
ordinary bacterial filters, as shown by the infectiveness of filtered
material. It is also evident from this that the viruses live out-

* See footnote on p. 73.

170 OTHER SPOROZOA

side the cells or blood corpuscles, at least during part of their
life history. On the other hand, in these diseases there have
been discovered bodies of various kinds within the cells, inter-
preted by some workers as true parasites, by others as reaction
products of the cells. These bodies have received zodlogical
names, e.g., the Negri bodies of hydrophobia were named Neuro-
ryctes hydrophobie, the cell inclusions in smallpox Cytoryctes
variole,andsoon. It is now a commoner belief that these bodies
consist of material extruded from the nucleus of the cell into its
cytoplasm where it surrounds one or many of the minute or- .
ganisms during the intracellular portion of their life history.

For these problematical organisms, minute in size, of uncertain
life history, and apparently enshrouded in a mantle of extruded
nuclear material during their intracellular life, the name Chlamy-
dozoa (meaning mantle animals) has been given. Whether these
bodies have been correctly interpreted as described above and —
whether they should be considered Protozoa is open to question.
Their animal nature has not been sufficiently demonstrated to
warrant more than brief mention of them and the diseases they
cause in a treatise on animal parasites.

In the following paragraphs the sporozoan parasites and ob-
scure or invisible parasites which have been briefly mentioned
above will be discussed in a little more detail in the following
order: (1) coccidians, (2) Rhinosporidium, (3) Sarcosporidia,
(4) Oroya fever, (5) the yellow fever group, (6) the spotted fever
group, (7) Chlamydozoa.

Coccidians

There are a number of serious diseases of animals which are
caused by parasites of the class Sporozoa known as coccidians.
These are very small animals, without distinct organs of lo-
comotion, which have both an asexual and a sexual phase in
their life history (Fig. 48). The asexual phase is not unlike
what takes place in the asexual phase of malaria parasites, ex-
cept that the parasites live inside of cells lining the intestine
instead of in the blood. Like the malaria parasites, a coccidian,
within the epithelial cell in which it is living (Fig. 48A—C), di-
vides into two, four, eight, sixteen, or perhaps twenty or more
daughter cells, arranged somewhat like the segments of an
orange (Fig. 48D). The young coccidians, escaping from the

COCCIDIANS 171

host cell which has been preyed upon and destroyed, invade fresh
cells, multiply again, and thus eventually destroy large portions
of the lining of the digestive tract. The daughter coccidians
are not adapted for withstanding conditions outside the intestine

In

intestine.

Fic. 48. Life history of Eimeria avium. A, infection of epithelial cells of in-
testine by sporozoites ingested with food or water; B, growth inside cell; C and D,
sporulation and formation of young spores; E and G, formation of female gamete;
F and H, formation of male gametes; J, fertilization; J, fully developed odcyst as
passed out with feces; K, LZ and M, formation of four sporocysts; N, complete
development of sporocysts, each containing two sporozoites; O, same, ingested by
susceptible animal; P, sporocyst liberated from odcyst in alimentary canal; Q,
liberated sporozoite ready to infect epithelial cell, as shown in A.

of the host, and therefore the. parasite would be exterminated
with the death of its host were it not protected in some manner
against this calamity. The sexual phase of its life history serves

te OTHER SPOROZOA

this important purpose. Probably stimulated by reactions
against them on the part of the host certain coccidians, instead
of multiplying in the usual manner, differentiate into sexual
forms, some transforming into large immobile egglike female
individuals or macrogametes (Fig. 48E and G), others dividing |
into numerous very active flagellated spermlike male individuals
or microgametes (Fig. 48F and H). One of the spermlike in-
dividuals penetrates an egglike individual and fuses with it
(Fig. 481), in precisely the same manner as a spermatozo6n
fertilizes an egg in higher animals. The fertilized individual
develops a thick resistant cyst wall and is then known as an
“odcyst’”’ (Fig. 48J). The parasite is now ready to hazard the
dangers of an exit into the outside world, and is passed out with
the feeces. Eventually, sometimes within a few days, the con-
tents of the odcyst divide into several parts, each known as a
“sporocyst ” (Fig. 48K, L and M). Each sporocyst in turn
develops within itself a number of “sporozoites” (Fig. 48N),
each capable of infecting a separate cell
in a new host. The odcysts with their
contained sporocysts and sporozoites can
exist in soil or dust for a long time,
awaiting an opportunity to enter a new
Rie 40. Ogee ets victim with food or water.

spora from British soldier | Infection with coccidians has not often
No eae eee been observed in man but it is pos-
sporocysts, each with four sibly more prevalent than is commonly
ees 1000. (After thought. A few cases have been re-

ported of human infection with a coc-
cidian very similar to Eimeria stiede, which infests the intestine
and liver of rabbits; some workers believe these cases to have
been caused by this very species, and that infection probably
resulted from eating infected livers of rabbits. Recently Wen-
yon has reported the not uncommon occurrence of odcysts of two
species of coccidians in the feces of British soldiers returning
from Gallipoli. The cysts of the commoner species, of the genus
Isospora, contain a single mass of protoplasm when first passed,
but in three or four days they become fully developed and con-
tain two sporocysts, each with four sporozoites (Fig. 49). The
cysts of the other species, referred to the genus Eimeria, differ
in producing four sporocysts, each with two sporozoites (Fig.

RHINOSPORIDIUM lis

50). Little is known of the symptoms produced by these para-
sites, but since they live inside epithelial cells of the intestine
or liver they must be injurious. Wenyon has recently reported
dysenteric symptoms in a case in which
no intestinal parasites except Isospora
were present. Coccidians are un-
doubtedly spread by means of water
or food polluted by mud and dirt, by
unsanitary habits, and by flies.

Rhinosporidium, a Parasite of the
Nose

In natives of India there is occasion- — yyg. 50, Odcyst of Eimeria
ally observed a peculiar infection of the containing four sporocysts, each
nose in which a red tumor, flecked with eee Oe,
whitish spots, and likened by some authors to a raspberry, grows
out from the partition or septum of the nose, remaining attached
by a narrow stalk. The tumors are not very painful, but they
tend to block the nasal passages. It has been suggested that
this disease, known as nasal polypus, may have the same in-
fluence on the intellect of children that other impediments of
the nose and throat are known to have.

When the tumor is cut the white spots visible on the surface
are seen to be scattered throughout the tissue and to be of very
variable size. Microscopic examination shows them to be the
cysts of a protozoan parasite in various stages of development.
The parasite has been named Rhinosporidium kinealyi, and is
classified as a member of the group of Sporozoa known as Hap-
losporidia.

The cysts in the tumor are filled with great numbers of spherical
or oval bodies, the pansporoblasts, each of these in turn contain-
ing from one to a dozen closely-packed spores (see small portion
of a cyst in Fig. 51). The manner of development of the cysts
and of the tumor can readily be discovered from the various
stages of development of different cysts and parts of cysts which
can be observed in a single tumor. The youngest cysts are small
granular masses of protoplasm, more or less irregular in shape.
As one of these minute animals grows there are developed within
it small bodies with definite shape which are destined to become
the pansporoblasts already mentioned. However, the proto-

174 OTHER SPOROZOA

plasm at the periphery of the animal continues to grow, constantly
becoming differentiated into new pansporoblasts. The young
pansporoblasts (Fig. 51, yg. pansp.), at first simple masses of
protoplasm, soon form within themselves one, two, four, and
ultimately as many as 12 spores, tightly clumped together so
as to resemble little mul-

O.W .-- = SS berries (Fig. 51, mat.
PES : CROSOH ae
BOS B200 pansp.). From the mode

US: PR ee "Ox of development of the
eysts it is clear that the
older pansporoblasts are
the ones near the center
of the cyst, the younger
ones those toward the
periphery. When the
cysts have reached a
certain size the growth
of the periphery ceases,

ae all the pansporoblasts ma-
Fic. 51. Portion of fully developed cyst of

Rhinosporidium; ce. w., cyst wall; yg. pansp., ture and the Cy’ st ruptures,

young pansporoblasts; mat. pansp., fully de- liberating the spores into
veloped pansporoblasts containing spores, sp. ef di i
xX about 100. (After Fantham and Porter.) € surrounding 1ssue,

each to develop into a
new cyst. How the parasites are transmitted to new hosts is
not known. :

A similar disease was found some years ago in South America
and a parasite, then named Coccidium seeberi, has been described
from the tumors. It is possible that this may be the same
organism as that of Indian nasal polypus, but according to Fan-
tham, who was one of the original describers of Rhinosporidium,
there are a number of differences between them.

=,

Sarcosporidia, Parasites of the Muscles

Brief mention should be made of a group of Sporozoa known
as the Sarcosporidia which develop relatively enormous cysts
in the muscles of vertebrate animals, especially in mammals.
These parasites are usually found in the striped muscles but they
also occur in other muscles. Infected muscles (Fig. 52B and D)
appear to have white streaks or patches in them, sometimes

SARCOSPORIDIA 1S

several inches in length. Microscopic examination shows that
these patches are cysts containing thousands of tiny spores,
segregated into chambers (Fig. 52A) which correspond to the
pansporoblasts of Rhinosporidium. The spores (Fig. 52C), es-
caping from the cyst, ultimately develop into new cysts in much

Tea LUA MUTOL THE maa
ae et 3 ! rm asl ATT eat ae
fi ore saa taeciowe a ee ree ae % cect Seal ie it
srraye ene orm it inn ui Fr re

Fic. 52. Sarcosporidia. A, Sarcocystis blanchardi of ox, longitudinal section of
infected muscle fiber (m. f.) showing spores (sp.) in chambers of compartments
(comp.); n., nucleus of muscle fiber, x 265. (After von Hecke from Wasilewsky.)
B, cross section of sarcocyst from human larynx, probably S. tenella, ~« 200. D,
same, longitudinal section. (After Baraban and St. Remy.) C, spore of S. tenella
of sheep. (After Laveran and Mesnil.)

the same way as is the case with the nose parasite. Although
the muscle parasites have been known to parasitologists for
many years there are portions of the life history which are not
yet known. Darling and others have suggested that these pe-
culiar protozoans may be “ side-tracked varieties of parasites of
invertebrate animals.”’ We have no definite knowledge of the
normal means of transmission although a number of possible
methods are known. It has been found that infections can be
spread by cannibalism, and that the feces of infected mice can
infect other mice; it has also been stated that spores occur in
the circulating bloéd, which would mean that blood-sucking ar-
thropods may be instrumental in the transfer. Fleshflies may
also play a part in dispersing the spores.

Erdmann has shown that when spores of Sarcosporidia de-
velop in the intestine a very powerful toxin, called sarcocystin,
is discharged and destroys the neighboring epithelial cells of the
intestine and thus breaks a way for the young parasite into the

176 OTHER SPOROZOA

lymphatics and ultimately into the muscles. Crawley has re-
cently described in Sarcocystis muris of mice what he interprets
as sexual differentiation of the spores and fertilization within
18 hours after the spores have been ingested by mice. Crawley
believes the Sarcosporidia to be closely allied to the Coccidia, and
suggests that there may be an unrecognized stage of development
in a carnivorous animal. It is quite evident from the various
hypotheses and speculations mentioned above that there is much
yet to be learned about these enigmatic parasites. ;

Only a few scattered cases of Sarcosporidia in man have been
recorded, and these may be looked upon as purely accidental.
The parts affected have been the muscles of the heart and larynx.
Many speculations as to how these infections occurred have been
made, but nothing definite is known about it. It is probable
that the human infections are due to Sarcocystis muris, a species
which produces a very fatal disease in mice, and infections may
have been due to contamination of food or water with the ex-
crement of infected mice. The use of meat of Indian buffaloes
infected with another species, Sarcocystis tenella bubali, seems to
have no injurious effect on man, but ingested spores cause ir-
regular fever.

Oroya Fever

The Disease. — Since at least the time of the Incas, Peru has
suffered from a strange disease which has swept over the country
from time to time in the form of frightful epidemics, some of
which have cost thousands of lives. One of the severest recent
outbreaks occurred among the workmen building the Peruvian
Central Railway between Lima and Oroya and it is estimated
that at least 7000 individuals died in it. In 1906 at least one-
tenth of 2000 workmen employed building tunnels and bridges
on the Central Railway died of the fever, and one bridge in par-
ticular, which was the scene of a great many deaths from the dis-
ease, has come to be known as the Oroya Fever Bridge (Fig. 53).

The disease is at present endemic in the deep cleft canyons or
quebradas (Fig. 53) characteristic of the west face of the Andes, at
an elevation of between 2500 and 8000 ft., but it is probable that it
has a wider distribution than is now supposed. It shows a marked
seasonal prevalence, most of the cases occurring from January to
April, especially toward the close of the warm, rainy season.

Se

OROYA FEVER 177

Fic. 53. Above, a typical ‘ quebrada’’ or canyon on the west slope of the Andes
where Oroya fever abounds. Below, the famous ‘‘Oroya Fever Bridge”’ on Peruvian
Central Railway where hundreds of lives were lost from Oroya fever. (Photos
kindly lent by Harvard School of Tropical Medicine, previously published by

Strong et al.)

178 OTHER SPOROZOA

Oroya fever has been constantly confused with other diseases
and it was not until the South American expedition of the
Harvard School of Tropical Medicine, under the leadership of
Dr. R. P. Strong, made an investigation of the disease that
some order was brought out of the confusion. Malaria, para-
typhoid, and particularly verruga peruviana are the diseases
which have been most frequently confused with Oroya fever.
Mixed infection of these diseases and others such as yaws and
tuberculosis with true Oroya fever has still further complicated
matters. From the time of the Incas verruga peruviana and
Oroya fever have been associated and regarded as different phases
of the same disease, and this view is still held by some investi-
gators. The fact that the characteristic nodules of verruga were
usually associated with a very mild form of fever and sometimes
with none at all, while oroya fever was of very severe type caus-
ing very high fatality, raised some question as to the distinctness
of the diseases. To settle this point a Peruvian medical stu-
dent, Daniel Carrion, vaccinated himself with blood from a
verruga nodule. Five or six weeks later he died of a severe
fever, and the question of the identity of the disease was ap-
parently settled, and the fever was called ‘‘ Carrion’s Fever ”’
‘in his honor. The notes regarding Carrion’s illness have been
lost.and it is now believed that he may have died of some other
disease or that the patient from whom he inoculated himself
may have been suffering from some other disease in addition to
verruga.

As a result of their own studies, Dr. Strong and his colleagues
believe that the diseases are quite distinct. They have shown
that Oroya fever is caused by a very minute parasite living in
the red blood corpuscles and multiplying in the endothelial cells,
and that it cannot be inoculated into animals; verruga peruviana,
on the other hand, is caused by a virus which is ultra-microscopic,
probably related to the smallpox virus, and can be successfully
inoculated into laboratory animals. It is easy to understand
how the two diseases were confused, since to a large extent their .
ranges overlap and a visitor to endemic regions would be likely
to contract both. Verruga, being less quickly contracted and
having a longer incubation period, would tend to appear later
than Oroya fever, and would therefore be looked upon as a later
stage of the same disease. The native belief that a general erup- -

BARTONELLA BACILLIFORMIS 179

tion was favorable to recovery, a belief undoubtedly based upon
the benign nature of verruga, leads to the adoption of all sorts of
methods to invoke a breaking out of the skin, such as applications
of turpentine, rubbing with irritant leaves, etc., and undoubtedly
a great many cases of eruptions following Oroya fever are really
only the eruptions caused by the artificial irritation of the skin.

Oroya fever, after an incubation period of about 20 days, begins
with a general feeling of malaise and aches in the joints, followed
by chills and fever, which last irregularly for many weeks. The
fever is accompanied by a rapid pernicious anemia, the red blood
corpuscles being reduced in some cases to one-fifth, or even less,
of their normal number. This causes severe prostration and
in a large per cent of cases death results within three or four
weeks. The skin assumes a yellowish waxy color, and there are
often slight hemorrhages of the mucous membranes and various
internal organs, as demonstrated by post mortem examinations.
The liver and spleen become moderately Sie and the lymph
glands are swollen.

The Parasite. — The true parasite of Oroya fever was first
discovered by Barton, of Lima, Peru, in 1905 and confirmed by
him in 1909, at. which time he
suspected that it might be a
protozoan. The parasites were
more thoroughly studied by
the Harvard expedition in 1913
and 1914 and named Barton-
ella bacilliformis. Dr. Strong 3232
and his colleagues describe ‘2Qy
them as minute rods or, more Fie. 54. Bartonella bacilliformis, liv-

: ing. <A, B and C, successive drawings of
r arely, rounded bodies occur- a single red corpuscle showing movements
ring inside the red blood cor- of parasite within it; D, H and F, corpuscle
- = containing two rod-shaped and four round
puscles (Figs. 54 and 55). parasites, showing migrations of the rod-
These parasites, the rod form shaped individuals. x 2000. (After
of which are cont 1D $052.5. 0 eae)
(less than ;,4,, of an inch) in length and the round bodies 0.5 to
1 » in diameter, are definitely motile, moving about freely inside
the corpuscles. In severe infections there may be found from
one to ten parasites in a single corpuscle.

A multiplicative stage of the parasite occurs in large swollen

endothelial cells in the lymph glands and spleen. . In these swollen

180 OTHER SPOROZOA

cells are minute
rounded bodies, some-
times a few, some-
times great masses of
them (Fig. 56B).
Some of these rounded
bodies contain only
one, two or four deep
stainng granules
(Fig. 56A), while
others contain large
numbers of them.
It appears that these
granule - filled bodies

break up into a large
sos 85, Bara cms, ined Hod number of parts each
parasites. Bodies with large dark nuclei are leuco- containing one gran-
cytes (leuc.). xX about 1000. (After Strong et al.) ule; these become
elongated, and finally
appear as distinct rods
containing the gran-
ule at one end. In
this condition they
are identical with the
parasites which occur
in the red blood cor-
puscles (Fig. 56C) and
indicate the manner
in which the corpus-
cular parasites arise.

| aol e% Dr. Strong and his

Fic. 56. Development of Bartonella bacilliformis . ..
in endothelial cells. A, endothelial cell, with large COlleagues believe
nucleus (n.) at left, containing five rounded bodiesin Bartonella bacilli-
early stage of development; B, endothelial cell show- .
ing rounded bodies developing large numbers of small f ormis to be a pro-

rod-shaped parasites; C, red corpuscles lying near tozoan probably re-
with parasites identical with those escaping from such
a cell as shown in B. xX 2000. (After Strong et al.) lated to the group of

parasites known as
the Piroplasmata, including the Texas fever parasite of cattle and
a number of other disease-causing parasites of wild and domestic
animals. Its exact classification cannot yet be determined, and

TRANSMISSION OF OROYA FEVER 181

it is simply looked upon as possibly belonging to a group of micro-
organisms intermediate, as perhaps are the spirochetes, between
Bacteria and Protozoa, but with a decided leaning toward the
latter.

Transmission. — The method of transmission of Oroya fever
is still in doubt, but it seems practically certain that some ar-
thropod acts as a transmitting agent. All the other parasites
of the group to which Bartonella belongs are transmitted by ticks,
but there is apparently no tick having habits compatible with the
occurrence of the disease. The Harvard expedition attempted
to obtain the development of Bartonella in a mosquito, Pha-
langomyia debilis, which is common in the infected zones, but
without success. That the transmitting agent is a nocturnal
blood-sucker of very limited distribution but abundant within
its range is strongly indicated by the limitations of the disease ~
and by the fact that in many cases a single night in the infected
zone is sufficient for contracting it, whereas there is apparently
no danger a short distance from the infected zone, or within it
in the daytime. According to Townsend, who spent two years
investigating verruga (which he considers identical with Oroya
fever) the only arthropod which fulfills all the conditions is a
sandfly, Phlebotomus verrucarum, which is a very abundant
nocturnal blood-sucker apparently limited in its distribution to
the verruga zones. Townsend attempted experiments with the
transmission of the disease through the agency of this insect but
his results have not been generally accepted. Whether or not
Phlebotomus is instrumental in transmitting Oroya fever is a
matter which will have to be proved by further research but the
circumstantial evidence against the insect is strong.

As pointed out by Townsend, the portions of Peru which are
haunted by Oroya fever and verruga have one of the most perfect
and healthful climates in the world and they would be ideal for
sanatoriums and resorts were it not for these diseases. It is to
be hoped that the diseases may soon be more thoroughly worked
out and gotten under control. However, if Phlebotomus is in-
strumental in the transmission of either, the hope of eradicating
them in the near future is slight, judging by the difficulties which
have been experienced in Mediterranean countries in controlling
these minute rock-breeding insects.

182 OTHER SPOROZOA

The Yellow Fever Group

More or less widely distributed in all warm countries are three
diseases, yellow fever, dengue and phlebotomus fever, which
have many features in common and in fact are often mistaken for
each other. They form a series, in the order named, of succes-
sively milder diseases. Yellow fever is one of the most vicious
of human diseases and is accompanied by a very high fatality;
it has been a source of terror in all countries in which it has
flourished. Dengue is a much milder disease and is seldom
fatal, though its after-effects linger for many months. Phle-
botomus or three-days’ fever is a still milder disease and, as its
name implies, of short duration. Like dengue it has lingering
after-effects but they are not so severe or so persistent as in the
former disease. |

All three of these diseases are caused by ultra-microscopic
blood parasites which are transmitted by dipterous insects in
which they apparently undergo part of their life cycle. The
diseases each begin with a sudden high fever and headache, and
pass through essentially similar stages, intense rheumatism-like
aches being very characteristic of all. Each disease confers
immunity, almost always permanent in yellow fever, often of
long duration in dengue, and very transitory in phlebotomus
fever. There seems to be little room to doubt that the parasites
of these three diseases must be closely allied, and the possibility
exists that immunity conferred by one may give at least partial
immunity to the others. Were this found to be the case the in-
oculation of the milder diseases, dengue or phlebotomus fever,
in regions haunted by yellow fever might be a proceeding well
worth the cost.

Yellow Fever

Distribution. — Yellow fever is a disease which is especially
characteristic of the seaport towns of tropical America, although
it is also endemic on the ,west coast of Africa, whence many
think it was imported to America with the slaves. Its approxi-
mate distribution is shown in Fig. 57. In the past, before the
days of the strict quarantine laws now enforced, serious epidemics
of this dread disease appeared during the summer in numerous
seaports of subtropical and temperate countries. At one time

DISTRIBUTION OF YELLOW FEVER 183

there was no city on the whole Atlantic and Gulf coasts of the
United States which was exempt from yellow fever epidemics, and
the disease exerted a serious influence on the economic conditions,
especially of our Southern States. In New Orleans there have

MA

Fig. 57. Map showing geographic distribution of the yellow fever mosquito,
Aédes calopus (black lines), and former distribution of yellow fever (red stipple).

been epidemics which have cost thousands of lives, the last one
occurring in 1905. In temperate cities the epidemics always
ended with the coming of frost and destruction of the transmitting
mosquitoes. Now the situation is quite different and there is
no reason to believe that the world will ever again see such a sight
as was formerly only too common — a frantic, terrorized city
helpless in the grip of a deadly yellow fever epidemic. No
epidemic has occurred in the United States since 1905 and many
of the tropical cities, such as Havana, Manaos and Rio de Janiero,
which were formerly famous as endemic centers of the disease,
~ and from which it was carried to seaports in all parts of the world,
are now practically free from it. It is only in such notoriously
unsanitary cities as Guayaquil in Ecuador and Buenaventura in
Colombia that yellow fever still rages, with little or no attempt
on the part of the inhabitants to stamp it out.

Nature of the Disease.— Our present knowledge of the
nature of yellow fever and of its dissemination, which has made
possible the scientific checking of the disease and will undoubtedly

184 OTHER SPOROZOA

result ultimately in its complete extermination, is largely the
result of the noble and self-sacrificing work of the American
Yellow Fever Commission appointed in 1900, consisting of Reed,
Carroll, Lazear and Agramonte. Three of these illustrious
men, Doctors Lazear, Reed and Carroll, lost their lives directly
or indirectly as the result of their work, but their achievements
are of inestimable value to the human race and their names will
not soon be forgotten.

Yellow fever was shown by the American Commission to be
not a contagious disease, but one which can be transmitted only
by the yellow fever mosquito, Aédes calopus, or by injections of
blood from an infected person. The “ germ ”’ lives in the blood
serum and not in the corpuscles, and is only infective for three
or four days after the appearance of the disease. It is in all
probability an ultra-microscopic protozoan since it can pass
through filters which will retain organisms on the borderland of
visibility and since no one has yet been successful in discovering
it. Numerous supposed yellow fever parasites have been found,
but none of them will stand the test of critical scientific exami-
nation. Conspicuous among these discoveries of yellow fever
parasites stand (1) Bacillus icteroides, discovered in the blood of
yellow fever patients by Savarelli and since shown to have no
causal relation to the disease; (2) Myzxococcidium stegomyie,
discovered in infected yellow fever mosquitoes by a “ Working
Party ” appointed by the American Yellow Fever Institute;
and (3) Paraplasma flavigenum, discovered in the blood of
- yellow fever patients and of experimentally infected animals
by Seidelin in West Africa, but also found by other workers in
uninfected animals and not generally accepted as the cause of the
disease. | |

Since the mosquitoes cannot transmit the disease by biting -
until 12 or 14 days after sucking infected blood the parasites
evidently undergo a cycle of development in the mosquito as do
the malarial parasites. The appearance and habits of the yellow —
fever mosquito are described on page 4438.

The Disease. — Yellow fever has an incubation period of
from three to six days. The first symptoms are severe headache
and aches in the bones, followed by a sudden fever during which
the face is flushed and swollen and the skin dry. This fever
slowly subsides, and after three or four days there is a period

YELLOW FEVER 185

of “calm ”’ during which the temperature is near normal but the
pulse very slow. By the third day the skin usually becomes a
characteristic yellow color, which, as the disease progresses,
changes to a deep coffee brown. A striking but not invariable
symptom, and one of ill omen, is the “ black vomit,” a gushing
up through the cesophagus of a coffee-colored or even black fluid,
consisting largely of fragments of red blood corpuscles and freed
hemoglobin, and sometimes even pure blood. The period of
“calm ”’ may lead to recovery in a few days or there may be a
second fever which lasts irregularly for a longer time than the
first.

Yellow fever is a very fatal disease. During the French
operations at Panama relay after relay of laborers were stricken
with the yellow plague and were turned loose to die without
mercy or help, to be replaced by a new set. Not only the laborers
but the engineers, nurses and others were stricken down. One
vessel is reported to have brought over 18 young French engi-
neers, all but one of whom died of yellow fever within a month
after their arrival.

Fortunately yellow fever gives a permanent immunity after
one attack has been successfully withstood. In children the
disease is often very mild so that it is frequently not even recog-
nized, yet the immunity it gives is permanent. Natural im-
munity is unknown in any race, sex or age, though the negroes
suffer less from the disease and have a much lower per cent of
mortality than the whites.

Treatment and Prevention.— There is no special drug so
far known which acts as a specific poison against the yellow fever
parasites. Careful nursing and perfect hygienic conditions are
the best remedies we have. The eradication of yellow fever
consists simply in the extermination of the yellow fever mos-
quito, Aédes calopus. The habits of the insect, as described on
p. 444, are such that it is not difficult to combat and successful
campaigns against it, with a resultant obliteration of yellow
fever, have been made in many places. In Louisiana the anti-
mosquito campaigns have been so effective that Aédes calopus,
once one of the most abundant pests, is now nearly exterminated
in all parts of the State, and there has been no endemic or epi-
demic yellow fever since 1905. Panama, Havana, Rio de Ja-
niero, and recently Manaos and Yquitos, are conspicuous examples

186° OTHER SPOROZOA

of tropical cities which have been cleared of the disease which once
made them highly dangerous to visitors and a menace to the
rest of the world. In connection with an incessant war on the
transmitting mosquito in all stages of its life history, all known
or suspected cases of yellow fever should be carefully screened
so that mosquitoes can have no access to them. © Personal pre-
vention in endemic regions consists in avoiding mosquito-haunted
places at all times when A édes calopus is likely to be active.

Dengue

Dengue, seven-days’ fever, or breakbone fever, is a disease of
tropical and subtropical countries. It is very common in the
West Indies and great epidemics have swept through Panama,
the eastern Mediterranean and southern Asian countries, the
Philippine Islands and various South Sea Islands. An epidemic
has recently been reported from Argentina and Uruguay, the dis-
ease supposedly having been introduced from Spain. Dengue also
occurs in southern United States where it is probably often over-
looked, being diagnosed as something else. In some places, e.g.,
southeastern Europe and India, there is some confusion between
dengue and phlebotomus fever. Both diseases vary somewhat
and mild types of the former and severe types of the latter may
easily be, and frequently are, confused. Dengue occurs in the
form of sudden and rapidly spreading epidemics which sweep
over limited areas, affecting a large per cent of the popu-
lation. 3 ae

Nearly every fluid and organ of the body has been examined
in an effort to find the organism causing dengue, but although
many supposed parasites have been found, the true cause of the
disease is still unknown. In at least one stage of its life history
the parasite, like that of yellow fever, is ultra-microscopic. That
the disease is transmitted by the tropical house mosquito, Culex
quinquefasciatus, and, in Australia at least, by Aédes calopus, has
been proven by experimentation. The distribution of dengue
coincides almost exactly with the geographic range of Culex
quinquefascratus.

Unlike yellow fever, dengue has a very short incubation period
in the mosquito—%in one experiment it was only 48 hours.
This fact, together with the short incubation period in the

DENGUE 187

human body (from two to five days), explains the rapidity with
which dengue epidemics spread.

The disease begins with startling suddenness. Within a few
hours a normal healthy individual acquires a prostrating fever,
a severe headache and terrible aches in the bones and joints
which make it necessary to lie still. His face and sometimes
his whole body becomes flushed and purple with congested
bloodvessels, and the patient is to say the least very miserable.
In a day or two the fever moderates, and usually is terminated
by a sudden crisis of nose-bleed and diarrhea, relieving the con-
gestion which has been felt in all parts of the body. Then follows
an interval of apparently normal condition during which the
patient feels perfectly well. After a few days there is a return
of more or less severe fever and aches accompanied by a measles-
like rash. The latter fades in from three to five days and is fol-
_ lowed by a powdery scaling off of the skin. If lucky, the patient
now quickly recovers but more often he has lingering and recur-
ring aches in various joints, especially the knees and ankles, and
he may be thus afflicted for several weeks before final recu-
peration, whence the name “ breakbone fever.’’ The disease is
dangerous to life only if complicated in some way.

An attack of dengue usually confers immunity on an individ-
ual but this sometimes lasts only a year and is sometimes not
established at all, since more than one attack during a single
epidemic has been known to occur.

There is no specific remedy known that will cure dengue.
Care of the general health, including measures to lessen the fever,
headache and bone aches, help in making life worth living during
the eight or ten days of suffering.

Once an epidemic has broken out, it is almost as useless to
attempt to stop it as to stop a tidal wave, as far as the mass of
the people is concerned. Houses screened against mosquitoes,
if available, are havens of refuge, but the tropical villages or
cities in which there are enough screened houses to care for even
a small per cent of the population are hopelessly lacking, and the
rapidity of the spread of the disease makes the isolation of early
cases in mosquito-proof wards almost futile. Anti-mosquito
~ campaigns, conducted not merely during an epidemic but at all
times, are the only methods now known of preventing epidemics
of dengue or of lessening their local prevalence.

188 OTHER SPOROZOA

Phlebotomus Fever

Of the same general nature as yellow fever and dengue, and
_ concluding this series of gradually milder diseases, is phlebot-
omus or three-days’ fever. This disease occurs especially on
the shores of the Mediterranean and in India, and possibly also
in other parts of the world. In endemic countries it occurs in
the form of annual epidemics. It is estimated that in the earth-
quake regions of Italy where the disease is especially prevalent,
50,000 persons are attacked annually, incurring a financial loss
of over $7,000,000 by the prolonged incapacitation for work which
follows the disease. In central India, every non-immune person
is said to be attacked by the end of June each year.

Phlebotomus fever begins suddenly, like dengue, with a high
fever, severe headache and aches in the bones and joints. The
nervous symptoms are marked, and the pulse and respiration
are accelerated. Usually the fever subsides on the third day,
though in India it often lasts four or five days. The aches and
general depression continue for ten or twelve days or even longer
after the disappearance of the fever.

The disease, the parasite of which has never been discovered,
is transmitted by the gnat or sandfly, Phlebotomus papatasii
(see p. 470, and Fig. 212), which is extremely abundant in the
regions where phlebotomus fever is endemic. The appearance
and habits of this insect are described on p. 471. The prevalence
of phlebotomus fever in the earthquake districts is due to the
abundance of ideal breeding places for the gnats furnished by
the ruined walls. It is possible that other species of Phlebotomus
may also transmit the disease.

The gnats become infective about a week after feeding on an
infected person. The incubation period of the disease in man is
about four or five days. Natural immunity is extremely rare,
but in most cases an immunity of long duration results from an
attack of the disease.

No specific cure has yet been discovered. Prevention lies
in avoiding the bites of Phlebotomus papatasit and in reducing
their numbers as far as possible by methods described on p. 478.
In case of prolonged residence in an endemic region, there is
little hope of escaping infection, and willful exposure to it at a
time when the disease will be least inconvenient is usually ad-
visable, in view of the usually persistent immunity which results.

ROCKY MOUNTAIN, SPOTTED FEVER 189

Spotted Fever Group

In the Rocky Mountain districts of northwestern United States
there exists a disease commonly known as Rocky Mountain
spotted fever. In certain parts of Japan and in some of the
East Indian Islands and Malay States there occurs a very similar
disease known as kedani or flood fever, in Sumatra called pseudo-
typhus. These diseases, widely separated as they are, have a
remarkable number of points in common. Both are caused by
parasites, presumably protozoans, which have not yet been dis-
covered; both are transmitted by members of the order Acarina,
spotted fever by ticks and
kedani by mites, though it is
believed that the Sumatra type
of kedani may be transmitted
by ticks also. Both diseases
have a short incubation period,
and both follow a very similar
course —a skin eruption, con-
tinued high fever, and fre-
quently high fatality. It is
quite probable that these two
diseases will be found to be
caused by closely related para-
sites. Their occurrence in such
widely separated localities as |
northwestern United States _ Fie. 58. Map showing distribution of
and eastern Asia is an inter- Rocky Mountain spotted fever. | Com-
esting fact.

Rocky Mountain Spotted Fever.— For many years certain
limited districts in the Rocky Mountain region of northwestern
United States (Fig. 58), particularly Idaho and Montana, have
been known to be affected by this very serious disease. Its
yearly occurrence in well-defined areas has given rise to panic
and hysterical fear of entering the ‘‘ haunted ”’ places. Houses
were deserted, land depreciated in value, and some of the richest
valleys in the Northwest left unpopulated. In 1906 it was
shown by Ricketts that the disease was invariably preceded by
the bite of a common local wood-tick, Dermacentor venustus (see
p. 361, and Fig. 156), which was experimentally shown to be
the intermediate host of the parasite.

190 | OTHER SPOROZOA

Various supposed parasites have been discovered but the dis-
coveries have never been substantiated by subsequent investi-
gations, and the disease germ of spotted fever is still unknown
unless the recent discovery of certain small bodies of supposed
protozoan nature by Dr. Fricks should be proved by future in-
vestigation to be the true cause of the disease.

Spotted fever is transmitted by Dermacentor venustus and
possibly by other closely allied species of ticks; experimentally
it can be transmitted by other ticks, including species found in
eastern United States. The incubation period in the tick is un-
known but it is probably only afew days. In man the incubation
period is usually from four to seven days. The disease begins
with a general feeling of illness followed by chills and aches. A
constant fever gradually increases until the tenth or twelfth day,
when death is likely to occur. In mild cases the fever gradually
subsides during the five or six days following. Usually on the
third day a rose-colored rash breaks out on the head and upper
part of the body, followed a day or two later by a characteristic
spotting of the arms and legs, and later of much of the body,
caused by the bursting of blood capillaries in the skin. The.
spots often become brownish or grayish in color, giving the spotted —
appearance from which the disease takes its name. In Montana,
especially in the Bitter Root Valley, the disease has a high fa-
tality, 75 per cent or more of the cases ending in death. The
fatality is also high in the endemic parts of eastern Oregon.
In Idaho, on the other hand, there is only a 4 per cent or 5 per
cent mortality, and this is approximately the case in the other
states in which the disease occurs, namely Utah, Wyoming,
Nevada, Colorado, Washington and in Lassen County, Cali-
fornia. The disease appears only in spring and early summer
when ticks are abundant. So far no specific remedy has been
discovered.

There is evidence that spotted fever may be harbored by
some of the wild mammals on which the wood tick normally
occurs, but this has not yet been proved. The tick, D. venustus,
which has been shown to transmit spotted fever is a species
which requires two years to reach maturity. In its immature
stages it infests many of the local rodents, nearly all of which are
susceptible to the disease, and capable of transmitting it to unin-
fected ticks. As adults the ticks live on many of the larger wild

KEDANI 191

animals and on domestic animals, especially cattle and horses.
Whether some of these animals may be carriers of spotted fever
has not been determined.

Prevention of spotted fever consists primarily in fighting ticks
by various methods (see p. 368), and in destroying rodents, both
to reduce the number of host animals for the young ticks, and to
prevent the possibility of their acting as carriers of the disease.

There is grave danger that spotted fever may be introduced
into other parts of the country where suitable ticks for trans-
mitting it can be found. The exportation by railroad of wild
deer, elk, goats or other tick-infested animals to zodlogical parks
or government preserves is a dangerous proceeding unless great
care is taken to destroy all ticks and to exclude any individuals
which might be harboring the disease germ. The occasional
occurrence of the disease in various parts of the United States
should be carefully watched for, and every precaution taken to
prevent local ticks from getting access to the infection.

Kedani or Japanese Flood Fever. — In certain parts of Japan
there occurs a disease usually called kedani, which in many re-
spects is reminiscent of American spotted fever. It begins after
an incubation of five or six days or longer with a fever and
breaking out of the skin, the fever reaching its height between
the third and seventh days. It lasts from one to three weeks and
is accompanied by a swelling of the lymph glands, especially in
the vicinity of the point of infection. This is usually the armpit,
neck or groin region, where a small ulcerous wound can be found
resulting from the bite of a mite.

The disease is transmitted by the bite of a very small reddish
mite, probably an immature mite of the genus Trombidium,
or harvest bug. These mites live in great numbers on a very
abundant local field-mouse, Micromys montebello.. The mice are
not only the hosts of the mites but are also subject to the disease
and undoubtedly are an important factor in its distribution and
control. Kedani is apparently most common in laborers working
in hemp fields in July and August, on the plains which are an-
nually flooded by the overflow of certain rivers. |

In Sumatra a similar disease, which is either identical or closely
related to kedani, occurs commonly among Chinese and Japanese
laborers in the tobacco fields. The disease as it occurs in Su-
matra, where it is called pseudo-typhus, differs in some slight

192 OTHER SPOROZOA

respects from the typical Japanese disease and has a very much
lower fatality. In its incubation period, eruption and general
course it resembles spotted fever more closely than does the
Japanese disease, and Schueffner, who has worked most with
it, thinks it may be transmitted by ticks as well as mites. The
disease has also been reported from the Philippines, and about
150 cases have been reported in the Malay States. It is not
improbable that it will be found to be widely distributed in
southeastern Asia, having been incorrectly diagnosed as other
diseases. ,

The disease germ of kedani lives in the blood of infected people,
and while it does not pass through certain filters it has never been
discovered with certainty. Ogata has described a mould which
he believes ‘to be the organism causing kedani, but his results
have not been generally accepted. More recently Nagayo and
his fellow workers have found a Piroplasma-like organism in the
spleen, lymph glands and blood of victims of the disease, and
they believe it may prove to be the cause. The incubation period
is not known.

Prevention in the endemic regions obviously consists in avoid-
ing mites by skin applications or other means. The extinction
of. the field-mice and with them most of the mites would un-
doubtedly lessen the danger of the disease.

Chlamydozoa

The protozoan affinities claimed for the parasites or parasite-
like bodies included in the so-called Chlamydozoa is, as said
before, doubtful, and new investigations do not, in most cases,
tend to substantiate the claim of these structures to considera-
tion as animal parasites. A brief account of the parasites or cell
inclusions in some of the principal diseases attributed to this group
is all that can be given here. |

Smallpox and Vaccine.— The youngest forms of the parasite
are minute granules or “elementary bodies” measuring about
0.5 u (so000 Of a inch) in diameter. As growth takes place
the granules increase in number and become surrounded by:
material which is usually interpreted as a reaction product of
the cell, forming the ‘ Guarnieri bodies” (Fig: 59A). These
eventually rupture, liberating the granules to infect new cells.

CHLAMYDOZOA 193

VACCINE

Cornea cells showing developmental stages of Guarnieri bodies, Cytoryctes vac-
cinie. (After Tyzzer.)

SCARLET FEVER

Epithelial cells of skin showing various stages in development of Mallory bodies,
Cyclasterion scarlatine. Radiate form shown in middle figure. (After Mallory.)

TRACHOMA
Epithelial cell of conjunctiva showing Prowazek bodies. (After Halberstaedter.)

RABIES OR HYDROPHOBIA

Nerve cells of Ammon’s horn of cerebrum showing Negri bodies, Neuroryctes
hydrophobie. (After Maresch.)

Fic. 59. — Various types of Chlamydozoa. Note that in each case the parasite-
like bodies are enclosed in a ground substance supposed to be extruded by the
nucleus.

194 OTHER SPOROZOA

The smallpox parasites differ from those of cowpox in that they
attack the nuclei as well as the cytoplasm of the cells.

Scarlet Fever. — In the skin cells of scarlet-fever patients are
found characteristic inclusions which have been referred to the
Chlamydozoa and named Cyclasterion scarlatine (Fig. 59B).
These bodies in one stage of their development are of irregular
shape with numerous enclosed granules, while in another stage
the granules become radiately arranged around a larger central
body.

Hydrophobia or Rabies. — There usually occur in certain brain
cells of animals suffering from hydrophobia specific bodies which
are popularly known as ‘‘ Negri bodies” in honor of their discoy-
erer, and which have been given the scientific name Neuroryctes
hydrophobie (Fig. 59D). At first thought to be simple parasites,
these bodies are now generally regarded, as are other Chlamydozoa,
as reaction products of the host cell surrounding one or many mi-
nute granules which are the true parasites. The minute size of
the granules and the difficulty of identifying them when they are
separated from their ‘‘ mantles” probably accounts for the
negative findings in infective parts of the nervous system in
which Negri bodies are not found, and also in the saliva, which is
highly infective. The weight of evidence seems to favor the
protozoan affinities of the microdrganism of hydrophobia, but
the nature of the parasite is still shrouded in uncertainty.

Trachoma. — The belief in the protozoan nature of the parasite
of trachoma, a disease of the eyes causing inflammation of the con-
junctiva, rests on similar ground. In the affected portions of the
eye are found numerous tiny granules known as “ Prowazek’s
bodies” (Fig. 59C), sometimes within the cells and even within the
nuclei and at other times free in the serum, which have been
thought to be the cause of the disease. The fact that these bodies
are sometimes found in other affections has thrown some doubt
on their relation to trachoma. Recent investigations by Anna
Williams of 4000 school children in New York with eye infec-
tions or inflammations, none of which were typical cases of ‘ tra-
choma,”’ showed ‘“‘ trachoma inclusions ” to be common, and gave
evidence that-these inclusions were in reality ‘‘ nests” of growing
bacteria, of various kinds, in the epithelial cells of the conjunc-
tiva. Miss Williams’ investigations throw doubt on the existence
of a specific disease to which the name trachoma can be applied.

OBSCURE PARASITES 195

Other Diseases Caused by Obscure Parasites

The diseases mentioned above are those which are most com-
monly thought to be caused by organisms of this problematic
group, Chlamydozoa. There are a number of others, however,
which may belong here, but on which much further investigation
is necessary. Among these are foot-and-mouth disease, in which
Stauffacher has recently found an organism, A phthomonas infes-
tans, which, however, is probably more closely related to Leish-
mania (see p. 76); verruga peruviana, which in some respects
resembles smallpox; the ubiquitous measles; and a number of
diseases which are of rare or of more or less limited distribution.
That all of these diseases, or even all of those separately discussed
above, are caused by protozoan parasites is very doubtful, and
only further investigation can determine the true status of their
causative microorganisms. The fact that typhus fever and
infantile paralysis were until very recently looked upon as quite
as probably caused by protozoan organisms as some of the diseases
named above, and that this opinion has been reversed as the result
of work done in the last two or three years (1914-1917), would
make it not at all surprising if more of the obscure or invisible
parasites of these diseases should be shown to be bacterial in
nature, rather than protozoan.

PART II— WORMS

CHAPTER XI
INTRODUCTION TO THE ‘‘WORMS”

Classification. — The name worm is an indefinite though sug-
gestive term which is popularly applied to any elongated creeping
thing which is not obviously something else. There is hardly
a branch or phylum of the Animal Kingdom which does not
contain members to which the term ‘‘ worm ”’ has been applied,
not excepting the great group Chordata, to which the back-
boned animals, including man himself, belong. In fact some
animals, such as many insects, are ‘‘ worms ”’ during one phase
of their life history, and something quite different during another.

In a more restricted sense the name ‘‘ worm’ is applied to three
great groups of animals, with a few outlying forms, which super-
ficially all resemble one another in being unquestionably “‘ worm-
like,” though in life and structure they are widely different.
To these animals, together with a few- other heterogeneous forms,
the collective name “ Vermes,’’ meaning worms, was applied by
the early workers on zodélogical classification. Upon more de-
tailed study it became obvious that different types of the “‘ Ver-
mes” differed from one another to such an extent that they
would have to be divided into several great branches or phyla of
the Animal Kingdom. At the present time the majority of these
animals are classified in three phyla, as follows: the Platyhel-
minthes or flatworms, the Nemathelminthes or roundworms
and the Annelida or segmented worms. There are a number of
‘““ worms ”’ which will not-readily fit into any of these groups but
are incerte sedis, showing affinity to one group in some respects
and to another in others. Some species are so profoundly modi-
fied by their peculiar modes of life that it is practically impossible
even to guess at their true relationships. All three of the phyla
of “ worms ”’ contain parasitic species, though none of them con-
tain parasites exclusively. |

Flatworms. — The group of lowest organization is the Platyhel-

minthes. The worms included in this phylum are flattened
196

FLATWORMS 197

from the dorsal to the ventral side, whence the common name
“flatworms.” Unlike nearly all other many-celled animals
they have no body cavity, the organs being embedded in a sort
of spongy ‘‘ packing”’ tissue. The digestive tract has only a
single opening which serves both for mouth and vent (Fig. 60A),
and in the tapeworms the entire alimentary canal is absent.
The nervous system is very simple. Performing the function
of kidneys is a system of tubes, the terminal branches of which
are closed by “ flame cells,” so called from the flamelike flickering
of a brush of cilia which keeps up a flow of fluid toward the

CS
Fic. 60. Types of digestive tracts in worms; A, fluke, — note branching and
absence of anus; B, roundworm, — note simple form, with only pharynx differen-

tiated, and presence of anus; C, leech, — note extensive pouches or cceca which
serve as reservoirs for surplus food.

larger branches of the system and ultimately to the excretory
pore, thus conducting the waste products out of the body. The
absence of any kind of blood system or other apparatus for trans-
porting food or waste products in the body necessitates a branched
condition of the digestive and excretory systems. The most
highly developed system of organs and one which occupies a
large portion of the body is that concerned with .reproduction.
Usually there is a complete male and female system in each
worm and in some tapeworms there is a double system of each
kind.

The flatworms are usually divided into three classes, the Tur-
bellaria, the Trematoda and the Cestoda. The Turbellaria are
for the most part free-living animals and include the “ pla-
narians ”’ which can be found creeping on the under side of stones
in ponds. The Trematoda include the flukes, all of which are
parasitic, some externally on aquatic animals, others internally

198 INTRODUCTION TO THE WORMS

on aquatic or land animals. They are flattened animals, usually
oval or leaf-shaped, furnished with suckers for adhering to their
hosts. The flukes which live as external parasites of aquatic
animals have a comparatively simple life history, while those
which are internal parasites of land animals have a complex
life history, in the course of which they pass through two or three
different hosts. The third class, Cestoda, is comprised by the
tapeworms. As adults they are all parasites of the digestive tracts
of various animals and are profoundly modified for this kind
of an existence. Their peculiar method of multiplication by bud-
ding results in the formation of a chain of segments, sometimes
of great length, which collectively constitute a tapeworm; each
segment, however, is practically complete in itself and capable of
separate existence if it had some method of retaining its position
in the host’s intestine. Some tapeworms have a life history
comparable in its complexity with that of the flukes but as a
rule it is much simpler. With the flatworms are usually asso-
ciated the Nemertinea, marine worms some of which are more
or less parasitic. None of them is of any interest in connection ©
with human parasitology.

Roundworms. — Of somewhat higher organization than the
flatworms is the phylum -Nemathelminthes or roundworms.
These worms are cylindrical instead of flattened, they possess a
body cavity, and they have an opening at each end of the digestive
tract (Fig. 60B). The excretory system usually consists of simple
tubes running the length of the body. The presence of a fluid-
filled body cavity through which food and other substances can
diffuse obviates the necessity for having branched organs. The
_gexes are separate, and the reproductive systems are much
simpler than in the flatworms.

Usually there is only a single class recognized as belonging to
this phylum, namely, the Nematoda or nematodes. Some of
the nematodes are not parasitic but many of them parasitize
either plants or animals. There are many important human
parasites among the Nematoda, for instance, the hookworms,
pinworms, Ascaris and other intestinal worms, Trichinella, Filaria
and the guinea-worm. In some of these the life history is fairly
simple while in others it is more complex and involves two dif-
ferent hosts.

Some zodlogists associate with this phylum two other classes

ANNELIDS 199

of worms, the Acanthocephala and the Nematomorpha. The
former class, as indicated by the name, include the spiny-headed
worms. These are cylindrical worms of peculiar anatomy,
notable for the complete absence of a digestive tract as in the
tapeworms. The head is furnished with a proboscis which is
armed with rows of thornlike hooklets. The adults live in the
digestive tracts of their hosts, burying the thorny proboscis
deep into the mucous membranes. They have a complex life
history, the larval stage being passed in insects of various kinds.
Several species are occasionally but rarely found in man.

The class Nematomorpha is comprised by the “ horse-hair
snakes,” so called from the popular belief that they develop from
horse hairs which fall into water. They are exceedingly long
slender worms, usually parasitic in insects. Occasionally they
are accidentally swallowed by man with drinking water and are
usually vomited, much to the surprise and horror of the tempo-
rarily infected person.

Annelids. — The most highly organized phylum of worms is
Annelida, including the segmented worms or annelids. In three
important respects these worms are the first animals in the scale
of evolution to develop the type of structure characteristic of
the vertebrate animals, consisting, namely, in a division of the
body into segments, in the presence of a blood system, and in
the presence of ‘ nephridia’”’ or primitive excretory organs of
the same fundamental type as are the kidneys of higher animals.
In addition the digestive system is highly developed and there is
a well-developed nervous system distinctly concentrated in the
head. In some annelids the sexes are separate, while in others
both reproductive systems occur in the same individual.

At least three classes of Annelida are usually recognized, namely
the Archi-annelida, including a few primitive marine forms;
the Chztopoda, including the worms which are furnished with
bristles or sete, such as the earthworms and marine sandworms;
and the Hirudinea or leeches, in which there are two suckers but
no sete. There are a number of other groups of worms which
many zodlogists include with the annelids, but as their systematic
position is doubtful and as they include no parasitic forms they
need not be mentioned here. The only class of annelids which
includes parasites of man are the Hirudinea or leeches. These
animals superficially resemble flatworms but they can readily

200 INTRODUCTION TO THE WORMS

be recognized externally by the segmentation of the body;
the internal anatomy is totally different. Both sexes are repre-
sented in each individual.

The number of different species of worms in these three phyla
which have been found in man is well up in the hundreds. In
the following pages each group of these worms which contains
important human parasites will be dealt with, but only those
species which are important, or which are particularly inter-
esting from some other point of view, will be individually
considered. :

Parasitic Habitats. — As to the parts of the body which may
be attacked by worms of one kind or another, there is hardly
any organ or tissue which is exempt. There are flukes which
habitually infest the intestine, liver, lungs and _bloodvessels,
and one species occasionally wanders to the muscles, spleen, -
brain and many other organs. The adult tapeworms are all
resident in the small intestine, but larval tapeworms are found
in various locations in the body. The majority of the parasitic
nematodes of man are found in the intestinal canal but there
are exceptions to this. The adult Trichinelle, for instance,
inhabit the intestine, but the larve are found in the muscles;
the adult Frlarte usually live in the lymph vessels, whereas the
larve swarm in the blood; the guinea-worm and some other
nematodes creep under the skin in the connective tissue; the
lungworm of the hog, Metastrongylus apri, which occasionally
occurs in man, infests the lungs and bronchial tubes; and Dvioc-
tophyme renale (or Eustrongylus gigas) is an occasional human
parasite which occurs in the kidneys and rarely in the body cavity.
The leeches, on the other hand, are parasitic on the surface of
the body or in the cavities of the nose and mouth.

Life History and Modes of Infection. — The life history and
mode of infection of worms varies with the habitat in the body.
Every parasitic worm must have some method of gaining aécess
to the body of its host, and must have some means for the escape
of its offspring, either eggs or larve, from the host’s body in
order to continue the existence of its race. Many species utilize
intermediate hosts as a means of transfer from one host to an-
other; others have a direct life history, i.e., they either develop
inside the escaped egg and depend on such agencies as food and —
water to be transferred to a new host, e.g., pinworm, or they

EFFECTS OF PARASITISM 201

develop into free-living larve which are swallowed by or burrow
into a new host when opportunity offers, e.g., the hookworms.

Most of the intestinal parasites apparently enter their host

by way of the mouth, and the eggs escape with the feces. Many
‘species enter as larve in the tissues of an intermediate host which
is eaten by the final host. Of such a nature are most of the
tapeworms and flukes and some nematodes, e.g., Trichinella.
Some nematodes of the intestine, as the pinworm and whip-
worm, enter contaminated food or water as fully developed
embryos in the eggs. Still other species, as the hookworms and
Strongyloides, usually reach their destination in an indirect way
by burrowing through the skin. All the intestinal worms except
Trichinella produce eggs or larve which escape from the body
with. the feces. In Trichinella the larve encyst in the muscles
and in order for them to be released the host must be eaten by
another animal. Many of the worm parasites of other organs
of the body also enter by way of the mouth and digestive tract,
' though they have various means of exit for the eggs or larve.
The liver flukes enter and escape from the body as do ordinary
intestinal parasites; the lung flukes enter by the mouth, but the
eggs are expelled with sputum; the blood flukes enter by bur-
rowing through the skin, and the eggs escape either with feces or
urine; the Filarie, like blood-dwelling protozoans, enter and
leave the body by the aid of blood-sucking insects; the guinea-
worm enters by the mouth, and the larve leave through the skin.
The larval tapeworms which infest man enter either by the
mouth or by accidental invasion of the stomach from an adult
in the intestine. Like Trichinella they are usually permanently
sidetracked in man, since they can escape only by being eaten
with the tissues in which they are imbedded.

Effects of Parasitism.— The effects produced by parasitic
worms depend in part on the organs or tissues occupied, in part
on the habits of the worms and in part on the poisonous qualities
of their secretions or excretions, to which the susceptibility of
different individuals is very variable. The effects of some kinds
of worms is a much disputed point. Some investigators tend to
minimize the damage done by worm parasites, especially intestinal
ones, while others undoubtedly overestimate it. Improved facili-
ties for discovering infection have demonstrated the presence of
intestinal parasites in so many unsuspected cases that we are

202 INTRODUCTION TO THE WORMS

likely to incriminate them in nearly every morbid condition for
which we cannot, with equal readiness, discover another cause.
It cannot be doubted, however, that many of the morbid con-
ditions really are, in part at least, produced by intestinal worms.
Much of the difference of opinion regarding the effects of these
parasites is no doubt due to the variable susceptibility of dif-
ferent individuals.

The amount of nutriment which is absorbed by worms such
as Ascaris and the pinworm, which live on semi-digested food in
the lumen of the intestine, is probably in most cases relatively
slight: Leuckart states that Tenia saginata, for instance, gives
off about 11 proglottids a day, which would amount to one and
two-thirds pounds in a year. This would not, of course, repre-
sent more than a fraction of the food materials used. Such a
loss would, however, be inappreciable in adults, though it would
be felt in growing children unless compensated for by increased
appetite. Many intestinal parasites, as the hookworms, devour
cells of the mucous membrane and suck blood, sometimes causing
extensive bleeding.

The most serious injury from intestinal worms is undoubtedly
the toxic effects of their secretions and excretions. We know
that the diseases caused by most Bacteria and Protozoa are
the result, not of the actual damage done by the parasites in
devouring tissues, but of the poisonous waste products and se-
cretions given off by these organisms. Until recently little was
known about the toxic effects of worms, but that toxins were pro-
duced by them was evident from symptoms disproportionate to
the mechanical injury the parasites could do, and from effects
which could in no way be the direct result of mechanical injury.
In 1901 a French worker, Vaullegeard, actually obtained from
certain tapeworms and from Ascaris toxic substances which
acted upon the nervous system and upon the muscles. Recent
investigations by Flury have shown that Ascaris, a nematode,
contains certain substances which are very irritating to mucous
membranes, other substances which have blood-destroying and
tissue-destroying properties, and still others which have an in-
toxicating effect on the nervous system, causing hallucinations,
delirium and other disturbances. These toxins, derived from
the body and excretions of Ascaris, when introduced into a ver-
tebrate animal, cause the same symptoms which often accom-

TOXIC EFFECTS 203

pany Ascaris infection, but which have usually been attributed
to other causes. With such an array of formidable chemical
compounds in the body substance of intestinal worms, it is not
necessary to search for mechanical factors to explain intestinal
disturbances, abdominal pains, nervous and mental symptoms,
and the various other apparently unrelated conditions which
accompany infection with such worms. When, as in the case
of hookworms, such effects are combined with blood-sucking and
bleeding from wounds, facilitated by secretions which prevent
coagulation of blood, it is not difficult to understand how such
profound anemia and loss of vitality are produced by compara-
tively few small worms. The presence in blood of toxins ab-
sorbed from worms in the intestine is further indicated by changes
in the blood itself. The anemia of hookworm disease, due both
to reduction of blood corpuscles and to diminution in percentage
of hemoglobin, is so well known that anemia is sometimes used
as a synonym for hookworm disease. - Similar though usually
less marked anemia occurs in cases of infection with other worms,
e.g., the fish tapeworm, Duibothriocephalus latus, the blood flukes,
etc. Another symptom of the presence of worms in the body is
a change in number and kinds of leucocytes or white blood
corpuscles. An almost universal symptom, though one which is
occasionally absent even in the infections in which it is most
characteristic, is an increase in the number of so-called “ eosin-
ophiles,’” white blood corpuscles containing granules which
stain red with eosin. These cells are supposed to be for the pur-
pose of destroying toxins in the blood just as some of the leuco-
cytes are apparently for the purpose of capturing and destroying
bacteria or other foreign cells. The mere presence of an in-
creased number of them is, therefore, sufficient reason for as-
suming the presence of toxins for them to destroy. The normal
number of eosinophiles varies from one per cent to four per cent of
the total number of leucocytes, whereas in infections with such
parasites as trichina, blood flukes, echinococcus cysts, etce.,
the number nearly always rises to five per cent or higher, and in
some cases reaches over 75 per cent.

Another factor which is undoubtedly of prime importance is
the portal of entry which intestinal worms give to Bacteria and
Protozoa. We have awakened to the importance of a “ whole
skin ” and the danger which accompanies the piercing of it by the

204 INTRODUCTION TO THE WORMS

unclean probosces of biting flies, bugs or other insects. We have
not yet fully awakened to the importance of an uninjured mu-
cous membrane. As has been pointed out by Shipley, the in-
testinal worms play a part within our bodies similar to that
played by blood-sucking arthropods on our skins, except that they
are more dangerous since, after all, only a relatively small per
cent of biting insects have their probosces soiled by organisms
pathogenic to man, whereas the intestinal worms are constantly
accompanied by bacteria, such as Bacillus coli, which are capable
of becoming pathogenic if they gain access to the deeper tissues
as they are able to do through the injuries made by hookworms,
whipworms, tapeworms, etc. Weinberg, for instance, found that
whereas he was unable to infect unparasitized apes with typhoid
bacilli, apes infested with tapeworms or whipworms readily con-
tracted typhoid fever, the bacteria presumably gaining entrance
through wounds in the mucous membrane made by the worms.
The relation of intestinal worms to appendicitis is more than
hypothetical, and it is probable that far more cases of appendi-
citis are the outcome of injury done by worms than is usually
supposed. Although it has been objected that very few of the
thousands of appendices removed yearly are reported to contain
parasites, it must be pointed out that parasites are very seldom
sought, could easily be overlooked, and might not be recognized
as such if found. It is furthermore possible that parasites which
initiated the inflammation and ulceration might no longer be
present in the appendix upon its removal, since they are able to
move about freely in the digestive tract. Shipley remarks that
appendicitis is a commoner disease now than it was when ver-
mifuges were more frequently given.

Diagnosis. — The diagnosis of infection with various species
of worms often depends on the identification of their eggs or
larve as found in the feces or other excretions by microscopic
examination. Nearly every species of parasite has recognizably
distinct characteristics of the eggs, the chief variations being in
size, shape, color, thickness of shell, amount of development,
appearance of the embryo if present and presence or absence
of a lid. Some of the commoner worm eggs are shown in a
comparative way in Fig. 61.

ph

by

Q

~ sshekc

Qry

-

ty

-

~

nN

i

=

-

EGGS OF PARASITIC WORMS 205

mu vy Yw

Fic. 61. Eggs of parasitic worms, drawn to scale. x 200. (After various

-

RoR

authors.)

Schistosoma hematobium, voided with O, Hymenolepis nana, voided with feces,

urine. usually in proglottids. ;
Schistosoma mansoni, voided with feces. P, Hymenolepis diminuta, voided with fxces,
Schistosoma japonicum, voided with feces. usually in proglottids.
Paragonimus ringeri, voided with sputum. Q, Dibothriocephalus latus, voided with feces.
Fasciola hepatica, voided with feces. R, Diplogonoporus grandis, voided with feces.
Clonorchis sinensis, voided with feces. S, Davainea madagascariensis, voided with
Opisthorchis felineus, voided with feces. feeces, usually in proglottids.
Opisthorchis noverca, voided with feces. T, Dipylidium caninum, voided with feces,
Fasciolopsis buski, voided with feces. usually in proglottids.
Gastrodiscoides hominis, voided with feces. U, Ascaris lumbricoides, voided with feces.
Heterophyes heterophyes, voided with feeces. V, Trichuris trichiura, voided with feces.
Yokagawa yokagawa, voided with feces. W, Ancylostoma duodenale, voided with feces.

, Tenia saginata, voided with feces, usually X, Necator americanus, voided with feces.

in proglottids. Y, Trichostrongylus orientalis, voided with

Tenia solium, voided with fzces, usually feeces.

N

in proglottids. ’ Oxyuris vermicularis, voided with feces.

CHAPTER Xii
THE FLUKES

General Account. — The flukes are animals of a very low order
of development in some respects and of very high specialization
in others. In shape they are flat and often leaflike, with the
mouth at the bottom of a sucker at the anterior end and with a
second little sucker, for adhesion, on the ventral side of the body.
They are all parasitic when adult and attach themselves to their
hosts, either externally or internally, by means of their suckers,
sometimes aided also by hooks. The development of the ner-
vous system is of a very low grade, and the only tendency towards
a brain is the presence of a small ganglion at the forward end of
the body which gives off a few longitudinal nerves. Sense organs
are almost lacking — there is usually no sense of sight and none
of sound; in fact no sensations whatever except a meager sense
of touch falls to the lot of these lowly animals. There is no blood
or blood system, the result being that the digestive tract and
excretory system are branched, often to a surprising extent, in
order to carry food to all parts of the body and to carry waste
products out from all parts. In these respects the flukes are
very primitive animals, but in other respects they equal or surpass
any other animals in their complexity. We would have to look
long to find more intricate and highly specialized reproductive
systems than they possess, and their life histories are so mar-
velously complex as to tax our credulity. We are accustomed
to think of a butterfly as having a wonderful life history in that
it passes through two phases of life, the first as a caterpillar, the
second as a mature butterfly, the two being separated by a third
inactive phase of existence. But by comparison with the flukes
this life history appears simple. Many flukes, especially those
which live as internal parasites in the land animals, pass through
four and sometimes even five distinct phases of existence, during
some of which they are free-living, and during others may para-

sitize successively two or even three different hosts.
! 206

REPRODUCTION . 207

In all flukes except those of the family Schistosomide both
male and female reproductive systems occur in the same individ-
ual, and occupy a large portion of the body of the animal. We
are familiar with animals which appear to live almost wholly
to eat; the flukes are animals
which seem to live merely for re-
production. They are reproduc-
tive machines, all the other or-
gans of their bodies being devel-
oped only to a sufficient extent
to ensure the proper develop-
ment and maturity of the eggs.
The eggs proper and the shell
materials are produced by sepa-
rate glands, and sometimes the
canal for conducting the sperms
from another individual into the
body to fertilize the egg is distinct
from that which conducts the very sinall intestinal fake of man; A.
eggs out of the body. The male adult; BCX 350), spines from genital

: Ting; g. r., genital ring; g. p., genital
system consists of two or more pores; other abbrev. asin Fig. 74. X 33.
glands or testes for the produc- Egg shown above, 500. (After
: : Looss.)
tion of the sperms, two sperm 3
ducts which meet and enlarge into a ‘cirrus pouch” for storing
the sperms until ready to be used, and a rectractile copulatory
organ. All these complex sexual organs in a single animal which
may be no larger than the head of a pin (Fig. 62)!

Almost as soon as the fluke reaches its final host and assumes
its mature form, development of the reproductive systems be-
gins. Although both sexes are usually in the same individual,
mutual cross-fertilization generally takes place, the sperms of
two individuals simultaneously fertilizing each other. The num-
ber of eggs maturing in a single fluke is enormous, and while it
undoubtedly varies in different species and in different individuals,
the eggs are probably always to be reckoned in the thousands,
and sometimes in the hundreds of thousands.

Life History. — The life histories of all the flukes which are
internal parasites have much in common, and all of them undergo
a series of marvelous transformations from egg to adult.

The fluke which is most thoroughly known in every respect

(4

208 THE FLUKES

is the almost cosmopolitan liver fluke, Fasciola (or Distomum)
hepatica, of sheep, goats and other ruminants. This species
occasionally establishes itself in man also, but it can be looked
upon only as an accidental parasite as far as man is concerned.
Its life history (shown diagrammatically in Fig. 63) will be
described in some detail since it is more thoroughly known than
is that of most of the flukes, and because it is typical of the group.

The adult of the liver fluke (Fig. 63A) lives normally in the
bile passages and liver tissue of its host. About three weeks
after the flukes have reached their destination in or near the
liver, reproduction commences. Eggs (Fig. 63B) begin to pass
out through the uterus of the fluke, and are carried by the bile
of the host to the intestine and thence out of the body by the
feces, a single fluke producing as many as 50,000 eggs. Since
there may be over 200 flukes in a single host, the number of
eggs voided may amount to many millions. These eggs, if they ©
chance to fall into water of moderate temperature, hatch out
little ciliated embryos known as miracidia (Fig. 63D), which
resemble ciliated protozoans. .They are about 100 uw (sh5 of an
inch) in length. Each of the embryos swims about for a day or
two, by means of its cilia, in an effort to find a suitable interme-
diate host, in this case certain species of snails of the genus
Inmnea (Fig. 63E), and if successful it bores into the snail by
means of a little pimple-like projection at the anterior end of
the body. It is obvious that only a small per cent of the embryos
are likely to survive the double risk of not reaching water, and
if safely in water of not reaching a suitable snail to bore into.
However, once safely within the tissues of the snail, the embryo
begins the second phase of its existence, during which it reproduces
to make up for the enormous mortality encountered in the trans-
fer from sheep to snail.

In the course of some days the ciliated embryo transforms into
a saclike body or ‘‘sporocyst”’ (Fig. 63F), the inner ‘ germina-
tive’ cells of which act as parthenogenetic eggs (i.e., eggs which
do not need fertilization), each developing into a larva of a new
type, known as a redia (Fig. 63G). The latter, when nearly
mature, burst the wall of the mother sporocyst and migrate into
other tissues of the snail. The rediz are very simple organisms
with a sucker and an unbranched blind pouch for a digestive
tract. Like the sporocyst they contain germinative cells within

LIFE HISTORY OF LIVER FLUKE 209

HEHE ne
| es

- Fic. 63. Life history of liver fluke, Fasciola hepatica; A, adult in liver of sheep;
B, freshly passed egg; C, egg with developed embryo, ready to hatch in water; D,
ciliated embryo in water, about to enter pulmonary chamber of snail (E); F,
sporocyst containing redize; G, redia containing daughter redie; H, redia of 2nd
generation containing cercariz; I, cercaria; J, same, having emerged from snail
into water; K, cercariz encysted on blade of grass; L, cercaria liberated from cyst
after ingestion by sheep; M, young fluke developing in liver of sheep.

210 THE FLUKES

their bodies and these develop into a second generation of rediz
(Fig. 63H) ultimately escaping from a little ‘“ hatching pore ”
in the body wall of the parent. In this way even a third genera-
tion of rediz may be developed, but usually the second generation
of rediz produce from their germinative cells a new type of larva,
the cercaria (Fig. 631), quite different from either the embryo
or the redia. The cercarie are furnished with a sucker and a
forked digestive tract, and have an actively moving tail. They
worm their way out of the body of the snail in which they were
developed and swim about in the water by means of lashing
movements of their tails (Fig. 63J). Eventually they attach
themselves to a submerged blade of grass or aquatic plant, lose
their tails, secrete a cyst about themselves (Fig. 63K), and wait to
be eaten or drunk by a sheep or a goat. When so swallowed the
cyst is dissolved off in the stomach, and the little parasite (Fig. 63L)
wends its way up the bile duct to the liver, there to begin again
the reproduction of eggs and start a repetition of the entire cycle.

Such is the life history of the liver fluke. In some flukes this
strange life is further complicated by the invasion of a third host
by the cercariz. In some fluke parasites of frogs, for instance,
the rediz inhabit certain snails, while the cercariz inhabit insect
larve, and infect their ultimate host by being eaten with the
insects. Several human flukes, including the lung fluke, Para-
gonimus ringert (westermant) have a life history of this type.
The encysted cercariz of the lung fluke are found in the tissues
of several species of fresh-water crabs and in the earlier stages
are believed to be parasites of a snail on which the crabs feed.
The Chinese liver fluke, Clonorchis sinensis, parasitizes succes-
sively a snail, a fish and a mammal.

In some species of flukes daughter sporocysts are formed in-
stead of redise, and in some the sporocysts give rise to cercarie
directly. The known types of life histories of flukes are graphi-
cally shown by the following diagram, copied from Leiper:

Host Transition Intermediate Host Transition Host
Encysted
Sporocyst in molluse
Egg Miracidium | Sporocyst...... Daughter Sporocyst in crustacean
(or ciliated { Sporocyst...... Redize Cercarize in insect Adult
embryo) Sporocyst...... Rediz, Daughter in fish
Redize on vegetation

Free-swimming

SCHISTOSOMA 211

-Adult flukes of different species differ widely in regard to the
organs or tissues of the host which they attack. The majority
of species live in the alimentary canal, in any part from mouth
cavity to anus, some species being very closely limited to certain
portions. Next to the alimentary canal the liver is the organ
most frequently chosen, and then the lungs. The urinary or-
gans, body cavity, bloodvessels and other organs and tissues
are chosen by some species. The brain and nervous system are
only accidentally invaded. One species lives in the eustachian
tube of an aquatic animal,
another in the conjunctival
sac in the eyes of birds.

The flukes which infest man
may be divided for conven-
ience into four groups, the
blood flukes, the lung flukes,
the liver flukes and the intes-
tinal flukes. Altogether over
20 different species have been
found in man, but only those
which are common or impor-
tant will be considered in the
following pages.

Blood Flukes

The most important flukes
parasitic in man are three
species of Schistosoma (or Fie. 64. Blood fluke, Schistosoma hema-
Bilharzia) which live in the tobiwm; male ($) carrying female (9) in
large bloodvessels of the ab- Yontal eoove: int. intestines gy.
dominal cavity. mouth; v. s., ventral sucker. x 8. (After

Schistosoma is one of the 1%
few genera of flukes in which the sexes are separate. The
relation of the sexes is one of the most remarkable in nature.
The mature male worm (Fig. 64) has a cylindrical appearance
due to the fact that the sides of the flat body are folded over
to form a ventral groove. In this groove, projecting free at each
end but enclosed in. the middle, is the longer and slenderer
female, safe in the arms of her lord. While young the sexes live

212 THE FLUKES

apart, but as soon as sexual maturity is attained they couple
together and spend the rest of their lives in this manner.

Unlike the liver flukes, the blood flukes do not develop great
numbers of eggs all at once, but instead develop them one by one
and have only a few in the oviduct at any one time. Such a
method of reproduction is facilitated, of course, by the constant
juxtaposition of the male and female worms. The blood flukes
live correspondingly much longer than the liver flukes, often
persisting for many years.

Schistosoma hzematobium. — The most important species
from the pathogenic point of view is Schistosoma hematobium
(Fig. 64). This parasite is common in the countries surrounding
the eastern end of the Mediterranean, southern Asia and many

Fic. 65. Eggs of Schistoma; A, terminal spined egg of S. hematobium from
urine; B, lateral spined egg of S. mansoni from feces; C, egg of S. japonicum, with
only rudiment of spine; note developed embryos in all. Xx about 200. (A and B
after Looss, C after Leiper.)

parts of Africa, especially the east coast. In Egypt over half the
population are said to be infected, and in an examination of
54 boys in the village of El Marg, near Cairo, 49 were found
infected.

These flukes, about one-half inch in length, abound sometimes
in hundreds in the abdominal veins of their host, living espe-
cially in the portal vein and its various branches. The eggs of
the worms, which are oval with a stout spine at one end (Fig.
65A), and about 0.16 mm. (45 of an inch) long, are carried to the
small vessels on the surface of the urinary bladder. By means
of the sharp spine they penetrate to the wall of the bladder and
are voided with the urine. As the eggs enter the bladder they
cause a certain amount of bleeding, resulting in a bloody urine.

,

SCHISTOSOMA HAEMATOBIUM pail

From this symptom the disease caused by infection with Schis-
tosoma hematobium is often called ‘ parasitic hematuria.’’ Ex-
cept in severe infections no serious symptoms appear, but when
numerous the worms cause much pain and give rise to a great
variety of abnormal conditions of the bladder. The damage they
do is partly the result of blocking of the veins, and partly the
result of inflammation and bleeding of the bladder caused by its
penetration by the spined eggs. Sometimes the kidneys, ureters
and other urino-genital organs are attacked and seriously affected.
In addition there can be little doubt but that the worms excrete
poisonous matter in the blood, as practically all parasitic worms
do to some extent, and this probably accounts for part at least
of the anemic and debilitated condition so common in infected
people. It is reported that of 625 British soldiers who became

Fic. 66. - Egyptian snails which serve as intermediate hosts for blood flukes; A,
Bullinus contortus, an intermediate host for Schistosoma hematobium; B, Planorbis

boissyi, an intermediate host for Schistosoma mansoni. (After Leiper.)

infected with blood flukes in South Africa during the Boer war,
359 were still on the sick list in 1914 exclusive of those perma-
nently pensioned. The cost to the British government for per-
manent and “ conditional ”’ pensions for these soldiers amounted

to nearly $54,000 a year.

The life history of Schistosoma hematobium has only recently
been worked out by Leiper, of the British Army Medical Corps,
in Egypt. It was long known that a ciliated embryo or mira-
cidium developed inside the egg shells, even before they left the -
body of the host, and that these embryos hatched out and swam
about when the eggs were immersed in water, but beyond this
point the life history could only be conjectured from analogy with
the liver fluke. Leiper, who had already made some investi-
gations in regard to the life history of S. japonicum in China,

214 THE FLUKES

worked on the life history of this species, chiefly at El Marg,
near Cairo, Egypt. He found that Schistosoma embryos are
attracted by several species of fresh-water snails and that they
penetrate the bodies of three species, Bullinus contortus (Fig.
66A), B. dybowskii and Planorbis boissyi (Fig. 66B). Here
they undergo transformation into sporocysts, from which daugh-
ter sporocysts bud off (Fig. 67). After leaving the mother
cyst the daughter sporocysts migrate into the tissue of the liver

Fic. 67. Larval forms of blood flukes teased from liver of Planorbis; A,
sporocyst containing daughter sporocysts; B, daughter sporocysts in liver tissue;
C, cercaria. Note forked tail, characteristic of Schistosoma cercarie. (After
Leiper.)

and grow rapidly. They become greatly elongated and eventu-
ally ramify throughout the organ, so increasing its bulk and color
that an infected snail can be detected at a glance. The sporo-
_ eysts move by wriggling movements, and absorb nourishment
directly through the body wall. When théy become over-
distended with the cercaria developing within them the wall
ruptures and the cercarie are set free in the snail. The cercarie
are discharged from the mollusc in ‘“ puffs,” a number being |
periodically shot into the water.

SCHISTOSOMA HASMATOBIUM 215

Examination of molluscs which were collected in the El Marg
canal resulted in finding 17 species of cercariz, among them the
cercarie with forked tails and no bulb in the cesophagus, the
typical form of Schistosoma cercarie (Fig. 67C). Infected
molluscs may continue to liberate cercarize for several weeks.
_ Leiper later found that S. hematobiwm developed only in the
species of Bullinus, the cercarie from Planorbis belonging to
another species, S. mansoni. In Natal and the Transvaal a
small dark-colored snail, Physopsis africana, acts as an inter-
mediate host. |

When fully developed the cercarie escape from the snails and
swim about in water in search of a final host. They do not live
at best as long as 48 hours, so a vast majority of the larve must
perish from failure to find a suitable host. It has been shown
that not only man but also various species of monkeys and
rodents may be infected by the cercariz.

Infection may occur in two different ways: by drinking water
containing cercariz, or by bathing in it, since the cercarize are
able to penetrate either the mucous membranes or the sound
skin, migrating through the body until they reach their desti-
nation in the abdominal veins. The natives of some parts of
Africa realize that infection may result from bathing, but from
the nature of the disease they believe that infection takes place
by way of the urinary passages and therefore employ various
mechanical devices to prevent infection in this manner. There
is little doubt, when infection occurs from drinking water, that
the cercariz adhere to the walls of the mouth and throat and bore
through them, since passage through the acid juices of the
stomach is apparently fatal for them.

The disease usually develops in from two to four months after
infection.

Treatment and Prevention. — Once infection has occurred
there is no known means of eliminating the worms from the
veins in which they live, or of destroying them. Several drugs
injected into the veins, especially salvarsan and thymobenzene,
have been recommended, but their use has not met with uni-
formly successful results. X-ray treatment has recently been
tried but with little success.

None of the injuries done by the worms can be readily allevi-
ated. Surgical treatment of the bladder to relieve growths or

216 THE FLUKES

“stones ” resulting from the inflammation is sometimes resorted
to but in most cases this is said only to aggravate the disease.
Even without reinfection some of the worms may continue to
live and produce eggs for years, but in most long-standing cases —
reinfection probably occurs frequently. -

Now that the life history and modes of infection are known,
definite preventive measures can be taken. Prevention of con-
tamination of drinking water by infected urine is, of course, the
ideal preventive measure, but in countries where the disease.
is most prevalent, as in Egypt, codperation of the natives in
such a matter is more than can be expected. Leiper has pointed
out, however, that the disease can be eradicated without such
cooperation by other means, depending upon local conditions.
In large towns and cities it is practical to destroy the free-swim-
ming infective stage of the worm by filtering or impounding
water, while in rural districts the worm must be deprived of ©
its intermediate host. Cairo, for example, obtains its water
supply from the Nile, part of it being unfiltered. Water used
for irrigation purposes above Cairo, and frequently contaminated,
is turned back into the river and. is probably the chief source of
infection at, Cairo, where 10,000 children are said to become in-
fected annually. In towns where filtering is impractical the
water could be rendered uninfective by impounding it in pro-
tected reservoirs for 48 hours, since the cercarie die in this time.
The objection to this is that the water loses valuable sediment,
but it is doubtful whether the agricultural loss from lowered
vitality resulting from Schistosoma infection is not greater than is
the loss in fertility from impounding water.

In rural agricultural districts prevention of infection is de-
pendent on the intermittent flow of water in irrigation canals,
under government control. The snails which serve as inter-
mediate hosts for Schistosoma are said to die if the water in which
they live is dried up. It is customary for water to be turned out
of most irrigating canals for periods of 15 days at a time, which
Leiper says would be sufficient to destroy molluscs in them except
in puddles left by an uneven floor, which must be treated by
chemicals, or the floors leveled. However, in view of the remark-
able resistance which most snails have to drouth and to other
adverse conditions, this conclusion ought to be proven by extensive
experimentation. Infected water to be used for washing can be

OTHER SPECIES OF SCHISTOSOMA 217

rendered non-infective by the addition of one part of cresol in
10,000 parts of water.

Leiper’s work shows that transient collections of water are not
sources of infection after recent contamination, whereas all per-
manent collections of water, as in rivers, canals and marshes,
are dangerous if inhabited by a suitable intermediate host.
The removal of infected persons from a given body of water
would have no immediate effect in reducing its infectiveness,
since the snails discharge cercarize into the water for a prolonged
period. The preventive measures briefly outlined above were
worked out by Leiper for the special conditions existing in the
infected parts of Egypt but in a broad way they are applicable
wherever Schistosoma hematobium occurs.

Other Species. — There are two other species of Schistosoma
which are pathogenic to man. One, S. mansoni, was long con-
fused with S. hematobium, the only apparent differences having
been observed in the eggs. The eggs of S. mansoni (Fig. 65B)
are provided with a lateral instead of a terminal spine, and are
voided in the digestive tract and its appendages, whence they are
liberated with the feces, instead of making an exit from the body
ya way of the urinary organs. By experimental infections of

ice Leiper showed that cercarie from the snail Planorbis boissyr
(Fig. 66B) developed into worms somewhat smaller than those
from the species of Bullinus, with certain distinct differences in |
anatomy. The cercariz from Planorbis produced only lateral-
spined eggs which were voided with the feces, thus showing that
S. mansoni was really a distinct species and not merely an abnor-
mal type of S. hematobium. This parasite occurs in common with
the foregoing species in many parts of Africa and is also common
in the West Indies, Venezuela and perhaps other parts of tropi-
cal America. Like the hookworm, it was probably introduced
from Africa in the slave days. The intermediate host in Ven-
ezuela has recently been shown by Iturbe and Gonzales to be
the snail Planorbis guadelupensis, whereas in Brazil Lutz has
shown P. olivaceus to be the intermediate host.

The anemia and debility caused by S. mansoni is similar to that
caused by S. hematobium. The irritation and inflammation of
the urinary organs is replaced, however, by similar symptoms of
the intestine, and a kind of dysentery often results. .—

The manner of transmission of the parasite is similar to that

7

218 THE FLUKES

of Schistosoma hematobium except that infected faeces instead of
urine contaminates water inhabited by a suitable intermediate
host, as Planorbis boissyt.

A third species of Schistosoma, S. japonicum, is endaaag in
parts of Japan, China and the Philippine Islands, and perhaps
in many other oriental countries. It is slightly smaller than
the other species (about two-fifths of an inch in length) and pro-
duces eggs (Fig. 65C) which do not have the spine that is so
characteristic of the other species of Schistosoma, but only a
rudiment in the form of a little lateral knob. The eggs of S.
japonicum, like those of S. mansont, are voided from the intestine
with the feces. They also frequently become lodged in the
liver gall bladder, walls of mesenteric bloodvessels, spleen, pan-
creas, and sometimes other organs, not even the brain being
exempt. The female worm must in some way deposit her eggs
outstde the bloodvessel in which she lives since they are ap-.
parently carried to their destination by the lymph streams.
Severe infections with this parasite usually prove fatal sooner or
later, and post-mortem examinations show many of the organs
of the body to be badly affected. Infection with S. zaponicum
is associated with a skin disease known to the natives as “ ka-
bure,” and probably caused by the burrowing of the cercarize
in the skin. According to Laning of the U. 8. Navy, it is not an
uncommon thing for large per cents of the crews of patrol gun-
boats in the Yangtze River to be completely disabled by infection
with this parasite. Laning divides the disease caused by S.
japonicum into three stages. The first stage, lasting from three
to six weeks, is marked by high afternoon temperatures, slow
pulse, respiratory troubles, transient cedema and rash on the
skin and mucous membranes, abdominal pains, digestive irregu-
larities and sometimes mental disturbances. The second stage
is marked by enlarged liver and spleen, dysenteric symptoms,
anemia and irregular fever. The third stage, which does not
always occur, but may appear in from three to five years where
there are constant reinfections, is marked by diseased liver,
cedema of legs and arms, emaciation, anemia and dysentery,
and death from exhaustion is not uncommon.

The life history and mode of infection in the case of S. japonicum
is undoubtedly very similar to that in other species of Schistosoma.
Miyairi, a Japanese investigator, found reproductive stages of

LIFE HISTORY OF SCHISTOSOMA JAPONICUM 219

S. japonicum in a species of Iamnea in Japan. Miyairi and
Suzuki, in further work on the life history of this fluke, found
that after sporocysts have developed in the tissues of infected
snails redie are produced, 50 or more from each sporocyst.
The long, coiled rediz crowd the liver and produce cercariz, the
latter reaching maturity in about seven weeks. If in autumn
the cercarie have become fully developed but have not left
the snails they remain in their hosts over winter.

Leiper obtained development of the characteristic fork-tailed
cercariz in another small snail, Blanfordia (or Katajama) noso-
phora, common in the rice fields of Japan. There is an interest-
ing tale connected with ,
Leiper’s experiments on
infection with these para-
sites. With great care this
investigator experimented
with the infection of snails
which he had imported
from Japan to work on in
his laboratory at Shanghai.
After having succeeded in
obtaining infection of the
snails, he teased out the
livers in water to liber-
ate the cercarie. Four
laboratory-bred mice, SSG
which are difficult to ob- Fic. 68. Mesentery of mouse with blood-
tain in the Orient, were cee infected with Schistosoma. (After
immersed in the water
in which the cercarie had been liberated, and a start was made
for England. But alas! a woman in a neighboring stateroom
objected to the presence of the mice so near and demanded their
relegation to the butcher’s cabin, where three of them died. At
Aden the few remaining infected molluscs were sacrificed and
the last mouse was subjected to infection. A month later when
the animal was examined in the laboratory of the London School
of Tropical Medicine many blood flukes, males and females in
couples, were found in the portal bloodvessels (Fig. 68).

It should be remarked in concluding this discussion of the
blood flukes that many snails, including members of the genera

220 THE FLUKES

Planorbis and Limnea, which could very probably act as inter-
mediate hosts as well as the species in which the development
has actually been observed, are abundant in the United States,
and there is great danger that if once introduced, at least in the
warmer parts of the country, these blood flukes might become
endemic. Careful examination of immigrants from endemic
countries and exclusion of Schistosoma-infected persons is impor-
tant if the infection is to be kept from becoming established.
An ounce of prevention in this country is worth a pound of cure.

Lung Flukes

In Japan, China, the Philippines, and other oriental countries,
a region which seems to be particularly afflicted with fluke dis-
eases, there occurs a very serious lung disease caused by a species
of fluke, Paragonimus ringeri (westermani) (Fig. 69). It is also

Fic. 69. Lung fluke, Paragonimus ringeri. Abbreviations as in Fig. 74.
xX about 7. (Partly after Looss, partly after Leuckart.)

found in dogs. In some parts of Formosa fully 50 per cent of
the population is infected. A closely allied species, P. kellicotti,
occurs in hogs in the United States, and probably in other parts
of the world.

The lung fluke is about half an inch in length, reddish brown
in color, and relatively very broad. The adult lives most fre-
quently in the lungs of its host, where it produces cavities an
inch or two in diameter. The cavities become filled with various

LUNG FLUKES . DaN

tissues through which the parasite tunnels out its burrows and
in which it deposits its eggs (Fig. 70). These excavations in the
lung connect with the bronchial tubes, through which the blood,
parasite eggs and other products are voided, thus causing the
characteristic blood-spitting. The
expectorations, resembling those
of pneumonia, are of a peculiar
brownish red color, due in part
to the blood corpuscles present
and in part to the dark brown
fluke eggs, which are often very
abundant.

Occasionally the lung fluke bur-
rows in other organs and glands yg. 70. Begs of lung fluke in
of the body, such as the liver, contents of cyst in lung of hog. x

. Sc about 50. (After Stiles and Hassall.)
spleen, muscles, intestine and

brain. Musgrave found in the Philippines that sometimes many

parts of the body are infested at once, and in one case he found
over a hundred mature parasites in a muscular abscess. When
they burrow in the brain they cause epileptic fits and usually in
time cause death.

The eggs of the lung fluke (Fig. 71A) when immersed in fresh
water for several weeks develop
within themselves typical ciliated
embryos or miracidia (Fig. 71B).
The latter burst away the little
cap at the end of the egg and
emerge as free-living animals.

Fie. 71. A, freshly passed ege Nakagawa has recently shown
of lung fluke; B, egg of lung fluke that if these miracidia are placed
with fully developed embryo. x . : : .
gen | (Atter Katsurada.) in water with certain species of

snails, particularly Melania lber-
tina, the inbacidia swarm about the snails and burrow into them,
shedding their cilia as they go. The entire cycle of development
in the snail has not been worked out but it is probably very similar
to that of Schistosoma. Sporocysts of various sizes occur in the
liver and other tissues of the snail, and it is probable that these
produce the cercariz directly.

Nakagawa discovered the encysted cercarie of this species,
proved to be such by experimental infection of animals, in three

222 THE FLUKES

species of crabs in Formosa, and Yoshida, another Japanese in-
vestigator, acting on the discovery of his countryman, found the
larvee in a fourth species of crab in Japan. The crabs most com-
monly infected are Potamon obtusipes, a coarse-shelled, chestnut-
colored crab about one and a
half inches in diameter, and
P. dehaani, a slightly smaller
species, grayish black or red-
dish in color. Both these
crabs bound in the shallow
waters of mountain streams,
and the former species is
: sometimes used as food. An-
Fig. 72. A common fresh-water crab other implicated species,
of Tepan, rive faponicns which sos Eriocheir japonicus (Fig, 72),
is abundant in all plains rivers
in Japan and is a common article of diet throughout the country.
It is a larger crab, reaching a diameter of three inches, and has
large hairy claws. The fourth species, Sesarma dehaani, is of
medium size, dark in color with light reddish claws, and inedible.
Miyairi has shown that in Korea another crab, Astacus japonicus,
is the intermediate host.
The lung fluke cercarie encysted in these crabs (Fig. 73A)
were found chiefly in the liver while young, but when older they

Fic. 73. A, encysted cercaria of human lung fluke, Paragonimus ringeri, from
gill of crab; B, larva emerging from cyst. o.s., oral sucker; int., intestine; ex. v.,
excretory vesicle; v. s., ventral sucker. x50. (After Yoshida.)

occur in the gills. They vary in number from a few to several
hundred. In some localities a very high per cent of crabs are
infected, Nakagawa reporting that practically 100 per cent are
infected in one district in Formosa where the lung fluke is very
common. The cysts containing the cercarie are nearly round,
0.5 mm. (45 of an inch) or less in diameter, and have relatively

LUNG FLUKES af

thick walls. The enclosed cercaria lies straight, unlike most
encysted cercarie, and the body is entirely covered by short
spines. In fully-developed specimens the suckers, digestive
tract and other parts of the anatomy of the enclosed cercariz can
be seen (Fig. 73A). While still in the cysts the cercariz are fairly
resistant to unfavorable environmental influences, but are easily
destroyed after hatching.

When an encysted cercaria is swallowed by a susceptible ani-
mal the cyst wall is dissolved off in the intestine, the active
liberated larva (Fig. 73B) bores through the intestinal wall,
wanders about in the abdominal cavity for some time, then
bores through the diaphragm into the pleural cavity, whence it
eventually penetrates the lungs from the outer surface. It
becomes mature in about 90 days. Occasionally the worms
apparently get lost and bore through the abdominal wall and
muscular connective tissues. It is probably in this way that
other organs than the lungs are penetrated by the flukes.

There are two ways in which man may become infected, namely,
by eating infected crabs which are not thoroughly cooked, or
by drinking water containing cysts discharged from infected
crabs. As already remarked, the mature cysts make their way
to the gills, whence they can easily be removed, and whence
they probably escape readily under natural conditions, thus
becoming free in the water. Here they may remain alive for
some time, probably 30 days or more. Yoshida states that the
cysts sink to the bottom, in which case human infection could
occur only rarely if ever from infected water. Nakagawa, how-
ever, observed that 20 per cent of the larve when freed float
on the surface of the water.

Prevention of infection, in Japan at least, obviously consists in
abstinence from raw crabs as food and in avoidance of water for
drinking which may possibly be infected. Whether or not other
animals may serve as hosts for the cercarie is unknown, but if
the allied Paragonimus kellicott: is truly endemic in the United
States, where no fresh-water crabs are found, some other animal
must serve as an intermediate host, possibly certain species of
crayfish. The fact that the lung fluke is not known as an en-
demic human parasite in this country suggests that the inter-
mediate host may be an animal which is not used as food and the
habits of which give little opportunity for the parasites to gain

224 3 THE FLUKES

access to the human body. The disease is said to have increased
in Peru, having been introduced there by Japanese and Chinese
laborers. If this is true some Peruvian animal, probably a
fresh-water crab, must serve as an intermediate host. This
suggests that the disease if once intro-
duced might flourish in other countries,
especially where fresh-water crustaceans
are eaten. Lung fluke infection is
evidently another disease for which a
quarantine should be established.

Liver Flukes

Although the liver fluke of the sheep,
Fasciola hepatica, and other flukes of
herbivorous animals are occasionally
found in man, they cannot be looked
upon as usual human parasites. Adult
E liver flukes are sometimes accidentally
Sh-i------t- eaten with raw liver, in which case

4 they attach themselves to the mem-
branes of the throat, causing irritation,
congestion, a buzzing in the ears,
difficult breathing, and other quite

Pp ee exe-P: alarming symptoms. Vomiting to ex-
Fic. 74. The Chinese fluke, ne] the worms usually gives immediate

Opisthorchis sinensis. X 3%. ;
m., mouth in oral sucker; ph., relief.

pharynx; gen. p., genital pores; = There are several species of flukes,
v. s., ventral sucker; sh. gl., so- :
called vittelline or yolk glands, however, which are apparently espe-
really shell glands; ut., coiled Gially adapted for parasitizing carnivo-
egg-filled uterus; int., intestine; : 4
sp. d., sperm duct; ov., ovary; TOUS animals, and which are common
sem. rec., seminal receptacle, hyman parasites in some eoumume-:
where sperms for fertilizing eggs i BAS
are temporarily stored; t., testis; Japan, China, the Philippines and other
exc. ¢., exeretory canal; exe. D., oriental countries are especially afflicted
excretory pore. (After Stiles.) 2
by these flukes. The commonest species
in man is the Chinese fluke, Clonorchis sinensis (Fig. 74) which
is found in all of southern Asia from India to Korea. In some
parts of Japan about 60 per cent of the population are said to
harbor it in their livers, sometimes in hundreds or even thousands.

Leiper found it common in both dog and man in the vicinity

i re -~----Sem.rec.

HUMAN LIVER FLUKES 225

of Shanghai. It is also found in the liver ducts of cats, hogs,
and probably other flesh-eating animals. It is from one-half to
three-quarters of an inch in length, and nearly four times as long
as wide. The ventral sucker is very small, and is situated on the
anterior third of the body. Some authors believe that a small
variety of this fluke found in Japan constitutes another species,
C. endemicus, but this view is assailed by recent investigations.
In Europe there’ occurs
a species, Opzisthorchis
felineus (Fig. 75A),
which is very common
in domestic cats and
dogs and is by no means
uncommon in man;
there is one record of its
having been found in
eight or nine out of 124
post mortem examina-
tions in Siberia. A very
closely related species,
O. pseudofelineus (Fig. § W} Zit: i
75B), has been found in_ | BN. as. es : Ni
eats and coyotes in the | Wait =i
central parts of the
United States. From
its similarity to the Old
World species it would
not be surprising to find
it occasionally parasitic

in man.
: Fie. 75. <A, Cat fluke, Opisthorchis felineus;
The European Species, B, American cat fluke, O. pseudofelineus. Abbre-
Opisthorchis felineus, 1S viations as in Fig. 74. x about 5. (A, after

usually a i lenlessiitian Stiles and Hassall; B, after Stiles.)

half an inch in length, and shaped very much like Clonorchis
sinensis. The American O. pseudofelineus is somewhat longer
and slenderer than the European species. Another species of
the same genus, O. noverca, occurs commonly: in pariah dogs
in India, and occasionally in man. It differs from the Euro-
pean species chiefly in having the skin thickly beset with
spines.

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226 THE FLUKES

Little is known of the life history of any species except the
Chinese fluke, C. sinensis. The eggs (Fig. 76A) are of charac-
teristic shape, and hatch in water into miracidia (Fig. 76B).
The encysted cercarie of this fluke (Fig. 77A) have been found
in the subcutaneous tissues and
muscles of 12 different species
of fresh-water fish. The cysts,
which are very small, measuring
only about 0.14 by 0.10 mm. (;4,
by z%o of an inch), are usually -
more abundant in the superfi-

Fic. 76. Egg and ciliated em- Clal than in the deeper tissues.
bryo of Chinese fluke, Opisthorchis Although cysts can be found in
sinensis. X 700. (After Katsurada.) fish throughout the eae
younger ones are more frequently met with in late summer and
early autumn.

When infected fish are eaten, according to experiments re-
cently made with animals by Kobayashi, the larval flukes escape
from the cysts (Fig. 77B) within three hours, and in fifteen hours
they may; already have
reached the bile duct and gall
bladder. The parasites reach
maturity and eggs are found
in the feces of the host within
26 days. The young flukes
have a spiny cuticle until
nearly mature, but the spines
finally disappear. SN

The first intermediate host Fic. 77. Larve of Chinese fluke; 4,
: : -;; cercaria encysted in fish; B, larva freed
into which newly hatched cili- from cyst; m., mouth in oral sucker; v.s.,
ated embryos penetrate is not ventral sucker; ex. v., excretory vesicle;
certainly ica yet, Bui ph., pharynx; int., intestine.
Kobayashi believes it is one or more of the several species of snails
of the genus Melania, especially Melania libertina. These snails
have been found to harbor cercariz which bear a distinct resem- .
blance to the young encysted larve of the Chinese fluke, and they
are abundant in rivers and swamps of regions where ie liver
infection prevails.

It is probable that the European liver fluke, O. felineus, and its
Indian and American allies all have histories very similar to that

HUMAN LIVER FLUKES Dalat |

of the oriental species. ‘Their occurrence in man in countries
where fresh-water fish is a common article of diet, and their’
frequency in animals which eat raw fish, strongly suggest fishes
as intermediate hosts.

These liver flukes, like the sheep fluke, live chiefly in the gall
bladder and bile ducts where they often cause much mechanical
obstruction on account of their large numbers. Severe infec-
tions such as occur in countries like Japan where raw fish is
commonly eaten cause symptoms of a very serious nature. One
of the most prominent of these is enlargement of the liver ac-
companied by more or less bloody diarrhea; the latter becomes
more and more constant as time goes on. The liver sometimes
‘becomes painful, and jaundice is a frequent symptom. The
patient becomes anemic, emaciated and weak;*and is ready prey
for other diseases. There are often periods of partial recovery
followed by relapses, probably due to reinfections, and the patient
ultimately becomes exhausted and succumbs to a cold, an attack
of malaria, or other ailment from which one would ordinarily
recover readily.

There is no specific treatment for the disease. The only
measures that can be taken are to remove the patient from any
possible source of reinfection and to keep him in the best possible
general health, with wholesome diet, good air and proper ex-
ercise. How long the flukes persist in the liver is not known.

Means of prevention of the disease are suggested by what is
known of the life history of the parasites. The most important
measure is unquestionably the suppression of the habit of eating
uncooked fish in places where the disease is endemic.

Kobayashi has shown that while the larve of C. sinensis are
killed at once on exposure to a boiling temperature and in a short
time when exposed to considerably lower temperatures, they are
not destroyed by exposure to vinegar for five hours, nor by re-
frigeration.

A second measure, which is far less reliable, is the prevention
of contamination of water in which fish live. It is impossible to
prevent some contamination of water by the lower animals which
carry the infection, and it is nearly as difficult to prevent con-
tamination by human feces. - The almost universal use of night
soil (human feces) for fertilizer in oriental countries is a serious
hindrance to the sanitary disposal of such infected material.

228 THE FLUKES

Leiper suggests that this problem may be solved by a chemical
treatment of night soil which would destroy all parasite eggs or
cysts and yet not injure its value as a fertilizer.

Intestinal Flukes

There are several species of flukes which appear to be common
parasites of the human intestine in certain parts. of the world,
especially in the oriental countries where the other human flukes
abound the most. Many of these flukes are very small, but they
may occur in great numbers, producing practically the same effects
as do tapeworms, — anemia, emaciation and general debility.
Many species are probably only accidental human parasites,
normally living in some other host but occasionally finding their
way into the human intestine with food or water and establishing
themselves there.

The smallest fluke known to be parasitic in man is Yokagawa
yokagawa, named after a Japanese parasitologist. It is widely
distributed in Japan, Korea, Formosa, parts of China, and
_ probably other oriental countries. It infects mice and dogs as
wellas man. The whole life history is unknown but the encysted
cercariz are known to occur in the “‘ ayu,”’ a Japanese fresh-water
fish which is commonly eaten raw, and in a number of other kinds —
of fish. The cysts are most numerous in the connective tissue
under the skin and about the fins, especially early in the season,
indicating that the fish become infected by free-swimming cer-
cariz which bore through the skin, and not by cercarie eaten
with another host. The encysted cercarize closely resemble those
of Clonorchis sinensis. The development in the final host is
said to take only from seven to ten days. Y. yokagawa inhabits
the upper portion of the small intestine, sometimes in consider-
able numbers, but it never seems to do enough damage to cause
more than a slight intestinal catarrh. It is remarkable for the
lack of a ventral sucker and is only about 1 mm. (about 3, of an
inch) in length, and about half as broad. Its body is covered
with a great many microscopic spines.

A very similar fluke, Heterophyes heterophyes (Fig. 62), only
slightly larger, occurs in a variety of animals from Egypt to
Japan, and occasionally parasitizes man. Two species of Hchi-
nostoma normally parasitic in other animals occur occasionally

INTESTINAL FLUKES 229

in man in the Malay countries. They are distinguished from

other flukes by the crown of spines around the mouth sucker.

One species, EH. ilocanum, about one-fifth of an inch long, was
found endemic among some Filipinos in a prison in Manila.
The other, EL. malayanum, about two-fifths of an inch long, oc-
casionally parasitizes man in the Malay countries.
Gastrodiscoides hominis (Fig. 78) is a species which is character-
ized by the expansion of the posterior end of the body into a great

Fic. 78. Gastrodicoides hominis. A, ventral view, showing disc-like .expansion
and posterior position of ventral sucker; B and C, dorsal views; D, lateral view;
E, eggs. A-D, x3; HE, x 65. (After Lewis and McConnell.)

concave disc. It is a small reddish brown parasite a little over
one-fourth of an inch in length, which inhabits the cecum and
large intestine of hogs, and occasionally of man, in India. A
closely allied species occurs in horses and
asses in many parts of Africa. Watsonius
watsom (Fig. 79) is a related species, also
reddish brown in color, found in the small
intestine of West African negroes. A
closely related species, Paramphistomum cern,
is found in the stomach of sheep and cattle
in Egypt and has a life history almost a
identical with that of the sheep liver fluke. jye.79. Watsonius
This or a very similar species occurs in the watsoni. Note promi-
stomach of cattle in the United States. oe panei tay a
Several large flukes of the genus Fasciolopsis posterior ventral
occur occasionally in man, especially F. buski aa Seay
(Fig. 80), found in many Hast Asian countries. from Stiles and Gold-
This species reaches a length of over an inch papers
with a width of about half an inch, and has the ventral sucker
very close to the mouth. It normally inhabits the small intestine
of the hog but occasionally parasitizes man. The larval stages
are said to encyst in shrimps, but Leiper had no success in in-
fecting hogs with the cysts which he found in shrimps.

230 THE FLUKES

The full life history of none of these intestinal parasites is
known, and we can only guess at them by analogy with more or
less closely related parasites about which we have more knowledge.
None of them do enough damage to cause more than slight in-

nat.size,

Fic. 80. Fasciolopsis. buski,-a large intestinal fluke of man. xX 24. Abbrevia-
tions as in Fig. 74. (After Odhner.)

testinal irritation or catarrh, and sometimes light dysenteric
symptoms. They are susceptible to most of the drugs used for
expelling tapeworms and roundworms. Some species are said
not to be affected readily by santonin, though they are expelled
by thymol and naphthalene, and presumably by oil of chenopo- -
dium.

CHAPTER XIII
THE TAPEWORMS

General Structure. —— Even more
peculiar and remarkable in their
structure and life than the flukes
are the tapeworms. A mature tape-
worm is not an individual, but a
whole family, consisting sometimes
of many hundreds of individuals one
behind the other like the links of a
chain (Fig. 81). In some respects
the tapeworms are more -degener-
ate than flukes, due to their in-
variably parasitic life in the digestive
tract of their hosts. Being continu-
ally bathed in semi-digested fluids
in the intestine they can readily
absorb food all over the surface of
their bodies, and have no need for a
digestive system of their own. The
digestive tract, therefore, is entirely
lacking, not even a vestige of it
remaining as an heirloom from less
dependent ancestors.

In general form the majority of
tapeworms are very long tapelike
organisms which attach themselves
to their host’s intestinal walls by a
“head ” or scolex at what is really
the posterior end of the chain of a
segments. This scolex is furnished fFic.81. Beef tapeworm, Tenia
with suckers and often hooks as well 877” 3. Note small head,

‘ gradual change in size of proglot-
(Fig. 82). Next to the head there tids, and irregular alternation of

is a narrow region or “neck” ee genital apertures. (After
which continually grows and forms
segments as it grows, each new segment thus produced pushing

forward the segments previous'y formed. This process eventu-
231

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232 THE TAPEWORMS

ally produces the characteristic chain of segments, each of which
is known as a proglottid. Obviously the oldest proglottid is the
one at the end of the chain, those just back of the neck being
young and immature. The nervous
system, which is developed into a
primitive brainlike mass in the scolex,
grows forward as two _ longitudinal
nerves which run continuously through
all the proglottids in the chain. The
muscles and excretory canals also run
js continuously through the chain. Each
Fie. 82. Armed and un- :

armed tapeworm “heads” or Proglottid, however, possesses com-
scoleces; A, unarmed head of plete reproductive systems of both

Tenia saginata; B, armed head 3
nt Mics Co Oe 10. sexes, fully as complex as in the
flukes, if not more so (Fig. 83). The
female system consists of an ovary, a pair of shell glands (usually
spoken of as yolk glands), a seminal receptacle for receiving and
holding the sperms until used for fertilization, a vagina for the

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Fic. 83. Sexually mature proglottid of beef tapeworm, Tenia saginata; exc. C.,
_ excretory canal; n., nerve cord; ut., uterus; ov., ovary; sh. gl., shell gland,
usually called yolk gland; vag., vagina; gen. p., genital pore; sp. d., sperm duct;
t., testis. Xx 7. (Partly after Leuckart.)

entrance of the sperms, and a uterus for the storage of the mature
fertilized eggs. The male system consists of a number of scat-
tered testes for production of sperms, all connecting by minute
tubes with the sperm duct. The latter, near where it opens at
the surface of the body, enlarges into a “ cirrus pouch ” where

REPRODUCTION 250

the mature sperms are temporarily stored. The sperm duct
ends in an extensible copulatory organ for conducting the sperms
into the vagina of the same or another proglottid. Though
hermaphroditic, 7.e., with both sexes in a single individual, a

Fic. 84. Ripe proglottids of various tapeworms of man, drawn to scale accord-
ing to average measurements: A, Tenia saginata (after Leuckart). B, Tenia solium
(after Stiles). C, Dipylidium caninum (after Diamare). D, Tenia confusa (after
Guyer). E, Dibothriocephalus latus (after Leuckart). F, Diplogonoporus grandis
(after Ijima and Kurimoto). G, Dibothriocephalus cordatus (after Leuckart). 4H,
Tenia africana (after von Linstow). I, Hymenolepis diminuta (after Grassi).
J, Hymenolepis nana (after Leuckart).

proglottid does not necessarily always fertilize its own eggs,
but cross-fertilization may often occur. This is generally in-
sured by the fact that the male reproductive system usually
becomes mature before the female. In the pork tapeworm,

234 THE TAPEWORMS

for instance, the male reproductive system reaches maturity
when the proglottid has been pushed back to about the 200th
position, whereas the female system does not mature until it
has been pushed 200 or 300 proglottids farther back. Copulation
then takes place by the doubling back of the chain of proglottids
on itself, bringing the young mature male segments into contact
with the older mature female segments.

After copulation, when the mature fertilized eggs begin to form,
great changes take place in the proglottid. The uterus begins
to enlarge and branch until it nearly fills the segment, crowding
aside and absorbing the other organs. Segments thus distended
with eggs are spoken of as “‘ ripe”’ proglottids and are ready to
break loose from the chain to be voided with the feces of the host.
Ripe proglottids of a number of species of tapeworms found in
man are shown in Fig. 84.

Life History. — The life histories of all tapeworms are much .
alike. Usually before the ripe proglottids become detached and
pass out of the host, the
eggs develop, inside their
tough shell, into little
round embryos with six
hooks (Fig. 85A). In

order to continue their

Fia. 85. <A, egg of beef tapeworm, 7’. saginata; d 1 t ii
—note contained embryo and external filaments; evelopment suc em-
B, freed six-hooked embryo. x 300. (After bryos must be eaten by

Leuckart.) : :

another species of animal
which acts as an intermediate host. Most often the adult
form of the worm occurs in carnivorous animals, while the in-
termediate host in which the larva develops is a herbivorous
animal, but there are numerous exceptions to this. ‘There is no
active search for a new host on the part of the tapeworm embryo
as there is by the embryos of flukes, but instead merely a
passive transfer.

When eaten by a suitable intermediate host, the shell nel
the six-hooked embryo is dissolved off, and the embryo is re-
leased (Fig. 85B). It migrates into the organs and tissues of
the body, aided by the blood and lymph circulation of the host,
some species having preference for certain organs, others es-
tablishing themselves with equal readiness in any parts which
they happen to reach.

TYPES OF TAPEWORM LARVA 2a0

Having reached the organ or tissue in which it is destined to
develop, the embryo loses its hooks and grows into some form of
bladderworm, that is, the body undergoes a series of transfor-
mations which usually result in the formation of a bladder-like
body filled with a watery fluid. Into the bladder there grows
an invagination and at the bottom of this, pushed inside out into
it, there develops a head or scolex. There are different types
of bladderworms which go under different names, as follows:
(1) the cysticercus (Fig. 86A), the simple type described above;
(2) the cysticercoid (Fig. 86B), in which the bladder part of the

Fic. 86. Types of tapeworm larve: A, cysticercus of Tenia solium with head
and neck evaginated, Xx 3; B, cysticercoid of Hymenolepis nana, X 12; C, plerocer-
coid of Dibothriocephalus latus, with head invaginated. (A, partly after Stiles, B,
from several figs. by Grassi and Rovelli; C, partly after Braun.)

worm is poorly developed; (3) the cenurus, in which multiple
heads form in the single bladder; and (4) the hydatid, in which
the bladder buds into multiple daughter cysts, each with multiple
heads (Fig. 95). The larve of the tapeworms of the family
Dibothriocephalide are quite unlike the bladderworms of other
tapeworms. They grow as long wrinkled wormlike .bodies with
the head invaginated in a little projection at the anterior end.
Such a larva is called a plerocercoid (Fig. 86C).

When the organs or tissues in which the larval stages are
developed are eaten by an animal of the kind from which the eggs
originally came, all but the scolex of the bladderworm is digested
off, the latter turns right side out, attaches itself to the wall of
the small intestine with the aid of its suckers and hooks, and be-
gins to bud off proglottids of another generation. Tapeworms
are usually looked upon as inert animals, but in reality they are
quite active, and their movements can often be felt.

236 THE TAPEWORMS

Damage to Host.— The amount of damage which adult
tapeworms do to their hosts is a much disputed question. There
are those who believe that the presence of an adult tapeworm is
more or less of a joke and as such is to be gotten out of the sys-
tem but not to be taken seriously. The experience of physicians
who have had wide dealings with tapeworms does not ordinarily
bear out this idea. The mere mechanical obstruction of the
intestine which a large tapeworm may cause must be consider-
able. The amount of food taken from the host for nourishment
of such a worm might well be compared with the food absorbed
by a growing embryo, and it usually produces a ravenous appetite.
The injury to the wall of the intestine caused by the adhesion
of the worm by its suckers and hooks is often the cause of serious
conditions, allowing the entrance of bacteria and sometimes
resulting in destructive ulceration. The waste products and
other toxic substances given off by tapeworms must be very con-
siderable and their poisonous properties cannot be doubted.
Only recently there came before the notice of the author a case
of tapeworm infection illustrating the toxic effect of the worms.
A patient came to a local physician for treatment, thinking he
had tuberculosis and having been so diagnosed by another doc-
tor. He was in an extremely anemic condition and was very
weak and easily exhausted. His cheeks were sunken, his eye
staring and he was subject to occasional mental disturbances.
Within a fortnight after the worm had been expelled he was prac-
tically a new man although he had been suffering for over a year.

Abdominal pains, anal itching, disordered appetite and di-
gestion, emaciation, anemia and many types of nervous derange-
ments, as giddiness, partial paralysis, false sensations and epilep-
tic fits, are common symptoms of tapeworm infection. The
degree to which each of these symptoms is felt varies remarkably
in different individuals. The nervous symptoms are all due to
intoxicating substances liberated by the worms. Sometimes
a partial immunity to the toxic effects of worms is acquired by
infected people, and in such cases the worms may be present
unnoticed for years.

The damage done by bladderworm stages of tapeworms is
often more serious, especially in the case of hydatids, the large
multiple bladderworms of Echinococcus granulosus. The bladder-
worms which occur in man most commonly develop in the lung

TREATMENT AND PREVENTION 237

or liver, but- may attack other parts of the body such as the
muscles, eye and even the brain. They do injury both by me-
chanical interference with the organs and tissues, and by the
accumulation of poisonous waste products which may be ac-
cidentally liberated. Only by surgery can such bladderworms
be removed, and surgery is often impossible on account of the
numbers and positions of the bladders.

Treatment. — Preparatory to treatment for adult tapeworm in-
fections the patient is put on a light diet and his bowels cleared out
so that the parasite may meet with no obstruction in its passage
through the intestine. The drugs which have been found most
useful in expelling tapeworms are male fern, pelletririne and
thymol. These drugs are dangerous if not taken properly, and
none should be taken without the supervision of a physician.
Thymol, for instance, while ordinarily quite harmless since it is
not absorbed by the intestine, is soluble in alcohol and certain other
substances and may cause death if taken along with these things.
Oil of chenopodium, which has recently come into great favor
for expelling hookworms and is even more efficient for certain
other nematodes, has been found valuable for expelling dwarf
tapeworms, Hymenolepis nana, and would probably be equally
effective for other species.

After the drug is administered a purgative is given which tends
to drive the parasite out. The latter should be passed into a
vessel of warm water, since sudden contact with cold stimulates
the nervous system of the worm and causes it to contract sud-
denly, thus often breaking it before it has been completely ex-
pelled. A careful search for the head should be made, and if
not found the treatment should be repeated in the course of a
week or ten days.

Prevention. — Prevention varies, of course, with the species of
tapeworm and its intermediate host, but since infection with all
the common human species, with the exception of the species
of Hymenolepis, occurs from eating raw or imperfectly cooked
meat of some kind in which the bladderworms have devel-
-oped, the exclusive use of thoroughly cooked meat is the best
preventive measure. Experiments show that pork bladder-
worms are killed when heated to 127° F. and beef bladderworms
to 120° or even less, but the difficulty of heating the center of a
large piece of meat even to this point is shown by the fact that

238 THE TAPEWORMS

in an experiment to test the penetration of heat, a ham cooked
by boiling for two hours had reached a temperature of only
115° in the center. When roasted, pork should always be cut
into pieces weighing no more than three or four pounds to insure
thorough penetration of heat. Beef which has lost its red or
“rare” color is quite safe.

Since bladderworms are unable to survive the death of their
host for more than a limited time, they are eventually destroyed
by ordinary cold storage — within three weeks in the case of the
beef bladderworm, Cysticercus bovis, but not always so soon in
the case of the pork bladderworm, C. cellulose. According to
Dr. Ransom temperatures of about 15° F. kill beef bladder-
worms within five days. Thorough curing or salting of meat is
also destructive to the parasites.

Infected persons should be careful not to contaminate the
food or water of domestic animals with their feces, bearing in

Fic. 87. Heads of some adult tapeworms found in man, drawn to scale; A,
beef tapeworm, Tenia saginata; B, pork tapeworm, TJ. solium; C, fish tapeworm,
Dibothriocephalus latus; D, heart-headed tapeworm, Dibothriocephalus cordatus;
E, African tapeworm, 7. africana; F, double-pored dog tapeworm, Dipylidium
caninum; G, dwarf tapeworm, Hymenolepis nana; H, rat tapeworm, Hymenolepis
diminuta. x 10.

mind the various ways in which the eggs may be disseminated
— by streams, rain, flies, ete:

The eggs of the dwarf tapeworm, Hymenolepis nana, are
thought to be able to develop through the bladderworm stage
to the adult in a single host, and should therefore be guarded
against by different measures (see p. 243). The larve of other
species of Hymenolepis develop in insect larvee such as mealworms,
and are therefore subject to still different means of prevention.

The tapeworms of man belong to two quite distinct families,
the Tzeniide, in which the scolex is rounded and furnished with
four cup-shaped suckers (Fig. 87, A, B, E, F, G and H), and the

BEEF TAPEWORM 239

Dibothriocephalide, in which the head is flat and possesses two
slitlike suckers (Fig. 87C and D). The latter family also differs
from the Teniide in having eggs with lids like those of the
flukes (Fig. 88A), and without developed embryos when passed
in the feces.

Family Teniide

Beef Tapeworm. — The commonest human tapeworm in most
parts of the world is the beef tapeworm, Tenia saginata. The
adult of this species as it occurs in the
human small intestine consists of over
1000 proglottids, and grows to a length of
15 or 20 feet; cases have been reported
of specimens of this tapeworm which
measured 35 to 40 feet, though in some
of these cases there were probably several
tapeworms infesting a single person.
When two or more worms are expelled
in pieces it would naturally be easy to
measure them as parts of a single one.

The scolex of the beef tapeworm (Fig.
82A) is hardly larger than the head of a
pin. It possesses four small suckers for
adhering to the wall of the intestine, but
there is no crown of hooks. The suckers
are apparently quite sufficient for main-
taining a hold, if one should judge from
the difficulty experienced in dislodging the re. 88. Gravid segment
worm from the intestine. of Tenia saginaia. x 4.

: ; ; (After Stiles.)

The proglottids gradually increase in
size as they get farther from the scolex (Fig. 81), and the organs
contained in them develop slowly. The general form of a sexu-
ally mature proglottid and the appearance and arrangements of
the organs are shown in Fig. 83. Shortly after sexual maturity has
been reached and the sperms for fertilizing the eggs have been
received, the uterus begins to grow and develop lateral branches
to accommodate the rapidly forming eggs. When fully developed
the gravid proglottid enlarges, becoming three or four times as
long as when sexually mature, and resembles a pumpkin seed
in shape. The greatly developed uterus, distended with eggs,

240 THE TAPEWORMS

occupies practically the whole segment, while nearly all the other
organs degenerate (Fig. 88).

A man infested by a beef tapeworm expels several hundred
proglottids a month, each one gorged with many thousands of
eggs. Fortunately the majority of these never get an opportunity
to develop further but it is easy to see how some of the eggs may
reach their intermediate hosts, cattle, if the people who harbor
the worms are at all careless. Disseminated by rain water,
washed by streams into drinking troughs, carried about on the
feet of flies, adhering to the heel of a boot, and in many other
ways the eggs passed with the feces may be transferred to the
grass or water eaten by cattle. In India, where this tapeworm
is common, cattle are said to devour human excrement if they
have access to it.

When eaten by cattle or other ungulates, as the pronghorn
antelope, giraffe and llamas, the six-hooked embryos (Fig. 85)
escape from the eggs and migrate into the muscles of the new
host, attacking especially the muscles of mastication. Here in the
course of from three to six weeks they grow into bladderworms,
Cysticercus bovis, about one-third of an inch in length. They are
grayish white in color with a little yellow spot where the head is
invaginated. The fact that the cysts lack any marked contrast
to the muscle tissue, and if not very numerous may be obscured
by it, causes them to be overlooked frequently. If present they
ean usually be found most readily in the muscles of mastication
or in the heart; these are the portions of the carcass regularly
examined in meat inspection. Beef which contains bladder-
worms is said to be “‘ measly.”

Infection of man results, of course, from eating measly beef
which is raw or only partially cooked. In Abyssinia the Moham-
medans, who are forbidden by religious law to eat raw meat, are
practically free from tapeworm infection, whereas practically
all the non-Mohammedans are infected. The ripe proglottids
begin to appear in the feces, several at a time, in the course of
two or three months after infection, and may continue to be
developed for years.

Pork Tapeworm. — Common in some parts of the world, but
very rare in the United States, is the species Tenia solium,
which passes its bladderworm stage in hogs. Wherever raw or
imperfectly cooked pork is eaten, infection with this tapeworm is

PORK TAPEWORM 241

likely to occur. The infrequence of these tapeworms in the
Philippines where the bladderworms are very common in hogs
is worthy of note.

The adult Tenia solium differs from the beef tapeworm chiefly
in the form of the scolex, which in addition to four suckers is >
armed with a double row of hooks, arranged on a conical pro-
jection or “ rostellum ” at its apex (Fig. 82B). The worms are
usually of less length than beef tapeworms, seldom exceeding
from six to ten feet; they consist of about 800 or 900 segments.
The ripe proglottids (Fig. 84B) can in most cases be distinguished
from those of the beef tapeworm by their usually smaller size
and fewer branches of the uterus (compare Figs. 84A and B).

The eggs, passed in the ripe proglottids with the feces, develop
into bladderworms when eaten by hogs or cer- hae
tain other animals. The usual filthy way in
which hogs are housed and fed gives ample
opportunity for infection if the infested people
are at all careless in their personal habits, or
if privies are built so that they leak and the
hogs have access to the surrounding ground or —
outflowing streams. Young pigs are especially
likely to become ‘“‘ measly ” from eating tape-
worm eggs.

As soon as the eggs reach the intestine yy44 89. Fragment
the six-hooked embryos are liberated from of measly pork. (After
the enclosing capsule and make their way ea
through the wall of the intestine, to be carried by bloodvessels
to the place where they are to develop. They may develop
in almost any or all of the muscles or organs of the hog’s body,
but they especially favor the tongue, neck and shoulder muscles,
and, next in order, certain muscles of the hams. Sometimes
the bladderworms, technically known as Cysticercus cellulose, be-
come so numerous as to occupy over one-half of the total volume
of a piece of flesh examined, 7.e., several thousand to a pound.
They appear as small elliptical bladders from one-fourth to
three-fourths of an inch in length (Fig. 89). They have a whitish
spot at about the middle of the length, in the center of which is
the opening where the head is invaginated.

Unlike the beef tapeworm, Tenia solium can pass its bladder-
worm stage in a number of animals, namely hogs, man and dogs.

242 THE TAPEWORMS

They have been reported in a considerable number of other
animals also but the cases are very doubtful. The fact that the
larval stage can develop in man makes the species particularly
dangerous on account of possibility of self-infection, either by
contaminated hands or by a reversal of the peristaltic movements
of the intestine which throws the ripe proglottids of the worm back
into the stomach where the embryos in the eggs are liberated by
the gastric juices. This is discussed further on p. 251.

The Dwarf Tapeworms. — The dwarf tapeworm, Hymenolepis
nana (Fig. 90A), is the smallest tapeworm found in man, but
it often occurs in such numbers as to
cause much irritation in the intestine.
It is a common parasite in Italy, and
occurs throughout the warm parts of
Europe, Asia, Africa and America. It
is probably much more common in the
United States than is generally sup-
posed, since it can easily be overlooked
unless the feces are microscopically
examined for eggs. It is probably a
common parasite of rats and mice as
well as of man, though the rodent par-

Fa. 90. A, dwarf tapeworm, aSite is believed by some parasitolo-
Hymenolepis nana, X 7 (after gists tobe adistinctspecies, H.murina.
tein): B, cae of H. nana, X 709 Stiles considers the rodent parasite a

sub-species, H. nana fraterna.

The adult worm, which consists of from 100 to 200 proglottids,
is usually little over an inch in length and less than one mm. (35
of an inch) in width. The scolex (Fig. 87G) has four tiny suckers
and a crown of little hooks. The ripe proglottids (Fig. 84J)
differ from those of the large tapeworms in being much wider
than long, with the enlarged uterus in the form of a solid mass,
partially divided into compartments instead of being branched.

As regards life history, the dwarf tapeworm is commonly be-
lieved to pass both its larval and adult stages in a single host,
contrary to what occurs, so far as is known, in any other tape-
worm. The eggs (Fig. 90B), eaten by a rat or man, liberate six-
hooked embryos in the small intestine, where they enter the villi
and transform into cysticercoid bladderworms (Fig. 86B), which
in turn fall into the cavity of the intestine, attach themselves

DWARF TAPEWORM 243

by the armed head, and become adult. It is said that eggs of
this parasite can be found in the feces within a month after an
ege of the preceding generation has been swallowed. Self-
infection with these eggs rarely occurs, since the eggs will not
develop unless acted upon by the gastric juices. There is still
room for doubt as to whether an insect is not commonly involved
as an intermediate host as in other species of Hymenolepis; in
fact, several investigators have found cysticercoids in rat fleas
which they ascribed to this
species. Ransom thinks
there is room for doubt
as to whether the larve of
Hymenolepis found in the
intestinal villi of rats and
mice break out and become
mature in the lumen.
The common presence
of this parasite or a variety
of it in rats and mice indi-
cates that infection in man
may occur from accident-
ally swallowing the “‘ pills”’
of these animals infected
with the eggs or ripe pro-
glottids of the worm.
Since a single mouse “‘ pill”’
might contain hundreds
of eggs, each of which ure
could develop into an » Fic. 91. Rat tapeworm, Hymenolepis dimi-
adult in another rat or nuta, from house mouse in Oregon. Natural
mouse, or in man, it is ~~ |
not difficult to understand the great numbers of this worm which
are often found in a single intestine.

The unique life history of this species, if true, makes it subject
to entirely different preventive measures from those used against
most other tapeworms. Since infection results not from eating

_ bladderworm-infected meat,-but probably from swallowing egg-
infected faeces, especially the “ pills” of mice and rats, and pos-
sibly also from swallowing infected insects which are acting as
intermediate hosts, prevention consists in the elimination of

244 THE TAPEWORMS

rats and mice from the household and in keeping food out of
their reach, and in guarding against the accidental ingestion of
such possible intermediate hosts as fleas.

A closely allied species, H. diminuta (Fig. 91), occurs rarely
in man. It closely resembles the dwarf tapeworm but is of
larger size (four to 24 inches in length) and has no hooks on the
scolex (Fig. 87H). The eggs develop in the larve or adults of
the mealworm, Asopia farinalis, and in adult beetles, forming
cysticercoids. When these are eaten by rats, mice or man they
transform into adults. In an experiment on man the eggs of
the adult worm were found in the feces 15 days after the eating
of an infected mealworm. The larve of a number of species
of fleas also become infected when they ingest the eggs. It is
evident that prevention consists in guarding carefully against
the accidental swallowing of mealworms with cereals or other
foods, and in cautioning children against putting beetles or
other insects into their mouths. Although
the worm is rare in man it is common in
rats and mice in many parts of the world,
and occurs in nearly all parts of the United
States.

Other Tapeworms (Teniidz). — A con-
siderable number of other tapeworms of this
family have been found in man, acciden-
tally occurring in him, or having a very
= limited distribution.

Fie. 92. Davainea mad- + Of those with limited distribution should
agascariensis; A, head and i : :
neck, B, gravid proglottids. be mentioned two species of Davainea. One,
Beh ere ne ee D. madagascariensis (Fig. 92), is a small

tapeworm reaching a length of ten or twelve
inches. It is found, chiefly in children, in many tropical countries,
especially in islands and seaports and on ships. The suggestion has
been offered that the intermediate host, so far unknown, may be
the ubiquitous sea-going cockroach. This tapeworm is interesting
in that there is not only a crown of hooks on the head, but there
are hooks on the suckers also. The other species of Davainea
is D. formosana, recently described by Akashi from children in
Formosa and Tokyo. It differs from the preceding species in
its larger size, lack of hooks on the suckers, larger size of egg
masses in the ripe proglottids and in other minor details.

DIBOTHRIOCEPHALID 245

The African tapeworm, Tenia africana, is a species found in
German East Africa. It is about four feet in length with no
hooks on the scolex (Fig. 87E) and with an unusual fanlike ar-
rangement of the uterus in the ripe proglottids (Fig. 84G). Von
Linstow, who described the worm, suggests that the zebu may
be the intermediate host since its flesh is eaten raw by the
natives.

A medium-sized tapeworm, Tena philippina, reaching a
length of about three feet, has been found among prisoners at
Manila. It very much resembles the African tapeworm but has
smaller proglottids. Other species have been described from
various parts of the world, especially southern Asiatic Russia,
but they are of such rare occurrence, some having been found
only once, that they need no description here.

Two specimens of the species Tenia confusa, of which the
scolex is unknown and which consists of from 700 to 800 proglot-
tids, were found by Ward in Nebraska many years ago, but so
far as the author is aware no specimens have been obtained since.
A ripe proglottid of this species is shown in Fig. 84D.

Of the accidental tapeworms of man there should be mentioned
especially the dog tapeworm, Dipylidium caninum. This species
is abundant in dogs, and sometimes cats, in all parts of the
world. It is a species about a foot in length, with three or four
rows of hooks on the rostellum (Fig. 87F), and a double set of
reproductive organs in each proglottid (Fig. 84C). The larva,
a cysticercoid, occurs in lice and fleas. It is stated that the eggs
of this tapeworm cannot be sucked up by the dog-infesting fleas,
but that they are readily swallowed by flea larve. The eggs hatch
in the intestine of the flea larve, the embryos pass to the body
cavity and the cysticercoids remain through the metamorphosis
of the larve to the adult fleas. Children who play with dogs
are occasionally infested by this worm, probably by accidentally
swallowing lice or fleas or by crushing them and then putting in-
fected fingers into the mouth.

Family Dibothriocephalide

The tapeworms of this family, as remarked before, are charac-
terized by a flattened head with two slitlike suckers (Fig. 87C
and D). The larve, which usually develop in fishes, are of the

246 THE TAPEWORMS

plerocercoid type, 1.e., they have long wormlike bodies with an
invaginated head at one end (Fig. 86C).

Fish Tapeworm.— The common fish tapeworm of man,
Dibothriocephalus latus, is an important species in the districts
in which it occurs. It is found in all countries where fresh-water
fish is extensively eaten, and especially in countries where it is
commonly eaten raw. In the Baltic countries, Switzerland,
Russia, Japan, and about the Central African lakes this parasite
is particularly common. Relatively few cases have been re-
ported in the United States, though the larve are said to be found
frequently in fish from the Great Lakes.

The fish tapeworm is a large species and commonly reaches a
length of from six to 30 feet, or even more,
with from 2000 to 4200 short, broad pro-
glottids, only the terminal ones of which
are as long as broad. The scolex (Fig. 87C)
is almond-shaped. Unlike the tapeworms
of the family Tzeniide, the genital openings
are near the middle of the under surface of
the proglottids, instead of at one side. In
the ripe proglottids (Fig. 84E) the uterus
is in the form of a rosette near the center
of the segment. The proglottids do not
usually retain the eggs until they break off
from the chain, but void them, as do flukes,

Fie. 93. An egg of fish through the genital pore. The empty pro-
Ste coion { glottids, shrunken and twisted, are broken
ee ee a oe off in short chains from time to time.

B00. “iCAeteriooss) The eggs (Fig. 983A), which are large and

brown with a lid at one end as in fluke
eggs, contain six-hooked embryos which are furnished with a
covering of cilia (Fig. 93B). The eggs hatch in water after several
weeks and the embryos swim for a time by means of their cilia,
though they often slip out of their ciliated envelope and creep
on the bottom. It is believed that the embryos first enter some
small aquatic animal, probably a crustacean, which ‘is eaten by
a pike or perch or other carnivorous fish. The larvz, which are
of the plerocercoid type, develop in the muscles of these fish.

When eaten by a susceptible host in raw or imperfectly cooked
fish, the larva, except the head, is digested, and the head,

LARVAL TAPEWORMS IN MAN 9247

attaching itself to the wall of the small intestine, begins to grow
into an adult worm at the rate of about 31 to 32 proglottids a
day. The mature eggs begin to appear in the feces within a
month.

The fish tapeworm is especially active in the production of
toxins which cause intense anemia. Its head has been found
to produce oleic acid, a substance which has blood-destroying
properties. Often the nervous symptoms produced by this
species are also very marked.

Two other species of Dibothriocephalide have been found in
man. One of these, Dibothriocephalus cordatus (Figs. 84G and
87D), occurs in dogs, seals and other fish-eating animals in Green-
land. It only accidentally establishes itself in man. Diplo-
gonoporus grandis is a very large species, found in Japan, in
which there is a double set of reproductive organs. The genital
openings are arranged in two longitudinal grooves on the ventral
side of the worm (Fig. 84F). This species is rare in man.

Larval Tapeworms in Man

There are several species of tapeworms which inhabit the human
body in the larval or bladderworm stage. Three types are found
inman. Most important are the huge multiple cysts or ‘‘ hyda-
tids”’ of Echinococcus granulosus, a small tapeworm of dogs.
Second, there are the bladderworms of the common pork tape-
worm, Tenia solium, which often occur in large numbers, and
may be of very serious nature if located in important organs.
And, finally, there are two species of Sparganum. This is not
a true genus but is a collective group of larval tapeworms of the
plerocercoid type which cannot be definitely classified because
the adult is unknown.

Echinococcus hydatids. — In some parts of the world infection
with the hydatids or larve of Echinococcus is very common,
especially in children. In Iceland, where there is very close asso-
ciation between the human and the canine population, two or
three per cent of the inhabitants are afflicted, and in certain dis-
tricts as high as ten per cent. In Australia, also, this tapeworm
is common in dogs and its larve occur in a considerable pro-
portion of human beings as well as in stock. In the United
States, especially in the southeastern states, it is fairly common.

248 THE TAPEWORMS

The adult of Echinococcus (Fig. 94) is a minute tapeworm
found in dogs and sometimes in other carnivorous animals. It
measures only from one-tenth to one-fifth of an inch in length.
The mature worm consists of a tiny scolex with four suckers and
a double crown of hooks, followed by an unsegmented neck and
three gradually larger proglottids, the ultimate
one of which is larger than all the rest of the
worm and contains about 500 eggs in the uterus.

Echinococcus may occur in hundreds or even
thousands in the intestine of dogs, though it
often escapes notice on account of its small size.

The eggs of the worm, dropped in pastures
with the feces of infected dogs, ordinarily de-
velop in sheep, cattle or other herbivorous
animals. Human infection usually results from
too intimate association with dogs, and children

__ to “ kiss” them or lick their faces with a tongue

Fie. 94. Echino- : ; ‘ ‘
coccus granulosus Which, in view of the unclean habits of dogs,
AE aioe ae may be an efficient means of transmission for

the tapeworm eggs.

The hydatids develop in many different organs of the body.
The liver is the favorite site, after which, in order of frequency,
come the lungs, kidneys, spleen, intestinal walls, membranes
lining the body cavity, heart, brain and various muscles. Some-
times a single host is invaded by the hydatids in several different
organs.

The development of the embryos is very slow indeed. In a
month after reaching their destination in the liver or other organs
they are in the form of little globular bodies, enclosed by a
capsule produced at the expense of the host. A cyst measures
about one mm. (s; of an inch) in diameter. By the end of the
fifth month it has grown to the size of a walnut. The membrane
of the bladderworm itself is very delicate, but the capsule formed
by the host is thick and tough. The enclosed fluid is transparent
and nearly colorless, and is composed of various materials which
have permeated in from the blood and tissues of the host, and
of the waste products produced by the growth of the parasite.

When the hydatid has reached this stage in its development
(Fig. 95) there grow into its cavity from the inner surface little

especially are liable to infection by allowing dogs -

a a ee eee

DEVELOPMENT OF HYDATIDS 249

vesicles or brood capsules, on the inner surface of which in turn
there grow a number of little heads or scoleces. Each of the
heads has the power ultimately to grow into an adult worm.
As there may be a dozen or more of the scolex-bearing brood cap-

Fig. 95. Diagram of portion of small Echinococcus cyst showing daughter cyst
(d.c.), brood capsules (br. cap.) and invaginated heads (h.). xX about 5.

sules in a single hydatid, and from six to 30 heads in a single
vesicle, the number of heads or scoleces produced may be enor-
mous. Sometimes there may be stall further multiplication by
the development of secondary cysts either inside or outside of
the original hydatid which may develop a
whole series of scolex-bearing vesicles of
their own. a

Sometimes instead of forming the usual
large vesicles and secondary vesicles, the
growth results in the formation of a great
mass of small separate vesicles (Fig. 96),
varying in size from a pinhead to a pea,
with few and scattered heads. These masses
of vesicles, known as “multilocular”’ cysts,
may be six inches or more in diameter; |

. . Fie. 96. Multilocular
they are most frequently found in the liver. gyc¢ from liver of steer, 2
Unless surgically removed they usually prove nat. size. (After Ostertag
from Stiles.)
fatal sooner or later. .

The fact that the “ multilocular’ cysts are not found in Ice-
land or Australia where the ordinary cysts are so common, and
that they occur to the almost total exclusion of the ordinary
kinds in some countries, especially in parts of Germany, suggests
that they may belong to a different species indistinguishable
from E. granulosus in the adult state.

950 THE TAPEWORMS

The great size to which hydatids may grow makes them
dangerous on account of the mere mechanical damage they may

do, especially if they occur in such organs as the heart, brain,

kidneys or liver. The liver of an ox containing hydatids has
been known to reach ten times its nor-
mal weight, and to be of such large
size as to cause much mechanical in-
jury to neighboring organs. But more
dangerous than the mechanical injury
is the possibility that the vesicles,
hemmed in by restraining tissues, may
burst and liberate into the tissues the
poison-bearing liquid which fills them.
Hydatids may grow persistently for
many years. ‘There is one case on
record where a swelling had gradually
Hagens developed during 43 years over a large
Fie. 97. Echinococcus cyst Portion of the face of a woman, and
in liver of man. (After Huber was as large as a child’s head. When
from Stiles.) ._ .
removed by an operation, this was
found to be a hydatid. Ordinarily growth does not increase
beyond the size of a baseball. The only treatment is a surgical
operation.
The conditions which exist in places where hydatid disease in
man is common gives us an idea of what to avoid in order to pre-

tj

vent infection. In Iceland from 30 to 100 per cent of the dogs in |

different regions are said to be parasitized by Echinococcus. A
large proportion of the sheep and many cattle are infested with
the hydatids. The dogs are fed on the uncooked entrails and
waste meat of slaughtered animals, and the dogs in turn are
allowed to run at will over the pastures, dropping the egg-laden
proglottids with the feces in places where the water or food of
the stock may be infected. Dogs are allowed the free run of
the houses, are given unbounded liberty in playing with children,
and not infrequently eat from the same dish as their human

companions. The resulting prevalence of Echinococcus in both ~

dogs, stock and man is hardly to be wondered at.

The precautions which should be taken to prevent the spread
and to bring about the control of this disease may be sum-
marized as follows: (1) avoidance of too great familiarity with

lect
i
Pee il -

CYSTICERCUS CELLULOS 251

dogs, (2) exclusion of dogs from shores of lakes or reservoirs from
which drinking water is taken, (8) extreme cleanliness in handling
of food, (4) prevention of dogs from eating the entrails or meat
scraps of animals which may be infected with hydatids.

Cysticercus of Tzenia solium.— The fact that the bladder-

worms of the pork tapeworm, Tenia solium, sometimes occur in
man has already been mentioned. Since self-infection with the
eggs of the worm is a dangerous possibility, the presence of a
pork tapeworm in the intestine is to be looked upon much more
seriously than infection with other tapeworms.
- The bladderworms, technically named Cysticercus cellulose
(Fig. 86A), develop from the six-hooked embryos which are
freed from the enclosing egg-shell by the gastric juices. The
embryos bore through the intestinal wall and Ee to various
organs and tissues to develop.

The effect of Cysticercus infection depends entirely upon the
number present and upon their location in the body. A few of
them in the muscles or in the connective tissue under the skin are
quite harmless. In the eye, heart, spinal cord, brain or other deli-
cate organs their presence may be very serious, the symptoms
being due chiefly to mechanical injury. Infection of the brain
is usually accompanied by epileptic fits, convulsions and other
nervous disorders. There is no treatment except a surgical
operation, and this is often obviously impossible, both on account
of the number and position of the parasites. Moreover, in a
great many cases a correct diagnosis of this infection is made only
in a post-mortem examination.

Sparganum.— The group name Sparganum has been given to
plerocercoid larve of tapeworms of the family Dibothriocephalide,
of which the adult form is unknown and the true genus there-
fore indeterminable.

The most common type of such tapeworm larve is Sparganum
mansoni (Fig. 98), a long, elastic rubber-like worm, varying
from about three to 14 inches in length. It is not segmented
but is transversely wrinkled so that a superficial glance gives one
the impression of a segmented worm. At the broader anterior
end there is a small conical projection on which is found the
scolex, somewhat invaginated. These parasites are found ir-
regularly coiled in the connective tissues of the body, often under
the lining of the body cavity, sometimes in the vicinity of the

252 THE TAPEWORMS

eye, under the skin of the thigh or in other situations. One
case is reported from Japan where the larva lay in the urinary
passage, its head appearing during urination. Often the pres-
ence of the parasite causes long-lasting tumors; a recent case is
reported of a specimen removed from a breast
tumor in a woman in Texas.

The cases of infection with Sparganum man-
sont have occurred in Japan, Egypt, East
Africa, British Guiana and Texas. Of 25 cases
so far reported, 20 are from Japan, a fact pos-
sibly related to the habit of eating raw fish
which is prevalent among the people of that
country. The source of infection is, however,
not definitely known.

Another type of Sparganum, which has been
termed 8S. proliferwm, was discovered by a
Japanese investigator, Ijima, in a Japanese
woman in 1904. The skin on a large part of
her body was much swollen and _ presented
numerous hard pimples. Examination showed
thousands of worms which were identified as
larval tapeworms of the Sparganum type, im-
bedded in little oval capsules varying in size
from less than one mm. (ss of an inch) in
length to six or eight mm. (4 of an inch).
Young slender worms not yet encysted were
also found. In 1907 a similar case occurred
in a fisherman in Florida, and the parasites
were believed by Dr. Stiles to be either identical
with or closely related to the Japanese worm.

Fic. 98. Spar- Two other Japanese cases, discovered in 1907
2a erm pa and 1911 respectively, have also been reported.
a ee In one of these the worms, most but not all

of them in capsules, were found in countless
numbers not only in the subcutaneous tissue but also in the
muscles and throughout most of the internal organs, including
even the brain.

The worms of this ae (Fig. 99) are in all cases white,
flattened organisms of very variable shape and size. They
usually vary from three mm. to 12 mm. (} to } an inch) in length,

|
q

Te =

SPARGANUM PROLIFERUM AS F

and from 0.3 mm. to 2.5 mm. (45 to yy of an inch) in width, but in
one Japanese case they were Haine larger, reaching a length
of three inches. Their peculiarly irregular shape is due to the
unique method of proliferation by the growth of buds or super-
numerary heads. These apparently
become detached, leave the cyst, and
become encapsuled themselves after
migrating in the subcutaneous tissue.
This explains the increasing num-
bers of acne-like spots or nodules
containing worms, which were re-
ported by the patients.

Attempts made by Ijima to pro-
duce adult worms by feeding the
larve to various domestic animals
failed, and nothing is known of the
life history or mode of infection be-
yond a suspicion that the eating of
raw fish is responsible for it. Dr. t1e.99. Sparganum proliferum,
Gates, who discovered the Florida ae aa? aur Much en-
ease, reported that there was prob-
ably a similar case in Florida a few years before, the patient
having moved to California where he died “eaten up with
worms.”

The rare occurrence of this peculiar and serious parasitic
disease is evidence that the mode of infection is unusual. The
suspicion that it results from eating raw fish is sufficient reason
for discrimination against this kind of food even in places where
this or other human parasites which come from raw fish are not
positively known to occur.

CHAPTER XIV
HOOKWORMS

History. — For many years it was customary in the United
States to look upon the shiftless people to be found in our South
as the product of wanton laziness and an inborn lack of ambition.
For decades the more fortunate Northerners considered the
“poor whites”? of the South a good-for-nothing, irresponsible
people, worthy only of scorn and of the sordid poverty and ig-
norance which they brought upon themselves as the fruits of
their own shiftlessness. When it became known, largely as the
result of investigations by Dr. C. W. Stiles, of the U. S. Public
Health Service, that these hopelessly incapable and pitifully
emaciated and stunted people were the victims, not of their own
unwillingness to work or learn, but of the attacks of intestinal
worms which sapped their vitality, poisoned their systems, and
stunted both their mental and physical growth, and that over
two million people in our own southern states were the victims of
these parasites, the “ poor whites’ and “ lazy rigeens of the
South became objects of pity and help rather than of scorn.

The hookworm, which is the cause of this deplorable condition,
is by no means a newly discovered parasite. A close cousin of
the American hookworm was discovered in Italy over 75 years
ago, and has subsequently been found to be prevalent in parts of
every warm country in the world, in some places infesting nearly
or quite 100 per cent of the inhabitants. It would probably be
well within the truth to say that over half a billion people in the
world are infected with hookworms. The disease caused by
hookworm, which has recently come to be used as a symbolism
for laziness, was known for ages before the cause of it was dis-
covered, in fact it was probably one of the ailments most familiar
to the ancient Egyptians, and descriptions of symptoms probably
representing hookworm disease appear in the medical papyrus
of 3500 years ago. The disease has gone by many names:

malcoeur or mal d’estomac in the West Indies, tuntun in Colombia, ©

254

oe ea

DESCRIPTION OF SPECIES 255

opilagco in Brazil, tunnel disease and miner’s itch in Europe,
_and-ehlorosis in Egypt.

The American hookworm, Necator americanus, was probably
introduced into America from Africa by slaves. In many parts
of the latter continent as well as in parts of Asia, especially
Ceylon, this hookworm is very common. It occurs in the
gorilla as well asin man. In the United States it is occasionally
found in all but the most northern states, but is a great menace
only in the southern ones — North and South Carolina, Georgia,
Florida, Alabama, Mississippi, Louisiana and Texas. It also
presents a serious problem in Cuba, Porto Rico and Brazil. In
most other warm parts of the world a closely allied species, the
Old World hookworm, Ancylostoma duodenale, is more prev-
alent. It is impossible now to know what was the origin or
natural distribution of either species, since both worms have
been introduced by infected travelers into every quarter of the
globe. In Europe Ancylostoma duodenale is far the more com-
mon. It first attracted attention there as the cause of “ tunnel
disease’ at the time of the building of the St. Gothard tunnel.
The infected laborers, dispersing after the completion of the
tunnel, spread the infection to all parts of Europe, and serious
epidemics broke out in the coal-mining districts of Hungary,
Germany and Belgium.

The Parasites. —— The two species of human hookworms are
similar in structure; they agree in all important details of life
history; and both produce the same symptoms, require the
same treatment, and can be prevented in the same ways. They
are round worms, belonging to the great group of nematodes,
which as adults live in the small intestine of their hosts and suck

- blood. An allied species, A. ceylanicum, found in civet cats and
dogs in southern Asia occasionally occursin man. The American
hookworm, Necator americanus (Fig. 100), is smaller than the
Old World species, Ancylostoma duodenale, the measurements
being about eight mm. (one-third of an inch) and ten mm. (two-
fifths of an inch) respectively in the males, and ten mm. and 15
mm. (three-fifths of an inch) respectively in the females. They
are normally whitish in color but when gorged with blood they
are reddish brown. The females, which are much more numerous
than the males, have simple cylindrical bodies, largely occupied
by the threadlike ovaries and egg-filled oviducts. In the Old

256 HOOKWORMS

World species the mouth (Fig. 101A) is armed with a number of
chitinous hooklike teeth, which in the American species are
replaced by hard ridges or lips (Fig. 101B). The male worms are

y,

Am.Hook
mH sue"

Old World Hookworm —
‘nat. size

Fic. 100. American hookworm, Necator americanus, male (6) and female (@);
b.c., buccal cavity; ph., pharynx; int., intestine; cerv. gl., cervical gland; t.,
testis; sp. d., sperm duct; b., bursa; ov., ovaries and oviducts; v., vulva or
genital opening; a, anus. X8. (Partly after Manson.)

also cylindrical but instead of tapering at the tail end they possess
an umbrella-like expansion known as a bursa, which is sup-

Fic. 101. Buccal cavity and mouth of Old World hookworm (A), and American
hookworm (B), showing teeth in former and cutting ridges in latter. A, x 100;
B, X 230. (After Looss.)

ported by clawlike rays somewhat suggestive of the ribs of an
umbrella (Fig. 102). The bursa is used for holding the female
during copulation. It was the clawlike ribs of this “ umbrella ”’

LIFE HISTORY 250

which first suggested the name “ hookworm ”’ for the parasites,
though the hooklike teeth in the mouth of the Old World species
might just as readily have suggested the name.

IN MAN
IN SANDY SOIL

———— eS =

Fie. 103. Life history of hookworm; A, adults, female and male, in intestine;
B, egg as passed in feeces; C, embryo hatching in ground, 24-48 hours later; D,
fully developed larva, enclosed in sheath, ready to infect human being; EL, larve
released from sheath, migrating in body of new host.

Life History. — (Fig. 103.) The female worms produce an
enormous number of eggs which are poured into the intestine of

258 HOOKWORMS

the host, usually in a continuous stream, but occasionally with
intermissions, to be passed with the feces. The thin-shelled
eggs, which are about 60 uw by 35 uw (445 by 73 of an inch) in size,
and slightly larger in the American species, undergo the first
stages of development while still in the intestinal canal, and by
the time they are voided with the feces they are segmented into
from two to eight cells
(Fig. 104). The segmented
condition, together with
the fact that they are clear
and not yellow or brown
from bile stain, distin-
guishes the eggs from those
of many other worms
_ Fie. 104. Eggs of hookworms in early stages found in the intestine.
of segmentation, —four-segmented type most ‘Further development does
common in feces; A, Necator americanus; B, not take place until the
Ancylostoma duodenale. A
feeces are exposed to air,
when, if moisture is present and the temperature is moderately high
(65° to 85° F.), the development continues and the embryo hatches
in from 24 to 48 hours (Fig. 103C). Below 65° F. development is
very slow, and above 85° F., although development is very rapid,
the eggs and larve are likely to die. The newly hatched worm is
about 0.2 mm. (less than a hundredth of an inch) in length with a
bottle-shaped cesophagus, a simple intestine, and practically no re-
productive organs. The most favorable conditions for the devel-
opment of the larve, in addition to the temperatures mentioned,
are a moderate degree of moisture, presence of air, plenty of food
in the form of decomposing organic matter, and not too rapid
putrefaction. According to Looss, the larve will not develop
well in feeces derived from a purely vegetable diet, a small propor-
tion of animal matter being essential for food. Enough animal
food for some development would always be provided by blood
from intestinal hemorrhages. On the other hand a purely meat
diet is unfavorable on account of the rapid putrefaction. If
suitable conditions are present, the larva grows rapidly for four
or five days, shedding its skin at the end of the second day. In
about five days, under ideal conditions, the skin begins to be-
come detached again but is not shed. It is retained as a flexible
protecting sheath for the larva, but does not hinder free motion

MODE OF INFECTION 259

(Fig. 103D). The larva has by this time grown to several times
its original size, being over 5 mm. (5/5 of an inch) in length, and is
now in the infective stage and ready to begin its parasitic life.
No further food is taken but the parasite begins an active migra-
tion in the neighboring soil or water. If even a trace of moisture
is present in the soil the larve are capable of traversing consider-
able distances and may thus give rise to infection far from the
place where the feces were originally deposited. They are said
to be able to travel through moist soil at a rate of probably not
less than five feet per hour, which, if kept up constantly in a
straight line would mean a wandering of forty yards in twenty-
four hours. While such continued travel in a straight line prob-
ably would never occur, it is evident that a single infective stool
would easily be able to infect the ground for several square yards.
Complete drying up is fatal to both eggs and larve in all stages.

The larve may remain just under the surface of moist soil or
mud or in water for a long time, awaiting an opportunity to enter
a human host. They have been kept alive in the laboratory
in plain water at a temperature of about 60° F. for 18 months
and unless attacked by predaceous insects or other animals
would undoubtedly live fully as long under outdoor conditions.
They are much more resistant to unfavorable conditions than
are the eggs or newly hatched larve. They can exist under de-
privation of air for a long time and may survive burial in snow
for at least six days.

It was formerly thought that infection occurred by way of the
~ mouth only, the larve entering with impure food or water. It
is now believed, however, that this means is not only not the
usual one, but that direct infection by swallowing may never
occur, since there is evidence to show that the parasites are un-
able to resist the acid juices of the stomach before they have
first passed through the blood and tissues of the body. It was
discovered purely by accident that the hookworm larve can
readily penetrate the skin and bore through the tissues until
they reach a vein. The feet of plantation laborers are often in
a bad state of soreness and ulceration due to the boring of the
larvee and to subsequent infection by bacteria. Walking on in-
fected ground with bare feet is undoubtedly the mode of infection
in the majority of cases. By the blood or lymph vessels the
worms are carried eventually to the heart and thence to the lungs;

260 HOOKWORMS

from the lungs they pass by way of the trachea to the cesophagus,
and thence to the stomach and intestine. Experiments show,
however, that the larvee may reach the intestine by other routes,
leaving the trachea and cesophagus out of the circle of migration,
but in any case they follow a rather roundabout path in the
bloodvessels. Probably in cases of infection by food or drink
the worms bore through the mucous membranes of the mouth or
cesophagus during the swallowing of the food and thus, even
when eaten, reach their ultimate destination by an indirect route.
The larve shed their skins twice more after entering the human
body, each time attaining more and more of the adult character-
istics and growing in size at the expense of the blood and mucous
membranes on which they feed. After the last moult the sexes
are differentiated but the larve are still less than a fourth their
full size and require five or six weeks from the time of infection
to become fully mature. The length of life of individual hook-
worms in the intestine is variously estimated in months or years.
The readiness with which reinfection usually occurs makes this a
difficult point to determine. |

The Disease. — The disease to which hookworms give rise
varies to a very great extent in different individuals, and is not
always dependent upon the number of worms present. It was
formerly supposed that the anemia and loss of vitality produced
by hookworms was due solely to the loss of blood devoured by
the parasites. In cases of severe infection, where perhaps several
thousands of worms may be harbored by a single patient, the
amount of blood devoured must be sufficient to account for a
considerable degree of anemia. However, in cases of infection
with relatively few worms the symptoms are sometimes fully as
marked and cannot be explained on this basis. The injuries
from hookworm infection result apparently from a number of
causes which may be summed up as follows: (1) ulceration or
infection of the skin from wounds made by the boring of the
parasites, often giving rise to an extensive affection of the feet
in the form of pimples or sores called ‘ ground itch,” ‘ water
sores,’’ etc., caused partly by entrance of bacteria into the wounds,
and partly by the irritation produced by the boring of the worms;
(2) loss of blood devoured by the parasites; (3) loss of blood from
the bleeding of wounds into the intestines, sometimes very con-
siderable, due to a secretion from the mouth of the worm which

PATHOGENIC EFFECTS 261

prevents the coagulation of blood; (4) the entrance of harmful
bacteria and other microscopic organisms into the wounds made
by the worms, resulting in the absorption of bacterial toxins and
in the formation of dangerous lesions; (5) a thickening and de-
generation of the mucous walls of
the intestine; and (6) the secretion
of poisonous substances or toxins
from glands in the heads of the
worms. These poisonous secre-
tions, which have blood-destroying
properties, probably account for
more of the symptoms of hook-
worm disease than does anything
else, though apparently they have
widely different effects on different
individuals. Sometimes the pres- Fie. 105. American hookworm;
z = section showing manner of attach-
ence of eggs in the feeces is the Ont ae ent eta aiccemall cycle (After
indication of infection. Negroes as Ashford and Igaravidez, from photo
ang by Dr. W. M. Gray.)
a class show far less susceptibility i
to the poisons produced by hookworms than do the whites; this
is especially well demonstrated in our southern states. The
symptoms are more severe in summer than in winter, very
probably due to the greater abundance of worms in the summer.
Hookworm disease is almost always preceded by a case of
ground itch, due, as remarked above, to irritation from the boring
of the worms and to secondary infection with bacteria. The
commonest symptom of the disease is anemia, usually accom-
panied by some fever or dyspeptic trouble, though often in mild
cases there is no evident emaciation. The significant name “ el
palido ”’ (the pale one) is applied to the hookworm victim on the
coffee plantations of Porto Rico. In severe cases of long stand-
ing the anemia and loss of vitality become extreme and so weaken
the patient that he succumbs to the least unfavorable circum-
stance; his unhappy career is usually ended by some slight illness
which in normal health he could easily have resisted. In Porto
Rico about 30 per cent of all deaths are attributed to hook-
worm.
Both the mental and physical development become abnormal.
A child of 12 or 14 years may have the degree of development
which should belong to an average child of six or eight and a

262 HOOKWORMS

young man or woman of 20 may present the general development
of a child of 12 or 14, though the face may appear either very
childish or prematurely old. Girls who are affected from child-
hood lack development of the breasts, but in general there is no
marked loss of flesh. The face has a stupid bloated appearance,
and the eyes have a hollow stare which is very characteristic.
The bloating carried to the abdomen results in “ pot-belly.”
The appetite, at first ravenous, diminishes with the progress of
the disease, and frequently becomes perverted so that patients
become dirt-eaters, i.e., have a mania for swallowing earth or
mud, possibly a reaction involuntarily prompted by the irritation
of the intestinal tract by the parasites. Over 25 per cent of the
hookworm patients of one physician in our southern states con-
fessed to ‘‘ dirt-eating.’”’ The diseased appetite, of course, only
adds to the infection. The nervous symptoms, which are rather
late in appearance, consist of dizziness, headache and profound
stupidity.

The loss of efficiency from hookworm infection is startling, and
the slow development of many countries may be largely attributed
to the handicap placed upon the citizens by the hookworm. The
effect of the disease can be appreciated from the following ex-
amples: the managers of large coffee ‘“‘ haciendas”’ in Porto
Rico state that hookworm reduces the average efficiency of the
laborers from 35 to 50 per cent. On a cocoa plantation in
Ecuador not over 33 per cent of the work which should have been
obtained from 300 laborers was available, due to anemias of
hookworm and chronic malaria. On a sugar plantation in
British Guiana, after the laborers had been treated for hookworm
on a large scale, the working power of the gangs increased 100
per cent. Dr. McDonald of Queensland, Australia, reports that
hookworm ‘‘is sucking the hearts’ blood of the whole com-
munity.’ The loss of efficiency of the miners in a single Cali-
fornia mine, due to hookworm, has been estimated at 20 per cent.
Estimating only 50 per cent of the miners to be infected, the
annual economic loss in this one mine would be $20,000 per year.
The economic loss due to the infection of 2,000,000 or more people
in the southeastern United States or to the infection of from
60 to 80 per cent of the 300,000,000 people of India must be
almost incalculable.

The retarding effect of the disease in education and civilization

TREATMENT 263

is not less terrible. There are many families in our South where
for at least four generations illiteracy and ignorance have re-
sulted from disablement by hookworm disease. In many com-
munities large proportions of the children are kept out of school
on account of physical or mental disablement from this cause.
Unlike many diseases, this one has no tendency to weed out the
weak and unfit; it works subtly, progressively, undermining
the physical and intellectual life of the community, each gener-
ation handing down an increased handicap to the next.

Treatment. — Treatment of hookworm disease consists, pri-
marily, of the administration of a drug which will kill and expel
the worms from the intestine. In severe cases this is followed
by treatment with a tonic to bring back some of the lost health
and vitality. Recently it has been shown possible to hasten
recovery after expulsion of the worms by vaccinations prepared
from bacteria which are found in abundance in the feces. This
indicates that some of the evil effects of hookworm disease are
due to absorption of bacterial toxins through the injured intestine.

Until recently the classical remedy for use against hookworm
has been thymol. This is a drug which is poisonous to the
human system but under ordinary circumstances is not absorbed
by the digestive tract. It is, however, very soluble in alcohol,
ether and various oils, so that certain precautions have to be
taken in its use, and it should not be taken except under medical
supervision. Thymol is not highly efficient except in repeated
doses, taken some days apart, and this is a severe handicap in
its use. During the five-year period from 1909 to 1914, however,
the American Hookworm Commission, largely by the codperation
of local physicians, treated nearly 700,000 hookworm patients
in southern United States with thymol.

A few years ago oil of chenopodium came into favor in some
parts of the United States as a remedy for hookworm, and is now
rapidly supplanting all other remedies in all parts of the world.
It is made from a common weed, usually called Jerusalem oak
or goose-foot, and is therefore very cheap and the supply inex-
haustible. It is more effective than thymol and is if anything
less dangerous to the patient. According to Hall and Foster,
oil of chenopodium is not entirely harmless, and among other
effects is distinctly constipating. To hasten the elimination of
the chenopodium as well as to counteract the constipating effect

264. HOOKWORMS

and the slow absorption through the intestinal walls, Hall and
Foster strongly advise giving castor oil with the chenopodium
and also afterward; this gives a maximum of both efficacy and
safety. The usual method of giving oil of chenopodium is five
to 15 drops at two hour intervals; each dose should be accom-
panied by castor oil.

A number of investigators have pointed out the superior effect
of oil of chenopodium when given with chloroform. Hall and
Foster, by means of extensive experiments on dogs, have demon-
strated that chloroform itself is more efficient against hookworms
than any other drug with which they have experimented, and they
could find no evidence of superior efficiency of a combined use
of both drugs, except in case of accompanying infection with
Ascaris, against which oil of chenopodium is particularly effec-
tive. Chloroform dissolved in castor oil can be given internally
in from three to four gram doses with as great a degree of safety
as can other drugs in common use for worms, its safety lying in >
its rapid elimination from the system. A dose of chloroform
should not be repeated, however, in less than three weeks, since it
does some temporary damage to the liver which may not be
completely repaired in less than that time.

Beta-naphthol is considered by some physicians better than
thymol, especially when distributed to laborers for use without —
medical supervision, since there is less chance of bad results, and
it can be taken safely by an ignorant person with a few simple
directions. This drug is used for treatment of -coolie laborers
in Ceylon, and new consignments of coolies are treated with it
whether infected or not, since a great majority of them are
parasitized.

Male fern is sometimes used for expelling hookworms but is
more dangerous than either thymol or beta-naphthol, is more
expensive and is if anything less efficacious. Oil of eucalyptus
has.also been used with some success. It has the advantage of
being less unpleasant and less dangerous than some of the other
drugs in common use.

Prevention. — Methods of prevention of hookworm disease
are suggested by the mode of infection, namely, contact with
soil or water contaminated by infected feces. The ways in
which such contact may be made are numerous, and vary with
the habits, occupation and wealth of the inhabitants. Plan-

PREVENTION 265

tation workers on our sugar and cotton plantations and on the
coffee plantations of Central and South America, and the coolies
working on the estates of China, India and other tropical coun-
tries, practically never wear shoes. The necessity for shoes is
unknown, the discomfort of using them when the habit of going
without them has been long established makes their use difficult
to encourage, and there are very few who could afford such
luxuries even if their value were appreciated. As shown above,
the hookworm larve in soil or water commonly gain access to their
hosts through bare feet. The readiness with which infection may
occur by contact with contaminated ground or water is shown by
the case of a prominent American in Porto Rico who became
infected by removing his boots and wading in a small pool.
Kneeling bare-kneed or resting the bare hands on the moist
ground beside a stream or pool to drink; drinking water which
has been directly or indirectly polluted; dirt-eating, which is a
common perversion of the appetite in intestinally diseased people;
eating with soiled or dirty hands; the chewing of dirty finger-
nails; in all these and a hundred other ways the agricultural
laborer may become infected.

Miners, working underground where they are continually in
contact with earth, are exposed equally-as much as agricultural
laborers, and more so in relatively cold countries such as those of
central Europe, since the warmth resulting from subterranean
location allows the parasites to thrive where on the surface they
would perish. Dirty hands, unsanitary habits and polluted
water are the cause of the high percentage of hookworm infection
‘in mines where no special preventive measures are practiced.

Sanitation. — Prevention of hookworm disease, were it not
for the inevitable ignorance and stupidity of many of the people
to be dealt with, would be a relatively easy matter. The com-
parative ease with which infections can be discovered, the read-
iness with which the parasites, once discovered, can be expelled,
and the ease with which heavy infection, even in badly infested
countries, can be prevented by cleanliness, sanitation and care
of exposed parts of the body are factors which should make the
hookworm relatively easy prey for the hygienic reformer. But
the hookworm has a valiant ally in the stunted brain and will of
its victim and in the unsanitary habits, established by countless
generations, which characterize the natives of almost every hook-

266 HOO KWORMS

worm-infested country, and for these reasons alone the eradi-
cation of the disease has in many cases been a greater stumbling
block to medical science than that of even malaria or yellow fever.
Mosquitoes are easier to control than are the hopelessly ignerae
and stupid victims of hookworm disease!

The keynote in the prevention and eradication of hookworm
disease is the prevention of pollution of the soil, in other words,
proper sanitation. Not only the hookworm, but almost all of the
true nematode parasites of the human intestine, are the direct
outcome of unsanitary conditions. The early stages of develop-
ment, so far as is known, are invariably passed in water or moist
soil, and for this reason the sanitary disposal of feces would
forever put an end to such of these parasites as are peculiar to
man. The difficulties involved in this simple hygienic principle
are infinitely greater than the average civilized and cultured
person would suspect. In southern United States, 68 per cent
of the rural homes are estimated to be without privies of any kind. ~
In many rural districts where privies do exist, their use is restricted
to the women and children or to the family of the manager.
In most tropical countries where coolie laborers are employed,
practically all of whom carry infection, no attempt is made to
provide any kind of place for defecation, not even a simple hole in
the ground. The condition in this regard among the “ jibaros ”
or plantation laborers of Porto Rico, for instance, is fairly repre-
sented by this case — of 61 hookworm patients at Utuado, 55
never had used privies of any kind, and of the six who did oc-
casionally use them only two lived in rural districts! The ex-
tent to which the unhygienic conditions may go, and the readi-
ness with which infection with various intestinal worms may take
place, is demonstrated by the occurrence in Brazil of three species
of intestinal worms in a baby three months old.

The time when the value accruing from proper sanitation will
be realized to an extent sufficient to make man as careful con-
cerning his personal habits as are some of his domestic animals is
still in the future; but it is reasonable to hope that it will soon
be at hand. It is a significant fact that the domestic cat, which —
sanitarily covers up its excreta, has, on the average, fewer intesti-
nal parasites than the less careful dog. Dr. Stiles has recently
tested the effect of sanitation and consequent reduction of in-
testinal parasites, both protozoans and worms, by examination of

PREVENTION 267

school children from sewered houses and from houses with privies.
The statistics compiled from the data obtained showed that the
children from sewered houses possessed fewer parasites and aver-
aged a higher grade in school than those from houses with privies,
even though the difference was undoubtedly reduced by the fact
that sewered homes suffered from proximity to the privies of
unsewered homes and from consequent infection by flies and other
agents of transmission.

The most important and effective preventive measure against
hookworm and other intestinal nematodes which can be inaugu-
rated is the enforcement of the building of privies or latrines
of some sort, if it be only a ditch which is occasionally covered
with earth or disinfected, for the use of laborers on plantations
and estates, and the placing of a penalty or fine for unnecessary
pollution of the ground or water where there is any danger of

spreading hookworm infection, especially along roads or on plan-
tations’ Naturally such practices as the use of night-soil (human
feeces) for manure, which is extensively practiced in China, should
be stringently forbidden, unless the material can be disinfected
by chemical treatment, as suggested by Leiper. The feces of all
infected persons, as well as those of any suspected persons, should
be carefully disinfected. The use of common salt as a disinfect-
ant against hookworm has been found efficacious, but it must be
used in rather large quantities. Nicoll, in Australia, in experi-
ments recently conducted with hookworms, obtained rather un-
satisfactory results with salt treatment of infected feces, unless
the salt was used in very large quantities and was very thoroughly
mixed with the infective material. The spraying of the earth
walls and floors of mines with a strong salt solution or other
disinfectant, and a similar treatment of factories, yards, etc.,
which are known to be infected, is a preventive measure which
‘is said to bring good results, but in the light of Nicoll’s experi-
ments this should be reinvestigated. Wearing of boots or shoes
by mine workers, agricultural laborers and all who work with
brick, pottery, earth roofing, etc., 1s recommended as a protective
measure by the boards of health in some countries. This cer-
tainly is a good recommendation when it can be followed, but it
should be remembered that many who need protection the most
are unable to invest in such luxuries as shoes, and that at best
little advance towards the final eradication of the disease is

268 HOOKWORMS

made by such measures. If money sufficient to buy shoes and
other protective garments were invested in improving sanitary
conditions much more permanent good would result. This does
not mean, however, that such protection as is gained by the use
of shoes and spraying of ground is not well worth while for such
individuals as can afford it and who are forced by occupation or
other circumstances to come in contact with polluted soil.

The isolation and treatment of infected persons is to be highly
recommended, especially in case of immigrants or new arrivals
from infected regions. In 1910 the Board of Health of San Fran-
cisco made an examination of a shipload of Hindus which had
just arrived and found 90 per cent to be infected, whereupon a
quarantine was established, and has since been maintained, for
hookworm patients. Every colony of Hindu coolies in California
is a center from which hookworm disease is spreading. Had a
hookworm quarantine been established years before, California
would have been to a great extent free from this parasite. Quar-
antine measures have been taken in Natal, where all infected
immigrants are treated before being assigned to plantations.
When the infection does appear in a mine or plantation the in-
fected persons should be treated, and not allowed to return to
work until their feces are free from eggs. .

The treatment of hookworm disease is of such vital importance
to the public of any endemic region that it should be supervised
and aided by the government. Such aid should consist in the
establishment of free dispensaries for hookworm patients, the
supply of necessary drugs at cost for the treatment of hookworm
disease, the appointment of inspectors to enforce sanitary regu-
lations, and the distribution of information regarding the disease
by free pamphlets, public lectures and school instruction. In
the United States this work has been done largely by the American
Hookworm Commission, financed by a gift. of $1,000,000 from
John D. Rockefeller. In 1914 the Rockefeller Foundation ex-
tended the work of hookworm eradication ‘‘ to those countries and
peoples where conditions invite.”” Such work has been begun in
a number of West Indian islands, Central America and Egypt.

It has been pointed out that demonstration as well as instruc-
tion is necessary to impress the natives of hookworm districts
with the advantages of sanitation and hygienic. conditions. It
is absurd to rely upon the ability of the average native, dwelling

SANITATION 269

in a filthy environment in which he was born and brought up, to
form a conception of community cleanliness, which he has never
seen, resulting in public benefits which he has never known. The
erection of schools, hospitals, residence sections, etc., which are
models of simple but efficient sanitation, would go much further
toward securing the codperation of natives in duplicating such
conditions than would any amount of instruction without such
practical demonstrations. |

CHAPTER XV
OTHER INTESTINAL ROUNDWORMS

General Account. — As compared with the hookworms all the
other intestinal roundworms, except trichina, which will be dis-
cussed in the following chapter, sink into relative insignificance,
but there are several species which are very common in some parts
of the world and some which are of very wide distribution. The
pathological effects of some of these worms appear to be slight
or almost entirely negligible, — while others, at least in individual
cases, cause severe symptoms and may even be a direct cause
of death. Recently, as has been remarked in a preceding chap- |
ter, more and more suspicion is being aroused against various
- intestinal worms, especially those which habitually inhabit the
coecum and appendix, as playing a leading part in producing
appendicitis. The relation of intestinal worms to bacterial in-
fections is discussed on pp. 203-204.

As regards the selection of a drug for treatment of any of
these rarer intestinal parasites, certain general principles should
be of value. As has been pointed out by Hall and Foster,
‘almost all anthelmintics (7.e., drugs used against worms) are
poisons, intended to kill or stupefy or otherwise disable and re-
move worms, while at the same time inflicting a minimum amount
of damage on the host animal by virtue of the comparative
insolubility of the drugs or their rapid elimination.” For worms
situated in the upper portions of the digestive tract, drugs such
as chloroform, which are rapidly absorbed and eliminated, can
be used, whereas for worms situated in the lower portions of
the digestive tract, insoluble drugs would in general be better.
That certain drugs have more or less specific action against
certain species of worms is true, as evidenced by the case of oil
of chenopodium against ascarids, and chloroform against hook-
worm. It is quite probable, however, that this apparently spe-
cific action may be due rather to a mode of life of the worm
affected which makes it particularly easily reached by the drug.
Hall and Foster, for instance, suggest that the striking efficiency

270

INTESTINAL NEMATODES

1.) teal
Rate

Besoh Lh ath

an
Sg

=
=
Oo
3
=)
oH

Belascaris

worm

Whip

Fic. 106. Intestinal nematodes of man, natural size. Male and female of each
Species shown, except Strongyloides, in which only the females is known. The
female of @sophagostoma is immature, the mature form being unknown.

272 OTHER INTESTINAL ROUNDWORMS

of chloroform against hookworms may be due to the fact that
hookworms are blood-suckers and that the chloroform rapidly
absorbed by the blood is ingested by the hookworms in amounts
sufficient to cause stupefaction or death.

The presence of intestinal worms of most species can be de-
termined by the finding of the eggs in the feces, and in most cases
the eggs are characteristic enough to make a determination of
the species fairly easy. It often facilitates the search for para-
site eggs to concentrate them in the following manner: Mix a
portion of the feces the size of a walnut with 60 cc. of distilled
water, strain through several thicknesses of wide-mesh surgical
gauze and centrifuge at high speed for about ten seconds. Pour
off most of the liquid, add more water, shake thoroughly and
centrifuge again. The material thrown to the bottom of the
tube contains the eggs, which can readily be found under a micro-
scope. A bit of the centrifuged material is placed on a slide with
a little distilled water. In two or three minutes the eggs will
settle on the slide, and the excess liquid can be poured off. The
eggs of parasitic worms vary in size, shape, color, surface mark-
ings and state of development. Most eggs are colored yellow
or brown from bile in the feces but the eggs of the hookworms,
Strongyloides, and a few others remain clear and colorless. The
characteristics of the eggs of the commoner parasitic worms are
shown in a comparative way in Fig. 61, p. 205. In the case of a
few intestinal nematodes eggs do not appear in the feces. In
the pinworms, for instance, the adult female containing the eggs
usually passes out entire, whereas in Strongyloides the eggs hatch
before leaving the host.

Preventive measures against practically all of the true nema-
tode parasites of the intestine consist mainly in proper sanitation,
a discussion of which will be found on p. 265. It is possible that
some of the intestinal nematodes may occasionally, at least,
utilize an intermediate host of some kind, but even if this were
true sanitary disposal of human feces would, as said before, be
sufficient to exterminate such parasites as are peculiar to man.
The nematodes which occur in other animals as well as man have
to be guarded against by other means also. The spiny-headed
worms, which are transmitted in the bodies of insects which
serve as intermediate hosts, are, of course, subject to quite dif-
ferent prophylactic measures.

ASCARIS Dike

Ascaris or Eelworm. — Of greatest importance of these lesser
intestinal parasites is the eelworm, Ascaris lumbricoides (Fig.
106). Ascaris is one of the largest nematode parasites known,
the female averaging about ten inches in length, and occasion-
ally measuring a foot and a half, while in diameter the body is
about as large as an ordinary lead pencil. The males are usually
several inches shorter. These worms are among the most fre-
quent human parasites. They occur in all parts of the world
and are found, especially in children, in the majority of temperate
countries, even in countries as far north as Greenland and Fin-
land. In the tropics they are abundant and are almost univer-
sally present in children, each individual harboring anywhere
from two or three to several hundred worms.

Ascaris can be recognized immediately by its large size and
robust form. The males (Fig. 107) can be distinguished by the

VW,
CRED
i

LO SFC OLAS ae eta ge,
SIUM EONS MSGS ze

Fic. 107. Ascaris, dissected to show anatomy; female above, male below.
Note ribbon-like intestine (cross-barred) with pharynx at its anterior end; the
coiled threadlike ovaries in female and testis in male; the large kinky oviducts in
the female, uniting to form a vagina near the external opening on the anterior third
of the body; and in the male the large sperm duct opening at the ventrally-curved
posterior end of the body in common with the intestine.

sharp downward curve of the posterior end of the body, the female
(Fig. 107) having a straight and rather stumpy tail. Both
sexes are more slender at the head than at the tail end. The
sexual organs occupy the greater part of the body. In the female
they consist of two coiled threadlike ovaries (Fig. 107) and a pair
of large oviducts in the form of kinky tubes which open about
one-third of the way back from the anterior end. In the male
there is a single coiled threadlike testis and a single sperm duct
(Fig. 107), the latter opening at a cloaca at the posterior end of
the body. The size and simplicity of the organs makes Ascaris
a favorite subject for class-room dissection. The human species,

274 OTHER INTESTINAL ROUNDWORMS

Ascaris lumbricoides, is now usually looked upon as a variety —
of the species which occurs in hogs in almost every country in
the world, and which is sometimes known as A. swilla.

The life history of Ascaris is usually thought to be very
simple. The eggs, of which thousands are deposited by a single ©
female, develop within the eggshell outside of the human body,
in water, soil or manure piles, wherever the proper conditions of
temperature can befound. The eggs (Fig. 108) are about 0.06 mm.
long by 0.04 mm. wide (43> by gts of an inch), elliptical in form
with a thick transparent shell,
usually bile-stained, covered
over outside by irregular albu-
minous coats which give them
a rough warty appearance.
Ry When passed from the diges-

or A B tive tract no sign of segmen- |

Fic. 108. Egg of Ascaris; A, surface tation can be seen. After a -
view showing warty albuminous coat; :
B, same in “optical section,” ¢.e.. with month or six weeks under favor-
microscope focused on center of egg in- able conditions in soil or water
stead of on surface. :

the embryo will have devel-
oped, and can then be seen rolled up within the shell. Even
eggs which have been dried and exposed to the sun for months
may contain active embryos. The egg may remain for months
or years in this condition, resistant to both drying and freezing,
until swallowed by a human being or other susceptible animal.
In the dry condition the eggs may be blown about by the wind
or carried on the feet of flies. The use of human feces (night-
soil) as a fertilizer undoubtedly results in wholesale contamina-
tion of vegetables and other garden products.

When swallowed by a suitable host the hard shell of the egg is"
dissolved off and the parasite is liberated in the small intestine.
After about five or six weeks sexual maturity is reached, and the
production of eggs begins again. |

Recent experiments by Capt. Stewart in Hong Kong indicate
that at least under some conditions Ascaris may go through an-
other phase of development in its life history. Ripe eggs in-
gested by rats hatch in the intestine, and the larve (Fig. 109B)
invade the tissues of the rats. In from four to six days some of the
larve are found in the bloodvessels of the lungs, liver and spleen,
giving rise to symptoms of pneumonia. None of them remain

LIFE HISTORY OF ASCARIS 215

in the intestine to develop further, though dead ones are found
in the feces. Only about one per cent ever reach the lungs. From
the sixth to the tenth days the larve pass from the bloodvessels
into the air sacs and bronchial tubes of the lungs and thence
through the trachea to the
mouth. If the pneumonia
does not prove fatal the host
recovers in 11 or 12 days and
by the sixteenth day is free
from parasites. The largest
larva observed (Fig. 109A)
was found in the lung of a rat
on the tenth day after infec-
tion; 1t measured 1.32 mm. Fic. 109. Developmental stages of
(about oly of an inch) in length. Ascaris; a, freshly hatched larva; }, larva
Ete slarve cannot live. in tap from Inne, rat on tanh, dy after infow
water but can survive 24 hours

on damp bread and two days in a rat’s lung. Capt. Stewart be-
lieves that these experiments suggest that man is infected by |
food contaminated by larve which have emigrated actively from
the mouth of a rat while the rat was nibbling. Hogs were suc-
cessfully infected by larval worms from the lungs of rats.

That this is the usual life history of Ascaris must certainly be
doubted. When it is remembered that a large per cent of chil-
dren in all tropical countries are infected, and often very heavily
infected, the improbability of more than a few at most of the
infections arising in the manner indicated above is apparent.
Of 5000 eggs ingested by a rat not more than 50 were recovered
by Stewart from the lungs, and of these only very few could
possibly be successful in reaching a human intestine by way of
moist foods nibbled by rats within the preceding 24 hours.
Moreover several very eminent parasitologists have been success-
ful in producing infection by feeding ripe eggs to hogs and also to
man. It seems much more probable that Capt. Stewart’s experi-
ments may be interpreted as suggesting that Ascaris normally
migrates through the tissues, as do the hookworms, before becom-
ing settled in the intestine, and that the worms recovered from
the lungs and mouth are on their way back to the digestive tract
of the rat. That they do not become established there may be
explained by their inability to live in the intestine of this host.*

* Since this book has gone to press Ransom and Foster have published

results of experiments which verify this conclusion, and which show that only
very young animals are readily susceptible to infection.

276 OTHER INTESTINAL ROUNDWORMS

The symptoms produced by Ascaris infection vary greatly
with different individuals. In some cases a great number of
Ascaris may be harbored with practically no ill effects. Often,
however, even when small numbers are present, peculiar mental
and constitutional ailments occur, such as feverishness, anemia,
restlessness, epilepsy, insomnia and deliriousness. In combina-
tion with these nervous troubles there is usually some dyspeptic
trouble, such as irregular appetite, nausea and stomach aches.
The nervous and other constitutional symptoms are the result
of poisoning or intoxication from sub-
stances given off by the worms in the
intestine, as explained in Chapter XI,
p. 203. The worms occasionally creep
forward into the throat or nose. Their
wandering into other organs through

into the body cavity through the in-
testinal walls often gives rise to serious
abscesses which call for an operation
and removal of the intruders.

Santonin has been the classical
drug for expelling Ascaris, but oil
of chenopodium has recently been
demonstrated to be considerably more
effective. According to Hall and
eter es Hepes Foster oil of chenopodium, properly
OvV., Ovary; ut., uterus; v., vulva; administered (see Chap. BE p- 264),
int., intestine; w., whiplike an- ig almost 100 per cent effective for
terior end containing cesophagus. : 3
x3. B, egg; note barrel shape ascarids, and is more dependable than
Bar anand bodies at ends. any other drug commonly used for

worms.

Whipworm. — With the possible exception of the hookworms,
the whipworm, Trichuris trichiura (Figs. 106 and 110), is the
most common intestinal worm parasitic in man. It is a nema-
tode related to the trichina worm in which the anterior end of
the body is drawn out into a long filament like the lash of a
whip. Closely related species are found in many other animals.
The narrow portion of the body in the human species occupies
about three-fifths of the entire length of the body, and contains
only the long slender cesophagus. The sexual organs and in-

ducts leading from the intestine or .

me

WHIPWORM Zk

testine occupy the thicker posterior part of the body. The fe-
male whipworms, which are always far more numerous than the
males, are about two inches long, while the males are a little
smaller.

The human whipworm is found in almost every part of the
world, but is especially prevalent in warm countries; it para-
sitizes both man and monkeys. It usually makes its home in
the ccecum but occasionally establishes itself in the appendix
or large intestine. It is usually said to transfix the wall of the
coecum with its threadlike anterior portion, but there is some evi-
dence to show that it merely buries its long head and “ neck ”
between the folds of the intestinal wall.

Usually the only evidence of the presence of whipworms is
the appearance of the characteristic dark-colored, barrel-shaped
eggs (Fig. 110B) in the feces. These eggs, like those of Ascaris,
develop in water or moist soil. The embryo-containing eggs are
very resistant to adverse conditions and may live for years
without losing their vitality. Infection, as far as known, occurs
as in the case of Ascaris. The worms may attain maturity
and produce eggs in less than a month after the eggs have been
swallowed. Although the whipworm feeds on blood to some
extent, and undoubtedly produces toxins, as evidenced by the
increase in eosinophiles (see p. 203) in the blood which nearly
always occurs in case of whipworm infection and by the occa-
sional mental disturbances and other nervous symptoms, this
worm usually produces very slight, in fact often unnoticeable,
effects. It is, however, thought by some workers to be one of
the intestinal parasites most frequently involved in causing
appendicitis. It is very difficult to dislodge the whipworm by
the usual methods used for expelling intestinal parasites, prob-
ably due to its very firm attachment by the long slender “ neck.”’
Oil of chenopodium administered as for hookworm (see p. 264)
is probably the most effective remedy.

Pinworm. — One of the most frequent and widely distributed
intestinal parasites of man is the pinworm, Oxyuris vermicularis
(Figs. 106 and 111). This parasite occurs almost universally in
children at one time or another in temperate as well as tropical
countries; it inhabits the lower part of the small intestine and
the coecum. Pra *

The adult females (Fig. 111 2) are whitish worms about two-

278 OTHER INTESTINAL ROUNDWORMS

fifths of an inch in length, and have about the diameter of an
ordinary pin. The males (Fig. 111 ¢) are only about half as
large and have the posterior end of the body rolled ventrally.
The adult females filled with eggs leave
the small intestine and coecum and wander
back to the rectum whence they are
passed out with the feces or creep out
of the anus, especially in the evening
or at night, causing intense itching.
These egg-filled females, or the free eggs
which already contain coiled embryos,
live in the moist groove between the
buttocks, in girls sometimes creeping for-
ward to the vagina. From the scratching
and rubbing which results from the itch-
ing in the vicinity of the anus the fingers ~
and fingernails become infected with the
egos. The eggs may then be transferred
to the mouth directly or indirectly, thus
causing reinfection, or they may be trans-
mitted from person to person by unclean
| hands. Infection may also occur by

swallowing the mature egg-filled female

Fie. 111. Pinworm,

Oxyuris vermicularis; 9,
female; ¢@, male;
pharynx; int.,
OV., Ovary; ut., uterus; an.,

anus; v., vulva; t., testis;
x 8.

sp. d., sperm duct.
(After Claus, from Braun.)

ph.,
intestine;

worms, or by the eating of raw vegetables
or other foods which have been polluted
by the eggs. As in the case of other
parasite eggs, those of the pinworm may
also be scattered by flies which have

visited infected feces. ,

When first deposited, the eggs, often hanging together like
short strings of beads, contain larve which resemble tadpoles
(Fig. 112A). In the feces or in the moist groove between the
buttocks the larve, still in the eggs, transform within a few hours
into worms of typical nematode form (Fig. 112B). Later stages
are shown in Figs. 112C and D.

After infection, which probably nearly always occurs by way
of the mouth, about two or three weeks elapse before sexual
maturity is again attained and the eggs and females reappear
in the feces.

While usually no inconvenience is felt from the presence of

STRONGYLOIDES 279

even large numbers of pinworms, since they do not suck blood
and seldom cause intestinal lesions, yet they sometimes produce
reflex nervous symptoms, probably by secretion of toxins, and
they may interfere with the normal action of the bowels. As

Fie. 112. Early development of pinworm, Oxyuris vermicularis. A, newly laid
egg containing tadpole-like larva; B, egg 12 hrs. later with nematode-like larva;
C, egg with fully developed embryo; D, newly hatched embryo. x 500. (A and
B after Braun; C and D after Leuckart.)

remarked elsewhere pinworms are believed to be sometimes,
and perhaps frequently, the original cause of lesions in the ap-
pendix which culminate in appendicitis. The intense itching
which they produce by creeping in the vicinity of the anus is
usually the most disagreeable effect of their presence.

On account of their situation in the lower part of the intestine,
treatment for pinworms should be by drugs which are not rapidly

. absorbed from the intestine but are relatively insoluble. Thy-

23

mol, male fern and, best of all, oil of chenopodium are effective
remedies. |
Strongyloides. — Another parasite of the intestine which is of

wide distribution and locally very common is Strongyloides ster-

coralis, a very small worm about one-tenth of an inch in length
which bores deep into the mucous membrane of the intestine. The
female strongyloid (Figs. 106 and 113A), which is the only
sex known, can be recognized by its small size, and microscopi-
cally by the chain of six or eight eggs, lying near the middle of

280 OTHER INTESTINAL ROUNDWORMS

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9
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Fic. 113. Life history of Strongyloides stercoralis. A, adult female in intestine
(note long pharynx, egg-containing uterus and vaginal opening on posterior third
of body; B, newly born embryo as passed with feces; C and D, adult female and
male, respectively, of free-living generation; E, ‘‘rhabditiform”’ larva, from female
of free-living generation; F, filariform larva, resembling grandparent, and formed
by metamorphosis of HZ, ready to infect by boring through skin. X75. (Partly

after Looss.)

STRONGYLOIDES 281

the body, visible through the delicate body wall. The eggs,
which are deposited deep in the intestinal coat, normally hatch
before leaving the digestive tract of the host and grow con-
siderably, so that when the feces of an infected person are ex-
amined microscopically the active writhing larve (Fig. 113B),
250 (75> of an inch) in length, can be seen darting about in
snakelike fashion. Further development of the larve takes
place in water of fairly high temperature, such as would be found
under the burning rays of a tropical sun. Under such conditions
the larve attain a sexually mature form, male and female (Fig.
118C and D), in which they are quite different from their parents.
They now copulate, and the females lay 30 or. 40 eggs, all within
two days. This second generation of eggs hatch into tiny free-
living larve (Fig. 113E) resembling the parents, but after their
first moult they lose the parental characteristics and become
like their grandparents (Fig. 113F). After having reached this
stage, they soon die unless they gain entrance to the digestive
tract of a human being again. An unusual phenomenon is
shown by these worms in that the life cycle, under less favorable
conditions, can be abridged, and the alternation of generations
eliminated. If, for instance, the larve in the feces be exposed
to the cooler water of a temperate country, they do not be-
come sexually mature and reproduce, but transform directly
into the parasitic type and reinfect without further repro-
duction.

The method of infection is similar to that of the hookworms.
While the larve may occasionally gain entrance to their host
with polluted water or food, they are able to bore through the
skin as do the hookworm larve, and it is probable that this is
the more usual method.

As a rule Strongyloides does not cause very serious ill effects
from its pursuit of life and happiness in the intestine. Nearly
all cases of diarrhea and dysentery, in which the strongyloids
were formerly supposed to be the chief agent, can now be ascribed
to some other cause, the strongyloids being more or less innocent
bystanders. Barlow, however, reports that in 23 cases in
Honduras, five of them uncomplicated, such symptoms as in-
termittent diarrhea without blood or mucus in the stools, colic
and certain nervous symptoms were in evidence. In many cases
where a diseased condition of the intestine is brought about by

282 OTHER INTESTINAL ROUNDWORMS

some other causes, the strongyloids increase in number and un-
doubtedly intensify the bad condition.

The worms are not so readily expelled by drugs as are most of
the intestinal parasites, being able, on account of their small size,
to stow themselves away in the folds and villi of the intestine
where drugs do not reach them.

Since the strongyloid occurs in the same countries as do the
hookworms, though more limited in distribution, and has a
similar mode of transmission and infection, the same preventive
measures which are used against hookworm are of service against
this comparatively harmless companion of it.

Other Species. — There are a great many other worms which
occasionally make their home in the human digestive tract, some
being locally common, others merely sporadic in their occurrence;
some, in fact, are not truly parasites at all, but have merely
established themselves temporarily after having been swallowed ©
with infected food. Stephens lists 59 species of nematodes as
having been observed in man. None of those not already
mentioned can be considered of great importance, since they
seldom cause serious ailments and are most of them rare. Only
those which are true parasites and have been recorded from man
more than once need be mentioned here.

Belonging to the same family as Ascaris (Ascaridz) or to
closely allied families are: Belascaris cati (or Ascaris mystaz)
(Fig. 106) and Toxascaris limbata (or Ascaris marginata), small
Ascarids two or three inches in length, normally parasitic in cats
and dogs respectively, found practically all over the world but
only occasionally in man; and Physaloptera mordens (Fig. 106),
a worm one and a half to two inches long, which appears to be
not uncommon in negroes in central East Africa. -

Allied to the hookworms and having an expanded umbrella-
like “‘ bursa ”’ at the posterior end of the male are several species
of Trichostrongylus (or Strongylus). TT. instabilis (subtilis) (Figs.
106 and 114) is a small worm from four to six mm. (one-fifth of
an inch) in length, somewhat resembling a hookworm but much
more slender. It is normally parasitic in the small intestine
(duodenum) of sheep, camels, baboons and other animals and
occasionally occurs in Egyptian “‘fellahs.” A closely allied
species, 7’. orientalis, is found in the duodenum of Japanese.
Other species of this genus normally found in herbivorous ani-

(ESOPHAGOSTOMUM 283

mals in Egypt occasionally parasitize man. The eggs of TJ'r-
chostrongylus (Fig. 61Y) resemble those of hookworms, but they
are a little larger and frequently contain more than four cells.
The life history is similar to that of the hookworms. Ternidens
(or Triodontophorus) deminutus (Fig. 106) is a worm about. half
an inch in length, normally found in the large intestine of monkeys
in central East Africa, and not uncommon in natives; Gsopha-
gostomum apiostomum (brumpti) is a parasite which forms tumors
in the large intestine of monkeys and occasionally man, in
central Africa and in the Philippines. It produces‘symptoms of

B (x10)
Fic. 114. Trichostrongylus instabilis;
A, female, showing pointed tail and Fic. 115. Msophagostoma stepha-
vulva (v.); B, male, showing smaller nostomum var. thomast. A, immature
size and bursa (b.). X25. (After female in cyst in large intestine of
drawings and measurements by man in Brazil; B, same, removed
Looss.) from cyst. (After Thomas.)

dysentery. An allied worm, O. stephanostomum var. thomasi,
a variety of a species normally found parasitic in gorillas in
Africa, has been found once in man in Brazil. In this case there
were 187 tumors (Fig. 115A) in the small and large intestines
each containing one worm (Fig. 115B). This species will prob-
ably be found to be normally parasitic in some species of South
American monkey.

These and a number of still rarer human parasites are of little
interest as far as man is concerned, except as medical curiosities.

In connection with the intestinal nematodes there should be
mentioned three species of spiny-headed worms (class Acantho-

284 OTHER INTESTINAL ROUNDWORMS

cephala) which occasionally have been found in man. These
worms are not true nematodes but are distantly related to them.
They are characterized by the presence, at the anterior end of
the body, of a prolonged proboscis which
is covered with thornlike, recurved spines.
This proboscis is sunk into the walls of the
intestine of the host to gain anchorage. Like
the tapeworms, the spiny-headed worms are
totally devoid of any digestive tract of their
own. The common species of the hog,
Gigantorhynchus hirudinaceus (gigas) (Fig.
116), is said to occur in man in southern
Russia. It is a large worm, the female ten
to 12 inches in length and about one-fourth |
of an inch in diameter and the male about
one-fourth as long. The larval stage is:
. S passed in certain species of beetles.

igs. Ak Meats aoe single case of infection with another
ryhnchus hirudinaceus species, Echinorhynchus hominis, which was
ae ‘i be lars only one-fourth of an inch in length, has been
B, x5. (After Raillet recorded, also from Russia. A species which
prom: Neuriaun is probably more frequently a human para-
site is Hormorhynchus (or Echinorhynchus) moniliformis, normally
parasitic in field mice, rats and marmots in Sicily. The female

Fic. 117. Development of spiny-headed worm of rats and mice, Hormorhyn-
chus (or Echinorhynchus) moniliformis. A, proboscis, X 50; B, larva from cock-
roach, X 23; C, egg, x 150. (After Grassi and Calandruccio.)

worm is a little over three inches in length, the male about half
this size. A species of cockroach serves as an intermediate host.
Grassi and Calandruccio found by experimentation that the larve
in cockroaches (Fig. 117B) would develop apparently equally well
in white rats and in man. An allied species, H. clarki, has

ACANTHOCEPHALA 2835

recently been described by Ward from a squirrel in Illinois; it
is a worm about four or five inches in length with a very minute
proboscis. Ward believes that this species would also probably
develop in man if the larve were accidentally swallowed with
some insect which presumably serves as an intermediate host.

CHAPTER XVI
TRICHINA WORMS

Or quite a different nature from other intestinal parasites is
the trichina worm, T'richinella spiralis. As far as the injurious-
ness of its presence in the intestine is concerned it is much less
serious than many of the other intestinal worms, since its length
of life as an adult is relatively short. The serious and often
fatal results of trichina infection are due to the peculiar life
history of the worm and are concerned with the offspring of the
infecting worms and not with these worms themselves.

There can be little doubt but that this worm, with the pork
tapeworm as an accomplice, was responsible for the old Jewish
law against the eating of pork. It was, however, many thousands
of years later, in A.D. 1828, that the worms were first dis-
covered. A little over 50 years later, 1880-1891, the trichina
worm was the cause of international complications between the
United States and Germany, and during this time American pork
was excluded from German markets on account of the alleged
frequency with which it was found to be infected. The outcome
of this trouble was the beginning of the present American system
of government meat inspection.

Prevalence. — Since the danger of infection from eating im-
perfectly cooked pork has been given wide publicity, and has
come about as near to being a matter of common knowledge as
any fact of parasitology, the prevalence of the infection has been
greatly reduced, but even now trichina embryos are found in
from 0.5 per cent to 2 per cent of the inhabitants of most civilized
countries, as shown by post mortem examinations. According
to Dr. Ransom, of the U. 8. Bureau of Animal Industry, statistics
based on microscopic inspection of 8,000,000 hogs in the United
States show only 1.41 per cent infection with live trichina worms,
and a total of 2.57 per cent infection with live trichine and
trichina-like bodies.

286

PREVALENCE 287

In some European countries the infection is somewhat less.
Some of the great epidemics of trichiniasis (or trichinosis) in
Europe have been attributed to American pork, but according
to Ransom there have been no authentic cases of the disease in
Europe from American pork up to recently, and, so far as known,
none recently. Our slaughterhouses have been referred to as the
great breeding centers of trichina, but this is true only as to
slaughterhouses not under federal inspection.

The rdle of the rat in the spread of trichiniasis can readily be
appreciated when the statistics concerning the infection of these
animals in slaughterhouses, stables, etc., are examined. Of 51
rats captured in the Boston abattoir some years ago 39 (77
per cent) were infected, and every one of 40 captured in a large
exportation slaughterhouse in the same city was infected. Rats
captured in stables where no hogs are kept, however, are usually
less trichinized. Rats in localities where an epidemic of tri-
chiniasis has recently swept through are usually extensively
infected. |

The prevalence of the disease in man is by no means parallel
with its prevalence in other animals. The great controlling
factor is the method of eating pork. Among such people as
Americans, English and French, where pork is almost always
eaten cooked, trichiniasis is rare and comes only from eating
pork not thoroughly cooked, thus allowing a few worms to escape,
though ordinarily not enough to cause serious disease. On the
other hand very fatal epidemics have occurred among the Ger-
mans, Austrians and Italians, who are very fond of raw pork,
especially in the form of sausage or “‘ wurst.” Nearly all the
epidemics in America have been among the Germans or Italians
who still cling to their native habits.

_ According to statistics compiled by Dr. Ransom in the five-
year period from 1909 to 1914, 320 cases occurred in the United
States, with 6 per cent fatality. The majority of all cases are
reported as being caused by raw sausage or raw ham, and usually
home-made or prepared in meat shops on a small scale. As stated
by Ransom, “ no eases of trichinosis have been reported which
trace back to sausage prepared in establishments conducted on
a large scale. While it is not impossible that such cases might
occur, the chances seem very remote, for the reason that in such
establishments any one lot of sausage is invariably made up of

288 TRICHINA WORMS

small portions from a large number of hogs, and the infection,
if any be present among the hogs involved, is necessarily greatly
diluted, with the result that no individual consuming the sausage
is at all likely to ingest a sufficient number of trichinz to produce
an appreciable effect, even though the parasites should happen
to survive the curing processes to which the commercially pre-
pared sausage is usually subjected.”

Life History. — The trichina worm, Trichinella spiralis, occurs
in quite a large number of animals, but the readiness with which
infection occurs in dif-
ferent species of ani-
mals varies greatly.
In America hogs are
most commonly in-
fected, and infection is
common in rats which.
have access to waste
pork; in Europe dogs
and cats commonly
show a higher percent-
age of infection than
hogs in a given local-
ity. Man is _ highly
susceptible, in fact so
susceptible that he
cannot be considered
a normal host of the
parasite. Rats and
mice are sometimes

: thought to be the pri-

Fic. 118. Larve of trichina worms, Trichinella host fia
spiralis, encysted in striped muscle fibers in pork. mary osts O €
Camera lucida drawing of cysts in infected sausage. worm, but the fact that

ae these rodents succumb
easily to infection while the parasites are still in the intestinal
stage tends to show that rats are not normal hosts. Rabbits
and guinea-pigs are easily infected when fed meat containing
the worms, and a number of other mammals can occasionally
be infected artificially.

The worms’ gain entrance to the digestive tract as larve en-
cysted in meat (Fig. 118). In the intestine of the host they are

LIFE HISTORY 289

freed from their cysts and take refuge among the villi and folds
of the mucous membrane of the small intestine. Here they
mature and copulate as early as the third day after being swal-
lowed. The female worms (Fig. 119) are from three to four mm.
(§ to $ of an inch) long, whitish in color, slender and tapering
from the middle of the body toward the anterior end. The
digestive tract of the worm consists of a long muscular pharynx,
followed by a simple intestine. The forepart of the intestine has
a very characteristic cross-barred ap- ,
pearance. The reproductive system in
both sexes is single, 7.e., with only one
ovary or testis, and occupies a large
portion of the body. The arrangement
is different in the two sexes, the male
reproductive system opening at the
posterior end of the body with the anus
while the female system opens on the
anterior third of the body. The male
worms (Fig. 119) are only about half
the size of the females. The ‘adult
intestinal worms are essentially short-
lived, the males usually passing out of
the intestine soon after mating, and
the females as soon as they have given
birth to all of their offspring. The
adults usually disappear within two or .
three months after infection. ate
siaapke F : Fie. 119. Adult trichina
Trichina worms are peculiar in that worms, Trichinella spiralis,
they bring forth living young, free of male (¢) and female (%);
the eggshell. They do not nourish ea ec een eee
their young within the body as do truly <5. (After Claus, from
viviparous animals, but merely retain ae eas
the eggs in the uterus until they hatch. Sometimes the young ©
worms begin to be born within a week after the parents have
been swallowed by the host. - They are most numerous in the
circulating blood between the eighth and 25th day after infection,
though the greatest invasion occurs on the ninth and tenth days.
When born they are scarcely 0.1 mm. (535 of an inch) in length.
The mother worms usually burrow into the walls of the intestine
x _ far enough so that the young can be deposited directly into a

290 TRICHINA WORMS

lymph or bloodvessel rather than into the lumen of the intestine.
The larve are carried in the blood or lymph stream, and are
distributed to nearly all parts of the body. They leave the
capillaries in the striped muscles and penetrate into the fibers.
Although young migrating larve may accidentally be carried
to other tissues, and have even been found in the cerebrospinal
fluid and in the mammary glands and milk of a nursing woman,
they are apparently incapable of developing in any tissue except

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Fic. 120. Larve of trichina worms burrowing in human flesh before encyst-
ment. From preparation from diaphragm of victim of trichiniasis. X 75.

voluntary muscle. They may settle in the heart muscle, but
degenerate there without continuing their development. The
muscles particularly favored by the worms are those of the dia-
phragm, ribs, larynx, tongue and eye, which, as noted by Staubli,
are among the most active muscles and the muscles with the
richest blood supply and largest amount of oxygen. According
to Flury trichine have a high glycogen content, and probably
subsist on the glycogen stored in the striped muscles; in fact

the abundance of glycogen may account for their location in
these muscles.

FORMATION OF CYSTS 291

When the larve have arrived at their destination in the muscles
they thread their way between the fibers towards the ends of the
muscles (Fig. 120), ultimately penetrating the individual fibers
where they coil up into loose spirals, constantly coiling and un-
coiling as much as their close quarters will permit. When worms
which are still boring are teased out of the flesh and warmed to
blood heat, they can be seen constantly tightening and loosening
their coiled form, reminding one of a fist being alternately clenched
and unclenched. After entering muscle fibers the worms grow
rapidly in size to a length of one mm. (3 of an inch), ten times their
original size, and become sexually differentiated. The inflam-
mation caused by the movements and waste products of the
animals results in the degeneration of the enclosing muscle fibers
and in the formation, beginning about a month after infection,
of connective tissue cysts around the young worms. The cysts
(Fig. 118), which are completely developed in from seven to nine
weeks, are lemon-shaped, from 0.25 to 0.5 mm. (z3>5 to s45 of an
inch) long, lying parallel with the muscle fibers. As a rule only
one or two worms are enclosed in a cyst but as many as seven in
a cyst have been observed. When first formed the cysts are
very delicate and can only
be seen by careful focusing
with the microscope, but
they gradually grow thicker
and more conspicuous, and
after seven or eight months
‘there begins a deposit of
chalky calcareous matter

(Fig. i Al A). This process Fie. 121. Stages in calcification of trichina;
A, ends calcified; B, thin layer of calcareous

ultimately results in the material over whole cyst, worm beginning to ~
entire cyst becoming hard- degenerate; C, complete calcification. (After

E Ostertag.)

ened into a _ calcareous

nodule (Figs. 121B and C), and even the enclosed worm,
which usually degenerates and dies after some months, becomes
calcified after a number of years. There are cases, however,
where the trichina worms do not die and disintegrate so soon, and
the calcification process is much slower. There are records of
these worms found living in cysts in hogs 11 years after in-
fection and in man 25 to 31 years after, though it is doubt-
ful whether in some of these cases a fresh infection did not

292 TRICHINA WORMS

occur unknown to the patient or tothe observers who made
the records.

The larval worms, which, as pointed out by Ransom, on account
of their advanced stage of development are comparable with
the nymphs rather than the larve of arthropods, when encysted
in the flesh of some susceptible animal never develop further
until eaten by another susceptible animal. If they are eaten the
cyst is dissolved off in the intestine of the new host, the larve
are set free in the digestive tract, and within three days be-
come sexually mature and copulate, to begin the performance
all over.

Obviously man usually if not always becomes infected from
eating infected pork, whereas hogs may be infected not only
by eating scraps of raw pork but also by eating the bodies of
infected rats and mice. The latter animals are infected in
a similar manner. The number of trichina worms which may be
harbored by a single host is almost incredible. According to
the writer’s investigations, the sausage which was the cause of a
recent epidemic in Portland, Oregon, contained over 2,000,000
larve to the pound at a very conservative estimate, and in a bit
of human muscle fromr the diaphragm of an Italian who fell
victim to the disease the number of worms was even greater.

The Disease. — The disease caused by trichina worms is more
fatal to man than to any other animal, the fatality sometimes
rising to 30 per cent or more of the cases. Even in man the

worms, if eaten only in small numbers, produce no serious or

even noticeable effect. When eaten in great numbers, however,
as would always happen in eating heavily-infected raw or under-
done pork, the worms produce symptoms so much like typhoid
fever that the disease is undoubtedly often diagnosed as such.
The course of the disease, as described by Ransom, is somewhat
as follows: the first symptoms of the disease — diarrhea, ab-
dominal pains and intestinal catarrh — are the result of irritation
of the intestine by the adult worms, especially the females, which
burrow deep to deposit their young. Except in very light cases,
a sort of general torpor is noticeable, accompanied by weakness,
muscular twitching, ete. A very striking symptom, which ap-
pears in about a week and lasts for a few days, is a marked puffi-
ness or edema of the face and especially of the eyelids. As
pointed out by Ransom, the gravity of the case cannot be judged

er. ye

SYMPTOMS 293

from the severity of the first symptoms. In some of the worst
cases the first symptoms are very mild. :

In nine or ten days or longer the second stage of the disease
appears, accompanying the period of migration of the larve.
This is the period which is frequently fatal. The most pro-
nounced symptoms are intense muscular pains and rheumatic
aches, with disturbances in the particular muscles invaded, in-
terfering with the movements of the eyes, mastication, respira-
tion, etc., the respiratory troubles becoming particularly severe
in the fourth and fifth weeks of the disease, in fact sometimes
so severe as to cause death from dyspnea or asthma. Profuse
sweating and more or less constant fever, though sometimes
occurring in the first stage also, are particularly characteristic
of the second stage. The fever is commonly absent in children.
The third stage, accompanying the encystment of the parasites,
begins about six weeks after infection. The symptoms of the
second stage become exaggerated, and in addition the face again
becomes puffy, and the arms, legs and abdominal walls are also
swollen. The patient becomes very anemic, skin eruptions occur,
the muscular pains gradually subside and the swollen portions
of the skin often scale off. Pneumonia is a common compli-
cation in the third stage.

Trichinella is unique among worms in causing constant fever.
It is probable that the fever as well as certain changes in the
blood corpuscles and chemical changes in the invaded muscles
is due both to poisonous substances given off by the worms and
to poisonous substances resulting from destroyed muscle tissue.
Such substances have been found by Flury and Groll and others
in cases of Trichinella infection. They are substances which
act on the muscles themselves, on the nervous system, and on the
bloodvessels. It is.quite evident, as pointed out by Herrick, that
with the invasion of the blood and tissues by millions of larve
and with the breaking down of large amounts of muscle tissue

a constant inoculation of the infected person with poisonous
protein material is taking place, a condition which always gives
rise to fever. Certain volatile acids are produced by the muscle
degeneration, and these are considered by Flury to account for
the muscular pains. Other toxic substances account for most of
the other symptoms of the disease, e.g., the marked increase in
certain kinds of white blood corpuscles, the eosinophiles.

294 TRICHINA WORMS

The duration and final outcome of the disease is variable,
according to the heaviness of the infection. Death, as remarked
before, may frequently result, and according to Ransom most
commonly occurs from the fourth to the sixth week. It rarely
occurs before the end of the second week or after the seventh.
Recovery usually does not occur in less than from five to six
weeks after infection, and often not for several months. Re-
current muscular pains and weakness may continue for years and
a stiffness may persist indefinitely in the invaded muscles. Com-
monly cases in which a copious diarrhea appears early in the
disease are of short duration and mild in type. Young children,
due either to smaller quantities of pork eaten or to greater tend-
ency to diarrhea, are likely to recover quickly.

Treatment and Prevention. — The search for a specific remedy
for trichiniasis has so far been futile. Even the adult worms in
the intestine are much more difficult to dislodge or destroy than -
are other intestinal worms, since they bore so deeply into the
intestinal walls that the ordinary drugs do not affect them. Even
were it possible to drive out the adults readily, this often could not
be done in time to prevent disease or death, since the infection is
seldom recognized before the larvee are already produced and are
migrating throughout the body. This is the critical stage of the
disease; if the system can endure the irritation and inflam-
mation produced by the burrowing of millions of worms and
can withstand the effects of the toxins produced both from the
worms themselves and from the destroyed tissues during the
first and heaviest onslaught of the newly produced larve, the
danger is past. The fever, the muscular pains, amounting to
agony for a time, and the intestinal disorders continue for weeks
but gradually subside. The treatment employed during all this
time can only be systematic and of general nature — efforts to
reduce the fever, to permit sleep, to keep the digestive system
in as good order as possible and to do all that can be done to keep
up the vitality and general health.

It is possible that if the trichina worms could be isolated and
ground up, and injected into the blood, an active immunity
could be built up as in the case of typhoid vaccinations. Passive
immunity by injection of serum from a convalescent has been
stated by Salzman to have some curative as well as preventive
value, but this work needs confirmation. The disease, however,

PREVENTION 295

is not so prevalent or so difficult to prevent by other means as
to make promiscuous immunization justifiable, even if possible.
A more hopeful though so far unproductive line of research
regarding the treatment of the infection lies in experiments
with drugs or serum to kill either the adult worms in the intestine
or the larve before they begin destroying the tissues.
Personal preventive measures against trichiniasis are easy
and consist simply in abstinence from all pork which is not
thoroughly cooked. Many experiments have been performed,
and are still in progress, by the U. 8. Bureau of Animal Industry
regarding the temperature necessary to destroy trichina worms.
Boiled pork must be cooked for a length of time proportionate to
its weight in order to insure the permeation of heat to the center.
Experiments show that at least 30 to 36 minutes should be al-
lowed to each kilogram of meat (2% lbs.). Hurried roasting does
not destroy the parasites as long as red or raw portions are left
in the center. Cold storage for 20 days or more at temperatures
below 10° F. has been shown by Ransom to be destructive to
trichine. The regulations of the U. 8. Bureau of Animal In-
dustry, relative to pork products customarily to be eaten without
cooking, require freezing for 20 days at a temperature of not higher
than 5° F., or curing in accordance with certain specified pro-
cesses. Temperatures above 10° F. are more or less uncertain in
their effects. Salting and smoking are not efficacious unless
carried out under certain conditions. Thorough salting is effec-
tive, provided the meat is left for some time for the salt to per-
meate it. Large pieces of pork placed in brine have been known
to contain’ living trichine for over a month. The parasites in
sausages are destroyed in 24 hours by hot smoking whereas they
resist cold smoking for three days.

Prevention of trichiniasis by meat inspection methods is at best
only partial, and, while meat inspection might help to lessen the
chances of the disease, it should not be implicitly relied upon.
Probably in an ordinary meat inspection all heavy infections
would be found, provided the inspector has been doing his work
properly. The inspection usually consists in the microscopic ex-
amination of a bit of muscle from tongue and diaphragm; if
the examination is negative, the hog is passed. Obviously light
infections must frequently escape notice, and the false sense of
security which is the result of knowledge that meat has been

296 TRICHINA WORMS

‘inspected’ may do much damage. There is no inspection
for trichine in force in the United States at the present time.

Much could be done to prevent the prevalence of trichina in-
fection in pork by preventing hogs from eating food which might
be infected. Hogs should never be allowed access to the car-
casses of other hogs or to the dead bodies of rats and mice, or
to waste scraps of pork. Dead hogs or waste pork, if there is
any possibility of their being infected, should not be thrown where
rats and mice could prey upon them. If these principles were
carefully followed out, there is no doubt but that trichiniasis
could be reduced to a much greater extent than it has been.

The symptoms of trichina disease in hogs are much less evident
than in man, and there is no certain diagnosis of it in living ani-
mals except by microscopic examination of the muscles for the
detection of the larvae. When heavily infected, hogs show severe

intestinal disorders, abdominal pains and stiff muscles, but there ©

is nothing diagnostic in these symptoms. A farmer who drives
sick hogs to market, however, in order to get rid of them, with-
out giving proper warning of their condition which might make
possible the discovery of trichina infection if present, should
be considered guilty of criminal negligence, and punished in
accordance with the damage done by this negligence. This is
particularly true if he feeds his hogs waste containing raw meat,
or allows them to feed upon dead animals —a very common
practice.

As has recently been pointed out by Stiles, there is no prac-
tical or proper method of inspecting meat by which the absence of
Trichinella can be guaranteed, and it is therefore unjust to hold
a butcher responsible for cases of trichiniasis which may result
from the eating of pork sold by him. There are laws which pro-
vide that “ diseased meat ”’ shall not be sold and that an implied
warranty of fitness for food goes with any sale of food. Neither
of these laws, however, can be unreasonably enforced. Techni-
cally all meat is diseased, since there are no market animals
which are not parasitized in some way. As to the “ implied
warranty,’ this can go only with an implied guarantee on the
part of the buyer that the food will be properly prepared before
being eaten. Clams in the shell, unhusked corn and uncooked
beans are guaranteed as being fit for food only when properly
prepared. In like manner pork is sold with the understanding

i ite aa

FITNESS OF PORK FOR FOOD’ 297

that it will be properly prepared, 7.e., thoroughly cooked. Raw
pork, since it is likely to contain Trichinelle which may cause
disease, and since the absence of these worms cannot be guaran-
teed by any practical inspection now known, is unfit for food and
therefore cannot be guaranteed if eaten raw. As Stiles has
pointed out, great and unjustifiable loss may result from too
stringent enforcement of the laws.mentioned above.

CHAPTER XVII
FILARILZ AND- THEIR ALLIES

General Account. — One of the most interesting and puzzling
groups of human parasites are the members of the nematode
genus Filaria. They are extremely common parasites in all
tropical countries, have a unique and extraordinary life history,
are associated with many serious pathological conditions and
have figured prominently in the history of medical science.

Sir Patrick Manson first discovered these worms swarming in
human blood, while working on tropical diseases in India. They
had previously been observed in various bodily excretions but
only in rare cases and in small numbers. Manson found them
in enormous numbers in the blood, but only at night. The
worms were evidently larve and since they only rarely and ap-
parently accidentally escaped from the body with excretions,
the thought occurred to Manson that they must be liberated
from the blood by some nocturnal blood-sucking insect. Man-
son and others later proved this theory to be correct, and thus
took the first step toward our present knowledge of the biologi-
cal transmission of disease by insects, a step which marked the
beginning of a new era in modern medicine.

Many species of Filaria from human blood have been described,
some of which undoubtedly are not valid species. Some species
apparently produce no pathological conditions whatever, while
others are associated with, and are usually considered te be the
direct cause of, a large number of diseased conditions. Some of
the species are of limited geographic distribution while others
are of world-wide range, probably due to differences in the ex-
tent of the distribution of the intermediate host. In some
tropical localities 50 per cent or more of the population are para-
sitized by these animals. In South China ten per cent of the entire
population is said to be infected and in some South Sea Islands
over half of the inhabitants are infected. Recently in an exam-
ination of 949 natives from the Congo-Cameron country of

298

LIFE HISTORY OF FILARIA BANCROFTI 299

Africa, about 74 per cent of the men, 79 per cent of the women and
33 per cent of the children were found to be filariated.

The blood-dwelling filariz which are readily observed are, as
remarked above, only larve, the adults being much larger, long,
slender worms which live in the lymphatic vessels, connective
tissue or other tissues of the body. It is to these adult worms
and not to the larve that the so-called “ filarial diseases’ are
supposed to be due; the blood-living worms apparently cause
no serious symptoms. The larve have been termed ‘“ micro-
filarie ”’ to distinguish them from the adult worms.

Filaria bancrof ti

The most widespread species and most important from a
medical point of view is Filaria bancroftit. This nematode occurs
more or less abundantly in all warm climates of the world, north
to southern United States and southern

Europe and Asia, and south to southern Qo)
Australia and Patagonia.
Life History. — The adult Filarie 2 Ss

were not discovered for many years pie 499. Adultsof Filaria
after the larve had been found in the bancrofti, female (2) and
blood, since they occur in the deep- Tiles Oe iain we
seated lymphatic vessels where they could
be observed only on post mortem examinations. They are very
long, slender nematodes (Fig. 122), the females three or four inches
in length and hardly greater in diameter than a horsehair, and
the males about half this size. In their
normal habitat in the lymph vessels the
males and females live coiled up to-
gether, sometimes several pairs of them

Fie. 123. Microfilaria of in a knot. The male worms, in addition
— asiainae tarent we to their smaller size, may be distin-
rounded by delicate mem- guished from the females by the coiled
ieee) Cer Babe.) tail which reminds one of a vine tendril.
The greater part of the body of the female is occupied by a pair
of uteri, which in the adult are always filled with eggs.

The eggs (Fig. 123) usually hatch before they are laid so that
living young swarm forth from the parent worm, but in excep-
tional cases the eggs are deposited before hatching. The young

300 FILARIZ AND THEIR ALLIES

worms reach the blood by way of the lymph stream and these
~~grow to about 300 u (a little over 09 of an inch) in length. They
end and tapering to a selene Point at the tail end, and are
entirely enclosed in a remarkably delicate transparent sheath,
which, although it fits as tightly as a glove over a finger, is too
long for the animal and can be seen projecting at either end. The
sheath may be looked upon as a wonderful adaptation to prevent
the worms from being able to
bore through the bloodvessels
and escape from the blood, in
which case they would miss
their chance for ‘ salvation.”
The internal organs are in a
very rudimentary condition.
The most remarkable cir-
cumstance connected with the
life of these microfilarie is the
periodical appearance and dis-
appearance of them in the
blood of the peripheral vessels.
If the blood of an infected
person is examined during the
day few if any worms can be
found, but as evening ap-
es proaches they begin to appear
Fie. 124. Comparison of microfilarie; and continue to increase until
Ah tera Cel eine ea, ies’ about midnight, after which
C, mf. loa (large, with sheath); D, mf. they decrease again until
Hence mmenguaty mal, sharp tall n° morning. During the night
when they are most abun-

dant there may be as many as 500 worms in a single drop of
blood. If the parasites are assumed to be evenly distributed
throughout the peripheral circulation, this would imply the
presence of several million worms in the body. The periodic
appearance and disappearance of microfilarie in the blood is not
invariable. When an infected person is made to sleep in the
daytime instead of at night, the appearance and disappearance
of the parasites in the peripheral bloodvessels can be reversed,
implying that the distribution of the parasites may be dependent

FILARIA BANCROFTI IN MOSQUITOES 301

on some physiologic condition of the host. Still stranger is the
fact that in many of the South Sea Islands, Samoa, the Fiji
Islands and the Philippine Islands, the microfilarize show no
periodic disappearance, although if a person infected in a place
where the parasites do show periodicity be transferred to one of
the above-named islands, the periodic phenomena still persist.
As stated before, Manson, the great English parasitologist, with
characteristic ingenuity, suspected that this parasite, so abundant
in the blood, must make use of some blood-sucking insect as a
means of transmission, and further concluded that the night
swarming of the parasites in the peripheral circulation might be
an adaptation to the nocturnal habits of an intermediate host.
Working on this hypothesis, he discovered that certain mosquitoes
acted as the liberating agents for the parasites. The fact that
in those islands where no periodicity is shown the usual inter-
mediate host is a diurnal mosquito Aédes (or Stegomyia) pseudo-
cutellaris, certainly bears out the adaptation hypothesis. On the
grounds of the apparently distinct habits and different adaptation,
the non-periodic microfilariz have been separated into a distinct
species, or at least subspecies, to which the name Filaria philip-
pinensis was applied by Ashburn and Craig in 1906. Zodlogists
are coming more and more to realize the importance of physio-
lologic as well as morphologic characteristics as a basis for sepa-
rating species and subspecies. The case of these filariw is by no
means unique in the organic world. Physiologic and biochemical
reactions are the main basis for the classification of the Bacteria,
and some Protozoa can be distinguished better by their patho-
genic effects and biochemical reactions than by their morphology.

To continue their development the larval worms must be
sucked up by the females of certain species of mosquitoes. A
considerable number of species of mosquitoes of several different
genera, including Anopheles, Aédes and Culex, may serve as
intermediate hosts for F. bancrofti (see p. 449). The commonest
and most widespread transmitting agent is the house mosquito
of the tropics, Culex quinquefasciatus (fatigans), a species which
also transmits dengue. A few hours after being swallowed by
a susceptible mosquito the microfilarie (Fig. 125A) become rest-
less and endeavor to escape from their sheaths. This they
eventually accomplish by butting against the anterior end,
having gained as much impetus as their close quarters will allow.

302 FILARILZ AND THEIR ALLIES

Once free, the little larve (Fig. 125B) move actively about in
quite a different manner from the ineffective wriggling in which
they indulged while enclosed in the sheath, and by means of which
they were unable to ‘‘ get anywhere.” The active liberated
worms make their way
to the thoracic muscles
of the mosquito, where
they lie between the
muscle fibers and par-
allel with them. The
body, growing rapidly,
by the fourth to tenth
day becomes thick and
sausage-like (Fig.
125C), with a, short,

Fic. 125. Development of Filaria bancrofti in Increases greatly in
mosquito; A,as withdrawn with blood (first 24 hours) lensth and decreases
in stomach; B, form found in tissues just outside ~~ 8 : :
stomach (48 to 72 hours after ingestion); C, form slightly nm thickness,
found in muscles on fourth day; D, mature larval thus becoming long and
form, ready for transmission, in proboscis (two or 8 ; 8 ;
more weeks after ingestion). 150. (After Lewis Slender again (Fig.

So onal 125D). Meanwhile the
internal organization of the animal undergoes a great change.
The central core of cells gradually becomes differentiated into a
digestive tract, separated from the body wall by a true body

—————
=~ a ssSSSSSSSSSSSSS

—
~
SN

Tim
Sg
= —— SS

wool

Fie. 126. Mature larve of Filaria bancrofti in thoracic muscles and proboscis
of mosquito. (After Castellani and Chalmers.)

i \\ _———
(2 a °
3

cavity. By the time the larva has reached its full size — about
1.5 mm. (,/g of an inch) in length — the digestive tract is a com-
plete tube with both mouth and anal openings. While these
changes are taking place, the larval worm, though capable of
activity, remains at rest between the muscle fibers (Fig. 126),

pointed tail, but it later

Nicaea

FILARIAL DISEASES 303

but it now becomes active again and migrates into the connective
tissue of the anterior parts of the body of its host, and ultimately
into the proboscis (Fig. 126). Here the worms lie in pairs, or
several pairs together, awaiting an opportunity to re-enter a
human host.

The length of time required for the metamorphosis and de-
velopment in the mosquito varies from about two weeks under
ideal conditions to several weeks under less favorable circum-
stances. When the infected mosquito bites a human being, the
worms emerge from the proboscis and bore through the skin
in the immediate vicinity of the wound, though not directly
through the puncture. Experiments have shown that the larve
can not be deceived into entering vegetable tissue, such as a
banana, even though for many days they have been at the tip
of the proboscis, ready to emerge when the mosquito bites into
warm-blooded flesh.

It is possible that these parasites may occasionally find entrance
to the human body by other paths than the mosquito’s bite but
- this has not yet been proved. The popular belief that bad water
is the cause of filarial infection is probably due to the effect of
stagnant water on the abundance of mosquitoes, and not to the
emergence of the larve from the bodies of mosquitoes into water.
Bahr has shown that the larve will live in water only seven
hours. 5

Once back in a human body from this period of “ purgatory ”
in the body of a mosquito the larve migrate to the lymphatic
vessels, there to attain sexual maturity, copulate and reproduce.
The larve of the next generation escape again to the blood as
microfilariz, and the cycle is complete. The adult worms may
live for many years and even the microfilariz are able to live for
a considerable time, as shown by their continued presence after
the death of the parents. :

Filarial Diseases. — The disease symptoms which are asso-
ciated with Filaria bancrofti can all be traced to interference
with the lymphatic system. In many cases there are no ill
effects of the infection felt for many years, or perhaps never,
though sooner or later there is usually produced anemia, en-
largement of the spleen and fever. More serious are the effects
produced by obstruction of the lymphatics. This causes great
enlargement of the lymph vessels and the diversion of the lymph

304 FILARIZ AND THEIR ALLIES

from its normal channel, and results in varicose lymph glands
(Fig. 127C) and vessels and in distended lymph sacs which may
burst into the kidneys, bladder or body cavity. Often the
microfilariz disappear from the blood, probably on account of the
death of the parents, but the obstruction of the lymphatics
continues to exist, as do the evil effects resulting therefrom.

Bia. 1275, 2% few extreme cases of elephantiasis; A, of legs and feet; B, of
scrotum; C, varicose groin gland; D, of scrotum and legs; H, of mammary glands.
(A and B sketched from photos from Castellani and Chalmers; C, D and HE from
Manson.)

One of the most frequent results of a blocking of the lymph
vessels is an enormous enlargement of the part of the body
in which the blocking occurs, known by the suggestive name,
“ elephantiasis ’ (Fig. 127). In most cases the lower limbs and
scrotum are the parts affected, though almost any portion of

FILARIAL DISEASES 305

the body may occasionally become enlarged. In some South
Sea Islands 50 per cent or more of the population are thus affected.
The disease begins by repeated attacks, at intervals of from a
month to a year, of ‘‘elephantoid”’ or filarial fever in which
chills and high fever accompany a painful swelling of the parts
affected. These attacks, also known as lymphangitis, end in an
emission of lymph and a partial subsidence of the swelling.
But each attack leaves a little more permanent tissue, so that in
time the growth, which is hard and unyielding, develops to enor-
mous proportions. Sometimes an affected leg may reach a diam-
eter of several feet. In one case recorded by Manson, a scrotum
affected by elephantiasis reached a weight of 224 pounds, though
it must be admitted that this is unusual.

Another condition resulting from filarial infection is the escape
of the contents of lymph vessels into the kidneys or bladder, a
condition technically known as “ chyluria.’”” The urine is milky
and coagulates after standing a short time. This condition lasts
for a few days or weeks, then ceases and returns at irregular
intervals. It produces severe anemia and a general feeling of
ennui, and saps the vitality.

Occasionally the presence of dead filarize in the body leads to
the formation of abscesses which sooner or later discharge. If
on any of the appendages, no further trouble results, but such
abscesses in the internal regions of the body may have serious or
fatal effects.

Though very probably some of these so-called “ filarial dis-
eases’ are caused directly by the filarie, the exact relation of
F. bancrofti to all of the pathological conditions associated with
its presence in the body is far from settled. Dutcher and Whit-
marsh, of the United States Army, in investigations of filarial
_ diseases in Porto Rico recently obtained pure cultures of a certain

type of bacterium from the blood or serum of 15 patients, all
but one of whom was affected by some form of filarial disease,
whereas in unaffected individuals, with one exception which was
looked upon as a “ carrier,” the cultures from the blood remained
uniformly sterile. In a few cases in which filarial diseases were
present the bacterium-was not found but it was believed that
either the infection was so light that the cultures did not happen
to become contaminated, or that the infection had died out.
A number of other observers have obtained cultures of bacteria

306 FILARIZ AND THEIR ALLIES

~

from blood and tissues of elephantiasis cases. Others, however,
have found the blood quite sterile. It is worth noting in this
connection that the number of cases of elephantiasis or other
filarial diseases in which microfilarize are not present in the blood
is considerably greater than those in which the larval parasites
are present. This is usually explained by assuming that the
parent filarie have died or that the larve cannot reach the blood
on account of a blocking of the lymph channels by fibrous growths.
Cruickshank and Wright, for instance, in 130 cases of elephantiasis
in Cochin, found only 12 with microfilarie in the blood. The
observations recorded above are certainly significant and may
revolutionize our ideas in regard to filarial diseases. However,
even if some of the “‘ filarial diseases ’’ were found to be due to
bacteria, the filarie might still be incriminated as carriers of
the bacteria, and therefore as an indirect cause of the diseases. |

Treatment and Prevention. — So far there is no widely-ac-
cepted treatment by which the parent filarie, and with them the
microfilarie, can be destroyed. The number of the larve is
reduced, however, by injections of thymol, ichthyol and other
drugs, and such injections might prove to be a useful preventive
measure. McNaughton has recently reported five cases of
filarial infection successfully treated by injections of salvarsan;
one case was of ten years’ standing. Usually the only course
of the physician is to relieve as far as possible the abnormal
conditions associated with the presence of the worms. Such
relief, of course, varies greatly with the diverse pathological
conditions which may arise. Varicose glands and vessels, un-
less causing great discomfort, are usually left alone, since they
are lymph channels substituted for the normal ones in the body
which have been blocked, and it is therefore dangerous to inter-
fere with them. In cases of elephantoid fever the only treat-
ment is such as would tend to relieve the pain in the swellings
and the fever, and perhaps in severe cases the pricking of the
swollen part to allow the exudation of the collecting lymph.
In chyluria the treatment consists in rest and in making the
pelvic regions as comfortable as possible to prevent pressure
which would tend to burst the lymphatics and force the lymph
into the kidneys or bladder. Elephantiasis, the commonest
expression of filarial disease, is seldom completely recovered
from. Formerly the only treatment was temporary reduction

FILARIA PERSTANS 307

of the swellings and prevention of further growth by care of the
general health, avoidance of violent exercise, massage and tight
bandaging. In severe cases of elephantiasis of the leg physicians
sometimes cut off great masses of the elephantoid tissue, grafting
on new pieces of skin to cover the parts operated on. Removal
of enlarged growths of the scrotum can usually be accomplished
successfully. Another method which has been used with some
success is an operation for the draining of the lymph from the
tissue all the way into the bone or even from the bone itself.

Castellani has recently found a method of reducing elephantoid
tissue which will probably supplant all of the above methods.
- This consists in the injection into the diseased tissues of a drug,
fibrolysin, which, as its name implies, has the property of destroy-
ing fibrous connective tissue. Elephantoid ‘swellings are re-
ported to have been cured by this method in a few months.

Prevention of filarial diseases can best be accomplished by
anti-mosquito campaigns. As far as is known at present mos-
quitoes are the only means of transmission which the parasites
have. The same preventive measures, therefore, which serve
as preventives against malaria, serve also against Filaria ban-
crofiz, and since the former disease is found practically every-
where that the filariz are found, it is possible to prevent the
two diseases with one effort. People who carry filarize in their
‘blood should be prevented, as far as possible, from exposing
themselves to mosquitoes. In the places where the micro-
filariz are periodic and the transmitting mosquitoes are nocturnal
this should be perfectly possible, although in such localities as
the Philippines and Samoa, where the intermediate host is largely
diurnal, it would present almost insuperable difficulties. In
places where Filaria is abundant and mosquitoes are not ex-
terminated the carrying at night of a bottle of disinfectant, as
alcohol or dilute lysol, for immediate application to mosquito
bites would be well worth while.

Other Species of Filaria

There are, as previously stated, a number of other species of
Filaria which inhabit the human body. Filaria (or Acantho-
cheilonema) perstans is extremely common in the natives through-
out Central Africa and also in parts of northern South America;

308 FILARLZ AND THEIR ALLIES

it is confined to regions of heavily forested tropical swamps.
In some districts in Uganda it has been found in 90 per cent of
the inhabitants. The microfilariz of this species (Fig. 124B)
are smaller than those of F. bancrofti, have a blunt tail and
lack the sheath which is so characteristic of F. bancrofti. Fur-
thermore they show no tendency to disappear periodically from
the peripheral vessels. The adult worm, which has rarely been
found, is smaller than F’. bancrofti (about three inches in length)
and occurs in the connective tissue of the abdominal and peri-
cardial cavities. The normal transmitting agent, probably some
species of mosquito, is not certainly known. No disease symp-
toms which can be correlated with the presence of the parasite »
have yet been demonstrated.

Another species, F. guncea (demarquaiz), of which the larva
(Fig. 124D) is small and without a sheath, as in F. perstans, but
with a sharp tail, occurs in the West Indies and northern South ~
America. It is not known to cause any diseased conditions.
The adults live in the mesenteric tissues. In many Indians in
British Guiana F’. perstans and F. juncea occur together in the
blood, and in some cases the presence of F. bancrofti compli-
cates the matter still more.

F. magalhaest is another species about which very little is
known. A pair of adult worms were found only once, in the
heart of a child in Rio de Janeiro. They were of unusually large

size, the female measuring over six inches in
length and the male about three and a half
inches. Nothing is known of the life history
or pathological effects.
3 The Loa Worm. — Of somewhat different
2 nature from the above species of Filaria is F.
. g loa or Loa loa (Fig. 128), a parasite found on
Fic. 128. Adult the west coast of Africa, especially in Congo,

loa worms, female
(2) and male (¢). which, as an adult, creeps in the connective
Ae size. (Alter tissue of its host just under the skin. The

female varies, probably with age, from two to
two and one-half inches in length, and is semi-transparent and very
slender. The male resembles the female, but is only from one to
one and one-half inches in length. Both sexes are characterized
by numerous irregularly distributed pimple-like elevations of the

skin. The loa worm shows a special preference for the connective

LOA WORM 309

tissue in and about the eyes, but may also be found creeping
under the skin of fingers, breast, back, etc. A loa is said to travel
at the rate of about an inch in two minutes, and to become
especially active in the presence of direct warmth on the skin,
as before a fire. The migration of the worms causes itching and
a “‘ creeping ”’ sensation, and in some unexplained way gives rise
to temporary swellings, from half an inch to four inches in diame-
ter, known locally as ‘“‘ Calabar swellings.”’ These swellings
may shift their position an inch or more a day, and may disap-
pear to reappear somewhere else. This relation of Loa to Cala-
bar swellings has not been definitely proved but there is strong
evidence for it. In one case Manson succeeded in finding
great numbers of microfilarie of Loa in lymph taken from one
of these swellings, a fact which gives color to Manson’s hypothe-
sis that the swellings might be due to the emission of larvee from
the parent worm into the connective tissue. The larve of the
parasite (Fig. 124C), very closely resembling the microfilarize
of F. bancrofti, occur in the blood in great numbers, but they
have a periodicity di-

rectly opposite to that R*?, 6d,
of the latter species in oe

that they swarm in the sO oe

peripheral blood in the
daytime and withdraw oF, hte
to the larger vessels at

night. The living
larvee of the two species

cannot readily be dis-
tinguished from each

other in fresh blood, F . E ‘|
. ae : 1G. 129. Comparison of killed and stained speci-
but in dried and stained mens of Microfilaria bancrofti and mf. loa. <A, mf.

preparations the dead _ bancrofti, — note graceful curves; B, mf. loa, — note
. eds irregular scrawl-like curves; C, tails of mf. loa; D,
organisms CaN €asuy DE tails of mf. bancroftt. (After Manson.)

identified. The micro-
filarie bancrofti are found lying in smooth graceful curves (Fig.
129A), while the microfilarie loa die in ungraceful and irregular
scrawl-like positions (Fig. 129B), with the tail nearly always
sharply turned back (Fig. 129C).

There is much evidence that the intermediate hosts of L. loa
are mangrove flies of the genus Chrysops, which belong to the

310 FILARIZ AND THEIR ALLIES

horsefly family, Tabanide, and resemble our deerflies (see p. 489
and Fig. 227). Leiper succeeded in obtaining a development of
microfilaria loa in two different species of Chrysops. In recent
investigations in a heavily infested district of Africa, Kleine
found over five per cent of 600 Chrysops infected with larval filarie,
which he took to be Loa loa. The worms were found developing
in the fatty connective tissue surrounding the trachez in the
abdomen of the insects and later making their way forward toward
the proboscis. In two cases larve were induced to emerge from
the fly’s proboscis into a few drops of salt solution. That these
worms were really the larve of ZL. loa is entirely probable, but
there is no definite proof of it.

The development of the parasites after they have been re-
turned to a human body is extremely slow, in fact the evidence
indicates that full sexual maturity is not reached for a number of
years. The length of life of the worms is unusual; there are
cases recorded in which these parasites were abstracted from
patients who had been away from endemic regions for ten or 15
years. Mlicrofilariz are not invariably found in the blood of
infected persons. Children, especially, are prone to infection
with the creeping worms, usually sexually immature, without
having any larve in their blood. Even sexually mature para-
sites apparently do not liberate larve constantly.

Surgical removal of the parasites when they present themselves
in the eye or subcutaneous tissue is the only remedy so far known.
Many of the parasites probably do not expose themselves at all,
but remain in the deeper tissues and organs of the body. When
they die in the tissues they probably become calcified as do the
adults of other filariz.

Onchocerca volvulus. — Closely related to the filarie is
another parasite of the subcutaneous connective tissue, Oncho-
cerca volvulus. It occurs over a large portion of the west coast
and central portion of Africa. Three cases of infection with the
same or a closely allied species has recently been reported by
Thézé from French Guiana. The adult female is several inches
in length, and slender as a hair; the male is stouter, and little
over an inch in length. The adults lie in couples in fibrous tumors
which can be seen readily under the skin. The tumors vary in
size from about one cm. (% of an inch) in diameter to the size
of a pigeon’s egg, and are found most commonly on the hip,

GUINEA-WORM

dll

sides of the chest and upper part of the back, and sometimes
in the arm and knee pits and on other parts of the body. Each
swelling consists of dense fibrous tissue in which several pairs of
parasites are imbedded, and contains small cystlike spaces into

which project the posterior end of the male
with its copulatory organs, and the anterior
end of the female with its vaginal opening.
These cystlike spaces are usually swarming
with sheathless microfilarie. The latter are
believed by some authors to leave the tumors
and to find their way ultimately to the blood-
vessels, whence they can be liberated by some
blood-sucking insect. However, attempts to
find them in the circulating blood practically
always fail, though the larve can usually be
obtained easily from lymph glands in the groin.
The intermediate host is unknown, but the
stable-flies, Stomozxys, and tsetse flies, Glossina,
have been suspected. The tumors are of long
duration in man, and in some adults are said
to have been present since childhood. It is
significant that practically all cases of elephan-
tiasis in the Welle district of Congo, where
Filaria bancrofti is said not to occur, are
accompanied by infection with Onchocerca
volvulus.

The Guinea-worm.— Another connective
tissue parasite, more distantly related to the
filarie, is the guinea-worm, Dracunculus medi-
nensis (Fig. 1380). This is a frequent parasite
in many parts of tropical Asia and Africa and
has been known for a very long time. The

“fiery serpents ’’ which molested the Israelites

by the Red Sea and were mentioned by
Moses were probably guinea-worms. These

Fig. 130. Guinea-
worm, Dracunculus
medinensis, female.
Natural size. (After
Leuckart.)

parasites creep in the deeper layers of the subcutaneous tissue
where they can be more readily felt than seen, but the females
always come to the surface of the skin to give birth to the myriads

of wriggling young.

The adult female worm, which is the only sex certainly ion

312 FILARLE AND THEIR ALLIES

may attain a length of four feet or more, though the average
length is about three feet, while the diameter is less than 7; of an
inch. The body is smooth, cylindrical and milky-white in color,
with the tip of the tail sharply hooked. The male worms are
believed to be much smaller than the females. When ready to
bring forth her young, the guinea-worm is instinctively at-
tracted to the skin, especially to such parts as are likely to, or
frequently do, come in contact with cold water, such as the
arms of women who wash clothes at a river’s brink, or the legs
and backs of water-carriers. The worm pierces the lower layers
of the skin with the front end of her body and the outer layers
of the skin form a blister over the injured spot. The blister
eventually breaks, revealing a
shallow ulcer, about as large
as a dime, with a tiny hole in
the center. When the ulcer is
douched with water a milky
fluid is exuded directly from
the hole or from a very deli-
cate, transparent projected
structure which is a portion
of the worm’s uterus. This
fluid is found to contain hordes
of tiny coiled larve with char-
Fie. 131. Cross section of guinea- acteristic straight projecting
vorm showing ules filed wit os tails, ‘The larve: (Hes ian
from 0.60 to 0.75 mm. (about 3}5

of aninch) in length. An hour or so later a new washing with cold
water will bring forth a fresh ejection of larve and so on until the
supply is exhausted, a little more of the uterus being extruded each
time. After each ejection of the larve the protruded portion of the
uterus dries up, thus sealing in the unborn larve. This process
can be looked upon only as a wonderful adaptation for the pres-
ervation of the race. As we shall presently see, the tiny larve
utilize various species of Cyclops (Fig. 132), small fresh-water
crustaceans, as intermediate hosts. If the larve were not de-
posited in water, or if they were all poured at once into any bit
of water with which the skin of the host came in contact, the
chance of their reaching a suitable Cyclops would be very small.
The result would usually be family suicide and eventually race

GUINEA-WORM IN CYCLOPS ale

suicide. The repeated birth of a limited number of progeny
each time the skin of the host comes in contact with water is
therefore a successful solution to a problem which to a blind
burrowing unmeditative worm must otherwise present insuper-
able difficulties. When
all her young have been
deposited, under the stim-
ulus of contact with water,
the parent worm shrivels
and dies and is soon ab-
sorbed by the tissues on
which she formerly preyed
and through which she
roamed.

The embryo worms,
safely deposited in water,
unroll themselves and be- pyg. 139.

; i { Cyclops sp. (?), some species of
gin to swim about in a which serve as intermediate hosts of guinea-

worms. X about 25.

fashion peculiar to them-
selves. Their bodies are somewhat flattened and they have a
slender tail. They swim by a few quick sculling motions of the
tail, followed by a pause, then a few more strokes, etc., in the
manner of a tadpole. In turbid water they remain alive for
two or three weeks but eventually perish unless they come in con-
tact with a Cyclops, into the body of which they make their way.

They usually enter by way of the mouth, sometimes as many
as six or ten entering a single Cyclops. In a day or two they
leave the stomach of Cyclops and enter the body cavity. In
spite of the relatively large size of the worms the crustaceans
seem to feel very little inconvenience, and seldom succumb
even to very heavy infection.

The young guinea-worms become fully developed in Cyclops
in from four to six weeks, according to the temperature, mean-
while having undergone one and perhaps two moults. They are
then about one mm. (qs of an inch) in length, and ready to in-
fect a new host. Entrance to the new host is probably accom-
plished by the accidental drinking of a Cyclops with unfiltered
water. The female worms become adult in their new host in
about a year so the larve can again be deposited at about the
time that Cyclops becomes abundant.

314 FILARIZ AND THEIR ALLIES

The guinea-worm, though annoying and to one of fine sensi-
bilities extremely disgusting, is not in any way dangerous if not
interfered with. Should she come to an untimely end, however,
or fail to pierce the skin, she may give rise to troublesome ab-
scesses, though more often the body becomes calcified and may
be felt for years as a hard twisted cord beneath the skin. The
crude method of abstraction of the worm which is frequently
practiced is the chief source of danger from infection with it.
This extraction consists in winding out the extruded part of the
worm around a stick, drawing it forth a little further each day.
Sometimes this method is successful but frequently it results in
the snapping in two of the worm beneath the skin, and the
consequent liberation into the tissues of thousands of young
worms with the fluid contents of the uterus. This gives rise
to inflammation, fever, abscesses and even death from blood-
poisoning. :

A much more effective and rational method of treatment is
to bathe the part of the body occupied by a mature worm at
frequent intervals until she has emptied her uterus, a process
which takes two or three weeks. When the birth of embryos
ceases, gentle pulling is likely to bring the worm forth, but if
not her body is quickly absorbed by the tissues. A more re-
cent and quicker method of dealing with a guinea-worm is to
inject her body, or the tissue in which she is coiled, with a very
weak solution of bichloride of mercury. This kills her and usu-
ally makes her extraction easy after a few hours.

Prevention of guinea-worm infection consists obviously in
keeping drinking water clear of Cyclops, or in thoroughly filtering
it, or, if these measures are impracticable, in preventing infected
persons from bathing in or otherwise contaminating rivers or
other bodies of water from which drinking water may be taken.
It has been suggested that portable steam generators be used to
heat the water in wells, water holes, etc., in which infected
Cyclops live, since these crustaceans succumb at a slightly ele-
vated temperature. Addition of small quantities of potash to
water is also effective in destroying Cyclops. The difficulty
connected with an attempt to exterminate Cyclops locally is
that the eggs resist desiccation and are blown about freely by
the wind, so that a new colony is likely to spring up at any
time.

CHAPTER XVIII
LEECHES

THE annelids as a group are not of such primary importance
as parasites as are the two other great groups of ‘‘ worms.”
In fact only one class, the Hirudinea or leeches, contain species
which are parasitic on the higher animals.

No boy who has ever experienced the unbounded delights of
hanging his clothes on a bush and immersing his naked body
for a swim in a muddy-bottomed river or pond is unfamiliar
with leeches or “‘ bloodsuckers.”’ Still more familiar with them
is any tourist who has journeyed on foot through the jungles of
Ceylon or Sumatra, or any explorer who has walked through
the warm moist valleys of the Himalayas or Andes, and who has
been attacked by hordes of bloodthirsty land-leeches: which in-
fest these places. Nor is it likely that the thirsty traveler in
North Africa or Palestine who stops to gulp a few mouthfuls of
water from a pool or stream and who accidentally inbibes one of
the leeches which infest such waters will not always remember
the bleeding and unpleasant sensations, and perhaps dangerous
symptoms, which follow the settlement of the leech in the mouth
or nasal passages.

General Anatomy. — The leeches are segmented worms be-
longing to the phylum Annelida, in company with earthworms,
kelpworms, ete. They are distinguished from other annelids
by the absence of any bristle-like outgrowths from the body
(sete) and by the presence of two suckers, one at the mouth for
sucking food, and a large one at the posterior end for adhering
to surfaces. The rings of the body as seen on the surface do not
correspond to true segments of the body as they do in other
annelids; there are several rings to most of the segments. The
bodies of leeches are extremely elastic, and can be stretched at
will to several times the contracted length. In fact the usual
method of locomotion, other than an undulating mode of swim-

ming, is by alternately expanding and contracting the body,
315

316 LEECHES

adhering first by the large posterior sucker, then by the smaller
oral sucker and so forth.

Nearly all leeches feed exclusively on blood. The digestive
tract (Fig. 60C, p. 197) is peculiar in that the cesophagus is sup-
plied with a series of ‘‘crops”’ or side pockets in which blood can
be stored up as a reserve supply to be gradually drawn back into
the stomach and intestine and digested as needed. Since some
leeches can fill up with three times their own weight in blood,
and can live on this supply for a year or more, meals are few and
far between. The saliva of the leech has the power of prevent-
ing the coagulation of blood, and therefore blood continues to
flow for some time after the leech has “ got his fill” and let go.
Like other annelids, leeches have a true blood system and a
series of nephridia, little coiled tubes, a pair in each segment,
which function as primitive kidneys. There are no special gills
or other respiratory organs; oxygen is absorbed directly through
the skin which is constantly kept moist.

Leeches are hermaphroditic, 7.e., both sexes are represented
in the same individual, but the egg of one leech is always ferti-
lized by a sperm from another. In most leeches the eggs are
deposited in a stiff mucous cocoon which is secreted by a por-
tion of the body. When the eggs are laid the cocoon is slipped
over the head like a jersey, the ends closing together to form
a capsule. After a little manipulation with the oral sucker the
mother leech imbeds the cocoon in moist soil, near the edge of
water in the case of aquatic species.

Importance as Parasites. — The ordinary pond and river
leeches which adhere to bathers are of little or no economic 1m-
portance as human parasites. Of these the well-known medici-
nal leeches, Hirudo, used for sucking out infections or bad
blood, are the best known examples. They are furnished with
powerful suckers and sharp-pointed pincer-like jaws, and can
therefore easily penetrate the skin and suck blood from any part
of the surface of the body. They can usually be persuaded to
release their hold when removed from water.

With the weak-jawed members of the genera Limnatis and
Hemopis, commonly known as horse leeches, it is quite dif-
ferent. These animals seek to penetrate the natural openings
of the body and fasten themselves to the mucous membranes,
especially in the mouth and nasal cavities, where they may cause

LEECHES IN MOUTH OR NOSE S17

such extensive bleeding as to bring about the death of the host.
Of perhaps even greater importance, because more difficult to
avoid, are the bloodthirsty land-leeches which have already been
mentioned as infesting many tropical countries. Leeches serve
as intermediate hosts for many species of trypanosomes of fishes
and other aquatic animals, and it is not impossible that they may
be found to transmit some species to man.

Leeches in the Mouth or Nose. — The leeches which habitu-
ally settle themselves in the mouth or nasal cavities of men or
animals are inhabitants of muddy-bottomed ponds, ditches,
reservoirs, troughs, etc., and enter the mouth or nose of their
host while he is drinking. According to Masterman, leeches of
the species Limnatis nilotica become so abundant in northern
Palestine in late summer and autumn that almost every horse
and mule passing through these parts has a bleeding mouth.
The Nile leech, Limnatis nilotica, is the most plentiful species
around the shores of the Mediterranean, but leeches of the
genus Hemopis, with similar habits, also occur over a large part
of Europe. Troublesome aquatic leeches have been reported
by travelers in the lake regions of central Africa also, and in
some other warm countries, especially Formosa.

The young leeches, which are usually the ones which enter
the mouth or nose during drinking, are only a fraction of an inch
in length, but the adults reach a length of several inches. The
average length of Limnatis nilotica is about one inch or less.

A person while drinking from infected pools, especially in
dusk or at night, is very likely to suck in one or more of these
leeches. During the process of swallowing the parasites attach
themselves to the walls of the mouth or pharynx and may mi-
grate into the nose or larynx. Seldom, if ever, are the leeches
completely swallowed, and even if they should reach the stomach
they would probably be killed at once and digested. It is a
peculiar and indeed unfortunate fact that, while the leeches
which attack the surface of the body fill with blood and then
let go, those which settle on the mucous membranes keep their
hold for days or weeks, though they shift their positions, leaving
the old bites to continue bleeding. As already stated, the loss
of blood from the wounds made by the leeches is often sufficient
to cause an extreme or even fatal anemia, though the hemor-
_ rhages of clear blood are never great in quantity at any one time.

318 LEECHES

The blood flows out of the nose or into the throat or trachea, in
the latter cases being constantly “‘ hawked” up. Masterman
describes the case of a man in Palestine, attacked by leeches, who
for nearly a week had been “ spitting blood ” and had a spittoon
full of practically pure blood by his side, every few minutes adding
more. His lips were blue, and he was unable to speak above
a whisper. Every few minutes he had a short cough. Often
when the leech is attached in the larynx beside the vocal cords,
the body flops back and forth during breathing, and has been
known to cause asphyxiation by blocking the trachea. Cases are
on record where leeches, having fallen into one of the bronchi,

have died and disintegrated, and thus caused destructive bac-

terial infections to set in. The presence of leeches in the mucous
membranes is often accompanied by severe headaches. Some-
times leeches which have settled in the nose have the revolting

habit of protruding themselves from the nostrils and allowing a.

portion of the body to wander over the upper lip. They are,
however, so elusive that they can be captured only with great
difficulty.

The treatment employed for leech infestations of the nose
or mouth varies greatly in different countries. According te
Masterman the natives of Palestine transfix the leech, if within
reach, with a thorn from a native tree, and muleteers extract
leeches from mules’ mouths with packing needles. When the
parasite is beyond reach of this transfixing process these people
smear some of the thick deposit which collects in their tobacco
pipes on a splinter of wood and endeavor to touch the leech with
it; this is said to cause the leech to lose its hold. Masterman
found the most successful means of removing a leech to be either
to seize it with a suitable forceps, or to paralyze it with cocaine.
Much difficulty is often experienced in seizing the writhing,
slippery creature with a pair of forceps even when it can be seen
clearly with a mouth mirror, partly on account of the spasmodic
contractions of the larynx and the frequent coughing. The

paralyzing of the worms with cocaine is a very successful method; ©

it is done by touching the worm with a 30 per cent cocaine solu-
tion on a bit of cotton. The worm becomes paralyzed in a few
minutes after being touched, and releases its hold. To avoid
the possibility of the leech falling into the trachea the patient is
made to lie on a couch with his head hanging over the edge.

“Co | Peon dae

LAND-LEECHES 319

Land-leeches. — Of perhaps greater importance, because far
less easy to avoid, are the attacks of the land-leeches of many
tropical countries. These leeches are found in Ceylon, Japan,
Sumatra, Philippine and East Indian Islands, Australia, and the
humid mountain meadows of the Himalayas in India and of the
Andes in South America. Sir J. Emerson Tennent in his book
on “ The Natural History of Ceylon” writes as follows: ‘‘ Of
all the plagues which beset the traveler in the higher grounds of
Ceylon the most detested are the land-leeches, Hemadipsa
ceylonica. They are not frequent in the plains, which are too
hot and dry for them, but among the rank vegetation of the
lower hill country, which is kept damp by frequent showers,
they are found in tormenting profusion. They are terrestrial,
never visiting ponds or streams. In size they are about an inch
in length and as fine as a common knitting needle, but they are
capable of distension till they equal a quill in thickness and at-
tain a length of nearly two inches. Their structure is so flexible
that they can insinuate themselves through the meshes of the
- finest stocking, not only seizing on the feet or ankles, but ascend-
ing to the back or throat, and fastening on the tenderest parts
of the body. In order to exclude them the coffee planters who
live among these pests are obliged to envelope their legs in
“leech garters”? made of closely woven cloth. The natives
smear their bodies with oil, tobacco ashes or lemon juice, the last
serving not only to stop the flow of blood, but also to expedite
the healing of the wounds. In moving, the land-leeches have
the power of planting one extremity on the earth and raising the
other perpendicularly to watch for their victim. Such is their
vigilance and instinct that, on the approach of a passerby to a
spot which they infest, they may be seen amongst the grass and
fallen leaves on the edge of a native path, poised erect, and pre-
_ pared for their attack on man and horse. Their size is so in-
significant and the wound they make is so skillfully punctured
that both are generally imperceptible, and the first intimation of
_ their onslaught is the trickling of the blood or a chill feeling of
_ the leech when it begins to hang heavily on the skin from being
distended with its repast. Horses are driven wild by them and
stamp the ground in fury to shake them from their fetlocks, to
which they hang in bloody tassels. The bare legs of the palankin
bearers and coolies are a favorite resort, and as their hands are

320 LEECHES

too much engaged to pull them off the leeches hang like bunches
of grapes round the ankles. Both Marshall and Davy mention
that during the march of troops in the mountains when the
Kandyans were in rebellion in 1818, the soldiers, and especially
the Madras Sepoys, with the pioneers and
coolies, suffered so severely from this cause
that numbers perished.

One circumstance regarding these land-
leeches is remarkable and unexplained: they

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I are helpless without moisture, and in the hills
a where they abound at all other times they
a entirely disappear during long droughts; yet
eae reappear instantly at the very first fall of rain,
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was visible an hour before, a single shower is
sufficient to reproduce them in thousands. ©
Whence do they reappear! May they, like
rotifers, be dried up and preserved for an
indefinite period, resuming their vital activity
on the mere recurrence of moisture? ”
Similar reports come from travelers in other
tropical countries. Alfred Wallace encountered
land-leeches in Sumatra where he found them
infesting the leaves and herbage by the side
of the paths through the forests. At the
approach of a traveler as indicated by foot-
steps or a rustling of leaves, the leeches stretched
themselves out at full length and attached
themselves to any part of the passerby which
they happened to touch. Their presence and
Fic. 133. Japa- the loss of blood was seldom felt during the
nese land-leech, F
Hemadipsa japoni- excitement of walking, but a dozen or so had
tps ae 2. to be pieked off every evening. Dean C.
, Worcester in his book on the Philippines
says “the moist earth swarmed with leeches which crawled
through my stockings and bit my ankles until my shoes were
soaked with blood.” One species, H. japonica (Fig. 133), is
common in parts of Japan. The land-leech of Australia belongs to
a different genus, Philemon.

In any of the localities infested by land-leeches it is advisable

PROTECTION FROM LAND-LEECHES 321

to bind the feet and legs in leech-proof cloth, this being preferable
to various ointments which are supposed to discourage the leeches
from their meal. In a tropical climate where so many diseases
and unfavorable conditions beset one on every side, it is impor-
tant to take every precaution to keep in perfect health. The
loss of blood from the attacks of leeches, and the portal given
for entrance of bacteria and other organisms in the wounds made
by them, might make all the difference between life and death
in the struggle for existence in these disease-plagued climes.

PART III— ARTHROPODS

CHAPTER XIX
INTRODUCTION TO ARTHROPODS

To the average person it is astonishing to learn that the insects
and their allies, constituting the phylum Arthropoda, include
_ probably more than four times as many species as all other.
animals combined. In this vast horde of animal forms are °
included some species which are distinctly valuable to the human
race, such as bees, the silkworm, the thousands of insects (Dip--
tera and Hymenoptera) parasitically destructive to injurious
species and the predaceous beetles; a great number which are
indifferent as regards their economic importance serving, perhaps,
only to arouse admiration for their beauties or disgust for their
loathsomeness; and many which are of great importance as
crop pests or as annoyers of domestic stock or of man himself.
Only relatively very few, a mere handful, are injurious to man as
parasites or as disease carriers, but these few are of almost in-
calculable importanee. As mere parasites the parasitic arthro-
pods are of minor importance, but it is in their capacity as inter-
mediate hosts of other parasites or as mechanical carriers of
disease germs that these animals have to be reckoned with as
among the foremost of human foes. Every arthropod, para-
sitic or otherwise, which habitually comes in direct or indirect
contact with man must be looked upon as a possible disease car-
rier. The role of arthropods in the dissemination of disease is a
matter about which practically nothing was known 35 or 40
years ago. A French physician, Dr. Beauperthuy, in 1853 was
one of the first to express a belief in the dissemination of various
diseases by mosquitoes and in the rdéle of the housefly in the
spread of pathogenic organisms. In 1879 Manson first proved
insects to be intermediate hosts of human parasites, in the case
of Filaria and the mosquito. Since that time many of the most

important human diseases have been shown not only to be trans-
322

RELATIONSHIPS o2o

mitted by arthropods but to be exclusively transmitted by certain
species or genera. In the latter category, as far as we know at
present, are malaria, by some physicians rated as the most im-
portant human disease; typhus fever, the unseen dragon of death
which hovers over every war camp in the world; yellow fever,
which formerly haunted South and Central America; sleeping
sickness, the scourge of Central Africa; Chagas’ disease of
South America; relapsing fever; Rocky Mountain spotted fever;
dengue; phlebotomus fever; Japanese flood fever; filarial dis-
eases; guinea-worm infection; lung fluke infection; some tape-
worm infections; and others of less importance. Some other
important diseases, such as kala-azar and oroya fever, are be-
lieved to be transmitted by arthropods but the transmitting
agents have not yet been discovered.

There are many other diseases which, although they may be
transmitted in other ways also, are commonly disseminated by
insects, often in a more or less mechanical way. Such are plague,
tuberculosis, leprosy and others. In the case of some of these
diseases, e.g., plague, the intestines of the transmitting arthro-
pods serve as culture tubes for the disease germs, whereas in
other cases, e.g., amebic dysentery, the arthropods are merely
passive carriers of disease germs which adhere to their feet or
bodies. It is evident that any insect may serve as a disseminator
of disease in this mechanical way in direct proportion to the ex-
tent that it associates with man and that its habits bring it in
contact with disease germs.

Relationships. — The insects and their allies, constituting the
phylum Arthropoda, are the most highly organized of inverte-
brate animals, and stand at the head of their particular line of —
evolution. They find their nearest allies in the segmented worms
or annelids, 2.e., earthworms, leeches, etc., but most of them show
a great advance over their lowly cousins. Like the annelids
they have a segmented type of body, though in some types, such
as the mites, all the segments become secondarily confluent.
_ Like the annelids, also, the arthropods are protected by an ex-
ternal skeleton which usually consists of a series of horny rings
encircling the body. The most obvious distinguishing character-
istic of the arthropods is the presence of jointed appendages in
the form of legs, mouthparts and antenne. Internally they are
distinguished from other invertebrates in that the body cavity,

324 INTRODUCTION TO ARTHROPODS

so conspicuous in the annelids, has been entirely usurped by a great
expansion and running together of bloodvessels so that in the
place of the usual body cavity or ccelom there is a large blood-
filled space. Within this space are bloodvessels and a so-called
heart, which retained their individuality while the other vessels
fused.

Classification. — The phylum Arthropoda is divided into five
classes. One of these, the Onychophora, includes only a single
genus of animals, Peripatus, which is very primitive, and helps
to bridge the gap between the more typical arthropods and the

annelids. Peripatus is a free-living wormlike animal and of no.

interest here. The remaining four classes are the Crustacea,
Arachnida, Myriapoda and Insecta.

The Crustacea, including crayfish, water fleas, etc., are pri-
marily arthropods of the water. They are geologically of great

antiquity and among them are the most primitive of the typical ©

arthropods. Their appendages are usually numerous and, taking
the group as a whole, show a wonderful range of modifications
for nearly every possible function. Crustaceans breathe by gills.
Although many are parasites of aquatic animals, none can be
considered as parasites of man or other land animals. In two
cases Crustacea are known to serve as the intermediate hosts of
human parasites, namely Cyclops as a host for the guinea-worm

(see p. 312), and the Japanese land crabs as the second inter-

mediate hosts of the lung fluke (see p. 222).

The Arachnida, including spiders, scorpions, mites, etc., are
for the most part highly developed arthropods, representing the
terminus of a separate line of evolution. They probably had a
common origin with the Crustacea, but have become adapted
to terrestrial life. 'The members of this class have four pairs of
legs as adults, two pairs of mouthparts and no antenne. They
breathe by means of invaginations of the body which contain
gills arranged like the leaves of a book, whence the name “ book
lungs.” Some of the higher arachnids also have a system of
branched air tubes or trachee in the body similar to those found

in the insects and myriapods. Two orders of Arachnida contain -

parasitic species, namely the Acarina,.or mites and ticks, and
Linguatulina, or tongue-worms. Many ticks are disease carriers.

The Myriapoda, including centipedes and millipedes, are
terrestrial arthropods which breathe by trachee. The body is

Sl

MOUTHPARTS OF INSECTS 325

furnished with a distinct head, followed by a considerable num-
ber of similar segments, each bearing one or two pairs of legs.
There is a single pair of antennse. Although some of the centi-
pedes are poisonous, none of the myriapods are parasitic, nor
are any of them known to be disease carriers.

The Insecta, or insects, represent the zenith of invertebrate
life. They are terrestrial arthropods which, like the myriapods,
breathe by trachee. Their appendages, however, are reduced
to one pair of antennz, two pairs of mouthparts and three pairs
of legs with usually the addition, if not secondarily lost, of two
pairs of wings. The wings are really mere outgrowths or folds
of the integument or “‘skin”’ of the insect, between the two layers
of which are branches of the trachee, represented by the “ veins”’
in the wings of adult insects. There is a fundamental plan of ar-
rangement of the veins which is variously modified in different in-
sects, but absolutely fixed in any given species. The venation
of the wings is often of great value in the identification of genera
or species of insects. An insect is always readily divisible into
three parts, the head, thorax and abdomen. The head, in addi-
tion to the antenne already mentioned, bears two compound eyes
sometimes of relatively enormous size, usually several simple eyes,
and the mouthparts.

Mouthparts of Insects. — Incredible as it may seem at first
thought, the mouthparts of all kinds of insects, from the simple
chewing organs of a grasshopper to the highy modified piercing
and sucking organs of biting flies and mosquitoes and the great
coiled sucking tube of butterflies and moths, are modifications
of a single fundamental type. This type is represented in its
simplest form in the chewing or biting type, as found in grass-
hoppers and beetles (Fig. 134). The mouthparts in these in-
sects consist (1) of an upper lip or labrum (Fig. 134, Lbr.);
(2) a lower lip or labium (Fig. 134, Lbm.), really formed of a
pair of organs fused together, each bearing a segmented appen-
dage, the labial palpus (Fig. 134, Lab. p.); (3) a pair of hard,
horny, toothed mandibles or jaws (Fig. 134, Mand.) lying just
under the lower lip, which chew up food by a horizontal instead |
of vertical movement; (4) a pair of maxille (Fig. 134, Max.),
lying between the mandibles and lower lip, each bearing a seg-
mented appendage more or less like those on the lower lip, and
called the maxillary palpus (Fig. 134, Max. p.) and (5) the

326 INTRODUCTION TO ARTHROPODS

hypopharynx (Fig. 134, Hyp.), a short fleshy organ lying in the
midst of the other organs, and comparable in both form and
function with the tongue of vertebrate animals. In addition to
these parts there is a horny lining of the upper lip and roof of

Sess
-Lbm.

Fic. 134. Simple mouthparts of a chewing insect (Stenopalmatus); Ibr., la-
brum, or upper lip; mand., mandible; hyp., hypopharynx or tongue; max., maxilla;
max. p., maxillary palpus; lbm., labium or lower lip (really a second pair of maxillze
fused together); lab. p., labial palpus.

the mouth cavity known as the epipharynx. This structure
is usually closely associated with the upper lip, so that the com-
bined organ is spoken of as the “ labrum-epipharynx.”

The extent of the modifications which these mouthparts may
undergo is wonderful, especially in insects where they are modi-
fied for sucking or piercing. In the true bugs the mandibles
and maxille are prolonged into needle-like organs, the maxille
often armed with sawlike teeth at their tips, and the lower lip
is developed into a thick, fleshy, jointed proboscis, grooved on its
upper side to form a sheath for the piercing organs (Fig. 164).
The labrum is a short movable flap, and the hypopharynx is very
slightly developed: In the Diptera, which include the mos-
quitoes, gnats, blackflies, tsetse flies and other biting flies as
well as houseflies and blowflies, there are several different types

: GENERAL ANATOMY OF INSECTS 397

of modifications. In mosquitoes the mouthparts (Fig. 191) are
much as in bugs, but the labrum-epipharynx and hypopharynx
are also modified into long piercing organs, and the latter is
fashioned into a true hypodermic needle for injecting salivary
secretions. In blackflies and tabanids (Figs. 220 and 225) the
parts are similar but the piercing organs are shorter and more
-bladelike, resembling daggers rather than needles. In the
tsetse flies and stable-flies (Figs. 220 and 225) the lower lip itself
is the chief piercing organ, the labrum-epipharynx and hypo-
pharynx contained in it being needle-like and capable of forming
a sucking tube by apposition with each other. The mandibles
and maxille are much reduced or rudimentary, but the maxillary
palpi are conspicuous, and in tsetse flies form a perfect sheath
for the proboscis. In the houseflies and their non-blood-sucking
allies the mouthparts are most modified, being all molded to-
gether to form a fleshy proboscis especially fitted for lapping
up liquid foods. In fleas the mouthparts (Fig. 178) are somewhat
as they are in the biting flies, but the mandibles are not modified
as piercing organs but as protective flaps, and the sheath for the
piercing organs is formed from the labial palpi instead of from
the labium or lower lip itself. The mouthparts of sucking lice
(Fig. 171) are still not thoroughly understood but the piercing
and sucking organs, whatever parts they really represent, can
_be retracted into a blind pouch under the pharynx. The mouth
parts of such insects as moths, bees, wasps, etc., are also remark-
able examples of structural adaptations, but they do not concern
us here.

General Anatomy. — The digestive tract of insects (Fig. 135)
is often highly developed and differentiated. The blood-sucking
insects have a muscular pharynx in the head which acts like a
suction pump. In the bedbug, for instance, the powerful muscles
which are used to expand the pharynx and thereby produce
suction occupy a considerable portion of the inside of the head,
and the area on top of the head to which they are attached is
distinctly visible on the outside. The pair of salivary glands
- open into the floor of the pharynx, but they themselves are
usually situated in the thorax. Often they are very highly de-
veloped. In the true bugs they have connected with them
accessory salivary glands, which in some species may serve at
least in part as storage vats for holding the secretion temporarily.

328 INTRODUCTION TO ARTHROPODS

In mosquitoes (Fig. 189) the salivary glands consist of three
lobes, one lobe being noticeably different in appearance and
secretion from the others. The pharynx connects with the
stomach by a slender cesophagus. Various means are used by
blood-sucking insects to increase
their capacity. In the bugs
(Fig. 185) the stomach is ex-
tremely distensible and serves as
a Storage reservoir. In fleas and
--connd. many biting flies there is an ex-
ON Oleg tae pansion of the cesophagus an-
pp --sal.gl terior to the true stomach, called
the proventriculus; in mosqui-
toes there are capacious pouch-
like food reservoirs or outgrowths
from the cesophagus in addition
to the proventriculus (Fig. 189).
_ Just behind the true stomach at
the beginning of the intestine
there open a number of long
slender tubes, the ‘“‘ Malpighian
tubules” (Fig. 135, malp. t.).
Fic. 135.. Digestive tract of a Re- These are the exCIeLOny, stele
duviid bug; acc. sal. gl., accessory corresponding to the kidneys Ol :
salivary gland; conn. d., connecting vertebrate animals. Their func-
duct between salivary glands; int., in- ., 3
testine; malp. t., malpighian tubules; tlon 1S to collect the waste
salivary gland, (Parily after Dufour) Stee! Ol Oise
blood and pour it into the in-
testine, whence it can ultimately be voided through the anus.
The length of the intestine varies, being usually longer in vege-
table-feeding insects than in carnivorous ones. It often has a
marked expansion, the anal pouch, at its posterior end. |
The trachez of insects, as already intimated, are really a ven-
tilation system consisting of air tubes ramifying all through the
body even to the tips of the antenne and legs. They open by a
series of pores along the sides of the insect known as spiracles,
which function as do the nostrils of higher animals. The prin-
ciple of oil sprays for insects is to form a film of oil over the
spiracles, so that the insects will suffocate.
The nervous system of insects is very highly developed for

LIFE HISTORY OF INSECTS 329

_ invertebrate animals. In some species the instincts, especially
those connected with providing for their offspring, simulate care-
ful and accurate reasoning, and it is difficult not to look upon
them as animals endowed with a high degree of intelligence.

Life History. — As regards life history, three different types
can be recognized among insects. In the primitive order Thy-
sanura alone there occurs “ direct development” in which the
newly hatched insect is nearly a miniature of its parent, and
merely increases in size. The two common types of development
are by incomplete and complete metamorphosis. Insects which
have an incomplete metamorphosis are those which differ more or
less from their parents when hatched, but which gradually assume
the parental form with successive moults or sheddings of the
skin. The young or “ nymphs” of such insects invariably lack
wings, and often have other characteristics different from their
parents. In such insects as lice, in which the wings are absent in
the adult, there is very little difference except in size between
the young and adult forms. Insects which have a complete
metamorphosis are those in which, as in butterflies, the newly
hatched larva is totally different from the parent, and does not
gradually assume the parentalform. Instead, it retains its worm-
like larval characteristics until full grown and then transforms,
during a resting and more or less quiescent period of relatively
short duration, into the adult form. This transformation, which
may amount to nothing short of a complete remodeling of the
entire body and all its organs, is sometimes accomplished in an
amazingly short time. Many maggots transform into adult flies
in less than a week, and some mosquito larve transform into
perfect mosquitoes in less than 24 hours.

The length of life of insects in the larval and adult stages
varies with almost every species and with environmental con-
ditions. The larval stage may occupy a small portion of the
life, as in the case of many mosquitoes and flies, or it may con-
stitute the greater part of it. There are some mayflies, for
- instance, which live the greater part of two years as larve but
exist as adults not more than a few hours. As a rule male in-
sects are shorter lived than the females; the length of life of the
latter is determined by the laying of the eggs — when all the
eggs have been laid the female insect has performed her duty
in life and is eliminated by nature as a useless being. The result

330 | INTRODUCTION TO ARTHROPODS

is the paradoxical fact that ideal environmental conditions
shorten the life of these insects, since they facilitate the early
deposition of the eggs.

Classification. — The classification a eee is based mainly
on three characteristics: the type of development, the modifi-
cation of the mouthparts, and the number, texture and venation
of the wings. All blood-sucking insects have mouthparts
adapted in some way for piercing and sucking, but the types
vary greatly in different groups. Many of the more thor-
oughly parasitic insects, e.g., lice, bedbugs and “sheep ticks,”
have secondarily lost their wings entirely, or have them in a rudi-
mentary condition. In the whole order of Diptera the second
pair of wings is reduced to inconspicuous club-shaped append-
ages known as halteres.

The only orders of insects which contain species of interest as
human parasites are the Hemiptera (Rhynchota), or true bugs;
the Anoplura, or sucking lice; the Siphonaptera, or fleas; and —
the Diptera, or two-winged flies. These four orders may be
briefly summarized as follows:

Hemiptera (suborder Heteroptera): metamorphosis incom-
plete; mouthparts fitted for piercing and sucking, the piercing
organs being ensheathed in the jointed lower lip; first pair of
wings, unless reduced, leathery at base and membranous at tip;
second pair of wings, when present, membranous with relatively
few veins. Human parasites: bedbugs, cone-noses, kissing bugs.

Anoplura: metamorphosis incomplete; mouthparts fitted for
piercing and sucking, and retractile into a pouch under pharynx;
wings secondarily lost. Human parasites: sucking lice.

Siphonaptera: metamorphosis complete; mouthparts fitted
for piercing and sucking, the piercing organs being ensheathed
in the labial palpi, and the mandibles modified as protective
flaps; wings secondarily lost. Human parasites: fleas, chiggers.

Diptera: metamorphosis complete; mouthparts fitted for pierc-
ing and sucking, for sucking alone, or rudimentary; first pair
of wings (absent in a few species) membranous with few veins;
second pair of wings represented only by a pair of clubshaped
organs, the halteres. Human parasites: Sandflies, mosquitoes,
midges, blackflies, gadflies, tsetse flies, stable-flies, maggots of
various species.

CHAPTER XX
THE MITES

General Account. — The mites and ticks, which constitute the
Order Acarina of the Class Arachnida, are only slightly known by
the majority of people. Popular knowledge of them is usually
limited to a few species of ticks, chicken mites, and perhaps two
or three other species of mites. Yet the group includes a large
- number of species, varying in size from some ticks which are half
an inch or more in length to mites barely visible to the naked eye.
The variety of body form is great and some species when magnified
appear ridiculously grotesque. The majority of the species are
more or less round or oval, with head, thorax and abdomen all in
one piece, but many have the cephalothorax (head and thorax
fused together) distinctly marked off from the abdomen, while
a few are quite wormlike in form. Many mites are free-living
and prey upon decaying matter, vegetation, stored foods and
the like; some are predaceous and feed upon smaller animals;
some are aquatic, even marine; and many are parasitic on other
animals during all or part of their life cycle, and some of these
serve as intermediate hosts for, and for dissemination of, danger-
ous disease germs.

Like other Arachnida (spiders, scorpions, etc.) the mites and
ticks usually have two pairs of mouthparts and four pairs of
legs, though the last pair of legs is not acquired until after the
first moult. The first pair of mouthparts or chelicere are some-
times needle-like, sometimes shaped like a grapnel hook, and
very often pincer-like, the pincers often being at the tip of a
long exsertile needle-like structure. The second pair of mouth-
parts, or pedipalps, are simple segmented palpi. In many kinds
of Acarina the anterior end of the ventral side of the body is
produced as a sort of chin or lower lip, the hypostome, which
may be needle-like or barbed and rasplike (Fig. 152).

The digestive tract is in most cases well developed. Waves

of muscular contraction make a very efficient sucking organ of
dol

Bon THE MITES

the pharynx. The stomach has pouches opening from it which
act as food reservoirs (Fig. 149), so that one meal may last for
a long time. The intestine is usually short and the excretory
organs, malpighian tubules, open into it not far from the anus.
The reproductive organs, as in other Arachnida, open on the ventral
surface of the abdomen but at different places in different species.
The nervous system is largely concentrated into a great mass,
the ‘ brain,”’ lying near the anterior end of the body and pierced
by the cesophagus. Many mites possess trachez, similar to
those of spiders and insects, for breathing, while others, soft-
skinned forms, simply absorb oxygen through the surface of the
body.

Life History. — The life histories of mites and ticks are some-
what variable, but usually there are four stages in their develop-
ment: the egg, the larva, the nymph and the adult (see Fig. 157).
The eggs are usually laid under the surface of the soil or in crev-
ices, or, In some parasites, under the skin of the host. After a
varying period of incubation, which depends on climatic con-
ditions, the larva hatches in the form of a six-legged creature,
often quite unlike the parent. After a single good feed of blood
or plant juices the larva rests, sheds its skin and appears with
an additional pair of legs and a body form more closely resem-
bling that of the parent but without developed sexual organs.
The nymph thus produced feeds again, sheds its skin from one
to three times and finally, after another period of rest during
which its body is remodeled for the second time, moults again
and comes forth as a fully adult male or female, ready for the
reproduction of another generation. There are all sorts of modi-
fications of this order of development, due to the slurring over of
one phase or another. One of the most aberrant species is the
louse-mite, Pediculoides. In this form the eggs develop within
the parent’s body and the adult males and females issue forth —
from the brood chamber improvised for them out of the abdomen
of the mother (Fig. 139).

The popular opinion that all mites are parasitic is, as remarked
before, far from being true. Over half of the known species are
not parasitic at any stage in their life history, while many others
are parasites only during part of their life cycle.

Parasitism. — The mites are an interesting group for the study
of the origin of parasitic habits since, as Ewing has shown, para-

HARVEST MITES 333

sitism has apparently arisen independently in different families
and genera at least eleven times. Nathan Banks in his treatise
on the Acarina, after giving a number of interesting examples of
peculiar parasitic habits, writes as follows: ‘‘ We can only explain
these remarkable habitats by the fact that mites, especially in
their immature stages, have an incontrollable desire to go some-
where, and get into every cavity and crack they discover in their
wanderings. When hungry they test their locality for food, and
if not too different from their previous diet this new habitat may
result in new species and genera.”’

A few species of mites have become adapted to live as internal
parasites, but all the species normally infesting man are either
external or subcutaneous in their operations. A few of the
species which are not averse to human beings as food are
troublesome and irritating enough to bring their whole tribe into
disrepute. The families of mites which contain species annoying
to man are the Jxodide and Argaside, the ticks; Trombidide, the
harvest mites and “red-bugs”’; Parasitide (Gamaside), including
the chicken mites; Tarsonemide, including the louse-mite; T'y-
roglyphide, including the cheese and grain mites; Sarcoptide, the
itch mites; and Demodecide, the hair-follicle mites. For con-
venience we may include with the mites the very aberrant arach-
nid forms known as tongue-worms, now usually placed in a
distinct order, Linguatulina. Since the ticks are popularly looked
upon as quite distinct from other Acarina, and form a very im-
portant group of the order on account of their réle as disease
carriers, they will be considered in a separate chapter.

Harvest Mites

The six-legged larvee of the harvest mites, family Trombidiide,
known as red-bugs or chiggers, are very annoying pests, and one
species, the Japanese ‘‘akamushi”’ or kedani mite, has been
proved to be the carrier of a dangerous disease, kedani or flood
fever. Harvest mites are little scarlet-red animals, and their
larve are tiny pale-colored creatures bare'y visible to the naked
eye (Fig. 136). According to one writer who had evidently
experienced them a red-bug is a “small thing, but mighty; a
torturer — a murder of sleep; the tormentor of entomologists,
botanists and others who encroach on its domains; not that it

334 THE MITES

bites or stings—it does neither; worse than either, it just
tickles.”

The adult harvest mites (Fig. 137) are law abiding members of
the community, and attack only such animals as plant-lice, cater-
pillars and other insects. They hibernate in soil or sheltered
crevices and in the spring lay their eggs, several hundred apiece,

in the ground or among dead
leaves. The eggs are very
14 £2 small, round and brownish in
color, and were once classified
iZ/ as fungous growths! The

tN oe

ae

iy fis c
} i a , Ree. ah
hi

Fic. 136. European red-bug, Leptus au-

tumnalis, larva of a Trombidium usually Fie. 137. An adult of the
thought to be T. holosericeum. x 150. kedani mite, a Trombidiid.
(After Hirst.) x 40. -(After Nagayo et al.)

newly hatched six-legged larve creep up on blades of grass
or plant stems and await an opportunity to attach them-
selves to an insect. If successful in finding a host, or rather in
being found by a host, the mites gorge themselves with the
juices of the insect, then drop to the ground, crawl to some snug
hiding place and undergo a transformation. The whole inside
of the body is remodeled, a fourth pair of legs is acquired, and
after a few weeks the skin is shed and an adult trombidiid mite
crawls forth.

It is while the larval mites are hungrily awaiting the arrival
of an insect upon which to feed that they attack human beings or
animals which may pass their way. They are so small that
they can easily pass through the meshes of ordinary clothing
and reach the skin, where they set up a severe irritation and

ANNOYANCE FROM HARVEST MITES aa

intense itching. Some authors claim that the mites burrow in
the skin and produce inflamed spots, but ordinarily they do not
go beneath the skin except sometimes to explore their way into
the long tubes of the sweat glands. The habit of attacking
warm-blooded animals is evidently abnormal, and the love of
blood proves ruinous to those individuals which get an opportu-
nity to indulge it, since they soon die victims of their own per-
verted appetites. How like some human beings!

The irritation caused by the mites is probably due to a spe-
cific poison secreted by the mites rather than to any wounds that
they make. The inflammation of the skin may not be felt for
12 or even 24 hours after infection by the mites. When the in-
flammation does commence there appear large red blotches on
the affected parts of the body which itch intensely and are made
worse by scratching. After a day or so the red blotches blister
and finally scab over. Red-bug rash is most frequent on tender-
skinned people and on those parts of the body which are most
exposed, though it may spread over the whole body and torment
the victim unbearably. Laborers who are continually exposed
to these mites seem to develop an immunity to the mite poison,
and suffer little or none from them. Herrick states that one of
the severest infestations he ever knew was contracted by a
delicate-skinned person who sat down on the ground for a few
minutes on some golf links which had recently been laid out on
an old pasture where there was still much long grass. This |
person’s body became covered with large inflamed spots even to
the neck. The torture was intense for a week, and the infection
persisted for a still longer period. A Mexican species, known by
the Aztec name “ tlalsahuate,’”’ meaning ‘ grain of earth,’’ shows
a decided preference for the eyelids, armpits, groins and other
thin-skinned portions of the body, where it induces itching and
inflammation, and even ulceration when scratched. The ‘ béte
rouge ”’ or “‘ colorado ”’ of the West Indies and Central America
is a similar if not identical species.

Sprinkling sulphur on the legs and inside the stockings is a
necessary preventive measure for those who are seriously affected
by red-bugs, and who have to walk through tall grass or brush
where these pests abound. A hot bath shortly after infection,
with soap or with soda in it, gives much relief. To allay the itch-
ing weak ammonia or baking soda applied to the affected parts is

336 THE MITES

good, and alcohol, camphor and other cooling applications are
also useful.

‘Since in: many instances the adults are unknown, the larval ~

harvest mites are, for the sake of convenience, placed in a col-
lective group, Leptus, and the name is used in the manner of a
generic name. The common red-bug of Europe, for instance,
which is supposed to be the larva of T'rombidiwm holosericeum is
known as Leptus autumnalis. The most abundant species of ©
red-bug in the United Statesis Leptusirritans. It occurs through-
out the southern United States and as far north as New Jersey
and the upper Mississippi Valley. An allied species, Leptus
americanus, also occurs in many parts of southern United States.
On the northern border of its range this mite does not appear
until the latter part of June and becomes especially annoying
during August, but its season becomes earlier and earlier the
farther south it occurs. .
The European harvest mites, the commonest of which is Leptus
autumnalis (Fig. 186), are well known pests throughout Europe,
especially in Central and Western France, where they are known
as the “ bétes rouges”’ or ‘‘ rougets.’”’ They are said to attack
small mammals, such as rodents, by preference. Unlike the
American species, the European harvest mites become espe-
cially abundant in the fall of the year. Japanese investigators
have recently cast doubt on the commonly accepted belief that
Trombidium holosericeum is the parent of Leptus autumnalis since
in Japan the parent of the kedani mite (Fig. 137), which very
closely resembles L. autumnalis, is quite different from T. holo-
sericeum, whereas an adult mite which very closely resembles
the latter, produces larve quite different from L. autumnalis.
The Japanese harvest mite, larva of Trombidium akamushi,
known locally as the akamushi (red-mite), tsutsugamushi (sick-
ness mite) and kedanimushi (hairy mite), has been proven to be
the carrier of a typhus-like disease known as kedani or flood
fever. These larval mites occur in countless numbers on the
local field mice, Micromys montebelloi, living especially on the
inside of the ear. They frequently attack the farm laborers
who engage themselves in harvesting and handling the hemp
which is raised on the flood plains of certain Japanese rivers. It
is among these people that the kedani or flood fever occurs,
always following the bite of a mite. The bite, usually in the

LOUSE-MITE 307

armpits. or on the genitals, is at first painless and unnoticed, —
but the mite remains attached at the wound from one to three

_ days before dropping to the ground to transform to the nymphal

stage. The bite of the mite is said to develop into a tiny sOre or
inflamed spot in the region of which the lymph glands become
swollen and painful and flood fever follows. The nymphs and
adults of this mite have recently been found by Nagayo and his
fellow-workers in Japan.

The transmission of kedani by this mite is the only positive
instance of human disease carried by Acarina other than ticks.

Other Occasionally Parasitic Species

There are many species of mites, of several different families,
which under abnormal circumstances or by sheer accident may
become troublesome parasites of man. Nearly all mites secrete
salivary juices which have
a toxic effect when injected
into the blood; therefore
any mite which will bite
man under any circum-
stances may become a pest.
In nearly all cases the symp-
toms of attacks by mites are
similar —hivelike or rashlike
eruptions of the skin, in-
tense itching and in severe
attacks fever. Fic. 138. Louse-mite, Pediculoides ventri-

Louse-Mite. — One of the cosus; ©, unimpregnated female; ¢, male,
most important Galion occas snes Sree ia Brucker from Webster;
sionally parasitic mites is |
the louse-mite, Pediculoides ventricosus (Fig. 138), belonging
to the family Tarsonemide. This is a very minute species,
barely visible to the naked eye, which is normally parasitic
on grain-moth caterpillars and other noxious insects, and there-
fore beneficial. These mites live in stubble, stored grain and
beans, cotton seeds, straw, etc., attacking the various insects
which infest these products and becoming numerous in pro-
portion to the abundance of their prey. The female has the
remarkable habit of retaining the eggs and young in her abdomen

308 THE MITES

until they have become fully developed males and females. Her
abdomen in consequence becomes enormously distended so that
the rest of the body appears as only a tiny appendage at one side
of it. A gravid female (Fig. 139) fully distended may reach a
diameter of 1.5 mm. (77 of an inch) whereas normally she measures
only 0.2 mm. (74s of an inch) in length. Under the most favorable
conditions only six days may elapse from the time the young
females emerge from the mother before they reproduce a brood of
their own. The brood varies
in number from a few dozen
to over 200.

Like many other beneficial
things, these predaceous little
mites may become a distinct
nuisance, and many serious

human beings by them are on
record, especially among the
grain threshers of the central
portion of the United States
and among laborers who handle
stored grains and other dry
foods. In our Middle West

Fie. 139. Louse-mite, gravid female. their attacks have often been
x about 75. (After Brucker from gttributed to harvest mites. In
Webster.)

Italy the rash produced by
louse-mites is called ‘ miller’s itch.” Several outbreaks have
occurred in the United States due to the use of new straw mat-
tresses. The transformation of all the grain-moth caterpillars
into moths leaves the mites with their normal food supply cut
off, and they are then ready to feed upon any flesh to which they
may have access in an effort to prevent starving to death.

The itching rash produced begins about 12 to 16 hours after
exposure to the mites. At first they produce pale hivelike spots,
which later become red and inflamed, and itch unbearably.
Little blisters, the size of a pinhead or larger, appear at the sites
of the bites and these later develop into little pustules. Scratch-
ing results in the formation of scabs, and when these fall off
dark spots which are slow to fade are left on the skin. The
rash and itching normally disappear within a week unless fresh

outbreaks of infestation of-

*
i i

GRAIN MITES 339

detachments of mites are constantly acquired. In severe in-
festations the irritation and poisoning is sufficient to cause
constitutional symptoms such as fever, high pulse, headache,
nausea, etc.

Since the mites cannot thrive on human blood, and remain
attached to the skin for only a short time, no treatment for
destroying them is necessary. Remedies to relieve the itching,
such as the application of soda or soothing ointments, or warm
baths with a little soda, are called for. To prevent infection
when handling infected produce, Dr. Goldberger, of the United
States Public Health Service, suggested a greasing of the body,
followed by a change of clothes and a bath after working with
the infected material. Riley and Johannsen suggest the use of
powdered sulphur as a preventive in view of its efficiency against
harvest mites. Control of the mite consists largely in keeping
grain and other dry produce as free as possible from the insects
on which the mites feed. Burning stubble in winter and threshing
wheat directly from the shock would tend to lessen the worms in
stored wheat and with them the mites.

Grain Mites. — The family Tyroglyphide, including many
species of mites which normally feed on grain, flour, sugar, dried
fruits, cheese and other foods, contains
several species which become annoying to
man and produce an itching rash on people
who handle infested goods.

According to Banks all the members of
this family are pale-colored, soft-bodied.
mites, with prominent pincer-like chelicerz
and no eyes. ‘Their bodies are about
twice as long as wide and are furnished
with a few scattered long hairs (Fig. 140). |

: : Fic. 140. Grain mite,

The life history of some members of the py,ogiyphus longior. X 30.
family is quite remarkable in that there is (After Fumouze and
added a phase of existence which does not — eae
occur in other mites. All the species scatter their eggs haphazard
over the infected material. Upon hatching the larve have six
legs and acquire a fourth pair after moulting, in orthodox mite
style. Some now develop directly into adults, while others go
through what is called a “ hypopus”’ stage. The hypopus (Fig.
141) is very different from the nymph from which it develops:

340 THE MITES

the body is hard and chitinous, there is no mouth or mouthparts,
the legs are short and stumpy, and there is usually a raised area
on the ventral surface with a number of tiny sucking discs. By
means of these suckers the hypopus attaches itself to insects or
other creatures and is thus transported to
new localities, the entire object of the
hypopus stage apparently being to secure
passage to new breeding grounds. After
dropping from its unwilling transporter
the hypopus moults into an eight-legged
nymph again, which, after feeding, develops
into an adult.

The Tyroglyphide are all quite similar

Fic. 141. Hypopus or jn anpearance, and the characters which
traveling stage of Tyro- 3
glyphus, ventral view. Separate the species, and even the genera,
Fe a (After are few and minute. A considerable num-.

ber of species may attack persons who

handle infested materials, and they are the cause of “‘ grocers’
itch.” This affliction is caused especially by various species
of Glyciphagus and Tyroglyphus. Of historical interest is a
case of dysentery apparently due to a Tyroglyphus, T. longior,
(Fig. 140) which occurred in one of Linnaeus’ students. The
mites were abundant in his feces, and were found to live and
multiply in a juniper-wood cup which he used. As shown by
Castellani, an itching rash known as “ copra itch,’”’ occurring
among the laborers in the copra mills of Ceylon where cocoanut
is ground up for export, is caused by a variety of this mite, called
T. longior castellanii. Copra itch occurs also among stevedores
who handle copra in London. Another species, Glyciphagus
buski, was taken from beneath the skin on the sole of the foot
of a negro in England; it had caused large sores. The negro
attributed the affliction to the wearing of a pair of shoes loaned
him by a similarly affected negro from Sierra Leone, Africa.
Another species, Rhizoglyphus parasiticus, which lives on roots,
bulbs, etc., in India, produces a skin disease among coolies work-
ing on tea plantations. It begins with blisters between the toes
and spreads to the ankles, causing very sore feet.

Other Species. — A few species of the family Tetranychide,
including the “‘red spiders”? or spinning mites, occasionally
become troublesome to man, although they are normally vege-

SPECIES OCCASIONALLY ANNOYING 341

table feeders and may do much damage to cultivated plants.
One species especially, Tetranychus molestissimus, which lives
on the undersides of leaves of a species of cockle bur, Xanthium
macrocarpum, in Argentina and Uruguay, attacks man during
the winter months from December to February. It produces
symptoms similar to those of the louse-mite, with intense itching
and some fever. The common “red spider,’ TJ. telarius, an
almost cosmopolitan species, also is reported to attack man oc-
casionally.

The common chicken mite, See gallinae, belonging
to the family Parasitide (Gamaside), frequently causes much
irritation and annoyance to those who come in contact with it.
Although it can thrive and multiply only on certain kinds of
birds, it sometimes remains on mammals for some time, causing
an eczema or rashlike breaking-out on the skin, attended, as in
other mite infections, by intense itching. Except in cases of
constant reinfection chicken mites are usually troublesome to
man for only a few days at most. Since these mites can live
for several weeks without feeding on their normal hosts, places
formerly frequented by fowls may be infective after the removal
of the birds. The mites normally remain on their hosts only long
enough to fill up on blood, usually at night, spending the rest of
the time in cracks and crevices in and about the coops. Various
sprays of sulphur, carbolic solutions and oils are used to destroy
them. An allied species, Holothyrus coccinella, living on geese and
other birds on Mauritius Island, attacks man, causing burning and
swelling of the skin, and frequently proves quite dangerous to
children by entering the mouth.

A very small mite, Tydeus molestus, belonging to the pai
Eupodide, attacks man in much the same manner as do the
harvest mites. It is common on some estates in Belgium, ap-
parently having been imported many years ago with some Peru-
vian guano. It appears regularly each summer on grass plots,
bushes, etc., in great numbers, disappearing again with the first
frost. It causes great annoyance in red-bug fashion, not only to
man but to other mammals and birds as well. |

042 THE MITES

Itch Mites

The itch mites, belonging to the family Sarcoptide, are the
cause of scabies or mange in various kinds of domestic and wild
animals, and of ‘itch’? in man. ‘This disease is one which has
been known for a very long time but was formerly supposed to be
caused by ‘‘ bad blood” or other constitutional disorders such
as cause the growth of pimples. Even at the present time the
true cause of the disease is not understood by the majority of
people. :

The Parasites. — The itch mites (Fig. 142) are minute whitish
creatures, scarcely visible to the naked eye, of which the females

Fic. 142. Human itch mite, Sarcoptes scabiei; 9, female; ¢, male. XX about
100. (Partly after Banks.)

burrow beneath the skin and lay eggs in the galleries which they —
make. They are nearly round and the cuticle is delicately
sculptured with numerous wavy parallel lines, pierced here and
there by stiff projecting bristles or hairs. There are no eyes
or trachee. The cone-shaped mouthparts are covered over by
the shieldlike upper lip. The legs are short and stumpy and are
provided with sucker-like organs, called ambulacra, at their
tips. In the female the two posterior pairs of legs terminate
in a simple long bristle, whereas in the male only the third pair
of legs terminates in bristles. The human itch mite, Sarcoptes
scabiet, is only slightly distinguishable from the itch mites which
cause scabies and mange in many of our domesticated animals.
Each infected species of mammal has its own variety of itch

ITCH MITES — LIFE HISTORY 343

mite, but many of them can be transferred readily from one
host to another. In the common human species the male is
only about 0.25 mm. (745 of an inch) in length, while the female is
about 0.4 mm. (¢5 of an inch) in length. A variety of this mite,
S. scabier crustose, causing the so-called ‘‘ Norwegian itch,” is
found in northern Europe and occasionally in the United States,
but is always rare. The disease caused by it differs in some re-
spects from ordinary itch. Still another species, Notoedres cati,
which causes a very persistent and often fatal disease in cats,
temporarily infests man, but is apparently unable to breed in
human skin, since the infection dies out in the course of a week
or two.

The impregnated females of itch mites excavate tortuous tun-
nels in the epidermis (Fig. 143) especially on such portions as

Fig. 143. Diagrammatic tunnel of itch mite in human skin, showing female
depositing eggs. x about 30. (Adapted from Riley and Johannsen.)

between the fingers and toes, on the groins and external genitals,
and in the armpits, where the skin is delicate and thin. The
tunnels are anywhere from a few millimeters to over an inch in
length, and are usually gray in color from the eggs and excrement
deposited by the female as she burrows.

The eggs (Fig. 143) vary in number from 15 to 50. After they
are all laid the female dies, having performed her duty in life.
But there is no respite on account of her death, for in less than a
week the eggs hatch into six-legged larve. These live for about
two weeks in the old burrow built for them by their mother, and
during this time they indulge in three moults and undergo a
metamorphosis which transforms them into nymphs similar in

344 - THE MITES

form to the parents, but not sexually mature. After a short
time the nymphs moult again, and are then fully developed males
and females. At this stage the mites, remaining hidden in the
burrows or in any crevice in the skin during the day, wander about
on the surface of the skin during the night and copulate there.
The males do not burrow or enter the burrows made by the
females, but merely hide under superficial dead cells of the epi-
dermis. Since they die very soon after copulation, they are
seldom found. The young impregnated females soon begin
fresh excavations, and produce more eggs. Fifteen or twenty
eggs each generation, of which approximately two-thirds are
females, and a new generation about every four weeks, results
in an enormous rate of increase. By working out the increase
mathematically it will be found that in less than six months the
progeny of one pair of itch mites theoretically would number
several millions! |

The Disease. — The “ itch ”’ is a disease which in the past has
swept over armies and populations in great epidemics, but it has
decreased with civilization and cleanliness, and is fortunately
comparatively rare at the present time, at least in civilized com-
munities.

As its name implies, the disease is characterized by itching of
the most intense kind where the mites burrow in the skin. The
itching is probably due only to a very slight extent to the me-
chanical irritation in the skin, but is induced rather by poisonous
substances secreted or excreted by the mites. Injection of fluid
containing crushed mites produces an eruption and irritation
similar to that caused by the burrowing of the living mites.

The excretions of the mites as they feed in their burrows form
little hard pimples, about the size of a pinhead or a little larger,
containing yellow fluid. When these are scratched, as they are |
almost certain to be on account of the unbearable itching, they
frequently become secondarily infected and may give rise to
larger sores. Ultimately scabs form over them.

Since the entire life history of the parasites is passed on a
single host, generation after generation may develop from a
single infection, and although the infection apparently may dis-
appear temporarily, it persists recurrently for many years. Since
the mites are sensitive to cold the infected areas of skin not only
do not spread but may become restricted during the winter, to

ITCH 345

spread with renewed vigor with the coming of warm weather.
So persistent is the infection that it is doubtful whether it ever
spontaneously dies out. ‘‘ Norwegian itch,’ caused by Sarcoptes
scabiei crustose@, is even more persistent than ordinary itch, and,
unlike the latter, may occur on the face and scalp as well as on
other parts of the body.

Infection can result only from the passage of male and female
mites, or of an impregnated female,-from an infected to a healthy
individual. Normally this takes place by actual contact, rarely
in the daytime on account of the secretive habits of the mites,
but commonly at night, especially from one bedfellow to another.
Gerlach experimented to determine how long the mites could
live away from their hosts and found that in the dry warm air of
a room they lost vitality so rapidly that they could not be re-
vived after three or four days. In moist places, on the other
hand, such as in the folds of soiled underwear or bedcloths, they
survived as long as ten days. From this it is evident that in-
fection may take place by means of bedding, towels, underwear
or other cloth which may come in contact with infected skin.
The author once witnessed an epidemic of itch arising from the
use of an infected wrestling mat in a college gymnasium. It is
also possible for infection to be derived from mangy animals,
though the mites, once adapted for several generations to a
given host, do not survive a transfer to a different species of host
more than a few days.

Treatment and Prevention. — The treatment of itch before
the nature of the malady was understood was considered very
slow and difficult, and even at the present time it is looked upon
by many people as a disease which can be recovered from only
after prolonged treatment. The fact that the mites burrow
beneath the skin to lay their eggs makes careless superficial
treatment almost as inefficient as the internal medicine which
was once taken to “ purify the blood.” The most effective
treatment for the itch is as follows: the patient rubs himself
vigorously with green soap and warm water for about 20 minutes,
_ and follows this with a warm bath for half an hour or more, dur-

ing which the soapy massage continues. In this manner the
skin is softened, the pores opened and the burrows of the mites
soaked so that the application of mite poison which is to follow
will penetrate more readily. When the skin is thus prepared

346 THE MITES

some substance for destroying the mites is applied. Sulphur
ointment made by mixing one-half an ounce of sulphur to ten
ounces of lard, is excellent; its virtue lies in the formation of
hydrogen sulphide in contact with the skin, sulphur itself being
inert. A still more efficient though more expensive remedy is
a beta-naphthol ointment, prepared as follows: beta-naphthol,
75 grains; olive oil, 25 fluid grams; sulphur, 1 oz.; lanolin, 1 oz.;
green soap, 1 oz. One of these applications, or some other, is
unsparingly rubbed into the skin of the infected portions of the
body, and of a considerable area around them. When rubbed
in for 20 or 30 minutes the patient goes to bed, leaving the oint-
ment on his body until morning when it is washed off with another
bath. Meanwhile the soiled underwear, bedclothes or other
possibly infected articles are sterilized by boiling or baking.
Since this course of treatment does not destroy the eggs it is
repeated in about ten days in order to destroy any mites which
may have hatched in the meantime.

For delicate-skinned individuals the treatment deseme above
is too severe and may, of itself, give rise to inflammation of the
skin not unlike that caused by the mites. In such case balsam
of Peru may be used satisfactorily instead of sulphur ointment,
but should be rubbed in several times at intervals of a few hours.
It does not cause any irritation.

Prevention of this annoying infection consists merely in avoid-
ing contact with infected individuals, and of shunning public
towels or soiled bed linen. A single infected individual in a
logging or railroad camp may be a means of infecting the entire
camp. Means should, therefore, be taken to guard against
such individuals whenever possible, and to prevent the spread
of infection from unsuspected individuals by care as regards the
use of towels and bed clothes.

Hair Follicle Mites

The hair follicle or face mite, Demodex folliculorum (Fig. 144),
of the family Demodecide, is a species which is most strikingly
adapted for its parasitic life. It is a wormlike creature, very
unmite-like in general appearance, which lives in the hair follicles
and sebaceous glands of various mammals. In man it occurs
especially on the face.

HAIR-FOLLICLE MITE 347

The wormlike appearance of the adult mites is due to the great
elongation of the abdomen which is marked by numerous fine
lines running around it. The beak is short and broad, and the four
pairs of legs, all similar, are short, stumpy, three-jointed append-
ages. The female mites are .35 to 40 mm.
long (about ¢; of an inch), while the males are
a little smaller.

The multiplication of these mites is slow.
The eggs hatch into tiny six-legged larve in
which the legs are mere tubercles. It requires
four moults to bring the larve to sexual
maturity.

In most cases these parasites cause no incon-
venience whatever and their presence is not
even suspected. In Europe a large proportion
of people are said to be infected, but in Amer-
ica, according to Riley and Johannsen, there is
reason for believing that the infection is far
less common than is usually supposed. Since
generation after generation may be produced
on a single host the infection is potentially Fre. 144. Hair-
indefinite in its duration. When the mites ee eee
become numerous in the hair follicles or 200. (After Meg-
sebaceous glands they sometimes cause “black- ™2”
heads”’ by causing a fatty accumulation to be produced, but
they are not the only or even the usual cause of ‘‘ black-heads.”’
The skin disease known as “ acne’”’ has also been attributed to
these mites, but probably erroneously. Follicle mites have been
suspected also of spreading leprosy.

The method of transmission of the mites to another host is
not definitely known but it is probable that the adults wander
on the surface of the skin at times, and may then be transmitted
by direct contact or by towels, as are itch mites. In dogs,
where the follicle mite, possibly a different species, causes a very
severe and often fatal form of mange, transmission from dog
to dog takes place in a very irregular manner, and there are
frequent instances cited of infected dogs associating for a long
time with uninfected ones without spreading the disease. Ex-
periments with transmission of the canine follicle mite to man
have invariably failed. Little is known about treatment of

348 THE MITES

Demodex infection, but it is probable that sulphur applications
in some form would reach and destroy them.

Tongue-worms

Related to the mites, but now placed in a distinct order, Lin-
guatulina, are the tongue-worms. These animals have become so
modified by parasitic life that the adults have lost nearly all re-
semblance to the other members of their group, and have become
so wormlike, both in form and life history, as
to have been classified by older writers with
the tapeworms (Fig. 146A). Only the larval
stage gives a clue to their real relationships.
Their long bodies are either flattened or
cylindrical, and distinctly divided into rings
or segments as in leeches. There is no dis- ©
tinct demarcation between head, thorax and

abdomen. On either side of the mouth are
ie ee Hea‘ two hooks which can be retracted into grooves
latus. X38. (After like the claws of a cat (Fig. 145). These are
eeeon) usually looked upon as the vestiges of some of
the appendages. At the bases of the retractile hooks there open
a number of large glands, the secretion of which is believed to have
blood-destroying power. The internal organization of the body
is degenerate in the extreme; there is no blood, no respiratory ©
system, no special sense organs, no organs of locomotion; little
more than the barest necessities of racial existence — a simple
nervous system, a digestive tract and a reproductive system.
The sexes are separate.

The adult worms live in the nostrils, trache or lungs of car-
nivorous reptiles and mammals, where they produce their myriads
of eggs. The latter are voided with the catarrhal products of
the respiratory system caused by the presence of the parasites.
The egg-laden mucous excretions from the nose of an infected
animal are dropped on vegetation and eaten by herbivorous ani-
mals, whereupon the eggs (Fig. 146B) develop into larve in the
new host. These larve (Fig. 146C), hatched out in the stomach,
are far more mitelike than the adults, inasmuch as they possess
two pairs of rudimentary legs and primitive arthropod mouth-
parts. The larve migrate to the liver, spleen or other organs

LINGUATULA RHINARIA 349

and there encyst (Fig. 146D). After a series of moults a second
larval stage is entered upon, this time with a wormlike appear-
ance much more like that of the adult (Fig. 146E).

At this stage a “ wanderlust ”’ seizes the tongue-worm and it
begins an active migration in an endeavor to reach a more satis-
factory site for adult life. The mites may settle in the res-

D (100)

Fic. 146. Life history of tongue-worm, Linguwatula rhinaria; A, adult female
from nasal passage of dog; B, egg containing embryo; C, larva from sheep, man or
other animals; D, encysted larva; E, 2nd larval stage, from liver of sheep or man.

piratory tract of their original host, or may abandon their host
by way of throat or anus to take chances on being snuffed up or
taken into the mouth cavity of another animal. Having gained
access to their final habitat in the nostrils or lungs, they attach
themselves by their hooks, moult, copulate and reproduce.

While both larval and adult stages of tongue-worms are oc-
easionally found in man, the larve, as liver parasites, are more
common.

The tongue-worm most frequently observed in man is Lingua-
tula rhinaria. The male of this species is a small worm, whitish
in color, about three-fourths of an inch in length, whereas the
female (Fig. 146A), which is yellowish or brownish due to the
eggs in her body, reaches a length of from three to five inches.
The adults occur most commonly in the nasal passages of dogs
_ (Fig. 147). The eggs (Fig. 146B) are dispersed with mucus
during the violent fits of sneezing to which the presence of the
parasite gives rise. The swallowing of food or drink, especially
grass or vegetables, soiled by this infective mucus, results in the
access of the larva-containing eggs to the intermediate host, which
is most frequently sheep, goats, rabbits, etc., but occasionally

300

THE MITES

man. In the course of five or six months the larve (Fig. 146C),
having migrated to the liver or lymph glands, transform to the

second larval stage (Fig.

146E), reach a length of about one-

Fie. 147. Head of a dog split in half to show three tongue-worms, Linguatula
rhinaria, (a) in the nasal cavity. Reduced in size. (After Colin, from Hall.)

fourth of an inch, and consist of from 80 to 90 rings or segments,
each one with very fine denticulations on the hind margin. For

Fic. 148. Porocephalus armil-
latus; 9Q, female; ¢, male.
Natural size. (After Sambon.)

a long time this larva was looked
upon as a distinct species. L. rhinaria
is nowhere abundant, even in its
normal hosts, though in some parts of
Europe about ten per cent of dogs are
said to be infected. The majority
of human cases reported have been
in Germany. 7
Another species which is occasion-
ally found as a parasite in man dur-
ing its larval stage is Porocephalus
armillatus (Fig. 148). Unlike Lingua-
tula, this worm has a cylindrical body,
only about 18 to 22 rings of segments
and a total length of about one-half
an inch. The segments have no fine
denticulations as they have in Lingua-
tula. This species is said to spend its

adult life in the lungs of the African python, the larve occurring
occasionally in man, but more frequently in giraffes, monkeys and
other African animals. Sambon thinks the eggs escape from the

POROCEPHALUS 351

nostrils of pythons into water, and that infection occurs through
drinking. The return of the larva from the intermediate host
to the python probably takes place by the intermediate host
being eaten. The larve as they occur in man or other animals
may either be encysted or freely migrating in the tissues or body
cavities. Such symptoms as emaciation, bronchitis, pleurisy and
offensive discharges from the lungs may be present. From 75
to 100 larve have been known to be expectorated by a single
patient.

A more slender species, P. moniliformis, bright yellow in color,
occurs as an adult in pythons in southern Asia and the Hast
Indies, and in two cases human infection has been reported.
One case of human infection with a Porocephalus in Montana in
1876 is of interest, since, as pointed out by Sambon, it may have
been the larva of P. crotali of rattlesnakes.

CHAPTER XXI
TICKS

WHILE mites as a group are extremely annoying pests, with one
exception they are not dangerous as disease carriers. The ticks,
on the other hand, are not only annoying but dangerous. Several
important diseases of domestic animals are transmitted solely by
ticks, and several human diseases are likewise dependent on
ticks for dissemination, especially African relapsing fever or
“ tick fever’? and Rocky Mountain spotted fever. In addition
to this, tick bites, at least those of some species, give rise to a.
serious form of paralysis, especially in children, which may end
in death. Tick bites also frequently give rise to dangerous
ulcerating sores which may result in fatal blood poisoning. The
economic importance of ticks as parasites of domestic animals is
not for consideration here, but it would not be amiss to state
that the annual loss in the United States from cattle ticks alone
is estimated at from $40,000,000 to $50,000,000. It is evident
that ticks should be looked upon as worthy candidates for ex-
termination wherever this is possible.

Although the ticks constitute only one of several divisions of
the order Acarina, they are so readily distinguishable and so
well known that in the popular mind the ticks are looked upon as
a group quite distinct from all other mites, and equivalent with
them. They are of relatively large size and usually exceed all
other Acarina in this respect even in their larval stages. Some
species when full grown and engorged are fully half an inch in
length.

General Anatomy.— The body of a tick is covered by a
leathery cuticle which is capable of great expansion in the fe-
males as they engorge themselves on their host’s blood, filling the
numerous complex pouches of the digestive, tract (Fig. 149).
When not engorged ticks are flat and oval or triangular in shape
(Fig. 154), usually tapering to the anterior end, but after en-

gorgement they resemble beans or nuts of some kind (Fig. 158).
352

3093

GENERAL STRUCTURE

Fig. 149. Digestive tract of Argas persicus; an., anus; ch., chelicera; int. c.,
intestinal coeca; ces., cesophagus; ph., pharynx; sal. gl., salivary glands; st.,
stomach. xX about 20. (Adapted from Robinson and Davidson.)

Se :
SS ors

MY

Q
y
4

Fig. 151. Tip of chelicera of a tick,

much enlarged; cut. p., articulated

Fig. 150. Head or capitulum of tick; cutting part; shaft, shaft; sh., sheath;

hyp., hypostome; chel., chelicera; pal., fl. t., tendon of flexor muscle; ex. t.,

palpus; bas. p., basal piece. (Partly after tendon of extensor muscle. (After
Nuttall, Cooper and Robinson.)

Banks.)

354 TICKS

Most ticks have a little shield or “‘ scutum ”’ on the dorsal sur-
face, quite small in the females, but nearly or quite covering the
back in the males (Fig. 156). Attached to it in front is a little
triangular piece, the capitulum or “head” which bears the
mouthparts (Fig. 150). The latter consist of a quite formidable
piercing organ, the hypostome, a pair of chelicere or mandibles
which are armed with hooks (Fig. 151), and a pair of blunt palpi
which are probably tactile in function. The hypostome is a
rasplike structure, beset with row after row of recurved teeth
(Fig. 152). So firmly do these hold in the flesh into which the

proboscis is inserted that

aN forcible removal of a tick
My often results in the tearing
Vi off of the body from the

<
<t<i-

ete =<
ee
—_—=

capitulum which remains at-
tached to the host. Like
other Arachnida, ticks have
four pairs of legs. These
are quite conspicuous when
the body is empty but are
H hardly noticeable after en-

gorgement. The breathing
Fig. 152. Hypostomes of ticks; A, ear

tick, Ottobius (or Ornithodorus) mégnini, apparatus consists of a SRS
nymph; B, Argas persicus, adult; C, Ixodes tem of traches which open
Taoder ‘cenperslionis, adulé female; M same, OY * Dt 00 gil aamam
male; G, Ornithodorus moubata, nymph; H, vicinity of the fourth pair
Ormthoders omit agate: Stl of loge, The tee

plates which cover the spir-
acles are sometimes used in distinguishing species. The ventral
surface has two openings, the genital pore just back of the pro-
boscis, and the anus some distance from the posterior end of the
body (Fig. 154).

Habits and Life History. — All ticks are parasitic during some
part of their lives. The majority of them infest mammals,
though many species attack birds and some are found on cold-
blooded animals. A very decided host preference is shown by
some species, whereas others appear to be equally content with
any warm-blooded animal which comes their way. In many
species the hosts or parts of hosts selected by the adults are not
the same as those selected by the immature forms.

ee

LIFE HISTORY 3595

The life histories of all ticks are more or less similar. After
several days of mating the female ticks engorge and soon after
drop to the ground and begin to lay their eggs (Fig. 153). These
are deposited on or just under the surface of the ground. Some
of the family Argasidze engorge several times, laying a batch of
from 20 to 50 eggs after each gluttonous repast. All of the
Ixodide, on the other hand, lay their eggs after a single engorge- -
ment. The eggs number from a few hundred in some species
to upwards of 10,000 in others and are laid
in rather elongate masses in front of the
female. Each egg as it is passed out by the
Ovipositor is coated with a viscid substance
by glands between the head and dorsal shield
of the tick and is then added to the mass in

front. The process of egg-laying occupies
several days, as not more than several hun-
dred eggs can be passed out and treated
with the viscid coating in the course of a
day.

The eggs develop after an incubation period
which varies with the temperature from two yp, 153 Texas
or three weeks to several months. Eggs de- fever tick, Margaropus
posited in the fall do not hatch until the fol- ara any reais
lowing spring.

The larval ticks which hatch from the eggs are much smaller
than the adult ticks and have only six legs (Fig. 157B). They are
popularly known as “seed ticks.”’ The seed ticks soon after
hatching climb up on a blade of grass or bit of herbage and assume
a policy of watchful waiting until some suitable host passes with-
in reach. Seed ticks must be imbued with almost unlimited
patience, since in many if not in the majority of cases long delays
must fall to their lot before a suitable host comes their way like
a rescue ship to a stranded mariner. The jarring of a footstep
or rustle of bushes causes the ticks instantly to stretch out to
full length, feeling with their clawed front legs, eager with the
excitement of a life or death chance to be saved from starvation.
If success rewards their patience, even though it may be after
many days or weeks, they feed for only a few days, becoming
distended with blood, and then drop to the ground again. | Re-
tiring to a concealed place they rest for a week or more while

356 TICKS

they undergo internal reorganization. Finally they shed their
skins and emerge as eight-legged but sexually immature ticks
known as nymphs (Fig. 157C). The nymphs climb up on bushes
or weeds and again there is a period of patient waiting, resulting |
either in starvation or a second period of feasting. Once more
the ticks drop to the ground to rest, transform and moult, this
time becoming fully adult and sexually mature. In this condition
a host is awaited for a third and last time, copulation takes place,
sometimes even before a final host is reached, and the females
begin their final gluttonous feeding which results in distending
them out of all proportions. In some species, especially those
which live on hosts which return to fixed lairs, copulation takes
place off the host. When this occurs, as in many species of
Ixodes, the male is often not parasitic at all, and may differ
markedly from the female in the reduced structure of its hypo-
stome (Fig. 152C, E and F). In all species the males die shortly -
after copulation.

This, in general, is the life history of ticks, but it is, of course,
subject to considerable variation in different species. In many
species there are two nymphal periods instead of one. In some
species, as in the Texas fever tick, Margaropus annulatus, the
moulting takes place directly on the host, thus doing away with
the great risk of being unable to find a new host after each suc-
cessive moult. In a few species the first moult-is passed through
on the host, but the second:is passed on the ground. The most
important asset of ticks to counterbalance the disadvantage of
having to find new hosts is their extraordinary longevity. Larve
of ticks have been known to live more than six months without
food, and adults have been kept alive in corked vials for five
years.

There are two families of ticks, the Argaside and the Ixodide.
The Argaside include the bird ticks and their allies, which are
distinguished from the Ixodide by the absence of a dorsal shield
and in having the head partially or entirely concealed under the
overlapping anterior margin of the body (Fig. 154). The fe-
males of this family do not become distended as do those of the
Ixodide, but take more moderate though more frequent meals.
They are chiefly inhabitants of warm countries. Both nymphs
and adults feed at night, usually dropping off their hosts im-
mediately after a meal, and thus seldom being carried from the

TICK BITES a

lairs or abodes of their hosts. The Ixodide, on the other hand,
inhabit the hosts rather than their lairs, and frequently remain
attached for several days, or even longer. In the less capacious
Argaside the females lay their eggs in a number of installments

0
0
Q
4
Oo,
8
°
0
°

Fic. 154. Comparison of dorsal and ventral view of Ixodid and Argasid females;
A, dorsal view of Ixodid 9; A’, ventral view of same; B, dorsal view of Argasid
Q; B’, ventral view of same. An., anus; cap., capitulum; d. sh., dorsal shield;
e€.s., eye spot; gen. op., genital opening; sp., spiracle.

after successive feeds, and the total number of eggs may be
counted in hundreds instead of thousands. The reason for this
difference is readily accounted for by the difference in habits in
the two families, since the progeny of the Argaside, reared in
the lairs of the hosts, have far better chances of finding a host and
of surviving than do the progeny of the Ixodide which live on
their hosts and may drop off to lay their eggs almost anywhere
in the wanderings of the host.

Tick Bites. — The status of ticks as human parasites, as stated
before, is one not to be passed over lightly. Aside from the

308 TICKS

transmission of diseases tick bites are dangerous to man in a
number of ways.

The wounds made by ticks, especially if the head is torn off in
a forcible removal of the parasite, are very likely to become
infected and result in inflamed sores or extensive ulcers, not in-
frequently ending in blood poisoning. The author, as the result
of the bite of a tick in northern California (probably Dermacentor
occidentalis), suffered from an ulcerating sore on his arm, over half
an inch in depth and three-fourths of an inch in diameter. Blood
poisoning set in early causing a very high temperature and great
pain in the arm, and it was only a timely return to civilization
and hospital care that saved his arm if not his life. Sanitary
removal of ticks and cleansing of the wounds, as described on
p. 367, would be well worth the consideration of every inhabitant
or traveller in a tick-infested country.

Tick Paralysis. — More serious than the painful wound made
by ticks is a peculiar paralyzing effect of tick bites, known as
tick paralysis. This occurs especially from tick bites on the back
of the neck or on the head; it affects the legs first, but spreads
forward in a few days to the arms and neck and may result in
death. Paralysis in man and animals from tick bites has been
reported from South Africa and Australia and in North America
from the parts of Oregon and British Columbia inhabited by the
spotted fever tick. Sheep are especially subject to tick paraly-
sis, to such an extent in British Columbia as to present a serious
problem. This peculiar effect of tick bites has been. reproduced
experimentally in sheep in places where it has not been known
to occur normally, by allowing a spotted fever tick, Dermacentor
venustus (Fig. 156), to bite along the spinal column. The bites
of this tick are particularly likely to cause paralysis, though it is
not yet known whether this is because of an especially toxic
secretion produced by this species or because of its preference for
biting along the spinal cord or on the head. ‘There has been
much controversy as to what really causes the paralysis, some
authors believing that it is due to a microérganism injected by
the tick, since it is usually six or seven days after the attach-
ment of the tick before the effect is felt. The fact, however,
that no such organism can be discovered, that inoculations of
blood and other parts of diseased animals into healthy ones does —
not result in transmission of the disease, and that the paralysis ~

TRANSMISSION OF DISEASES 359

is usually accompanied by little or no fever, makes this seem
unlikely. A single attack of tick paralysis seems to confer
immunity and it is probable that many children are naturally
immune. The most reasonable explanation is that the ticks
secrete a toxic substance, especially when rapidly engorging,
which has a specific action on the motor nervous system. Pos-
sibly the bite must pierce or come in contact with a nerve or
nerve ending in order to produce the effect.

Numerous cases of tick paralysis in children have occurred
in British Columbia and in the Blue Mountains of Eastern
Oregon. One doctor in the vicinity of Pendleton reported no
less than 13 cases. The disease begins with paralysis of the
legs and usually results in complete loss of their use; the paraly-
sis ascends in the course of two or three days, affecting the arms
and finally the thorax and throat. Unless the heart and respi-
ration are affected, recovery follows in from one to six or eight
days after removal of the ticks. The latter, often in pairs, are
usually found on the back of the neck or along the middle line
of the head, especially just at the base of the skull. If the ticks
are not removed, the disease may result in death or in spon-
taneous recovery after a few days or a week. ©

Unfortunately in most of the cases of tick paralysis in chil-
dren the ticks have not been identified, but it is well known
that the spotted fever tick is the most frequent cause of paralysis
in sheep and the only species by which such a disease has been
reproduced experimentally. In South Africa, however, a similar
paralysis in sheep results from the bites of Ixodes pilosus, and
paralysis in children in Australia from the bités of other but
undetermined species. The scrub-tick, Ixodes holocyclus, is said
to be troublesome as a cause of paralysis in young stock in New
South Wales. In the regions of Oregon and British Columbia
where tick paralysis is especially prevalent there occur a number
of different ticks, and there is no evidence that any tick which
attacks man along the spinal cord or on the head may not cause
paralysis.

| Ticks and Disease
The role of ticks as disease carriers has been well established

since Dutton and Todd in 1905 proved that African relapsing
fever was transmitted by a species of tick known as the tampan,

360 TICKS

Ornithodorus moubata (Fig. 155). A year later Dr. Ricketts
showed that spotted fever in the United Stated was dependent
upon a tick, Dermacentor venustus, for its transmission. It is
now known that ticks serve as intermediate hosts for a consider-
able number of disease germs of two different groups, the spiro-
chetes and the Piroplasmata. The various forms of relapsing
fever of man are caused by spirochetes, and it is possible that
all the different types of this disease may be transmitted by
ticks, though in some of the types other arthropods act as the
usual transmitters. Many diseases of domestic animals are
caused by organisms of the group Piroplasmata (see p. 182),
including Texas fever of cattle in North America, East Coast
fever of cattle in Africa, biliary fever of horses in Asia and Africa,
and similar diseases of sheep, dogs, rats and monkeys. The only
human disease positively known to be caused by an organism
of this group is Oroya fever of Peru, caused by Bartonella bacilli-
formis (see p. 178). Whether or not a tick is instrumental in
transmitting this disease is not yet known. Rocky Mountain
spotted fever was at one time thought to be caused by a member
of the Piroplasmata, but the parasite of this disease is still un-
known. . The fact that it is transmitted -by a tick suggests that
it may be found to belong either to the spirochetes or to the
Piroplasmata. Ticks have also been suspected of carrying the
East Indian form of kedani fever which in Japan is transmitted
by a larval mite, but this has not been proved.

Ticks and Relapsing Fever.— The fact that tick bites frequently
give rise to serious fever and illness, now known as relapsing
fever, which not infrequently result in death, has been well known
in Africa for many years, in fact Livingston in his “ Darkest
Africa” speaks of this disease as resulting from tick bites. The
implicated ticks, Ornithodorus moubata, known as “ tampans”’ or
‘“carapatos,” are very common pests in shaded places in the
dirty thatched houses of the natives, and are difficult to avoid.
They occur chiefly along the routes of travel, being readily
carried and dispersed by caravans. They live also in the bur-
rows of warthogs. A detailed account of the réle played by
the tick in harboring and transmitting relapsing fever spiro-
chetes and a description of the disease can be found in Chap.
TVespr a2:

The tampan is a broad oval tick (Fig. 155), mud-colored,

DERMACENTOR VENUSTUS 361

about five-eighths of an inch in length, belonging to the family
Argasidez. Like the other members of the family it has no
dorsal shield and has the margin of the body produced in such
a way as to conceal most of the head and legs. Unlike most
ticks the larve are weak and do not feed
but transform to nymphs very soon after
the eggshell splits. The nymphs are
said to produce more painful wounds than
the adults and they can just as readily
transmit relapsing fever.

An allied species, O. samgnyi, occurs
from Abyssinia through Arabia to India
and Ceylon and attacks man, camels and
horses. It is said to transmit the Indian is

' : 2 Fie. 155. The tampan,
form of relapsing fever in these countries. Qrnithodorus moubata. 3.
Like O. moubata it attacks its host in its
resting place, hiding in the daytime in dust or sand in or around the
squalid huts of the natives. Except in coastal towns, where it is
abundant everywhere, it is found chiefly in camps of long stand-
ing inhabited by men and animals. Burrowing to a depth of an
inch in dusty soil it can live without food for months. In Persia
O. tholosani is said to transmit African relapsing fever which has
been introduced there. O. talaje of Mexico and Central America
has habits very similar to those of the tampan in Africa; it fre-
quently occurs in the adobe houses and attacks the occupants
at night. O. turicata, the “carapato”’ of Central America, is
another very annoying species. Its bites are so severe that hogs
are said to have been killed in a single night by its attacks.
Though not proved it is very probable that one or both of these
species may be instrumental in transmitting the milder American
form of relapsing fever. It is almost certain also that another
tick, the “‘miana bug” of Persia, is capable of transmitting
European relapsing fever (see p. 364).

Ticks and Spotted Fever. — The tick which is responsible for
the transmission of Rocky Mountain spotted fever (see p. 191)
is a weod tick, Dermacentor venustus (andersoni) (Fig. 156). This
is a handsome reddish brown species, the male of which has the
whole back marked with black and silvery-white lines, while
the female has only the small dorsal shield marked with silver,
the abdomen being deep reddish brown. This species is one

=

362 TICKS

which requires two different hosts to complete the life cycle.
The six-legged larve (Fig. 157B), of which there are about 5000
in a brood, attach themselves to any of the rodents which abound

Fic. 156. Spotted fever tick, Dermacentor venustus, male (g) and female (9).
x 123

Fic. 157. Development of spotted fever tick, Dermacentor venustus; <A, eggs;
B, larva; (Cy nymphe equ:

in the country where the ticks occur, especially squirrels of

various kinds. Usually the larve, and the nymphs also, attach

themselves about the head and ears of their host. After a few

days the larve drop, transform into nymphs (Fig. 157C) and

TRANSMITTERS OF SPOTTED FEVER 363

again attack their rodent hosts. After dropping off these and
transforming into adults they no longer pay any attention to the
-rodents but seek larger animals, especially preferring horses and
cattle, though they readily attack other large wild and domestic
animals and man. Their original wild hosts were probably the
mountain goats, elk and other wild game of the region, but with
the supplanting of these by domestic animals the latter have
become the main host animals of the ticks. Unlike most ticks,
this species may take two or even two and a half years to com-
plete its life cycle under unfavor-
able conditions. The winter is
passed in either the nymphal or
adult stages.

Dermacentor venustus is found in a
limited area in northwestern United
States and British Columbia, east
to eastern Montana and eastern
Wyoming, west to the Cascade
Mountains and south into Nevada
and Colorado. This distribution
somewhat exceeds the present dis-
‘tribution of spotted fever (Fig. 58,
p. 191). 3

Several different species of ticks ye. 158. Spotted fever tick,
have been found capable of trans- Dermacentor venustus; engorged
mitting spotted fever from rodent seam
to rodent under experimental conditions. Several species of ticks
other than D. venustus are found in the spotted fever districts,
but none of these can have any hand in the transmission of the
disease to man since they do not attack him. A tick closely
related to D. venustus, the Pacific wood tick, D. occidentalis, oc-
curs west of the Cascades and Sierras in Oregon and California
and frequently attacks man. There is little doubt but that if
spotted fever once got. a foothold in the territory occupied by this
tick, the latter would act as an efficient disseminator. In southern
and eastern states other ticks which attack man would probably
disseminate the disease were it once introduced. For this reason
it is of the utmost importance. that the infection should not be
carried to parts of the country which are not now infected.
Measures for the prevention of this are discussed in Chapter X,
under “‘ Spotted Fever.”

364 TICKS

Other Troublesome Ticks

Although there are a large number of species of ticks which
will attack man, there are a few in addition to the disease-causing
species named above which deserve special mention on account
of the particularly bad effects of their bites. The family Argaside
includes a number of species which produce very venomous bites
when they attack man. The various species of Ornithodorus,
some of which have already been mentioned as carriers of relap-
sing fever, produce very painful bites. Another species worthy
of mention is the famous “‘ miana bug,” Argas persicus (Fig. 159),
which is especially renowned in Persia, but which also occurs in
many other parts of the Old
World. This species is often a
great tormentor of human be-
ings, especially in dirty huts
where it can breed readily. It
is primarily, however, a parasite
of fowls, and is believed to be
identical with the American fowl
tick, Argas miniatus. The bites
of the miana bug are dreaded
not only on account of their
painfulness, but also because
they are believed to be a means
of transmission of European re-

Fie. 159. Persian tick or fowl lapsing fever, in common with
tick, Argas persicus. <5) (Atters.2
Beau) lice and perhaps other insects.

A closely allied species, A. re-
flecus, is 4. common parasite of pigeons in Europe and North
Africa, and frequently attacks people who come in contact with
infested birds or cotes.

Another argasid tick which deserves special mention is the -
“pajaroello,” O. coriaceus of California. Herms states that
“natives, principally Mexicans, in the vicinity of Mt. Hamilton
fear this* parasite more than they do the rattlesnake, and tell
weird tales of this or that man having lost an arm or leg, and in
one instance even death having ensued, as a result of a bite by
the Pajaroello. There seems to be a suspicion in that region
that three bites will result in certain death. The stories all

SPINOSE EAR TICK 365

agree in the essential detail that the bite results in an irritating
lesion which is slow to heal and often leaves an ugly deep scar.”’
The tick is about two-fifths of an inch in length, irregularly oval,
with thick turned-up margins, roughly shagreened, and of a
yellowish earthy color spotted rusty red. It occurs in the Coast
Range mountains of California and in Mexico and according to
Herms is most commonly found in the dry leaves under live
oak trees where cattle or other animals are accustomed to lie
in the shade. It passes through from four to seven moults to
reach the adult state, occupying 3
from one to two years to com-
plete its life history, according
to its success in finding suitable
hosts. The bites of this tick
produce sharp pain, accompanied
by a considerable discoloration
around the wound, and if on an
arm or leg the whole limb may
become greatly swollen as in the
case of a snake bite. After scab-
bing over, the wound may con-
tinue to exude lymph and to be
irritable for several weeks, and it
is possible that infection and con-
sequent blood-poisoning might
readily occur, thus giving a basis ‘ce
for the tales mentioned above. eal aN Ta a ein
Another noteworthy member of ini. x 10. (After Marx from
the Argaside is the spinose ear ?@2**?
tick, Otiobius (or Ornithodorus) mégnini (Fig. 160), of south-
western United States and Mexico, and now becoming common
in parts of South Africa. It is very troublesome to man as well
as to horses and other domestic animals. The nymphs, which
- develop from the larve in the ears of their hosts, are peculiar in
having very spiny bodies, quite different from the smooth larve
and adults. The nymphs remain attached to their hosts for
months but finally drop off to transform into adults. The
adults are not parasitic but lay their eggs without further feed-
ing. The pain and annoyance caused by the spiny nymphs in
the ears of domestic animals is sufficient to cause them to be- —

366 TICKS

come ill-tempered and emaciated. Children sometimes suffer
a great deal from their attacks, and have difficulty in dislodging
the invaders from their ears. This can readily be done, however,
by pouring olive oil or some other harmless oil into the ears.
Although there are a large number of species of the family

Ixodide which may attack man, they do not as a rule prove as
great pests or produce as severe bites as some of the Argaside.
The characteristics of some of the principal genera are given in

Fic. 161. Diagrams of rostra or capitula of important genera of Ixodid ticks,
useful in identification. (After Nuttall.)

With long rostrum Other characteristics

AE TODS ep ee Anal. groove in front of anus, no eyes,

no festoons.
Be AV alommas ccs ee Cees oe ee eyes present, festoons present.
C, Amblyomma eee eee eyes present, festoons present, ornate.
or
Aponomma..............+......eyes absent, festoons present, ornate. —

With short rostrum

D Hema plyscisin «- eee oe eyes absent.

He VRAGTIGTO DUS A) et oie ee circular spiracles.

By ehipicepialus.. |, pee ee ee ee comma-shaped spiracles.

G, Dermacentor...................eyes present, ornate.

Fig. 161 and accompanying table. Only a few species need
special mention here. Dermacentor venustus is, of course, of —
preéminent importance on account of its réle as a transmitter —
of spotted fever and in producing tick paralysis. D. occidentalis,
the ‘“ wood tick ”’ of the Pacific slope of the United States, is
another member of the genus which very commonly attacks man;
its bites are particularly likely to cause ugly ulcerating sores.
Experimentally, as said before, it has been shown to be capable af
transmitting spotted fever, and it would probably act as an effi-

TREATMENT OF BITES 367

cient disseminator if the disease were introduced into its terri-
tory. The same might be said of D. variabilis, the dog tick of
eastern North America, though this. species less commonly
attacks man.

Of particular interest is the effect produced by the larve of
certain ticks in southeastern Africa, especially the bont tick,
Amblyomma hebreum. Its larve produce itching and painful
wounds which may be followed in a week or so by fever, head-
ache, skin eruptions and other general symptoms. The name
_ “ tick-bite fever ’’ has been applied to this malady. Whether it
is caused by a microérganism is unknown. Immunity rapidly
develops, so that usually only new arrivals are affected. In
Europe one of the most troublesome species of Ixodide, as far
aS man is concerned, is the common dog tick, Ixodes ricinis,
which attacks a great variety of animals, and is evidently quite
fond of human blood. A _ particularly obnoxious species in
tropical America is Amblyomma cajennense. Not only the
nymphs and adults but also the larve of this species are pests
of man.

Treatment and Prevention. — As shown above tick bites may
be attended by a number of serious results, such as fever, ulcer-
ating sores, paralysis or disease transmission. The treatment
of the bites, therefore, may be of considerable importance. It
_has been shown that ticks, at least in the case of the relapsing
fevers, do not ordinarily infect directly by biting, but by con-
taminating the wound with infected excrement. It is obvious,
_ therefore, that disinfection of the wound after removal of the
tick would be a precaution of great value in places where ticks
carry diseases to which human beings are susceptible. Such
treatment would also prevent bacterial infections of various
kinds from entering the wounds and causing ulceration or blood-
poisoning.

Ticks should never be removed forcibly since if so handled
the head is likely to téar off from the body and remain in the
wound, held there by the ugly barbed proboscis. A drop of
_ kerosene, creoline or some other oil on the head of the tick will
cause it to withdraw its beak and drop off in the course of a
minute or two. Disinfection of the wound with alcohol, weak
carbolic, lysol or other disinfecting agent should follow imme-
diately.

368 TICKS

Precautions against tick bites where serious diseases are likely
to result are of the greatest importance but very difficult. King,
while investigating spotted fever, spent a whole season in the
heart of the Bitter Root Valley in Montana where spotted fever
infection was most dangerous. He wore high-topped shoes and
cotton outer garments soaked in kerosene and had pieces of
khaki cloth soaked in kerosene sewed to the tops of his boots or
fastened by drawstrings higher up on his leg. A leg covering of
oil-proof material with crude oil applied on the outside would
be of benefit, according to King. In Abyssinia the attacks of
Ornithodorus savignyi are prevented by rubbing the feet with
turpentine.

Means of control of tick pests vary considerably with the dif-
ferent species, depending on the hosts, their Seen. history,
their varying life histories and other factors.

Most of the species of ticks which attack man are normally
parasitic on domestic animals, and therefore means of extermi-
nating ticks on the latter would tend to reduce the human pests.

Ticks on domestic animals may be destroyed either by hand
treatment or by dipping, or by the elimination of ticks from
pastures by starvation. The cattle tick, Margaropus annulatus,
has been eliminated from many ranches by a skillful manceuvering
of the cattle, driving them from field to field in such a way that
in the course of a number of months the ticks would all have
dropped and perished from starvation. Such a plan is not
feasible for many species since a variety of hosts may be
utilized, and long periods of starvation can be endured without
injury.

Dipping of infested animals is a good control method. An
arsenical dip has been found best adapted for destruction of
ticks on their hosts, a description of which, with methods of
preparing and using, is given in Farmers’ Bulletin No. 378 —
of the U. 8. Department of Agriculture.

Hand treatment with arsenical dip by means of rags, mops or
sprays 1s sometimes found more practical.

The systematic dipping of domestic animals in the spotted
fever districts of Montana for a period of three years has been
recommended by the U. 8S. Department of Agriculture for the
elimination of the spotted fever tick from these regions. In
this particular case supplemental means of control consist in the

CONTROL 369

destruction of indigenous rodents in a wholesale manner, and
the clearing away of brush land in tick-infested areas.

Another means of destruction of spotted fever ticks has been
found in grazing sheep on tick-infested lands. Range sheep have
been found to destroy ticks in large numbers by the ticks becom-
ing entangled in the wool and starved. Five hundred sheep were
found to destroy 25,000 ticks in a season.

Ticks which infest the lairs of their hosts, attacking only at
night and for brief periods, can be more easily handled. In
this case thorough disinfection by fumigation or by spraying
with a disinfectant, and thorough cleanliness in stalls, coops,
kennels, huts or other host homes will effectually destroy them.
The disease-carrying tampan, Ornithodorus moubata, of Africa is
an example of a tick which can be controlled by such methods.
Dirty, poorly kept native huts are the ideal habitats for tampans,
which secrete themselves during the day in crevices, thatched
roofs or débris, after the manner of bedbugs. Plastering houses
with mud, building of smudges, fumigation and cleanliness are
methods which usually succeed in keeping out ticks. Crevices,
bed sheets and other places which might harbor ticks should be
dusted with pyrethrum insect powder.

The nearly allied O. savignyt of Abyssinia, which conceals itself
in dusty soil to a depth of one inch, can best be destroyed in in-
fested camp sites, environs of wells, etc., by harrowing the sur-
face of the ground, strewing dry grass and brush over it, and ©
-burning it from around the edge of the infested area toward the
center. Spraying with antiseptics has been found practically
useless, since even the total immersion of ticks in strong antisep-
tics for an hour or more fails to kill them.

The fowl tick or ‘‘ miana bug,’’ Argas persicus, and the Ameri-
can hut-infesting species of Ornithodorus, O. talaje and O. turicata,
ean be controlled by methods similar to those used for the
tampan.

CHAPTER XXII
BEDBUGS AND THEIR ALLIES

The Order Hemiptera. — The order of insects, Hemiptera (or
Rhynchota), which includes the true bugs, contains a number
of species which habitually or occasionally attack man. The
most important of these are the bedbugs, which are found all .
over the world in temperate and tropical climates. There are
few objects which are more disgusting than bedbugs to good
housekeepers, yet there are few who, at one time or another,
have not had to contends with them or at least guard against.
them. Belonging to an allied family are the cone-noses, larger
than bedbugs and not devoid of wings, fiercer in disposition and
capable of producing much more painful bites. A considerable
number of species of these bugs
are known and are found in all
warm countries. The relation of

meee SED - bugs to disease is still very im-

Fic. 162. A hemipteran wing perfectly known, but these para-

eta: sites are positively known to.

transmit at least one important disease, and are suspected of
transmitting several others.

The true bugs, order Hemiptera, are characterized by having
piercing and sucking mouthparts contained in a jointed beak
and by an incomplete metamorphosis, 7.e., not undergoing a
complete transformation from a larval to an adult form during a
period of rest, as do such insects as butterflies, beetles, etc. The
newly hatched young may differ quite considerably from the
adult, but the mature characteristics are gradually attained with
each successive moult. The order is divided into two suborders,
only one of which, the Heteroptera, concerns us here. In the
members of this group the first pair of wings, if present, have a
thickened, leathery basal portion and a membranous terminal
portion (Fig. 162). The second pair of wings are always mem-
branous when present.

370

STRUCTURE OF BEDBUGS 371

Bedbugs

General Account. — The bedbugs belong to the family Cimi-
cide. They have broad flat bodies, and are devoid of wings,
except for a pair of spiny pads which represent the first pair of
wings (Fig. 163). The first segment of the thorax has winglike
expansions at the sides which grow forward and partially sur-
round the small head. In the —
male the abdomen is quite
pointed at the tip, whereas in
the female it is evenly rounded,
the contour of the abdomen
being almost a perfect circle in
unfed bugs. The eyes project
prominently at the sides of the
head, the flexible four-jointed
antenne are constantly moved
about in front of the head,
and the jointed beak is folded
under the head so that it is
entirely invisible from above.
The legs have the usual seg-
ments, the tarsi being three-
jointed. The greater part of i
the body is covered with bristles Fic. 163. Bedbug, Cimex lectularius,
set in little cup-shaped depres- een ae
sions. ‘These depressions are perforated at the bottom to allow
for the passage of muscles which move the bristles. Murray
describes having seen bugs raise the bristles upon meeting each
other as cats raise their hairs or birds their feathers. The bristles
are of two kinds, one a simple slender spine, the other with a>
stouter flattened end, with sawlike teeth along the thinner edge.
In addition to both kinds of bristles, the legs also have a dense
brush of hairs at the end of each tibia. When a bug is distended
with blood a smooth shining band can be seen at the base of each
abdominal segment where no bristles occur (Fig. 163). These
bands are the portions of the segments which are not ordinarily
exposed, being overlapped by the preceding segment.

One of the most striking characteristics of bedbugs is the
peculiar pungent odor so well known to all who have had to con-

312 BEDBUGS AND THEIR ALLIES

tend with these pests. Many other bugs are characterized by
similar odors, as, for example, the common “‘ stink-bugs.’”’ The
odor is produced by a clear volatile fluid secreted by a pair of
glands of very variable size which
open between the bases of the hind
pair of legs. Although in most
‘“‘wild”’ bugs the stink glands are
supposed to be distinctly bene-
ficial in that they make the owners
obnoxious to enemies which would
otherwise prey upon them, they
are a decided handicap to the do-
mestic bedbugs in the struggle for
existence, since the odor draws

Fic. 164. Head and part of thorax attention ‘ the Pree of bugs
of bedbug, ventral view. x20. Note which might otherwise escape
jointed beak, eyes and stout spines. jotice. Nor does the scent ap-
pear to be any protection to them against such enemies as cock-
roaches and red ants. Murray suggests that it may be of some
use to them in their social intercourse
in the dark recesses in which they
spend their lives.

The nasty odor of bedbugs has
evidently inspired some faith in their
medicinal value. Seven bugs ground
up in water was said by Pliny to
arouse one from a fainting spell, and
one a day would render hens immune
to snake bites. Even at the present
time there are places in civilized coun-
tries where bedbugs are given as an
antidote for fever and ague.

There ag number of species of 5. 165, Indian bedbug, Cimex
bugs in the genus Cimezx, but some hemipterus (rotundatus), female. X
of the species confine their attentions ®: ne Castellani and Chal-
to poultry and other birds, bats, ete.

There are two widely distributed species which attack. man:.one
is the common bedbug, Cimex lectularius, found in all temperate
climates; the other is the tropical or Indian bedbug, Cimex hemip-

terus (rotundatus), prevalent in many tropical countries, includ-

Ee ee ee a ee ee ee

HABITS OF BEDBUGS 373

ing southern Asia, Africa, the West Indies and South America.
The tropical bug (Fig. 165) differs from the common one only in
minor details, such. as greater length of body hairs, darker color
and more elongate abdomen. It is less dependent on human ©
blood than its relative of temperate climates, and readily attacks
not only rats and mice but also bats and birds. Both species are
reddish brown in Sie becoming deep red when gorged with
blood.

Habits. — Bedbugs are normally night prowlers, and exhibit
a considerable degree of cleverness in hiding away in cracks and
crevices during the daytime. When hungry they will frequently
come forth in a lighted room at night, and have even been known
to feed in broad daylight. Favorite hiding places are in old-
fashioned wooden bedsteads, in the crevices between boards,
under wall paper, and other similar places, for which their flat
bodies are eminently adapted. Like other animals which have
long associated with man, bedbugs have developed much cun-
ning in their ability to adapt themselves to his habits. Marlatt
says ‘‘ the inherited experience of many centuries of companion-
ship with man, during which the bedbug has always -found its
host an active enemy, has resulted in a knowledge of the habits
of the human animal and a facility of concealment, particularly
as evidenced by its abandoning beds and often going to distant
quarters for protection and hiding during daylight, which in-
dicate considerable ‘apparent intelligence.” Their ability to
gain access to sleepers at night is hardly less remarkable. Cases
are reported of bedbugs creeping along ceilings and dropping down
on beds in order to reach their hosts, but these pees have been
accidental.

The bedbug makes himself a great pest wherever he occurs
by the unsparing use of his piercing and sucking mouthparts.
The latter consist of four needle-like organs lying in the long,
jointed lower lip or beak, a pair of flattened sharp-pointed man-
dibles and a pair of slightly shorter maxille with serrated edges.
- The beak is grooved in such a way that the sides of the groove
almost close together, thus forming a protective sheath for the
stilettos inside. ‘When about to indulge in a meal the beak is
bent back, and the piercing organs, gliding up and down past
each other, are sunk into the flesh of the victim (Fig. 166). A
strong sucking motion of the pharynx, into which a bit of sali-

374 BEDBUGS AND THEIR ALLIES

vary juice has already been poured, draws blood up through a
tube made by the piercing organs, through a thickened “ bottle
neck ’’ ring to the cesophagus and then into the relatively enor-
mous stomach. The muscles for dilating the pharynx in order
to make a suction pump out of it occupy the greater part of the
head. According to Cragg, who has worked
on the alimentary tract and digestive proc-
ess of bedbugs, there are about 70 pulsa-
tions of the pharynx per minute in young
: bugs, in which this can be observed through

Fic. 166. Diagram the body wall. Bugs seldom cling to the
cere tae acetaR skin while sucking, preferring to remain
of proboscis. (After on the clothing. Since a fresh meal appar-
Rutray?) ‘ ently acts as a stimulus for emptying the
contents of the rectum, the adherence to the clothing is a fortunate
circumstance, inasmuch as it precludes to some extent the danger
of bedbugs infecting their wounds with excrement, as do ticks.

In the course of ten or 15 minutes a full meal is obtained and
the bug, no longer flat but round and distended with blood, re-
treats to his hiding place, having first deposited a bit of excrement.
According to Cragg, in the case of C. hemipterus (rotundatus), a
single meal, much of which is temporarily stored in the stomach
which acts as a food reservoir as well as a digestive organ, is not
fully assimilated for at least a week, although the bug is ready to
feed again in a day or two, thus having parts of several meals in
the stomach at once. This is quite a different condition from
that found in most blood-sucking insects, where a meal is com-
pletely digested before another is sought. Observations made
by several authors on C. lectularius do not indicate that this
species has similar habits. As in other bugs, the digestive juices
change the absorbed blood into a dense black mass, described
~ by Murray as almost like lamp-black.

The bite of the bedbug seldom produces pain or swelling unless
rubbed or scratched, a fact which indicates either that the saliva
is not irritating or that it does not ordinarily reach the wound
before sucking begins. In some people, however, a stinging, hard,
white swelling is produced. ;

Under normal conditions the common bedbug, C. lectularius,
has only rarely been found feeding on anything but human blood.
The bugs which infest the nests of swallows and other birds are

LIFE HISTORY OF BEDBUGS ano

of different species from the human pests, and are not known to
annoy man voluntarily, although they occasionally enter rooms
from the nests of chimney swifts. Bats are often accused of
carrying bedbugs into houses, but they, too, are attended by
their own particular species which does not attack man. The
assertion that bedbugs can be found under bark and moss out
of doors also arises from a misapprehension. These bugs are
really the immature stages of certain other species of bugs which
resemble bedbugs closely enough to be mistaken for them by a
casual observer.

Although human blood is their normal food, bedbugs are able
to subsist on the blood of such animals as rats, mice, rabbits,
cats, dogs and even chickens. It has also been shown that bugs
will suck blood from freshly killed mice. By utilizing mice
and rats as a food supply they are able to exist in deserted build-
ings for a long time. Furthermore they are able to endure long
fasts; they have been kept alive without any food whatever for
a year. -Murray has found that bugs which have been starved
even for a long time pass unaltered blood corpuscles in their
feeces, and suggests that a small quantity of food may be re-
tained undigested in the rectum to be drawn upon very slowly in
time of need, though when a fresh supply of blood is obtained
the old store is cleared out. Bugs also store up a great deal of
fat for use in time of famine. Sometimes, however, after a house
has been deserted for some time, and their normal supply of
food is cut off, the bugs migrate in search of an inhabited house.
In cold weather bugs hibernate in a semi-torpid condition and
‘do not feed, but in warm climates they are active the year around.
The common bedbug, according to Marlatt, is sensitive to
temperatures of 96° F. to 100° F. or more if accompanied by a
high degree of humidity, and is killed in large numbers under such |
climatic conditions: According to Bacot, unfed newly hatched
bugs are able to withstand cold between 28° F. and 32° F. for
as much as 18 days, though they are destroyed by exposure to
damp cold after a full meal.

Life History. — The eggs of bedbugs (Fig. 167A) are ‘meet
white oval objects, furnished with a little cap at one end which
is bent to one side. As in the case of lice, the eggs are relatively
large, being about one mm. (z's of an inch) in length, and are
therefore laid singly or in small batches. The ovaries hold about

316 BEDBUGS AND THEIR ALLIES

40 eggs at a time, all near the same stage of development, so
they must undergo rapid increase in size shortly before being
deposited. Girault, who has carried out extensive breeding
experiments, saw one female lay 111 eggs during the 61 days
that he had her in captivity, and another laid a total of 190
eggs. Often a female returns to lay more eggs in the same
place so that batches of 40 or more can be found in the crevices
where the adult insects hide.

The eggs hatch in from six to ten days during warm weather,
but are retarded in their development by cold. A week of
freezing temperature reduces the
hatching to 25 per cent. The
freshly hatched bugs (Fig. 167B)
are very small, delicate and pale

meal they have a much more
robust appearance, and grow
rapidly. The skin is normally

Fic. 167. Egg and newly hatched adult stage is reached, at least
larva of bedbug. xX 20. (After Mar-

latt.) one gluttonous feed being neces-:

sary before each moult in order
to insure normal development and reproduction. Although
apparently not necessary to its development, the bug may gorge
itself several times between moults, at intervals of about one to
six days. Marlatt found the average period of time between
moults to be eight days. Allowing a similar length of time
for the hatching of the eggs, the time occupied from laying of
the eggs to maturity is about seven weeks. Girault has found
the development from the hatching of the eggs to maturity to
take place in as short a time as 29 days. On the other hand,
starvation, cool temperatures and possibly other conditions may
drag out the period of development to great length. Bacot
found that the newly hatched larve could live unfed four and a
half months and with .one feed for nine months. The several
larval stages of the insect resemble each other quite closely except
in the constantly increasing size and deepening color. The
wing pads appear only after the last moult.
Bedbugs and Disease. — The relation of bedbugs to human
disease is a Subject which, although a problem of the most vital

in color. After their first hearty —

moulted five times before the final —

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BEDBUG AS DISEASE CARRIER. SEL

interest in preventive medicine, is still very indefinitely known.
Various authors have associated bedbugs with a number of
human diseases but the evidence brought forth in support of
these insects being the normal transmitters of the diseases in
question rests on insecure foundations. Ordinarily bugs are
handicapped in the extent to which they are able to spread
disease by their non-migratory habits. Unlike many parasites
they are not. usually carried about by human beings, but remain
- permanently in places occupied by their hosts. It is obvious,
therefore, that bugs are limited in the spreading of disease to the
occupants of the infested place. Should this be a private home,
spread of disease by bugs would be practically limited to a single
family. In case of infested hotels, rooming houses, sleeping
cars, boats, etc., conditions are ideal for the spread of disease by
bugs, and it can hardly be doubted that it is in such places that
most of the damage is done.

One of the first accusations against the bedbug as a disease
carrier was made by Patton, of the British Medical Service in
India, who in 1907 brought evidence against this insect as a
-earrier of Indian kala-azar (see p. 79). Patton followed what
he believed to be developmental stages of the parasite of kala-
azar, a species of Leishmania, in the gut of the Indian bedbug,
Cimex hemipterus (rotundatus). Subsequent investigations, es-
pecially recent ones by Cornwall, have shown that infection of
bedbugs by feeding on kala-azar patients is very rare, and that
the bugs cannot, apparently, transmit the infection either by
biting or by means of infected feces. The rare infectivity of
bugs which have fed on kala-azar patients, however, may be
correlated with the fact that the kala-azar parasites are rare in
the peripheral blood. As pointed out by Price and Rogers,
even if only a small per cent of bugs become infective, where
they are as numerous as they are in the coolie huts in India,
‘they would be able to spread the disease successfully. Donovan
believes the kala-azar parasites may utilize the Malay bug, 7'r-
atoma rubrofasciatus (see p. 381), as an intermediate host, but
recent work is tending to throw doubt on the necessary in-
strumentality of any insect in transmitting the disease. Bed-
bugs have also been associated with another Leishmania disease,
oriental sore, but it is doubtful whether the bugs act as more
than mechanical disseminators of the parasite, if at all. Yaki-

378 BEDBUGS AND THEIR ALLIES

moff in Turkestan and Cornwall in India were unable to infect
bedbugs with parasites of oriental sore even when the bugs were
fed directly on the ulcers. On the other hand, the fact that one
species of Cimex, C. pipistrelli, transmits a trypanosome disease
of bats would lead one to suspect their ability to transmit a
Leishmanian disease, since the two groups of parasites are
certainly near relatives. Several workers have incriminated
bedbugs as carriers of European relapsing fever, especially in
Serbia and in the southeastern part of Europe, but there can be |
little doubt but that lice are the normal transmitters of the
European as well as the North African form of relapsing fever.
In Moscow, for instance, Bayon found that relapsing fever was
practically unknown among the better class of people who were
personally clean, even though living in bug-infested quarters,
whereas the fever was very prevalent among the lower classes,
most of whom were lousy, even though they were kept in hos-
pitals where no bugs existed. On the other hand, Hagler, who
worked with the American Red Cross expedition in Serbia in
1915, points out that while typhus disappeared with the exter-
mination of lice, relapsing fever continued to develop in the
Belgrade hospital until the latter was fumigated for bedbugs.
The Indian bedbug, C’. hemrpterus, is believed by some workers
to be a common transmitter of Indian relapsing fever, though
evidence points strongly to the instrumentality or lice and ticks
in spreading the disease. Spirocheta carteri, the organism of
Indian relapsing fever, has been observed to remain alive for
from four to seven days in the alimentary canal of bugs which
have fed on infected monkeys, but bugs seldom become infected

from human cases. |

As remarked elsewhere, bedbugs have been found capable of
acting as intermediate hosts for the trypanosome, 7’. cruzi, of
Chagas’ disease, but they usually remain infective for a much
shorter time than do bugs of the genus Triatoma. Bedbugs have
been found capable of transmitting the infection to guinea-pigs
in from 21 hours to 77 days after an infective feed.

That bedbugs may act as mechanical spreaders of various
diseases is unquestionable. Experiments show that the bacilli
of bubonic plague can develop in the gut of bugs, though more
slowly than in fleas, and with a much higher mortality for the
bugs. That they may act as transmitters of the disease is quite

TRIATOMA 379

certain, and bugs have been found to remain infective for 48
days if they did not early succumb to the disease. Leprosy also
ean probably be spread by bugs in a mechanical manner, and it
is reasonable to believe that such diseases as tuberculosis and
syphilis may likewise be carried by them.

Other Parasitic Bugs

Most of the other true bugs which may be looked upon as
normally human parasites belong to the family Reduviide. This
is a large family of rapacious bugs, many of them bright colored,
which are especially numerous in the tropics. Most of them
prey upon other insects, but nearly all of them produce painful
wounds when they bite man. Nearly all are active runners and
good fliers.

Triatoma. — By far the most important species are the mem-
bers of the genus Triatoma (Conorhinus), popularly known as
cone-noses, “‘ big’? bedbugs and by numerous local names.
There are about 40 species, most of them in South and Central
America. T'. sanguisuga of southern United States is the well-
known ‘‘ Mexican bedbug.”’ It is a bug about one inch in length
with a flat, dark brown body, the edges of which, not covered by
the wings, are marked with pinkish bars. The long conical head
is furnished with a strong beak. Its bite, like that of others of
the family, is very painful and causes swelling, sometimes fol-
lowed by effects which may last a year.

The salivary secretion is evidently very poisonous and not
unlike snake venom in the extensive swelling and irritation which
it causes. The adult bugs attack not only man but other mam-
mals also, while the nymphs often annoy chickens. Unlike the
bedbug this insect can fly, and will readily enter rooms at night
to attack sleepers unless screened out. The eggs are white,
oval objects when first laid, soon turning yellowish and then
brownish; they are laid in small batches under logs or stones
outdoors. They hatch in about 20 days into young bugs which
probably prey very largely on other insects. After four moults
the insect reaches the adult winged condition in which it is
most troublesome as an invader of houses. This species is re-
placed by T. protracta in southwestern United States.

The most important species of the genus are those which are

380 BEDBUGS AND THEIR ALLIES

naturally infected with Trypanosoma cruzi in South America.
On account of its domestic habits, Trzatoma megista (Fig. 168)
is the most important species in the transmission of the disease
to man. This bug is a large, handsome, black and red insect,
locally known as the “ barbeiro,’’ which infests the dirty thatched
houses of the natives in the state of Minas Geraes in Brazil.
It is nocturnal in habit, coming forth from its hiding places in
the thatch of the roof or in the débris of the floor to feed upon
its human victims after the man-
ner of bedbugs. The bugs are
so active and hide so rapidly
when a light is produced during
their foraging in the dark that
they can seldom be caught. The
details of the development of the
trypanosome of Chagas’ disease
in this insect and the relation
of the insect to the disease are
described in Chapter VI, p. 110.
Torres believes the bugs almost
invariably become infected by
feeding on infected vertebrates,
since T'riatoma does not devour
excrement of its own species,
or @ as does the allied Rhodnius pro-
\ S y/ 9 lizus, and cannibalism is rare

among these bugs, except in young
larvee which sometimes feed on
each other.

The life history of the barbeiro is quite like that of other
members of the genus, except that the eggs are laid in or about
human habitations. The eggs hatch in from 20 to 40 days and
the young pass through five moults to reach maturity, the whole
life cycle occupying about a year. The females begin depositing
eggs about a month after the last moult. These insects suck
blood at intervals of from four days to several months.

A number of other South and Central American species of
Triatoma have been found to harbor Trypanosoma cruzi or a
species indistinguishable from it. Triatoma geniculata, which
inhabits the burrows of the armadillo and various rodents, is

Fig. 168. The “barbeiro,” Tria-
toma megista. X14. (After Chagas.)

TRIATOMA 381

known to infect these animals in nature, and the armadillo is
possibly an important reservoir of the disease. Triatoma chagasi
which had fed on a rodent known as the “ moco,’”’ Cerodon
rupestris, in an uninhabited desert region was found to be infected.
T. vitticeps, occurring near Rio de Janeiro, T. sordida of Sao
Paulo and T. dimidiata of San Salvador in Central America
have been found infected with trypanosomes thought to be iden-
tical with the species causing Chagas’ disease, and these species
have been shown to be capable of transmitting the infection to
guinea-pigs. In Argentina, as well as throughout most of
Brazil, T. infestans, the vinchuca or “ great black bug of the
Pampas,” described by Darwin in his ‘‘ Voyage of a Naturalist ”’
as a vicious human pest, has been found to harbor a similar
trypanosome, but whether or not Chagas’ disease exists in
Argentina is still in doubt. T. protracta of southwestern United
States has been shown recently by Kofoid and McCulloch to
harbor a trypanosome which exhibits only slight differences from
Trypanosoma cruzi, and, as intimated by the discoverers, may
possibly be merely a variety of the same species though named
by them T’. triatome. The widely distributed TJ. rubrofasciata
was shown by Neiva to become infected with trypanosomes after
feeding on an infected guinea pig. From all this evidence, and
from the fact that other species of bugs of different genera and
families, including the bedbugs, are experimentally susceptible
to the infection and capable of transmitting it to rodents, it is
possible that all the species of T’riatoma and allied genera in South
and Central America may be potential transmitters of the in-
fection. Cannibalism is common among many of these bugs,
and may make possible a direct spreading of trypanosome in-
fection from bug to bug.

The “ Malay bug,” 7. rubrofasciata, of tropical Asia and some
parts of Africa and Madagascar is a closely allied species. With
its huge proboscis it produces a nasty sting which is followed in

a few minutes by acute pain and swelling. Although it feeds on
-man by preference, it attacks a number of other mammals and
even insects. Large nymphs or adults, which are an inch or
more in length, are said to consume about one ce. of blood at
a meal, and they feed at intervals of from three to six days. The
breeding habits are similar to those of other cone-noses. In
the islands of Mauritius and Réunion the stomach and intestines

382 BEDBUGS AND THEIR ALLIES

of this bug have been found to contain trypanosomes in all
phases of development, and. of very variable form, possibly
representing several species. These trypanosomes can be
inoculated into mice and rats and it is suggested that under
certain conditions they or others living in the gut of the bug may
cause disease in man. A number of cases are on record where
irregular fevers have followed the bites of this insect. Since these
fevers were shown to be non-malarial and showed symptoms of
typical trypanosome infection, it is possible that such an infec-
tion may really be transmitted to man by this bug as well as
by its close relatives in South America. It is also possible that
the bug may serve as an intermediate host for the kala-azar
parasite.

Other Species. — Several other species of bugs of this family
occur in Africa. One, Acanthaspis sulcipes, has been thought
to be the possible transmitter of a form of endemic goitre in
tropical Africa. In North America the family is further repre-
sented by the ‘‘ kissing bugs,” of the genus Melanolestes. The
common kissing bug or “ black corsair,” M. picipes, became very
abundant in the United States a few years ago and gave op-
portunity for many startling newspaper stories. It is a large
black bug with reddish marks on the back and legs. Its bite
much resembles that of a wasp, though often much more serious,
occasioning more than local symptoms and even vomiting.
Allied bugs of the genera Reduvius, Rasahus
and Melanolestes occur in the warm parts of
North and Central America, and frequently
attack man and other mammals, though
their normal food in most cases is insects.

In Venezuela and other parts of northern
South America a very common bug which in-
fests houses is Rhodnius prolixus, a species
7 which has been found capable of transmitting

Fic. 169. Pito bug, T’rypanosoma cruzi. This species is not only
Dysodius lunatus. . Sonate :

Citic Aiceek) cannibalistic in habits, but also devours excre-

ment of other bugs, thus suggesting the possi-
bility of direct dissemination of trypanosomes from bug to bug.
Of other families, there are many bugs which occasionally attack
man but few which commonly do so. One which is worthy of
mention is the malodorous pito bug, Dysodius lunatus (Fig. 169),

FUMIGATION 383

of South America, belonging to the family Aradide. It is a
large broad bug which frequents houses and bites severely.

All the species of bugs which infest houses may be destroyed
by the fumigation methods described below, but all but the bed-
bugs must be kept out by screening, since they are not handi-
capped in their migrations by degeneration of the wings.

Remedies and Prevention

Prevention of “ bugginess,”’ at least in the case of bedbugs,
consists chiefly in good housekeeping, but occasional temporary
infestations are likely to occur in almost any inhabited building.
A number of remedies for bugs have been advocated, of which

the best is undoubtedly fumigation with hydrocyanic acid gas,
as described below. Sulphur is also valuable for fumigation but
is not so harmless to household goods as is hydrocyanic acid gas.
When the infested parts of houses or rooms can be easily located,
good remedies are kerosene, gasolene, turpentine or other coal-tar
products painted into all the infested cracks and crevices, es-
pecially in the woodwork of beds. An effective remedy of this
nature is a mixture of one ounce corrosive sublimate, two cups_
alcohol, one-half cup turpentine. These substances should be
applied several times at intervals of a week in order to destroy
newly hatched bugs. Some housekeepers take infested beds
apart and pour boiling water into the “ buggy” parts, thus
effectually killing both bugs and eggs in the bed but this does
nothing against bugs which may hide elsewhere than in the bed.
Bedbugs have a number of natural enemies, among which may
be mentioned especially cockroaches, red ants and large preda-
ceous bugs, but all of these are pests themselves, and are, there-
fore, hardly to be encouraged as bedbug hunters, efficient as they
might be in this capacity.

Fumigation

Hydrocyanic Acid Gas. — Of the remedies for bugs mentioned
above, fumigation with hydrocyanic acid gas is the most effective.
This gas can be used with good success for fumigation of houses,
mills, granaries, greenhouses or any other closed structure,
against any kind of insect pest. But since the gas 1s extremely

384 BEDBUGS AND THEIR ALLIES

poisonous not only to insects but also to other animals and to man,
its use must be accompanied by great care and precaution. A
few deep breaths of the gas is sufficient to cause asphyxiation.
On the other hand it has great advantages in that it is not in-
flammable or explosive, and, unlike sulphuric fumes, does no
damage to dry foods or to household goods, except to tarnish
nickel slightly. Wet foods may absorb some of the gas and
should be removed before fumigation. Care should also be
taken that there is no possible avenue of escape for the gas into
adjoining rooms or houses which are occupied. The character-
istic peach-kernel odor, however, makes its detection easy, thus
removing danger of asphyxiation without warning.

The gas is generated by the action of sulphuric acid on potas-
sium cyanide. The. procedure as advised by Herrick is as fol-

lows: . Estimate the number of cubic feet in the room or house |

to be fumigated, and allow one ounce of potassium cyanide to
every 100 cubic feet. Make the room or house as near air tight
as possible, stopping all the large openings such as fireplaces and
chimney flues with old rags or blankets. Seal cracks about win-
dows and doors with strips of wet newspaper. Such strips when
thoroughly wet can be applied quickly and effectively over cracks
and will stick tightly for several hours, and can be removed easily
after the operation. While the room is being made tight some-
one should measure out the required ingredients for fumigation,
allowing one fluid ounce of crude sulphuric acid and three fluid
ounces of water to each ounce of potassium cyanide. The water
first should be poured into a stone crock holding two gallons or
more, 7.e., large enough so that the reacting fluid will not spatter
on floors or carpets. The croek had best be placed on several
thicknesses of newspaper or on an old rug or burlap sack. The
required amount of sulphuric acid should then be poured slowly
into the water. Never pour the water into the acid. The cyan-
ide should be weighed out and put into a paper bag beside the
jar. All articles which might suffer from the gas or which will
be needed before the operation is over should be removed from
the room. When everything is ready the operator, holding his
breath, should drop the paper bag of cyanide gently into the
acid jar, and walk out shutting the door behind him. The time
required for the acid to eat through the paper bag in order to

reach the cyanide gives ample time to leave the room before the

1
‘
)

HYDROCYANIC ACID FUMIGATION 385

steamlike gas arises. If preferred, however, the paper bag may
-be suspended by a string passing through a screw eye in the
ceiling and through the key hole of the door (Fig. 170). The
operator may then lower the bag into the jar after leaving the
room. When stringing a room in this manner, care should be
taken not to place the acid jar under the bag until everything is
ready. The fumigation should extend over a period of five or
six hours at least, a good method being to start the aan
toward evening and let it run
all night. Better results will
be obtained at a temperature
of 70° F. or above, than at
a lower temperature.

Two or three hours after
the doors and windows have |
been opened the gas will have
disappeared sufficiently to
allow safe entrance into the aye :
room, though it should not gyante acid gas fumigation from Le
be occupied until the char- The bag of cyanide can be lowered into the

ae . crock of sulphuric acid and water by means
acteristic odor is Sone: The of the string. (After Herrick.)
contents of the generating
jar should be dumped in some safe place and the jar washed
before being used again. When-a whole house is to be fumigated
each room should be made ready as described above and then
set off in regular order beginning on the upper floor and working
downward, since the gas is lighter than air and therefore rises.
Herrick describes clearly and in detail the method which he
has successfully used in the fumigation of large dormitories.
For this account the reader is referred to Herrick’s “ Insects
Injurious to the Household,” pages 448 to 452.

The effectiveness of this method of fumigation against bedbugs
was proven by experiments conducted by Herrick. Bugs. were
placed in perforated pill boxes and wrapped in various manners,
some with three inches of excelsior, some in two folds of a thick
comforter, some in two inches of cotton batting and others in two
folds of a woolen blanket. Others were placed in a cork stop-
pered vial, the cork of which was punched twice with a pair of
curved forceps. In each box several newly laid eggs were en-
closed to determine the effect of the gas on their hatching. In

386 BEDBUGS AND THEIR ALLIES

every case every bedbug was killed and none of the eggs showed
signs of hatching in 12 days. According to experiments made by
the U.S. Public Health Service five ounces of powdered potas-
sium cyanide per 1000 cubic feet is sufficient for the destruction
of bedbugs, four ounces for mosquitoes, two and one-half ounces
for fleas and ten ounces for lice.

Sulphur. — The fumes of burning sulphur, sulphur dioxide,
rank next to hydrocyanic acid gas as both a disinfectant and an
insecticide, but they have a serious disadvantage in their tendency
to bleach fabrics and to tarnish metals, especially in a humid
atmosphere. Sulphur dioxide is considered the most effective
remedy for mosquitoes in cellars, barns, etc., since it kills these
insects even when very dilute, and it has remarkable penetrating
power. The methods of sealing rooms or buildings are similar.
to those described for hydrocyanic acid fumigation. All dyed
goods and metallic articles, however, must be removed or covered
with vaseline. Two pounds of sulphur is used to 1000 cu. ft.,
more if the building cannot be tightly sealed. The sulphur is
placed in some suitable dish with a little wood alcohol poured on
it to make it burn more readily. In order to avoid danger of fire,
the dish of sulphur should be placed on bricks or in a tub of shal-
low water before igniting. After two hours the place may be
opened and ventilated.

Other Fumigants. — Another effective insecticide is the vapor
of carbon bisulphide, a poisonous gas which is not nearly so
virulent as hydrocyanic acid gas. As its vapor is heavy it
settles rapidly. Its effect on many insects is less certain than in
the case of the hydrocyanic acid gas and it has the additional
disadvantage of being both inflammable and explosive. Re-
cently cresyl or creolin, a very volatile substance, has come into
favor as a fumigating medium, especially for destroying mos-
quitoes. It is not injurious to higher animals in the strength
used (125 ec. to 1000 cubic feet), does not injure household goods
and is destructive to all exposed insects. It is volatilized by
means of an alcohol lamp. Cresyl does not, however, have the
penetrating power of hydrocyanic acid gas or sulphur, and is
therefore of less value for such secretive insects as bedbugs,
though highly valuable for exposed insects, such as mosquitoes,
since they may be destroyed without having the rooms vacated.
Formaldehyde, though a valuable disinfectant, 7.e., active in
the destruction of microérganisms, is not an effective insecticide.

CHAPTER XXIII
LICE

ALTHOUGH the disrepute of human lice has grown with civiliza-
tion and with the knowledge that lousiness and cleanliness are
incompatible, lice are even yet among the most important of
external human parasites. In former times the louse apparently
was not an object of disgust and loathing even among the better
class of people. In Herrick’s entertaining book, ‘‘ Household
Insects,” the following quotation from Hooke, an English zodélo-
gist of the 17th century, is given concerning the head louse.
“ This is a creature so officious that ’twill be known to everyone
at one time or another, so busie, so impudent, that it will be in-
truding itself into everyone’s company, and so proud and as-
piring withall that it fears not to trample on the best, and affects
nothing so much as a crown; feeds and lives very high, and that
makes it so saucy as to pull anyone by the ears that comes its
way, and will never be quiet till it has drawn blood.”

Unfortunately, even at the present time, and in the face of
present knowledge concerning the role of lice in the spread of
disease, there are many individuals, many communities and even
some races which make no effort to exterminate them. Still
more unfortunate is it that there are many people who of neces-
sity must associate with these unwelcome companions. In
logging camps, jails, ships, railroad camps, etc., where close
association with people who are dirty by nature is unavoidable,
lice very often become prevalent. Most of all, however, are
lice associated with war. The deadly typhus fever, which has
ravaged the armies of almost every war in the history of the world,
as far as is known, apparently is spread exclusively by lice. These
parasites are the guerillas of war; they bring suffering and death
not only to armies but also to the innocent non-combatant popu-
lation of the war-stricken countries through which the armies
have passed. This phase of the subject will be discussed in more

detail under the section on “ Lice and Disease.”’
387

LICE

388

4,
!
‘
'
‘
'

dp sal.di en upli

Fic. 171. Mouthparts of a body louse; A,

longitudinal section through head; B, mouthparts -

from sac under pharynx and cesophagus; buc. t.,
buccal tube; m., mouth cavity; ph., pharynx; ces.,
cesophagus; retr. sac., retractile sack for mouth-
parts; prot. m., protractor muscles of pharynx;
ret. m., retractor; dil. m., dilators; d. p., dorsal
piercer; sal. d., salivary duct; v. p., ventral piercer;
v. pl., ventral plate =labium (?). (Adapted from
Harrison.)

Fig. 172. Head of bird louse (from golden
eagle); ant., antenna. Note breadth of head as
compared with thorax, a feature which readily
distinguishes bird lice from sucking lice.

General Structure. —
Lice are small wingless
insects constituting the
order Anoplura. They
were formerly classified
as a suborder of the
Hemiptera or true bugs,
but recent studies have
shown the erroneousness
of this grouping. The
mouthparts are adapted
for piercing and sucking.
The piercing apparatus
(Fig. 171B) consists of
four needle-like organs,
one of which is the deli-
cate salivary duct, which
can be withdrawn into
a little pouch under the
pharynx (Figo i7iea
This type of mouthparts
readily distinguishes the
true lice from the bird
lice, which constitute
the order Mallophaga
(Fig. 172). In the latter
there are nipper-like
mandibles fitted for bit-
ing instead of sucking,
and these parasites feed
only on hair, feathers,
etc., and not at all on
blood. In other respects
the sucking lice and bird
lice show a considerable
resemblance to each
other, and are now gen-
erally believed to be

closely related. The feet of the true lice are armed each with a
very large curved claw, quite grotesque in appearance in some

oe ve a

‘BODY LOUSE 389

species, which closes back like a finger against a thumblike pro-
jection of the next segment of the leg (Fig. 173). There are not
even rudiments of wings.

The body of a louse is clearly divided into head, thorax and
abdomen (Fig. 174). The thorax is always broader than the
head, a characteristic
which distinguishes at a
glance a true louse from
the broad-headed bird
louse (Fig. 172). The
abdomen is divided into
segments, six to eight of
them in the human spe-
cies; the terminal one

Wis
ib i.
fy! jt

= 4 . e fi!" i

is indented in the female, NPS | a 77a

but is rounded in the Se ee A
Sew

male with the large SSeS
spikelike copulatory or-

gan often projecting at Fie. 173. Front leg of body louse, Pediculus
ep 300), Formers. Note ure clay gud thumbite op
The digestive tract, as in

most other blood-sucking insects, is furnished with capacious
pouches branching from the stomach, which serve as food reser-
voirs. The tracheal system is well developed and opens by

_ prominent spiracles on the sides of the abdominal segments.

Most species of lice are quite closely limited to a single host,
and sometimes even genera are thus limited. Kellogg has
suggested that the evolutionary affinities of different birds and
mammals may be demonstrated by the kinds of lice which in-
fest them. There are only three species which infest man, each
selecting a different portion of his body as a habitat; these are
the head louse, Pediculus capitis, the body louse, Pediculus

humanus (vestmenti) and the crab louse, Phthirius pubis. The

genus Pediculus is peculiar to man and the apes, with the ex-
ception of one species which infests the monkey, Ateles. The
genus Phthirius is represented only by the human species.

Body Louse. — The body louse (Fig. 174) is by far the most
common, as it is the most important, louse infesting man. It

very closely resembles the head louse, but it is larger, more ro-

bust and less active. Fertile offspring result from hybridization

390 | LICE

of these two species. The females, which are somewhat larger
than the males, reach a length of about one-eighth of an inch.
Due to their dirty white or grayish color these lice are familiarly —

(as

known as ‘‘ gray-backs.’”’ This species is known to be instru-—
mental in transmitting both
typhus fever and European
relapsing fever.

As the name “body louse”
implies, this species inhabits
the trunk rather than the
head. The German name
‘“ Kleiderlaus”’, meaning
“clothes louse’’, isstill better,
since this louse has so far
adapted itself to its host as
to have broken away from
the custom, prevalent among —
all other species of lice, of
living in the hair of the body,
and to have established the
habit of living on the cloth-

NZ ing. Just when, in the proc-

Fic. 174. Body louse, Pediculus humanus, ess of our evolution from a
male; ant., antenna; e., eye; p., penis; sp., > A
spiracles; th., thorax. X 25. hairy ancestor, this louse

shifted its position from the
waning hair to the more and more habitually worn clothes would
be interesting to know. Not unlikely both this louse and the
closely allied head louse have evolved from a species which once
roamed the hairy bodies of our forefathers, each species coping
with the unfavorable circumstance of the developing hairless-
ness of its host in a different way, the more conservative head
louse withdrawing to the fine hair of the head; the body louse
adapting itself to living on the clothing.

A person infested with thousands of body lice may remove his
clothing and find not a single specimen on his body. An exami-
nation of the underwear will reveal them adhering by their long
claws to the surfaces which were next to the body. Here they
live and lay their eggs, leaving the clothing only long enough to
suck a meal of blood, even then usually adhering to the clothes
by their hind legs.

LIFE HISTORY OF BODY LOUSE | 391

Habits and Life History. — Although there has been very
close association between lice and human beings probably since
man’s first appearance in the world, little definite knowledge
concerning the life history of any of the three species was ob-
tained until recently. The importance of lice in the great anti-
German war has stimulated much research on them.

One of the first experiments with the breeding of body lice was
made by the great zodlogical pioneer, Leeuenhoek, in the 17th
century. He placed two female lice in his stocking and tied
them in; after six days he opened the brood chamber and found
a cluster of 50 eggs beside one
of the lice and another cluster
of 40 eggs, probably laid by
the other insect which had
escaped. He found 50 more
eggs in the remaining louse.
He left the eggs in his stocking
ten days more, when he dis-
covered 25 young lice, where-
upon he abandoned his experi-

ment in disgust.

The eggs of lice, commonly A
called mts,” are oval, whitish Fic. 175. <A, egg of head louse, Pedi-
objects fitted with alittle lid atu coms: oe, of body, Jou,
the larger end, through which

the hatching takes place. The eggs of the body louse are about
one mm. (3s of an inch) inlength. They are glued to the fibers of
clothing (Fig. 175B) especially along seams or creases, although
in all other lice the eggs are glued to hair. Under experimental
conditions the body louse will sometimes lay eggs on hairs, but
it nearly always selects the crossing point of two hairs and shows
less skill in attaching the eggs. The body louse shows a marked
‘homing ” instinct in laying her eggs and shows a strong desire to
lay eggs where others have been laid, until clusters of from 50°
to 75 or more have been formed. |

According to recent experiments by Sikora in Germany and
Bacot in England, the number of eggs laid by the single female
body louse may frequently reach 200 or more. Bacot obtained
295 eggs from a single specimen in one case. During the first
three or four days only two to four eggs are laid daily, the num-

My.

“wp fibres

\ S
BN
Ser
A |
Bi ~<a
Be
re

392 LICE

ber gradually rising, until after a week or so of egg-laying seven
to ten or more eggs may be laid each day. A day or two before
the end of egg-laying and the death of the louse the daily number
drops again. Eggs are laid whether copulation has occurred

or not, but in no case have unfertilized eggs been observed to

develop. One copulation is not sufficient to fertilize all the eggs,
but fertile eggs may be laid for at least 20 days after a single
copulation. According to Sikora, copulation normally takes
place at intervals of from one to three days. Egg-laying ceases
at temperatures below 77° F. and a daily exposure to a tempera-
ture of 60° F. for only two or three hours causes a ete falling
off in egg production.

According to Sikora the eggs hatch in about six days at the
optimum temperature of 95° F. At a temperature of 77° F.
the incubation period is prolonged to 16 days, whereas at 68°,

lowered from 42° to 60° F. during the latter part of the night, or

at a constant temperature of 60° F., no hatching at all takes place.
At temperatures above 95°, also, the eggs suffer a high mortality
probably due to the difficulty in obtaining proper conditions
of humidity rather than to the direct effect of the heat itself.
Either excessive humidity or complete drying is fatal to the
eggs: It is evident that in winter the laying off of the clothing
at night in a cold room or the leaving of mattresses or bed clothes
in the daytime is sufficient to prevent the laying of eggs or the
hatching of eggs already laid, thus resulting in the extermination
of the lice.

The newly hatched lice are almost perfect miniatures of the
adults, and are ready to feed almost as soon as they emerge from
the egg; in fact, they usually die in less than 24 hours if not
allowed to feed, though the adults can survive as much as five
days of starving. According to Sikora, the rapidity of the
development of lice is dependent on temperature and on amount
of food. At a temperature of 95° F. and with as many daily
feeds as would willingly be taken, namely six, the lice pass through
their first moult in three days, the second in five or six days, and
the third, which brings them to maturity, in eight or nine days.
Reduction of daily feeds to two increased the period of develop-
ment to nine or ten days, whereas reduction of temperature to
75° F. by day and 95° F. by night, with two daily feeds, prolonged
the development to from 13 to 15 days. 3

|
|
:
|
:

*
—————oa ss Le le

HABITS OF BODY LOUSE 393

According to observations by Sikora, copulation may take
place within ten hours after the last moult has been passed, and
Bacot also observed cases in which copulation took place on the
day of reaching maturity. Egg-laying begins in from one to four
days after the final moult and continues at the rate described
on the preceding page until the death of the insect. The aver-
age length of life for the females is about 35 or 40 days, and
probably a little less for the males.

According to Bacot, hungry lice do not show a tendency to
wander on the skin, but proceed to pierce the skin and suck blood —
at once. Nor do they shift to make another stab, as fleas fre-
quently do, if the first stab does not immediately furnish blood.
They apparently place great reliance on the power of the sali-
vary secretion, which is poured into the wound, to dilate the
capillaries by its irritation and thus cause a flow of blood. Some-
times blood is not drawn for several minutes after the puncture
is made. Bacot states that lice fill their crops in from two to
15 minutes, but Sikora observed that adult lice, if fed only twice
daily, sucked for an hour to an hour and a half, and, if left in con-
tact with the skin for several hours, have a tendency to pump
blood intermittently with short pauses, meanwhile voiding ex-
crement containing undigested blood corpuscles. Sikora also
observed that hungry lice placed on the well-shaved skin of a
puppy made repeated attempts to draw blood without success,
and also that dog lice, Hematopinus ventricosus, tried in vain to
draw blood from the human skin. He concludes therefrom
that not only is it necessary for lice to penetrate the skin with
their piercing apparatus, but that they must also produce an
irritation by means of a salivary secretion, apparently specific
in its action for certain kinds of blood, in order to cause blood
to flow from the tiny puncture. Apparently the salivary se-
cretion deteriorates in unfed lice, for though starved lice may
still be able to drive their piercing apparatus into the skin, it
takes them three times as long to draw blood.

__ A fact of far-reaching significance, if found to be commonly true,
has recently been reported by Hall in Texas. This author
found that a female body louse taken from a Mexican baby,
when placed in a bottle with a head louse taken from the same
baby, devoured the head louse. Two head lice were then fed
to the body louse daily for three days, and the same louse was

394 LICE

induced to eat crab lice, small black ants, bedbugs, and raw beef.
When body lice were placed in a bottle with head lice, bedbugs,
and a piece of beef, they ate first the head lice, then the bedbugs
then the beef, and finally became cannibals to the extent of the
survival of the fittest! This would readily explain such facts
as that body lice (according to Hall) can be found in empty box
cars used to transport Mexican troops weeks before, and it
would account for louse-borne diseases lying dormant in isolated
places. A freight car once infected with typhus would be a source
of danger for a longer period than the few days a louse can live
without food. However, before insectivorousness can be ad-
mitted as a usual habit of lice in the absence of normal food,
further investigation is necessary.

Digestion is very rapid. An entire two-hour feed may be
digested in from eight to ten hours at 95° F., but digestion is"
slower at lower temperatures and the stomach contents remain
unchanged for ten hours or more at 45° F. or below. At tem-
peratures above 95° F. digestion is even more rapid, but there is
a high mortality.

It is evident from Sikora’s experiments that 95° F. is the op-
timum temperature for the development and reproduction of
lice. The absence of lice from hot countries — observable in
Mexico, for instance, where they are abundant on the central
plateau above 5000 to 6000 feet, but absent from the hot coastal
strips —is apparently not due to the high temperature but
probably to the disastrous effect of profuse perspiration and
consequent excessive humidity between the clothes and skin.

The bites of the body louse produce itching red pimples which
become covered by a brownish crust, the results of the action
of the toxic salivary juices. Scratching produces characteristic
white scars, surrounded by brownish pigment; in fact, large
areas of the skin may take on a mottled bronze color. The color-
ing of the skin is said to be due to the stimulation of pigment
formation in the skin by toxins secreted by the louse. Many
individuals develop an insensibility to the bites of lice, a fact
which probably explains the indifference of some communities —
to them as, for instance, the people of Russian Poland.

Head Louse.— The head louse, Pediculus capitis, is very closely
related to the body louse, and is, in fact, thought by some workers
to be a mere variety of the latter. Aside from its different habits,

HEAD LOUSE 205

however, it differs from its relative in a number of respects. It
is smaller in size, has only seven instead of eight abdominal seg-
ments, is quite distinctly festooned along the sides, due to con-
strictions at the joints between the segments, and the abdomen
is hairy instead of naked. There are other minor differences
in form, but both species vary to such an extent that specimens
are not always easy to identify.

The head louse although usually preferring the fine hair of the
head as a habitat occasionally wanders to other parts of the body
as well. It is found in every part of the world.. Different vari-
eties are said to occur on the different human races and to vary
in color with the color of the skin on which they live. The
lice which live on the white race are pale gray with a dark line
along each side of the abdomen, those on negroes are blackish
or brown, on Hindoos smoky brown, on Japanese and Chinese
yellowish, and on American Indians dark reddish brown. What
a wonderful case of protective coloration, except that, as in so
many other cases of so-called protective coloration, there is no
practical protection. A negro is as likely to scratch out a black
louse as a white one!

As in the case of the body louse reproduction is very rapid but
the egg production is lower, due to the smaller capacity of the
body, even taking into consideration the slightly smaller size
of the eggs. The course of development is practically the same
in both species. The average number of eggs, according to
Bacot’s observations, is from 80 to 100. Only one mature egg
can be developed in the louse’s body at a time, but the suc-
cession of them is so rapid that eight or ten may be laid in a
day. Each egg or “nit” is glued by the lower end to a hair
(Fig. 175A), the favorite “‘ nests” being the vicinity of the ears.
The young lice hatch in ten or 12 days and reach maturity in
two or three weeks, and are then ready to reproduce again. At
this rate of reproduction, allowing only a 50 per cent hatch, a
single pair of lice theoretically could produce over three-quarters
of a million offspring in the fourth generation, and in the course
of less than three months!

Although the bites of this species are not quite so irritating as
are those of the body louse, yet the frequent piercing of the skin
for a gory meal results in much scratching. Often the bites
swell into pimples which may bleed when scratched, or which

396 LICE

form a little pus, sufficient in very negligent individuals to make
the hair mat together. According to Stiles, if this is allowed to
run on, a regular carapace may form, called trichoma, in which
fungous growths may develop, and under which the lice abound,
and the head may exude a foetid odor.

Crab Louse. — The crab louse, Phthirius pubis (Fig. 176), is
quite distinct from the other two species of human lice. It has
a very broad short body with long, clawed legs, presenting the
general appearance of a tiny crab, from which it derives its name. ~
The first pair of legs are smaller than the others and do not

Fig. 176. Crab louse: -Phihirine puoi om ee

possess a “thumb” in apposition to the curved claw. The
abdomen is composed of six segments, and is markedly festooned
along the sides. This louse is grayish white in color, with dark
shoulder patches and slightly reddish legs. ‘The females are
about 75 of an inch in length, the males somewhat smaller. The
favorite haunts are the pubic regions and other parts of the body
where coarse hair grows, as in the armpits and in the beard and
eyebrows. Unlike the other human lice this species is almost
exclusively confined to the Caucasian race.

The females produce from ten to 15 eggs and glue them, one
at a time, to the coarse hairs among which they live. A number

LICE AND DISEASE 397

of eggs may be glued to a single hair, and often at some distance
from the skin. The eggs hatch in six or seven days, and the young
become sexually mature in about 15 days. This species, even
under favorable conditions, will live apart from its host only
ten or 12 hours. The eggs are said not to develop except at
temperatures between 68° F. and 86° F., which are approxi-
mately the temperatures to which eggs attached to hairs beneath
the clothing would be exposed.

Lice and Disease

The role of lice in the spread of disease has long been sus-
pected in an indefinite and uncertain way. Only recently, and
at the cost of the lives of several great investigators, has the
whole portentous truth regarding the transmission by them of
typhus and relapsing fever (North African and European types)
been brought to light. Foremost among the investigators of
louse-borne diseases stands the name of Nicolle and his associates,
who in 1909 proved that typhus fever could be transmitted by
the body louse, and in 1913 that the Algerian type of relapsing
fever could be transmitted likewise. Two American investi-
gators, Ricketts and Wilder, working independently of the French
workers, proved in 1910 that the body louse was instrumental
in transmitting typhus (tarbardillo) in Mexico, and in 1912
Anderson and Goldberger showed that the head louse could also
transmit it. Opinions differ as to whether the infection can be
transmitted through the eggs to the lice of the succeeding genera-
tion. : 3
There is every reason to believe that typhus fever is normally
‘transmitted exclusively by lice. Wherever the hording together
of promiscuous crowds of people becomes necessary and when
scrupulous cleanliness, either of necessity or of choice, is not en-
forced, there the lice will thrive and sooner or later the dread
disease will break out. The cause of typhus fever* is not yet.
absolutely certain. A bacillus discovered by Harry Plotz of
New York in 1914 has been found to be intimately connected
with the disease, and is believed by many to be the actual cause
of it, though others believe that another organism will be found
to be associated with it. The bacillus has been obtained from
cultures made from lice taken from typhus patients. Nicolle

* See footnote on p. 73.

398 LICE

and his fellow workers have shown that lice which are fed on in-
fected patients do not become infective until the eighth and usu-
ally the ninth or tenth day afterward. The same results were
obtained both in experiments with crushed lice and with the
excrement of the lice.

Typhus is a disease which has a tendency to remain in a mild
epidemic state in many parts of Europe and North America,
ready to burst into flame when opportunity comes, giving rise to
terrible epidemics. Epidemics usually occur in winter and in
cold countries, due to the huddling together of people in warm,
poorly ventilated’ houses where lice thrive, and where the un-
hygienic conditions lower the vitality of the people. Typhus
has followed in the wake of nearly every army which has ever
been assembled. During the present great European war typhus
has been largely absent from the armies and population of
Britain, France and Germany, due solely to the intensive anti-
louse measures which have been enforced by these countries.
The less scientific and less cleanly nations have suffered enormous
losses. An epidemic began in Serbia in January, 1915, among
some Austrian prisoners who were allowed to disperse all over
the country. The disease spread with them, and for a time raged
almost at will in that war-stricken country. The majority of
the small number of Serbian doctors were affected, no sanitary
measures for the suppression of lice were understood or enforced,
and no adequate accommodations for the sick could be provided.
The epidemic continued to rise, and reached its height in April,
when there were estimated to be 9000 deaths per day. It was
largely through the heroic efforts of the American Red Cross
expedition that the epidemic was finally checked, after having
destroyed over 150,000 people. In December, 1916, another
epidemic was reported to be raging in Syria with over 1000 deaths
per day.. Milder epidemics have occurred in Austria, Bulgaria
and Russia, all countries where science and cleanliness have
not been worshipped as they have in the greater nations of
Europe. Mexico has suffered also; in December, 1915, 11,000
cases of typhus were reported in Mexico City and its environs.
The disease is endemic and quite prevalent at all times on the
high plateaus of Central Mexico, where it is known as “ tabar-
dillo.”” Among the American troops along the border and in
Mexico, however, no typhus exists, due to the constant and in-

TRANSMISSION OF RELAPSING FEVER 399

tensive fight against lice. It is practically certain that no nation
which profits by the discoveries of science will ever again be
cursed by a great typhus epidemic.

The réle of lice in the transmission of the European and North
African form of relapsing fever has long been suspected but was
not proved until 19138, when Nicolle and his fellow-workers
scientifically demonstrated it in Tunis and Algeria. Noting
that the louse was the only constant factor affecting the occur-
rence of the disease, these French workers undertook extensive
experiments which resulted in proving that the body louse, and
probably also the head louse, serves as a medium for the develop-
ment of the spirochetes of relapsing fever, and that these insects
transmit the disease not by biting but by inoculation of the
wounds which they make with the infected contents of their
bodies when crushed. ~-

Nicolle and his associates also showed that sometimes, at least,
the spirochetes, probably in the granule stage, are hereditarily
transmitted through the eggs to the young of the next generation,
as is the case with the African relapsing fever parasites in the
tick. Experiments on the transmission of the relapsing fever of
Algeria with other parasites such as bedbugs, fleas, biting flies
and ticks were negative. Some observers, however, believe that
in Europe other insects also, notably bedbugs, may be instru-
mental in transmitting relapsing fever. The evidence furnished
by the epidemiology of the disease is, however, very strongly in
favor of lice as the normal transmitters. The Indian form of
relapsing fever is also probably transmitted by lice. Further
details of the development of the spirochetes in the lice are
given in Chapter IV, p. 44.

Being transmitted by lice, relapsing fever shows the same pe-
culiarities of occurrence as does typhus; epidemics always rage
fiercest in winter, and usually break out during war times.
Serbia, which was so stricken by typhus, was held in the grip
of an epidemic of relapsing fever earlier in the war.

Lice may also serve as mechanical transmitters of still other
diseases. The bacilli of bubonic plague have been found alive
in both body lice and head lice taken from victims of the disease,
and both this species and the body louse have been experimen-
tally proved to be able to transmit plague from rodent to rodent
in Java. De Raadt in Java infected rodents with plague by in-

400 LICE

jecting them with ground bodies of head lice taken from plague
patients. The practice among some natives of killing lice by
mashing them against the head of the host, accompanied by the
frequent scratching due to irritation from bites, may well be a
frequent cause of plague infection if there has been any oppor-
tunity for the lice to migrate from an infected to a healthy person.

There is no reason why syphilis could not be transmitted in
a similar manner, especially during the second stage of the dis-
ease, when the spirochetes are present throughout the blood.
The readiness with which spirochetes of other kinds will live in

insect or tick bodies makes it reasonable to believe that the

spirochetes of syphilis might live in the bodies of human lice,
at least long enough to be conveyed from person to person.
Prevention and Remedies. — The prevention of lousiness con-

sists primarily in personal cleanliness. However, no amount

of personal hygiene and cleanliness will prevent temporary
lousiness if there is association with unclean and careless com-
panions. Lousiness and human wretchedness and degradation
have always been companions, but this does not imply that lice
have any inherent abhorrence of a clean body if they can get
access to it. From the nature of their habitats the common
modes of infection of the three different species of human lice
vary somewhat. Any of them will spread by contact or close
association, but each has its own special means of finding new
hosts. The head louse depends largely for distribution on a
promiscuous use of combs and brushes or borrowed hats and
caps, and on the free-for-all trying on of head gear in haberdash-
eries and millinery shops. The body louse is dispersed by cloth-
ing and bed linen and finds fresh hunting grounds by night
migrations from one pile of clothes to another. The crab louse
frequently utilizes public toilets for dissemination. Where men
are crowded together in prisons or war camps lousiness is almost
sure to develop unless particularly guarded against, since some
uncleanly persons are nearly always in the aggregation, and con-
ditions are such that the infestation is given every opportunity
to spread. There are, however, many ways in which lice may
be dispersed among clean people in ordinary life. Stiles reports
a case where a large number of girls in a fashionable boarding
house in eastern United States developed lousiness shortly after
traveling from Chicago to New York in a Pullman sleeper.

PREVENTION OF LOUSINESS 401

In Washington and other cities where negresses do much of the
laundering the family wash is a common source of infestation.
Closely packed street cars, school cloak rooms, unclean rooming
houses — all these and many other means may serve to start
a new colony of lice.

Perfect cleanliness will usually result in their quick elimination.
A shampoo with warm water and soap, frequent baths, clean
underclothes, pressed suits, and other items of personal care are
inimical to the welfare of the unwelcome visitors. Certain
remedies are, however, useful in the quick destruction of these
pests. Head lice can best be destroyed by a thorough washing of
the head with a two per cent carbolic acid solution or a kerosene
emulsion (equal parts kerosene and olive oil). When one of
these remedies has been thoroughly rubbed into the hair the
head should be covered with a cloth. After several hours the
ointment is washed off in warm water and soap and the dead
lice removed with a fine-tooth comb. In long hair this treat-
ment is applied by having the patient lie down with the hair
hanging over the edge of a bed into a pan of the carbolic solution
or kerosene emulsion, the hair being sluiced backward and forward
for ten minutes until thoroughly saturated. The treatment may
have to be repeated after about ten days to destroy lice which
have hatched in the meantime, but usually the eggs are des-
troyed as well as the adult lice. Crab lice can be destroyed best
by the use of mercurial ointment applied to the infected parts,
accompanied by washing with soft soap and warm water. A
close clipping of the hair in the infested regions is the safest and
quickest method of getting rid of the nits.

Eradication of body lice is in some respects aie than that
of other lice, since it is the clothes instead of the body which are
to be treated. Much work has been done since the outbreak of
the war in Europe on testing the effect of various chemicals and
methods of treatment on lice. This problem is recognized as
one of the most important minor considerations in war.

The methods usually employed for getting rid of body lice are
to sterilize the clothes, either by steam, by fumes of carbon bi-
sulphide or sulphur dioxide (if no wool is present), by dry heat of
- 160° F., or by treatment with volatile odorous substances, such as
kerosene, naphthaline, ether, anise oil, oil of turpentine, oil of
eucalyptus or anisol (methylphenylether). The last is a new

402 LICE

remedy reported by Frankel, and is said to stun lice in four
minutes and to kill them in ten minutes. Soaking for one hour
in a 14 per cent cresol solution is said to destroy all lice on clothing.
The eggs are not so easily destroyed as are the adults, but they
succumb to heating, to exposure to carbon bisulphide (100 grams
per cubic meter), or to immersion in any of the oils mentioned
above. Ammonia gas destroys the eggs on clothing in a closed
receptacle. On the Mexican border of the United States a mix-
ture of vinegar and kerosene is used for dipping louse-infested
clothing. The French soldiers are said to have kept largely free
of lice by the simple expedient of having a hot iron run along the
seams of the underwear when laundered, to kill nits.

Preventive measures against lice, simple as they are under
ordinary conditions, often constitute a very difficult problem,

especially in army camps. Common methods employed are the -

treatment of the clothes with odorous or poisonous substances,
the use of underclothes with smooth inner surface, such as silk
or oil cloth, to which lice cannot attach their eggs, or the dusting
of naphthaline powder into the shoes, stockings and underwear.
A substance which has been found most efficient by the British,
and has been used extensively on the western front in France is
the now famous NCI, a powder consisting of 96 per cent com-
mercial naphthaline with two per cent creosote added to increase
the toxicity and to give lasting qualities and two per cent iodoform
to increase the adhesiveness of the powder when dusted on the
inside of the clothing. The shepherd people of the Carpathians
are said to protect themselves against lice by saturating their
underclothes in melted butter which prevents the lice from
fastening their eggs to the fibers of the clothes, and probably the
fatty acids of rancid butter are also directly deleterious to the
pests.

When louse prevention is undertaken on a large scale, as it
has been as never before in the present war, enormous difficulties
are encountered, largely due to the fact that the soldiers, es-
pecially of the less enlightened nations, do not codperate with
the officials. Germany, menaced by louse-borne diseases more,
perhaps, than any others of the principal warring nations, due to

the constant contact of her troops with the less efficiently cared- -

for troops of Russia and of the Baltic nations, has largely solved
the problem by the erection of ‘‘ disinfection stations.” In

!

an oe Ce en a ee ee

eee ee ee ee

. ptatinth ee

DISINFECTION STATIONS 403

October, 1915, there were eight of these on the Polish front,
and more were being built. Through these stations men are
passed as clothes might be passed through a laundry. Enter-
ing at the “unclean side,” dirty, lousy and unhygienic, they
emerge from the “clean side” fresh, clean and free from ver-
min. Each institution consists of eight separate buildings,
grouped around a central power house in which 200 tons of coal
are burned daily to supply steam for disinfection, light, power,
etc. Laundries, kitchens and administrative quarters are also
provided. Each of the eight buildings consists of a clean and
an unclean part, with a chief surgeon in charge, and each has a
capacity of 500 men every eight hours, a total of 12,000 per 24
hours for the entire institution. At the entrance on the unclean
side each man receives a net for whatever apparel he may have,
such as boots, helmets, etc., which must be sterilized by dry heat,
and a smaller net to receive his valuables, such as notebooks,
tobacco, etc. A check number is hung about his neck, and a
similar number placed on his belongings. He is now given a
pair of slippers, and enters a large waiting room where he disrobes,
placing his clothes in another net which has been given him, to
be sterilized by steam. If in need of it he is given a hair-cut and
is then subjected to a fifteen minute shower bath with soap, after
which he is presented with a towel, clean slippers and clean under-
wear. He is then allowed to pass to the clean side of the build-
- ing where he is given his own disinfected clothing, given a meal
and conducted to disinfected railroad coaches. The greatest
disadvantage is the non-coéperation of Russian prisoners, who
by all sorts of subterfuges try to avoid being “ laundered.”
However, Germany has, by this method, practically converted
her whole eastern front into a huge filter to guard against lice
and lice-borne diseases. Without such radical measures Ger-
many could never have kept herself as free as she has from the
diseases of war.

CHAPTER XXIV
FLEAS

Davip Harum says, ‘“ A reasonable amount of fleas is good
for a dog. They keep him from broodin’ on bein’ a dog.” A
goodly supply of fleas might likewise keep man from brooding over
anything deeper than the presence of these fleas, but in many
cases this in itself is a rather serious thing to brood over. Not
only are fleas very annoying pests and a common cause of in-
somnia, but they may also serve as the disseminators of a number ~
of serious human diseases, among which the terrible bubonic
plague stands foremost.

General Structure. — Fleas are insects which are more or less
distantly related to the Diptera or two-winged flies, but which
have become so specialized by their particular mode of life as
external parasites as to necessitate their segregation into a dis-
tinct order of their own, the Siphonaptera. Their bodies are
ordinarily much compressed to facilitate gliding between the
hairs or feathers of their hosts. The head is broadly joined to
the thorax, which is relatively small. The abdomen is large and
much compressed from side to side; it consists of ten segments,
the first seven of which are simple rings, each protected by two
horny plates, a dorsal ‘‘tergum’” and a ventral “ sternum ”
(Fig. 177). The last three segments are modified differently in
the male and female in connection with the sexual organs. In
both sexes the “ tergum ”’ of the ninth segment has a pitted area
covered with little bristles which is called the pygidium, and is
probably sensory in function. All parts of the body are furnished
with backward-projecting bristles and spines which aid the flea
in forcing his way between dense hairs and in preventing him from
slipping backward. The efficiency of these spines is apparent
when one attempts to hold a flea between his fingers. Many
fleas have specially developed, thick, heavy spines arranged
in rows suggestive of the teeth of combs and therefore known as —

ctenidia or ‘‘ combs ”’ (Fig. 179). Such a comb may be present
404

STRUCTURE 405

either along the ventral margin of the head or along the hind
edge of the pronotum (the dorsal plate covering the first segment
of the thorax) or in both places. The presence or absence of
these combs and the number of teeth in them is of considerable
use in identification of species.

The legs of fleas are very long and powerful, and at first glance
seem to possess one more segment than do the legs of other in-

Fig. 177. The Indian rat flea, Xenopsylla cheopis, male. X50. (After Jordan
and Rothschild.)

sects. They really consist of the usual number of segments,
however, but are peculiar in the enormous development of the
first segments of the legs (coxze), which in most insects are quite
insignificant (Fig. 179). The shape of the sternal plate to which
the coxz are attached is suggestive of still another segment.
The great development of the cox as well as of the other seg-
ments of the leg gives unusual springiness and consequently
enormous jumping power. The human flea, Pulezx irritans, has
been observed by Mitzmain to jump 13 inches horizontally and
seven and three-fourths inches vertically. An equivalent jump
for a man of average height would be over 450 feet horizontally
and over 275 feet vertically! The jumping power must over-
come to some extent the disadvantage of winglessness and render
migration from host to host comparatively easy. All the legs

406 FLEAS

are furnished with rows of stout spines and are sea at the
tip with a pair of large stout claws.

Eyes are present in some species of fleas but not in others.
The antennz are short and club-shaped, and when not in use are
folded back into special grooves for them on the sides of the
head (Fig. 178, ant. gr.). The mouthparts (Fig. 178) are fitted
for piercing and sucking. In the normal resting position they ap-
pear to consist of a long jointed proboscis, blunt at the tip, with

vant.
N

ant.gr. ‘ SSS eS eee hee be

4
/

YJ

'

’
j
'

Gten:
proth or. “

Fic. 178. Head and mouthparts of a flea (squirrel flea, Ceratophyllus fasciatus) ;
ant., antenna; ant. gr., antennal groove; cox., coxa of Ist leg; cten., ctenidium;
hyp., hypopharynx; lab. palp., labial palpi, which together form a tube for pro-
tecting the lancets; mand., mandibles; max., maxilla; palp., maxillary palpi;
prothor., prothorax; st. pl., sternal plate of skeleton with which leg is articulated.

a pair of stout triangular flaps-at either side at the base. The
triangular parts are the maxilla and each is provided with a
stout four-segmented palpus, which might easily be mistaken for
an antenna. The proboscis really consists of a pair of segmented
gouge-shaped structures, the labial palpi, which fit together to
form a more or less perfect tube, in which lie three piercing
organs. The latter consist of a pair of thin bladelike mandibles
serrated on each edge, curved at the tip, and provided with a
longitudinal groove, and a single bristle-like organ, the epiphar-
ynx. In piercing the skin of the host the epipharynx first bores

- CLASSIFICATION 407

a tiny puncture, and then the serrated mandibles enlarge the
hole by an up and down sawing motion. As these organs are
sunk into the flesh of the host the labial palpi bend back like a
bow under the flea’s head. The two grooved mandibles, placed
in apposition, form a tube for the outflow of saliva, while the
epipharynx, which is also grooved, forms a tube with the man-
dibles for the inflow of blood. The digestive tract is provided
with a pharynx which acts like a suction pump, and a very large
and distensible stomach.

Classification. — Several hundred species of fleas have already
been described and it is probable that many more species will be
found. Although some authors split the fleas into a consider-
able number of families, it is more usual to recognize only two

’

Fic. 179. Heads of common fleas, showing distribution of ctenidia or ‘‘combs”’;
A, human flea, Pulex irritans, without combs; B, dog flea, Ctenocephalus canis,
with combs on both head and pronotum; C, rat flea, Ceratophyllus fasciatus, with
only pronotal combs.

well-defined families or groups — the Pulicide and the Sarcopsyl-
lide. Theformer family includes all the ‘‘ordinary” fleas, whereas

the Sarcopsyllide is a very specialized group of fleas with a much
shortened thorax, which appears as if mashed between the head

~_ and abdomen, with slender anterior and middle legs, and with

- feeble labial palpi of only three segments. Whereas all of the
Pulicide lay their eggs singly, or in small groups, and develop-
ment of the embryos occurs after the eggs are deposited, in some
of the Sarcopsyllide the eggs, during their early development,
are retained in the abdomen of the female, which swells up to
such a size that the head and thorax appear as a small append-
age at one end of it.

408 FLEAS

The exact identification of fleas, especially if the host is un-
known, is difficult, being based largely on such minute charac-
teristics as relative lengths of different segments of the legs,
number and distribution of spines, etc. Most species of fleas,
however, are quite closely confined to their respective hosts, only
a few species being able to thrive on a number of different hosts.
Some of the commoner species of the fleas which are of most im-
portance to man can be fairly closely identified, if the host and
geographic locality is known, by the presence or absence of the
“combs ”’ on the head and thorax. The common human flea,
Pulex irritans (Fig. 179A), and the Indian rat flea, Xenopsylla
cheopis (Fig. 177), have no combs, the common rat and squirrel
fleas of temperate climates (Figs. 179C and 178) have only the
thoracic comb, while the cat and dog fleas (Fig. 179B) have both
facial and thoracic combs. .

Life History and Habits. — The life history of all fleas is
quite similar. Like the Diptera, or flies, they pass through a
complete metamorphosis,
v.€., undergo a complete
reorganization from larval
to adult form during a
resting pupal stage. The

Fie. 180. Larva of Indian rat flea, Xenop- eggs are oval, whitish in
sylla cheopis. X12. (After Bacot and Ride- hee
SN color and relatively large,

often one-third the length
of the parent flea, and are laid singly, except in the chiggers,
being dropped at random in the fur of the host or in the lairs or
habitations of the hosts. The human flea, for instance, lays its
eggs in the dust and débris in cracks in floors, under carpets,
etc., whereas the fleas of most mammals lay their eggs loosely in
the fur of the host, whence they drop off when the animal shakes
himself or prepares to sleep. The time required for the eggs to
reach the hatching stage varies with the species and with climatic
conditions from two or three days to over two weeks.

The larvee (Fig. 180) are tiny cylindrical maggot-like creatures
with neither legs nor eyes. They have small brown heads and
whitish bodies composed of 13 segments, which are provided with
rather sparse bristly hairs to aid in crawling. The last segment
is terminated by a pair of tiny hooks.

The larve squirm about actively in the dirt or débris of the

LIFE HISTORY 409

lairs or rubbish piles in which they hatched, avoiding light and
feeding upon what bits of organic matter they can find, such as
mouse pills, crumbs, hairs, epidermal scales from their hosts and
the excrement of adult fleas. Some species, if not all, devour their
shed skins after moulting. According to Bacot and Ridewood,
who have recently made observations on the larve of a number of
species of fleas, the larve become very excited and impatient
when disturbed. They sometimes lie quiet, coiled like a watch
spring,-for repose or concealment, but when about to moult they
stretch out at full length. They crawl by alternately expanding
and contracting the body like an earthworm, first securing a hold
with the hooks at the posterior tip of the body, then with the
head which is bent under to hook over some irregularity on the
surface. The duration of the larval stage varies with the tem-
perature and humidity and to some extent also with the species.
Under favorable conditions, 1.¢., at rela-
tively low temperatures and high humid-
ity and with plenty of food, the larve of
some species pass through their two
moults and enter the pupal stage in a
week, whereas under unfavorable condi- Fic. 181. _ Cocoon of
tions the duration of the larval existence See es
may be drawn out to over three months.

When ready to undergo their transformation into adults, the
larve spin little silken cocoons which are somewhat viscid, so
that particles of dust and lint readily adhere to them and give
them a dirty, dingy appearance (Fig. 181). According to Lyon
the adult insects may emerge from the cocoons of the cat flea,
Ctenocephalus felis, in from two to 14 days, but in most species
at least a week is required for the transformation to take place,
and this time may be greatly increased by unfavorable climatic
conditions. Strickland, in his work on the rat flea of England, -
Ceratophyllus fasciatus, found that the average pupal existence
-was 17 days and was extended to four months or more by low
temperatures, the fully formed adult insect remaining dormant
within the cocoon until exposed to a temperature of about 70° F.
There is much probability that the winter in temperate climates
and the hot dry season in tropical climates is tided over by fleas"
in the cocoon, the emergence of the adults coinciding with the
advent of moderately high temperatures and humidity.

410 FLEAS

The adult fleas, according to Strickland’s work on the rat flea,
do not. become sexually mature for some days after they escape
from the cocoon, and copulation does not occur until this time,
nor, in the case of the rat flea, until after a feed of rat’s blood, the
latter apparently acting as a stimulus to reproduction. Soon
after copulation the eggs begin to be laid.

In the dog flea, Ctenocephalus canis, the entire cycle from egg to
adult is said to be passed through in a minimum of two weeks, in
the human flea, Pulex irritans, in 19 days (in southern Europe)
and in the rat fleas in about three weeks. Ordinarily, however,
the life cycles occupy a considerably longer time, the average
being from one to three months.

The length of life of adult fleas depends largely on food supply,
temperature and humidity. Unfed fleas, unless allowed to bury
themselves in rubbish, usually die in less than a month, though |
when buried in débris they may be kept alive many months.
Well fed rat fleas kept at low temperatures (about 60° F.) and high
humidity may live for nearly a year and a half, according to
Strickland’s experiments. The optimum climatic conditions and
normal length of life probably vary a great deal with different
species.

Unlike most blood-sucking insects, fleas usually feed at fre-
quent intervals, usually at least once a day, and sometimes much
oftener than this. The frequent biting is due to the fact that
fleas are very easily disturbed while feeding and seldom complete
a meal at one bite. Moreover, the capacity of the stomach is
not so great as in many other blood-sucking insects. The human
flea and some others are mainly nocturnal, visiting their hosts
chiefly at night, whereas others, such as the cat and dog fleas,
remain in the fur of the host nearly all the time. Some species
show a decided preference for certain parts of the body of their
host.

Fleas and Disease. — Like most other blood-sucking parasites,
fleas are intimately connected with the spread of disease. The
most serious charge against them in this connection is the dis-
semination of bubonic plague, which as a human scourge ranks
with such diseases as smallpox and leprosy. In fact, few diseases
have ever ravaged the human race with more terrible destruc-
tiveness than plague when it breaks forth as an epidemic and
becomes rampant. It is estimated that in the epidemic of the

FLEAS AND PLAGUE 411

14th century in Europe one-fourth of the population of that
continent, or 25 million people, died of the disease. Superstition
and unreasoning terror led to horrible persecution and torture of
innocent people who were supposed to cause the plague. At-
present the disease is practically confined to tropical countries,
and is especially prevalent in India, where an average of about one
million deaths a year are caused by it. The practical disappear-
ance of plague from Europe is thought by some authors to be
associated with a change in the rat fauna of Europe, the do-
mestic and gregarious black rat, Epimys rattus, being replaced
by the wilder and more scattered brown rat, Epimys norvegicus.
The disease, however, has often been introduced from the tropics
into other countries, and there is constant danger of this wherever
the strictest preventive regulations are not enforced. In 1900
the disease was introduced into San Francisco, and there is every
reason to believe that had knowledge of preventive medicine
been at the point where it was 300 years ago, the United States
would have been swept as was Europe in the 14th century. In-
stead, knowing that rats were the chief reservoir of the disease,
and that rat fleas were instrumental in transmitting the disease
from rat to man, the U.S. Public Health Service took hold of the
situation and instituted an anti-rat campaign such as had never
been thought of before. Over a million rats were caught, ex-
amined and destroyed in the city of San Francisco. The infec-
tion spread, however, and became established in the ground
squirrels of several counties in California. From July 1, 1913, to
November, 1914, over 20,000,000 ground squirrels were destroyed |
in infected districts in California. So strenuous were the efforts
to stamp out the disease before it could get beyond control that
only 187 cases of the disease in man occurred in California,
with none since 1914. New Orleans has also had a taste of plague,
and infected rats have been taken in the vicinity of the water
front in Seattle.

The steps which have made possible an intelligent fight against
plague were the discovery of the plague germ, Bacillus pestis,
by Yerson in 1894, the establishment of the identity of the disease
with that of rats by the same worker, the discovery of the mul-_
tiplication of the plague germs in the gut of rat fleas, Xeno-
psylla cheopis, by Liston in 1905, and finally conclusive experi-
mental proof by the British Plague Commission in India in

412 FLEAS

1906 that the rat flea was the principal means of transmission of
the bubonic form of the disease.

As far as is known the plague bacilli live only in the digestive
tract of the fleas and do not infect either the saliva or the body
cavity. From this fact it is evident that the germs are inoculated
into the wound made by the flea, either with the excrement which
is commonly voided while sucking blood or with regurgitated
blood. It has been pointed out that a rat flea’s stomach will
hold about one-half a cubic centimeter of blood and could there-
fore take 5000 germs with a single feed from an infected animal.
These often multiply to such an extent as to form a solid mass of
organisms, blocking the digestive tract of the insect (Fig. 182).
It has been stated that when the stomach and
intestine of a flea are plugged with plague
germs the normal action of the valves of the

ments of the pharynx result in regurgitating
infected material into the wound instead of
sucking fresh blood from it. Fleas were found
by the British Plague Commission to remain
infective for 15 days during the height of an
a yee? eee epidemic, though during the non-epidemic
tive tract of flea Season no individual remained infective for
plugged with solid more than seven days. In Java the Indian
growth (in black) of coe i
plague bacilli. (After rat fleas have been found to remain infective
Lease aS for 33 days and Bacot has found the European
rat flea, Ceratophyllus fasciatus, to remain infective, when kept
away from a host, for 47 days.

The Indian rat flea, Xenopsylla cheopis (Fig. 177), is the species -

most intimately associated with plague transmission. This spe-
cies has been introduced with rats on ships into all parts of the
tropics, and into seaports in many temperate countries, especially
such ports as San Francisco, which trade extensively with the
Orient. This species, however, is by no means the only one
which can serve in the transmission of plague. It is probable
that any species which will attack both man and other sus-
ceptible animals, such as rats and ground squirrels, may transmit
the infection. Thus in India the human flea, Pulex irritans,
and the European rat flea, Ceratophyllus fasciatus, have been
proved experimentally to be plague carriers, and in California

digestive tract is lost, and the pumping move-—

—_ 7. a om,

DISEASES TRANSMITTED BY FLEAS 413

the squirrel fleas, Hoplopsyllus anomalus and Ceratophyllus acutus,
also have been shown to carry the infection. It is evident also
that other animals besides rats and man are susceptible to the
disease. Ground squirrels, Citellus beecheyi, guinea-pigs and
monkeys have been shown to be susceptible. A marmot or
ground hog, Arctomys bobac, common in Manchuria, is thought
to have been the chief reservoir of the disease in the Manchurian
epidemic in the winter of 1910-11, the flea Ceratophyllus silan-
tiewr being the transmitting agent.

Doubtless any fleas which attack these animals and which
also attack man may be instrumental in spreading the plague to
human beings in direct proportion to the willingness with which
they will bite man, and to their opportunities for doing so. It
must not be inferred that only fleas can transmit the disease.
The pneumonic form of plague, which is relatively uncommon,
is transmitted by particles of sputum or mucus from the mouth or
lungs. The bubonic plague may also be transmitted by bedbugs
and perhaps by other parasitic insects. A head louse taken from
a plague patient was found to be infected. There can be no
doubt, however, that the rat fleas are by far the most important
spreaders of this terrible disease. |

A similar but milder disease of rodents has recently been dis-
covered in the United States, caused by Bacterium tularense, and is
believed to be transmissible by fleas. Flies have been shown to
mechanically transmit the disease but the réle of fleas is only
conjectured.

‘Another disease which is commonly believed to be transmitted

_by fleas is the Mediterranean or infantile form of. kala-azar

(see p. 83). This is prevalent in dogs throughout many of the
regions bordering the Mediterranean, especially in parts of Italy
and North Africa, and is the cause of a high mortality in the
numerous cases which occur among children. A number of
authors have carried on experiments to prove the instrumentality
of the common dog flea, Ctenocephalus canis, and also of the |

~ human flea, Pulex irritans, with varied results. (See Chap. V,

p. 83.) The rdéle of fleas in the transmission of this disease is
still uncertain but there is enough evidence against the fleas to
warrant their being looked upon with extreme suspicion until
definitely proved innocent.

Another instance of the instrumentality of fleas in the trans-

414 — FLEAS

mission of disease is their relation to the spread of certain species
of tapeworms, especially the common dog tapeworm, Dipylidium
caninum. The larval stage of this tapeworm is passed in the body
cavity of the dog flea, Ctenocephalus canis, the eggs of the parasite,
adhering to hair in the vicinity of the anus, being ingested by the
flea. Occasional infection of human beings, especially young
children, occurs by the accidental swallowing of infected fleas, a
thing which could easily happen in cases of too great intimacy be-
tween children and their pet dogs. As many as 50 larve of Dipy-
lidium have been found in a single flea. The larve can also de-
velop in the human flea. The rat flea, Xenopsylla cheopis, has
been found to harbor the larval stages of tapeworms of the genus
Hymenolepis, as many as nine cysticercoids having been found
in a single specimen. These tapeworms are normally parasitic in
rats and mice but occasionally parasitize man also.

The relation of fleas to other diseases is suspected. A German q

writer has put forth the theory that fleas are instrumental in
the transmission of typhus. If typhus is purely a bacterial
disease, its spread by fleas and other parasites as well as by lice
would be quite possible, but if it should be found to be caused by
an organism which requires a true intermediate host, it would
be doubtful whether such widely different insects as lice and
fleas could both function in the same manner. That fleas
might act as mechanical transmitters of such diseases as tuber-
culosis and syphilis is quite possible, though it is doubtful if
this often occurs. |
Important Species

Human Flea. — The only species of flea which is known to be
a parasite of man primarily, with the exception of the chigger,
is the appropriately named human flea, Pulex irritans, though
in many places man is annoyed more by certain other species

which are primarily parasites of his domestic animals. The

human flea is not exclusively a parasite of man. It also attacks
badgers, skunks, dogs and other carnivores, occasionally occurs
on rats and mice, especially in houses and ships, and has been
taken on the blacktail deer, Odocotleus columbianus.! It is now

1 Specimens of fleas taken in considerable numbers on deer in northern
California by F. C. Clarke, of the California Fish and Game Commission,
were identified by Prof. R. W. Doane of Stanford University as Pulex irritans.
On account of the distinctive habits of these deer fleas, Clarke (in litt.)
pelieves that they should be considered a variety of P. irritans, for which he
proposes the name P. irritans cervi.

HUMAN FLEA 415

cosmopolitan in distribution, probably having originated in
Kurope, whence it was introduced with Europeans to all parts
of the world. This flea is the species which has made California
as famous for its fleas as is New Jersey for its mosquitoes. The
relatively cool humid summer climate combined with a mild
wet winter make the Pacific Coast of the United States an ideal
place for this pest. Though more or less of a nuisance through-
out the year in mild climates, this flea is less troublesome in
winter, due to relative inactivity, to slower reproduction, and
to the fact that small mammals are more commonly attacked at
this time of year.

The human flea is readily distinguished from most common
' species in temperate climates by the absence of any combs,
_ either on the head or thorax. From the Indian rat flea, Xeno-
- psylla cheopis (Fig. 177), it is difficult to distinguish, the essential
difference being the presence in the rat flea and absence in the
human flea of a vertical chitinous thickening of the mesoster-
num, 7.e., the plate to which the middle leg is articulated on
either side. The antenne of the human flea are shorter and
more knoblike than are those of Xenopsylla.

The human flea secretes itself in crevices and cracks of houses,
in floors, rugs, bedding, etc., coming forth chiefly at night to
pierce the flesh and suck the blood of its hosts. The suscep-
tibility of different individuals to flea bites is variable. The
irritation that is normally produced, probably chiefly as a result
of the injection of the insect’s salivary secretions into the wound,
causes the formation of a reddish pimple with more or less swell-
ing. Some people, however, are apparently entirely immune to
flea bites and feel no pain from them. The writer is one of these
fortunate individuals. On his first visit to California he had
been fully warned concerning the ravages of the fleas but found to
his pleasant surprise that the only discomfort felt from fleas was
the tickling occasionally caused by their movements beneath
his clothing. A college roommate, however, was attacked to
such an extent as to be unable to sleep, and spent a considerable
part of many nights in pursuit of the wily fleas and in violent
massaging of painful wounds.

As has been noted, the human flea may act as a transmitter
of plague, infantile kala-azar and tapeworm (Dipylidiwm) in-
fection, though it is not the chief villain in the spread of any one
of these diseases.

416 FLEAS

Dog and Cat Fleas. — Next in importance to the human flea
as a parasite of man is the dog flea, Ctenocephalus canis, and the
closely allied cat flea, C. felis. In the southeastern United States
where the flea scourge is as great if not greater than in Cali-
fornia, the dog flea is the species usually met with. During the
moist hot summers this species becomes exceedingly abundant.
Although primarily a parasite of dogs this flea willingly includes
man in its bill of fare if opportunity offers, and also attacks
cats, rats and other mammals. The usual fleas of cats, how-
ever, are now generally considered to be specifically distinct from
the dog flea. The cat flea is the only one of the two species
found in India, where it is a common parasite of dogs as well
as cats. The cat flea has a longer and more slender head than ~
its near relative. Both species can readily be distinguished
from any other common species with similar habits by the pres-_
ence of two conspicuous combs, one along the ventral margin of
the head, the other on the pronotum (Fig. 179B).

The eggs of dog and cat fleas are usually laid loosely in the fur
of their host, whence they readily fall out when the host shakes
himself or is settling himself for a nap. They develop in the
dust and dirt of kennels, woodsheds, house floors or other places
where infested animals are likely to go. Houses, of course, be-
come infested through the agency of infested animals, and since
the fleas, once in houses, encounter man more readily than they
do the original hosts, man is very likely to suffer from their at-
tacks. Patton and Cragg found the inside of a hat, in which a
kitten had slept overnight, so full of flea eggs that it looked as if
it had had sugar sprinkled in it from a sifter. Another author
collected a teaspoonful of eggs from the dress of a lady who had
held a kitten in her lap for a short time. The writer has been
able to find a similar quantity of eggs by dusting a smooth hard-
wood floor after an infested dog had indulged in one vigorous ©
shake. With these instances in mind one can readily understand
how houses into which infested pets are admitted become over-
run with fleas.

The dog flea, from its habits, is the species most frequently
implicated in the transmission of kala-azar (see p. 83), and is
the species usually instrumental in transmitting tapeworm
(Dipylidium) infection to children. Since this species will feed
on rats there is no reason for doubting that it may act as a trans-

RAT AND SQUIRREL FLEAS 417

mitter of bubonic plague, though its preference for dogs or cats
would preclude a frequent occurrence of this.

Rat and Squirrel Fleas. — The various species of rat and squir-
rel fleas are only accidental parasites of man. They readily at-
tack him if opportunity offers but do not remain adherent to him
as they do to their normal hosts. If it were not for their enormous
importance in the spread of bubonic plague, they would hardly
need special consideration.

From its intimate connection with the spread of bubonic
plague, the Indian rat flea, Xenopsylla cheopis (Fig. 177), is of
prime importance. Though other members of the genus are
confined to Africa and Asia, this species has now a world-wide
distribution, having accompanied its normal host, the rat, to all
warm seaports in both the Old and the New World. It is a
rather short, stout flea, resembling the human flea in the absence
of combs. Although the normal hosts of Xenopsylla cheopis are
rats of various species, the domestic habits of these rodents
bring the fleas into close association with man, and they will
readily feed upon him if hungry. Furthermore, deRaadt has
recently demonstrated that these fleas do not remain constantly
in the fur of their normal hosts, but that 80 per cent drop off in
the course of 48 hours. This species is not migratory and sel-
dom reaches anyone but the inhabitants of the house in which its
host occurs, unless carried by the rats themselves. Swellen-
grebel states that in Java this flea will willingly bite man on the
first day of fasting. In many tropical countries the Indian rat
flea is the commonest flea found in houses; in Egypt 96 per cent
of fleas caught in plague-infested houses were of this species.

The European rat flea, Ceratophyllus fasciatus, is a species
having habits quite similar to those of Xenopsylla cheopis. It
replaces the latter species in temperate climates except in sea-
ports, where the Indian rat flea is often more common. The
common rat flea of China and Japan is Pygiopsylla ahale. The
larve of C. fasciatus develop best under cool humid conditions
in an abundance of rubbish. Strickland, who has worked out
the biology of this flea in detail, found that it would actually
attack man in preference to rats, although a feed on the blood of
rats seemed to be necessary before any eggs were laid. Another
species of the same genus, C. galline, attacks chickens in Europe,
and has been introduced into several parts of the United States.

418 FLEAS

It is said to be very annoying to man also. The common squir-

rel flea in North America, C. acutus, is found on a number of
species of wild rodents, and also occasionally on rats and mice.
It does not attack man so readily as does C. fasciatus, but is
nevertheless not averse to human blood. This species has
come into great importance in California as the transmitter of
plague from rats to ground squirrels. It is probable, how-
ever, that other species of this genus and of allied genera
may quite as readily transmit plague, depending only on the
extent to which their habits bring them in contact with infected
animals. :

Chiggers. — The chigger, chigoe, jigger or sand flea, Derma-
tophilus (or Rhynchoprion) penetrans (Fig. 183), as it is vari-
ously called, is one of the most de-

It is a very small flea of the family
Sarcopsyllide, about one mm. in
length, with no comblike spines
and relatively slender legs. It has
a very comical pointed forehead,
like a helmet worn with the point
forward. The males and virgin

_ females of this species are similar
hen “Dernutophien penctass are to other fleas in habits, except that
impregated female. x 30. (After they attack a wide range of hosts.
Karsten from Riley and Johannsen.) Wansaethe principal host of this
particular species, but pigs are also very commonly attacked.
Chiggers occur especially in sandy regions where there is much
underbrush, and here they lie in ambush on the vegetation, dead
leaves or sandy soil, ready to attack any host which may come
their way. The particular importance of this flea les in the
fact that the impregnated females have the aggravating habit
of burrowing into the skin especially in such tender spots as under
the toe nails, where, nourished by the blood of the host, the eggs
develop and cause the abdomen to swell into a great round ball
as large as a pea, leaving the head and legs as inconspicuous
appendages (Fig. 184). Only the two posterior segments of the
abdomen do not enlarge; these act as a plug for the hole made in
entering the skin. The eggs, up to a hundred in number, mature
in about a week and are then expelled by the female through the

Ma “9 det Lied
—_ = > ow

spised pests of tropical countries. |

CHIGGER | 419

protruding end of the abdomen. Sometimes the entire female
is expelled with her eggs by the pressure of the inflamed tissue
which surrounds her. The
eggs, which fall to the
ground, soon hatch into
typical flea larvee (Fig. 185).
‘These, if they happen to
fall on sandy soil under
conditions suitable for
their <development, grow
to maturity, pupate in a
cocoon and emerge as adult
insects in the course of ten
days or two weeks. Fig. 184. Chigger or burrowing flea, Der-
The wounds made by the matophilus penetrans, gravid female. xX 18.
3 : . (After Moniez.)
burrowing female in the skin
become much inflamed and very painful. Frequently the dis-
tended abdomen of a flea is crushed and the eggs released in the
wound. In such cases the inflammation is greatly increased un-
less the crushed body and eggs are immediately expelled. As
soon as the eggs are laid, or even before, the skin surrounding the
wound ulcerates and pusisformed. The empty female flea is ex-
pelled. The sore which is left
is very liable to infection by bac-
teria and frequently results in
Fig. 185. Larva of chigger, Dermatoph- LHI ES OU Meets Sha ge
‘ilus penetrans. Blt Ne eicad) limbs through blood-poisoning.
Quiros has recently pointed out
that in Central America, where chigger infection is very common,
especially in boys: who play barefooted in the streets along which
infected hogs are driven to public market, deaths from tetanus
and gas gangrene from chigger wounds are very common.
Although usually only a few chiggers are present at a time,
there are cases where hundreds infest a person at once, literally
honeycombing the skin and making the feet or other parts of
the body so sore that the victim is rendered a complete invalid.
This obnoxious flea formerly existed only in the tropical por-
tions of America, especially in the West Indies, but it was intro-
duced to the West Coast of Africa in 1872, and has since become
abundant throughout the tropical parts of that continent and_

420 FLEAS

in the neighboring islands. It has also been introduced by coolies
into India, but does not seem to thrive there as it does in tropical
America and Africa.

The treatment of chigger wounds formerly consisted in the
destruction of the fleas while imbedded in the wounds. This was
done by applying various insecticides or pricking with a needle,
the dead insect being removed after ulceration. A much better
method is to enlarge the entrance hole of the flea with a clean
needle and remove the parasite entire. The wound should then
be carefully dressed and protected until healed. An ointment
recommended by Quiros consists of 21 grams salicylic acid and
10 grams ichthyol in 10 grams of yellow vaseline. Bathing of
infected parts with kerosene oil is also recommended.

Chiggers can be avoided to a large extent by the use of high

boots, or shoes and leggings. Walking barefooted in chigger- —

infested regions is almost sure to result in attacks by these pests.
Houses, yards, ete., in chigger regions should be kept carefully
clean of dust, dirt and débris which might favor the develop-
ment of the parasites. In Central America Quiros recommends,
as one of the best preventive measures, a prohibition against
driving hogs affected with chiggers through the streets, along
with regulations for treating affected hogs where they are raised.
According to Penschke, in German East Africa, attacks by chig-
gers can be prevented by thoroughly rubbing the feet every two
or three days with vaseline to which has been added a few drops
of lysol or cresol soap (15 drops to 3% oz. of vaseline).

Sticktight Flea. — The “ sticktight ” flea, Echidnophaga galli-
nacea (Fig. 186), is another member of the family Sarcopsyllide
which may be a human pest. It is a small dark-colored flea which
very commonly attacks chickens in nearly all tropical and sub-
tropical countries, including the southern United States in
America. Although the normal host is the chicken, other poultry,
dogs, cats, domestic rabbits, rats and other animals, as well as
man, are attacked. This species gets its name from the tenacity
with which it adheres to its host. It is gregarious, collecting in
dense masses on the heads of poultry (Fig. 186), in the ears of
mammals and in other places. It is not averse to attacking
man, especially children, but since it is not so active as other
fleas it can easily be found and removed. No disease is known to
be transmitted by this flea.

i

= sa." ee lee ee

ie) sh ee bel in

PREVENTION 421

Prevention. — Strict cleanliness in private homes or public
buildings prevents fleas from breeding in them. Uncared-for
carpets and straw mattings afford excellent breeding grounds
for the human flea, as do dusty cracks :
between floor boards, unswept corners
under sinks, and any other place where
the eggs and young, undisturbed, may
obtain enough moisture to keep them
from drying up. The use of bare hard-
wood floors with rugs which can readily
be taken up and swept and thorough
sweeping in corners and under pieces
of furniture, sinks, etc., do not give
fleas an opportunity to breed in the
home or in public buildings, and are ye ig6. Head of chicken
therefore valuable preventive measures. infested with chicken flea,

One of the best means of ridding an nee a CAS ae
infested house of fleas is to sprinkle
the floors with naphthaline and close the rooms for a day or
two. This will effectually kill all adult and larval fleas, and the
eggs may then be destroyed by washing the floors with hot soap-
suds, a five per cent formalin solution or one-tenth per cent
solution of corrosive sublimate. It is claimed that alum swept
into carpets or a solution of alum soaked into carpet paper pre-
vents fleas from breeding.

Fleas are very susceptible to fumigation with hydrocyanic
acid gas. Experiments by the U.S. Public Health Service show
that fleas succumb to the amount of gas generated by two and
one-half ounces of potassium cyanide in 1000 cubic feet of space.
Fumigation with sulphur is also effective. Details of methods
of fumigation with these substances will be found on p. 388.
Sodium fluoride in the form of a crystalline powder scattered
-on floors or blown about by means of a dust-gun will probably
prove effective against fleas, as it has against cockroaches
and other insects. It is inexpensive and not dangerous to
handle.

Various traps for the capture of adult fleas have been devised,
one of the simplest and most effective being to clothe the legs in
sticky fly paper, and wander about in the infested rooms. A
badly infested building in Cornell University was cleared of fleas

422 . - FLEAS

in this manner. Another device, used by the Chinese, is a rod
of bamboo, smeared with bird lime, fitted inside of a larger piece
of bamboo which has holes cut in it. A trap
of similar type may be constructed by fitting a
piece of broomstick wrapped with sticky fly
paper inside a wire cylinder (Fig. 187). Such
a ‘‘ flea stick”’ can be rolled about on floors or
in beds and will collect a large proportion of
the flea population. Another trap consists of
a glass of water with about an inch of oil on
the top of it fitted with a little wick in the
center of a floating piece of cork. This is
placed in the center of a dish of strong soap-
suds and lighted at night. The light attracts

oF se

—s
SG SEAS

ZS

SEF LON LBS) Bie SE EB

iy aa
CLI SF WEF LI LBS

:

EDT ET
ET 1 NEED DE

NS ase
WY LEEZEAY,

suds.
PRR The destruction of fleas, especially cat and
| dog fleas, on domestic animals is often neces-

Fic. 187. A Sary in order to do away with a flea scourge.
modification of the Dogs and cats, or other hosts, may be cleared
Gainese fica tap of fleas by washing them in two or three per
broomstick wrapped cent solution of creolin (about one tablespoon-
mith sticky fy papery fu) +o a quart of warm water), or some other
fitted in a cylinder *U q y
of wide-meshed wire derivative of creosote, or a similar solution of
cee eee potassium sulphide. According to Bishopp,
the solution should be worked into the hair with a brush,
and care should be taken to wet the fleas which crowd
toward the head of the animal. After about ten minutes
the solution should be washed off with warm water and soap,
at least in delicate-skinned animals such as cats, to avoid a
burning effect. Another method of treatment is to rub
powdered moth-balls (naphthaline) into the fur. This causes
the fleas to emerge from the fur in a stupefied condition in
which they are easily captured and destroyed. Except to sicken
cats slightly for a day or two this treatment has no ill effect
on the host.

Of temporary value in flea-infested places is the use of repel-
lents, such as oil of pennyroyal, eucalyptus oil, etc., smeared on

shoes or clothing, or between bed sheets. Beds may be isolated -

by elevating them to some distance from the floor, or by sur-

the fleas, which leap headlong into the soap- .

:
Ss
:
i
4
3
a
¥

Te es le Se hl ae

.
ee ee a ae

REPELLENTS | 423

rounding them with a band of sticky fly paper 12 to 14 inches
wide. Where perfect protection from fleas is desired, as in a
plague-smitten city, all of these protective measures, as well as
fly-paper wrapped legs, and any other means which may come to
mind should be made use of. These should be followed up by
the more permanent measures leading to the extermination of
both larval and adult fleas.

CHAPTER XXV
MOSQUITOES

Importance. — Of all existing insect pests mosquitoes are the
greatest enemies of mankind. The mere annoyance which the
enormous numbers of them cause by their constant attacks and
painful bites is sufficient to have made some parts of the world
practically uninhabitable. There are rich pieces of country which
have remained absolutely unsettled on account of this pest alone.

Some of the choicest hunting and camping grounds in North |

America, and in other continents also, are practically closed to
the camper by the countless millions of mosquitoes which trans-
form a camper’s Paradise into an intolerable hell, and drive any
bold human invader to frenzy. When travel through such places
is necessary no comfort can be hoped for without the presence
of a dense smudge or without almost constant application of
~ “ mosquito dope,’ and even then the unceasing ‘“‘ zangs”’ of the
mosquitoes as they threateningly approach is hardly less trying
on the nerves than are the actual attacks. Unlike most insect
pests the mosquitoes of cold northern countries are if anything
more abundant than they are in the tropics. The far northern

mosquitoes do not, however, act as carriers of disease; terrible as _

they are, they wage clean warfare, whereas tropical mosquitoes
have their spears poisoned with death-dealing disease germs.
The northern mosquitoes bite, suck their fill of blood if they can,
and are through; the tropical mosquitoes often leave months or
years of suffering and disease, or even death, in their wake. No
less than four different diseases are believed to be transmitted
by mosquitoes exclusively, namely, malaria, yellow fever, dengue
or breakbone fever and filariasis, while a fifth, a form of myiasis
in South America, is believed to be transmitted sometimes by
mosquitoes. Mosquitoes have been suspected of complicity in
the transmission of still other diseases, but their relation to the
first four diseases mentioned above is sufficient to brand them as
the greatest insect enemies of the human race.
424

STRUCTURE 425

General Structure. — Mosquitoes are members of the great
insect order Diptera, to which so many human pests belong.
Their nearest relatives, outside the mosquito family itself, are
the midges (Chironomid), craneflies (Tipulide), sandflies
(Phlebotomus), and blackflies or buffalo gnats (Simuliide). The
members of the mosquito family, Culicide, can be distinguished
from other Diptera which look more or less like them by the
characteristic and quite conspicuous fringe of scales on the hind

= & - = - vf. res.

\
a —— pree
— ———,
ae -malp. t.
PA / -~-— rect
A y
//

\ Fig. 189. Digestive tract of a

mosquito; d. f. res., dorsal food
reservoirs; malp. t., malpighian
: tubules; ph., pharynx; prov., pro-

Fic. 188. Diagram of adult female mos- ventriculus; rect., rectum; sal. d.,
quito (Aédes sollicitans); abd., abdomen; salivary duct; sal. gl., salivary
ant., antenna; e., eye; halt., haltere; palp., gland; st., stomach; v. f. res., ven-
palpus; prob., proboscis; th., thorax. tral food reservoir.

margin of the wings. Most of the Culicide have a long promi-
nent .proboscis containing needle-like organs for piercing and
sucking, but in two subfamilies, including the midges of the
-genus Dixa, and the so-called phantom midges, Corethra (Fig.
192), the adults of which resemble true mosquitoes and are often
mistaken for them, there is no long proboscis.

The general appearance of adult mosquitoes is so well known

426 MOSQUITOES

as to need no description, but the details of their structure is as
little known by most people as are those of the structure of other
insects. The diagram on page 425 (Fig. 188) illustrates the
details of the parts of a mosquito which are of most use in iden-
tifying and classifying. The sexes can be distinguished most
readily by the antenne; in the female (Fig. 190A) they are long
and slender with a whorl of short hairs at each joint, whereas in
the male (Fig. 190B) they are shortened and have a feathery
appearance, due to tufts of long and numerous hairs at the
joints. In many mosquitoes the palpi also furnish a means of

F a eC pees) Sue ea ||| W
AR Hae CH ie Nii
4 Hi y Ht i /
j mA Hi | vi
ft { ce F/I! Va
an it x A y
2 ae
label.- ye
g ‘a

Fic. 190. Heads of female (9) and male (¢) mosquito, Culiseta incidens:
ant., antenna; b. j. ant., basal joint of antenna; label., labellum; palp., palpus;
prob., proboscis. -

distinguishing the sexes; they are usually long in the males
but short in the females, but in Anopheles they are long in both
sexes, and in some mosquitoes, e.g., Uranotenia, they are short in
both.

The proboscis, which is the most fearful part of a mosquito,
also differs in the sexes, and fortunately is so constructed in the
male that a mosquito of this sex could not pierce flesh if he would.
At first glance the proboscis appears to be a simple bristle, some-
times curved, but when dissected and examined with a micro-
scope it is found to consist of a number of needle-like organs

ea a ne

STRUCTURE 427

lying in a groove in the fleshy lower lip, which was the only part
visible before dissection. In the female mosquito there are six
of these needle-like organs the nature and names of which’ are
shown in Fig. 191. The “labrum-epipharynx” and “ hypo-
pharynx ” act together to form a tube for drawing up blood into
the mouth. A tiny tube runs down through the hypopharynx,
opening at its tip, through which saliva is poured into the wound
as through a hypodermic needle to prevent blood from coagu-
lating. The ensheathing lower lip does not itself penetrate the
wound, but bows back as the mosquito bites, the flexible tip or

¢
pap.”

Fic. 191. Side view of head of female Anopheles showing mouthparts; ant.,
antenne; clyp., clypeus; ceph. s., cephalic scales; hyp., hypopharynx; lab.,
labium; label., labellum; labr. ep., labrum-epipharynx; mand.; mandibles; max.,
maxille; palp., maxillary palpi. x 20. (After Nuttall and Shipley.)

~“dabella ” acting as a guide for the piercing organs as they are
sunk into the flesh. In male mosquitoes the piercing organs are
much degenerated, only the suctorial part of the apparatus being
well developed.

Besides the variations of the parts mentioned already, mos-
quitoes vary as regards the form, distribution, color and other
characteristics of the scales which clothe much of the body and the
edges and veins of the wings; the details of the male reproductive
organs at the tip of the abdomen; the relative length of parts of
the leg; and in other respects.

All mosquitoes have good “‘ capacity” as far as the digestive
traet is concerned, having three food reservoirs connected with the

)

428 MOSQUITOES

cesophagus, in addition to a large stomach (Fig. 189). Connected
with the proboscis is a pair of salivary glands consisting of three
lobes each. One of these lobes in each gland differs from the
others and instead of secreting ordinary saliva is thought to secrete
the poisonous substance which prevents coagulation of blood and
produces the inflammation and pain attendant upon a mosquito

Fie. 192. Larva and adult of Corethra, a member of the Culicids which is not
a bloodsucker, but is often mistaken for a mosquito. The larve prey on mosquito
larve and other aquatic organisms. Note anterior and posterior ‘‘floats’”’ in the
larva, and mosquito-like appearance of adult, except for lack of proboscis. (Larva
after Howard, Dyar and Knab; adult after Smith.)

bite. Schaudinn, however, has adduced some experimental evi-
dence that it is the contents of food reservoirs which cause the
inflammation. It is in the salivary glands that the malaria para-
sites, and probably the parasites of dengue and yellow fever also,
collect, and whence they are poured with the secretions of the
glands into the wounds.

Life History. — Mosquitoes, like other Diptera, pass through
a complete metamorphosis in the course of their life history, 1.e.,
they undergo a transformation from larval to adult stages during
a period of rest. In a general way the life histories of all mos-
quitoes are much alike, but in details there is much variation

EGGS . 429

among them. Without special adaptations in habits and physi-
ology to meet the exigencies of their diverse environment there
would be little chance for the mosquitoes of the frozen north
or of the parched tropical deserts to meet successfully the struggle
for existence. A great store of interesting facts concerning the
life history and habits of mosquitoes has been collected by
Howard, Dyar and Knab in Part I of their “ Monograph of the

Oy

S 9: inet att
Ree SUS sas

23h
: Bs ces

’
ee
me

ee
er, ro
2

Fie. 193. Eggs of mosquitoes; A, Culiseta inornatus; B, Mansonia perturbans;
C, Aédes calopus; D, Anopheles punctipennis, dorsal view; D’, same, ventral view.
x 75. (After Howard, Dyar and Knab.)

- Mosquitoes of North and Central America and the West Indies ”’
and much of the information incorporated into this chapter
has been taken from their work.

The eggs of mosquitoes (Fig. 193) are usually oval, with vari-
ous surface markings, and in Anopheles with a peculiar “ float ”’
of air cells. The number of eggs laid by a single female mos-
quito varies from 40 or 50 to several hundred. Some species

-

430 MOSQUITOES

lay their eggs singly (Fig. 194) while others lay them all at one
time in little boat-shaped rafts called egg-boats, the individual __
eges standing upright (Fig. 195). The fact that the eggs are a :
little larger at the lower end makes the whole egg-boat slightly
concave, thus making it difficult to overturn. Most of the com-
mon mosquitoes of temperate climates lay their eggs on the
open surface of water or at-
tach them to some partially
submerged object; a few
species lay eggs which sink.
Many species, however, °
especially those of the far
north and of the tropics, lay
their eggs in dry places which
are likely subsequently to
be covered with water. - In.
most mosquitoes of temper-

Fie. 194. Eggsof Anopheles quadrimacu- é
latus on surface of water. Xx 13. (After ate climates the eggs hatch

‘
lOve, in a few days, or even within :
24 hours. In the species of the far north the eggs probably —
never hatch until the following spring, being laid in depressions
on the ground which are usually not immersed until the melting 2
of the winter snows. Such hibernating eggs are said not to hatch
unless they have been exposed to freezing temperatures. On the : 4
other hand the mosquitoes :
f
7
q
i

of dry hot countries: lay
eges which are highly re-
sistent to desiccation and ==_—
do not lose their vitality SS eee
during months of dryness. Fic. 195. Egg boat of Culex floating on 4
Such species must almost water. X about 8. 5
“live while the rain falls,”’

and to win in the struggle against an unfavorable climate they

o66 aca Recsentan AG re manne nan
PR TREC
Ui FRAO

4

must be prepared to utilize the most transitory pools for the
completion of their aquatic immature stages. In such cases

the embryo within the egg shell develops to the hatching point,
so that it is ready to begin the larval existence almost with the
first drop of rain. Such mosquitoes further fortify their race
against the unkind environment by laying their eggs in a number
of small batches instead of in a single mass, as is the habit with

ree) ee ee ee

LARVA OR “WRIGGLERS ” 431

mosquitoes where water is plentiful. Just as a man runs less
risk of ruin if he deposits his money in a number of insecure
banks rather than in a single uncertain one, so it is with mos-
quitoes and the places where they deposit their eggs. The
gamble for life in a dry climate would be too risky if all eggs were
deposited in one place, and species with this habit have probably
long since been weeded out in the struggle for existence. An-
other remarkable adaptation of dry-climate mosquitoes is the
variation in the hatching periods of the eggs in the same batch;
not all hatch with the first drops of moisture, but some lie
over until subsequent immersions, thus insuring a much better
chance that some of them, at least, will not waste their life on
the desert air with too little water to enable them to reach
maturity.

The eggs of mosquitoes never hatch except in the presence of
water. The larve, which are always aquatic, are very active
wormlike creatures, well known as “ wrigglers ”’ or “ wriggle-tails”’
(Fig. 196). When first hatched they are almost microscopic,
but they grow rapidly to a length of from a quarter of an inch to
almost an inch. The bunches of long bristly hairs on the body
take the place of legs, and aid the larva in maintaining a position
in the water. The “rotary mouth brush” is a brush of stiff
hairs which is used to sweep small objects toward the mouth;
in predaceous species these are sometimes modified into rakelike
structures or into strong hooked bristles for holding prey. The
trumpet-shaped breathing tube (Fig. 196A) is present on all
mosquito larve except Anopheles (Fig. 196B), in which it is
undeveloped. It is used to pierce the surface film of the water to
draw air into the air tubes or trachee inside the body, for, al-
though aquatic, mosquito larve are air breathers, and make
frequent trips to the surface to replenish their air supply, re-
maining suspended by the breathing tube from the surface of the
water while breathing. The leaflike “ tracheal gills’ on the last
segment of the abdomen differ from true gills in that air tubes
or tracheze instead of bloodvessels ramify in them. In one
species of mosquito, Mansonia, the larve absorb air from the air-
carrying tissues in the roots of certain aquatic plants, piercing
them with the apex of the breathing tube and thus avoiding the
necessity of rising to the surface of the water. In well-aérated
water the larve can live without surface air for a long time by

432 MOSQUITOES

using their tracheal gills, but they die within a few hours if
shut in water without dissolved air.

Mosquito larva, unless suspended from the surface film by
means of the breathing tube, have a tendency to sink and they
rise again only by an active jerking of the abdomen, using it as

Fig. 196. A, Larva of tropical house mosquito, Culex quinquefasciatus; ant.,:
antenne; br. t., breathing tube or siphon; m. br., mouth brushes; th., thorax;
8th s., 8th abdominal segment; 9th s., 9th abdominal segment; tr., trachez;
tr. g., tracheal gills. B, Larva of Anopheles punctipennis; note absence of breath-
ing tube, and starlike groups of scales on abdominal segments; m. br., mouth
brushes; br. p., breathing pore; other abbrev. as on Fig. A. xX 10. (After
Howard, Dyar and Knab.)

a sculling organ. Some species are habitual bottom feeders,
others feed at the surface; some live on microscopic organisms,
others on dead organic matter, and still others attack and devour
other aquatic animals, including young mosquito larve of their
own and other species. )

The larve shed their skins four times and then go into the

_ HABITS OF ADULTS 433

resting pupal stage. Mosquitoes of temperate climates usually
take from five days to two weeks to complete the larval existence,
depending almost entirely on temperature. In the mosquitoes
adapted to take advantage of transitory rain-pools the larve may
transform into pups within two days and the pupal stage is a
mere matter of hours. On the other hand, some mosquitoes
habitually pass the winter as larve.

The general form of the pupa can be seen in Fig. 197. Alcock
has aptly described this stage of a mosquito as resembling a
tiny lobster deprived of ap-
pendages and carrying its
tail bent. The pair of ear-
like breathing tubes on the
cephalothorax (head and
thorax fused) take the place
of the trumpet-like tube of
the larva and are used in
the same manner. Unlike
the larva the pupa is lighter
than water, and requires

muscular effort to sink in- Fic. 197. Pupa of house mosquito, Culex
pipiens: ant. c., antennal case; br. t., breath-

stead of to rise. ing tubes; leg. c., leg cases; pad., paddles;
As remarked before, the Wing c., wing case. X 10. (After Howard,

2 : Dyar and Knab.)

transformation into the

adult during the pupal stage may be a matter of a few hours in
the case of the dry-climate mosquitoes, but in most species it re-
quires from two days to a week, depending on the temperature.
The adult mosquito emerges head first through a longitudinal
slit along the back of the thorax. After its exit it rests for a
moment on the old pupa skin, stretches and dries its eae) and
then takes flight.

Habits of Adults. — Adult mosquitoes vary to a remarkable
degree as regards habitats, feeding habits, mode of hibernation,
choice of breeding grounds, and other habits. The knowledge,
only recently gained, that each species of mosquito has habits
and habitats more or less peculiar to itself, is of great economic
importance, since it does away with useless expenditure in com-
bating harmless or relatively harmless species, and aids in the
fight against particularly noxious ones. The fact, for instance,
that one of the commonest summer mosquitoes of northeastern

434 MOSQUITOES

United States, Culex territans, does not annoy man does away
with the necessity of combating this species, and obviates the
necessity of destroying larve in certain kinds of marshes and
pools where this is practically the only breeder. Again, the
fact that mosquitoes breeding in crab holes do not annoy man
eliminates the necessity of attempting the almost impossible
task of destroying such breeding grounds in order to be free of
mosquitoes. The fact that a certain species of Anopheles, A.
malefactor, which is a tree-hole breeder, is not a malaria carrier,
saved thousands of dollars in the anti-malarial fight in the
Canal Zone.

Habitats. — A classification of mosquitoes according to habi-
tats and breeding grounds has been attempted by some authors.
Dr. J. B. Smith, for instance, divides the mosquitoes of New

Jersey into four ecologic groups, the salt marsh, house, swamp, —

and woodland mosquitoes. However, almost as many different
ecologic groups could be made as there are species of mosquitoes
or possible breeding and foraging places. There are species
which breed in reedy swamps, woodland pools, eddies of rivers,
slow-flowing streams, holes in trees, pools of melted snow, salt
marshes, tide pools, crab holes, pitcher plants and other water-
bearing plants, or in broken bamboo stems filled with water.
There are species which have become ‘“‘ domesticated ”’ and occur
almost always in the vicinity of houses, laying their eggs in
water troughs, street gutters, rain barrels, water-filled cans in
garbage heaps, flower vases, water bottles, and any other col-
lection of water in or about human habitations. Some species
show almost no preference as regards breeding places, others,
especially those breeding in such specialized places as in water-
holding plants, are very closely limited; some species prefer pure
clear water, others filthy water, while still others are apparently
indifferent.

Migration. — That mosquitoes are seldom found far from
their breeding grounds is another fact, only recently recognized,
of great economic importance. The evidence points to the fact
that most kinds of mosquitoes seldom stray more than from half
to three-quarters of a mile from their birthplace, and usually not
over a few hundred yards. The supposition that mosquitoes
utilize a strong wind to carry them long distances is entirely false,
since mosquitoes are so delicate as to be unable to fly at all with a

4
3
:

TIME OF ACTIVITY 435

strong wind but remain hidden away at times when such wind
storms occur. Some mosquitoes are able to resist moderate winds,
but nearly always fly against them instead of with them. The salt
marsh mosquitoes are apparently an exception to the sedentary
nature of mosquitoes, as shown by Smith’s work in New Jersey.
These mosquitoes commonly migrate for a number of miles and
may goas much as 40 miles inland from the salt marshes which
bred them. ‘The common salt marsh mosquito, A édes sollicitans
(Fig. 188), the mosquito that made New Jersey famous, breeds in
enormous numbers in the extensive coastal marshes of New
Jersey, whence it migrates inland, and sometimes crosses the
- Hudson River and invades New York City in hordes. The
author has seen mosquitoes (not positively identified as this
species) literally in clouds on the roofs of buildings in the down-
town section of New York, where the day before not a mosquito
was to be found. With the exception of a few of the salt marsh
species, however, an abundance of mosquitoes can almost al-
ways be looked upon as evidence of the existence of breeding
places within a mile, and usually within a few hundred yards.

Although most species are not migratory, railroad trains,
street cars, ships and other conveyances are efficient means of
transfer for mosquitoes. Hawaii is said to have been free of
these pests until they were introduced with sailing vessels, in
which mosquitoes can usually find plenty of water for breeding.
The great number of trains daily running inland in New Jersey
from the marsh-studded coast is undoubtedly a factor in keeping
more distant suburban towns stocked. Well established cases
are on record of places once free of mosquitoes becoming infested
after the advent of railroad train or boat service.

Time of Activity. — Although mosquitoes are usually looked
upon as strictly nocturnal, and though this is true of most of
the common species of temperate climates, it is by no means
characteristic of the whole group. Many species, including all
Anopheles, are active chiefly at twilight, in the evening, or early
morning. Knab found that the mosquitoes of northern prairies,
where the nights are too cold for them, are active throughout the
day only. A large proportion of forest-living tropical species,
at least in America, are said to be diurnal. Some of the mos-
quitoes of the northern woods are apparently ready to bite
when a victim approaches, whether it be day or night. The

436 MOSQUITOES |

widely distributed yellow fever mosquito, Aédes calopus (or
Stegomyia fasciata) (Fig. 201), feeds by preference in the early
morning or late afternoon. Here again a knowledge of the
habits of particular species is of importance, since it. may aid in
the intelligent avoidance of particular disease-carrying forms.

Food Habits. — Heretical as it may sound, mosquitoes feed -

mainly on plant juices, honey, etc. It is doubtful if the males
of any species normally suck blood, and even the females of some
species are strict vegetarians. On the other hand, the females
of many species have a voracious craving for warm blood. Some
species indiscriminately attack any warm-blooded or even cold-
blooded animal, while others show strong preferences. The
yellow fever mosquito normally feeds chiefly on man, and even
discriminates against the black race. The other “ domestic”
mosquitoes apparently have a strong liking for human blood also,
and it is not unlikely that their domestic habits are the result
of their taste for human blood. Knab found that A édes spenceri
of the Saskatchewan prairies would fly toward any large object.
On the prairies such an object would usually be a large animal
and the mosquitoes would fly toward it instinctively in the
hope of satiating the craving for food.

Hibernation. — The method employed by mosquitoes for
passing the winter in cold climates, and the dry season in the
tropics, varies with the species. Many of the mosquitoes of
temperate climates and many in the tropics hibernate or pass the
dry season in the adult stage, the females stowing themselves
away in hollows in trees, caves, crevices in rocks, cellars, barns,
etc., to come forth and lay their eggs in the spring. A few species
hibernate in the larval stage, the larve of one species, Wyeo-
myia smith, becoming enclosed in solid ice in the leaves of the
pitcher plant in which they live. Most hibernating larve retire
to the bottom of their breeding pools during cold weather and
do not survive freezing. The majority of temperate- and warm-
climate mosquitoes and all of the northern ones pass the un-
favorable season in the egg state, and this may be looked upon as
the common method of hibernation. |

Length of Life. — The length of life of mosquitoes varies with
the species and with the sex. Male mosquitoes seldom live more
than from one to three weeks; their duty in life is done when they
have fertilized the females. The latter usually die shortly after

CLASSIFICATION 437

they have laid their eggs but some species may live for four months
- or more. The species which lay all their eggs in a mass at one
time are short lived, and have several generations a year, whereas
those in which the eggs are laid in small lots, at intervals, live for
several months. Species in which the females hibernate are still
longer lived, but since they are not active in winter their effec-
tive life is short.

Classification. — Over 500 species: of mosquitoes have been
described, the majority of which belong in the tropics, although
the north is richer in individuals. The task of classifying all of
these species into subfamilies and genera is one which has taxed
the wits of many scientists. The wide discrepancies in the work
of different men as regards mosquito classification is the best
_ possible proof of the difficulties in the way. As in'many other
groups of animals, intensive study has tended to magnify the
value of certain characteristics as criteria of genera or subfamilies,
the result being the breaking up of what would ordinarily be
looked upon as a single group into a number of poorly defined
and intergrading groups. Theobald, who has written a mono-
graph of the mosquitoes of the world, separates the Corethrine
(forms without a long proboscis) from the mosquitoes, and
divides the remainder of the family into ten subfamilies and a
very large number of genera based largely on scale character-
istics. On the other hand, Howard, Dyar and Knab, whose classi-
fication is adopted here, recognize only two subfamilies — the Core-
thrine and the Culicine, the latter including all the true mos-
quitoes. The Culicine are further divided into two tribes, the
Sabethini, including chiefly forest-dwelling non-blood-sucking
forms, and the Culicini. The genera of the latter are arranged
in a series from the primitive forms of the genus Anopheles to
such highly specialized forms as Megarhinus.

The identification of species of mosquitoes, or even of genera,
is often very difficult for anyone but a specialist. Fortunately
~ some of the most important disease-carrying species are so
marked that they can quite readily be distinguished even by
a novice. Only a few of the eager e: species can be
separately described here.

438 MOSQUITOES

Mosquitoes and Malaria

As was shown in Chap. IX, malaria is one of the most important
and one of the most deadly of human diseases. This being true,
the mosquitoes, which are the sole means of transmitting the
disease, must be looked upon as among the most important and
most deadly enemies of the human race. The role of mosquitoes
in causing disease, especially malaria, has been suspected by
various peoples as far back as any records go. The steps which
led to the proof of the relation of mosquitoes to malaria are briefly
outlined on pp. 148-149.

Fortunately not all mosquitoes are malaria carriers; in fact,

only one genus, Anopheles, com- —

prising a number of more or less

been considered genera by some
workers, is known to be able to
transmit the human malarial dis-
eases, and not even all of the
species of this genus are incrimi-
nated. As will be seen below,
some species of Anopheles are able
to transmit one type of malaria,
but not another. A_ species of
Culex has been shown to be instru-
mental in transmitting a disease

Abophetéd A A eet ge cot (ainda aelncetn eras to malaria.
rimaculatus; C, A. punctipennis; D, The role of the mosquito in the
a rs nee na (After spread of malaria and the develop-
ment of the parasites in the mos-

quito’s body have been discussed in Chap. IX, pp. 154-156. Suffice
it to repeat here that the sexual phase of the life history of all
malaria parasites occurs in the digestive tract of mosquitoes, after
which a rapid multiplication of the germs takes place, resulting
ultimately in the collection of large numbers of the parasites in
the salivary glands of the insect, whence they are poured into the
capillaries in the skin of the subsequent victims of the mosquito.
Identification of Anopheles.— The Anopheles mosquitoes,
fortunately, are fairly easy to identify in all stages of their de-
velopment except as pupe. They represent a primitive group

© ~ —— es
Se eS ee eee ee | pe -

well-defined subgenera which have ©

a ———— a —_

MALARIA-CARRYING SPECIES OF ANOPHELES 439

of mosquitoes, and in many respects are less specialized than
other members of the family. The different species of the
genus vary a great deal as regards choice of breeding places,
habits and appearance, so that it is necessary in any malarial
district to determine, if possible, which species are malaria
carriers, how they may be identified, where they breed, and what
their habits are. The majority of the species have mottled or
spotted wings, and the arrangement of the markings is a good
means of identification (Fig. 198).

The following comparative table (Fig. 199) shows in a graphic
way how Anopheles may ordinarily be distinguished from other
common mosquitoes, such as Culex, A édes, etc., in their different
stages.

Malaria-Carrying Species. — Over a hundred species of Anoph-
eles have been described and they occur all over the temperate
and tropical parts of the world. Although not more than about
half of these species have been proved to be able to harbor ma-
larial parasites and nurse them to the weaning point, the num-
ber of incriminated species is constantly growing, and it is the
safest plan to look upon any Anopheles as a potential malaria
carrier until proved otherwise. The fact that a given species
of Anopheles may transmit one type of malaria but not another
complicates the task of determining the role of a species, and has
caused discrepancies in the results of workers. A. quadri--
maculatus (Fig. 200) in North America, for instance, may carry
tertian and quartan malaria, but not the more deadly estivo-
autumnal type. A. crucians, on the other hand, carries xstivo-
autumnal malaria but only rarely carries tertian malaria. The
third common North American species, A. punctipennis, has
recently been proved to be able to nurse and transmit tertian
and quartan malaria, but not nearly so readily as does A. qua-
drimaculatus. The situation among these American species
fairly illustrates what is found elsewhere — considerable differ-
ences among the species of Anopheles as regards their ability to
nurse the several types of malaria and the readiness with which
they may do so. In most countries, though there may be several
species which transmit malaria, there is usually one species which
is especially responsible for the disease. In North America it is
A. quadrimaculatus and in the southern states A. crucians and
quadrimaculatus; in tropical parts of America, A. albimanus and

440 MOSQUITOES

Anopheles

Culex, Aédes, etc.

EGGS

Eggs laid singly on surface of water;
provided with a partial envelope, more
or less inflated, acting as a “‘ float.”’

_ TaRRNA

Eggs laid in rafts or egg-boats, or

singly on or near water, or where water
may accumulate; never provided with
a ‘‘ float.”

LARV 4

Larve have no long breathing tube or
siphon; rest Just under surface of water
and lie parallel with it.

Larve have distinct breathing tube
or siphon on 8th segment of abdomen;
hang from surface film by this siphon,
except in Mansonia, which obtains air
from aquatic plants.

PUPA

Pupz have short breathing trum-
pets; usually do not hang straight down
from surface of water.

\

Pupz have breathing trumpets of va-

rious length; often hang nearly straight
down from surface of water.

HEADS OF ADULTS

Palpi of both male and female long
and jointed, equaling or exceeding the
proboscis in both sexes.

Palpi of female always much shorter

than proboscis, those of male usually
long, but sometimes short.

RESTING POSITION OF ADULT

Adult rests with body more or less at
angle with surface, the proboscis held
in straight line with body.

Adult usually rests with body parallel

to surface, though sometimes at an
angle.

Proboscis not held in straight
line with body, giving ‘‘ hump-backed ”
appearance.

Fia. 199.

ae. ee a

HABITS OF ANOPHELES 441

argyrotarsus; in Europe, A. maculipennis; in Africa, A. costalis
and funesta; in India, A. cultcifacies, stephenst and listoni; in
Malay countries, A. umbrosus and willmori; in China and Japan,
A. sinensis and listoni; and in Australia, A. bancrofti.

These species are only a few of the most widely distributed and
~ commonest of the efficient malaria
carriers. Many other species may
_ be locally more important.

Habits of Anopheles. — Be-
sides the ability to nurse the
parasites of malaria, an efficient
malaria spreader must have habits
which will insure the use of such
ability. The important malaria
carriers are, therefore, species
which readily attack man, and
especially those which are more
or less “‘domesticated.”” Nearly Fic. 200. The common North
all species of Anopheles are active A ea goers
only at twilight, and forage out-
doors neither in bright daylight nor in the darkness of night,
though such species may bite at any hour of the day inside houses.
Different species are known to come forth at different times
in the evening, some with the first shade of the late afternoon,
others not until almost dark. A few species, e.g., A. brazilensis,
are diurnal, and many forest species will readily bite in the day-
time if disturbed. Nearly all Anopheles hibernate as adults,
but a few, notably A. bifurcatus of Europe, hibernate as larve.

Anopheles may breed in almost any standing water providing
it contains microscopic organisms on which to feed. Dr. Smith,
of New Jersey, says he has found no pool so insignificant and
no stream so rapid that Anopheles could not breed in it some-
where. He says ‘no other mosquito has as wide a range of
_ breeding places as have the species of Anopheles.”’ Nevertheless,
it is apparently true that each species has its favorite breeding
grounds and some species are quite particular. A. willmori
of the hilly parts of Malay, for instance, will breed only in swift-
running streams, the banks of which are cleared, whereas A.
umbrosus of the coastal plains of the same country breeds only
in jungle-edged streams; A. eiseni of Central America breeds

442 MOSQUITOES

only in tree holes; A. cruzi of Brazil breeds in accumulations of
water in the leaves of certain tropical plants. A number of
species of Anopheles will breed in brackish water, and some in
pure or even concentrated sea water. <A. ludlowi of the Philip-
pines is believed to breed only in sea water. Some of the coral
islands of the East Indies are practically uninhabitable for new-
comers on account of the prevalence of malaria which is carried
by Anopheles that breed in quiet pools within the coral reefs.

The larvee of Anopheles are chiefly surface feeders. Some feed
upon anything floating on the surface of the water which is
small enough to enter the mouth. Others, however, reject many
things after they have been swept into the mouth by the mouth
brushes, and some feed exclusively on vegetable matter. Only
a few species are predaceous.

Apparently neither the eggs nor larve of Anopheles are resistant
to drying, though they may live on moist mud for some time.
Eggs of Anopheles laid in such mud develop to the hatching point
but do not hatch until immersed, and die if the mud dries to the
extent of losing its glistening surface.

Anopheles are not rapid in development as compared with
some mosquitoes. At Washington, D. C., in early summer, A.
quadrimaculatus was determined by Dr. Howard to develop in a
minimum of 24 days — three for the eggs, 16 for the larve, and
five for the pupze. In some species the development may be
more rapid, but about two weeks is probably a minimum. Ac-
cording to observations by Kulagin near Moscow, Russia, in
1906, there was but one generation of Anopheles in a year, the
females always resting over winter before depositing their eggs.
This point of the number of generations of Anopheles deserves
further local study everywhere.

It is important to note that Anopheles mosquitoes are very
sedentary in habit, and seldom fly more than a few hundred
yards from their birthplace, and usually not this far. As a
group, the insects of this genus are physically incapable of as long
flight as are most other mosquitoes. It is frequently reported
that Anopheles is found several miles from its nearest breeding
places, but the difficulty of knowing with certainty that no
water-filled hoofprint or tin can exists in the intervening area is
obvious. That an Anopheles may occasionally wander half a
mile or more from its breeding ground is unquestionable, but not

AEDES CALOPUS AND YELLOW FEVER 443

enough individuals do this to make it necessary to look for
breeding places more than three or four hundred yards from the
infested locality. The conveyance of mosquitoes in trains,
boats, etc., must, however, be taken into account.

The effect of anti-Anopheles campaigns on the prevalence of
malaria is discussed in Chap. IX, pp. 165-167.

Mosquitoes and Yellow Fever

Following upon the heels of the discovery of the relation of
mosquitoes to malaria, and second only to it in importance, came
the discovery of a similar relation to yellow fever, in 1900. As
in the case of malaria, some physi-
cians suspected the instrumentality
of mosquitoes in the dissemination of
this disease before there was any
proof of it. The proof came as the
result of the illustrious work of the
American Army Yellow Fever Com-
mission, composed of Doctors Reed,
Carroll, Lazear, and Agramonte, at
the cost, indirectly, of the lives of
three of them. What is known of
the nature of yellow fever, and of
the réle of the mosquito in trans-
_ mitting it, is discussed in Chap. X,
pp. 182-185. It should be repeated }
here, however, that the ‘“‘germ”’ of the }
disease is still unknown, though be-
lieved to be a protozoan. The blood XN
of a patient can infect a mosquito Fic. 201. Yellow fever mos-
only during the first three days of Le ee ne anes
illness, and the mosquito cannot —
transmit the disease in less than 12 days later. In one case,
hereditary transmission of yellow fever from an infected mosquito
to its offspring has been shown to occur.

The Transmitting Species, dédes calopus. Unlike the condi-
tion as regards malaria, yellow fever can be transmitted by only
one species of mosquito, Aédes calopus (or Stegomyia fasciatus)
(Fig. 201). This is a small black mosquito, conspicuously
marked by white bands on the legs and abdomen, and a white

444 MOSQUITOES

lyre-shaped design on the thorax. The female, which, of course,
is the only sex connected with the transmission of disease, since
the males do not suck blood, has very short palpi which are white
at the tip. The wings are clear and somewhat iridescent.

Habits of Aédes calopus. — The yellow fever mosquito is the
most thoroughly ‘‘ domesticated’”’ species known. It is seldom
found except in the vicinity of houses and shows a decided pre-
. ference for human blood. As a rule it

seldom leaves the rooms of houses ex-
cept to find a suitable place to lay its
eggs. Long familiarity with man has
made this mosquito one of the most
elusive and well-adapted pests of the
human race which nature has ever
evolved. Its stealthy attack from be-
hind; its habit of crawling up under the |
clothing to bite in preference to attack-

Fic. 202. Head of Aédes Ing the exposed ankles; the suppres-
a male. (After Gold- sion of the characteristic mosquito

“song,” so that its bite comes silently
and without warning; its habit of concealing itself in pockets,
folds, etc., of garments; its hiding behind pictures, under chairs,
etc.; the wariness of its larve; — all these are the result of
lessons learned from long and close association with man.

Aédes calopus is principally a diurnal mosquito, and becomes
particularly hungry in the early morning and during the after- —
noon. It will bite in lighted rooms, but will never bite in the
dark. The French Yellow Fever Commission in Rio de Janeiro
stated that Aédes calopus is nocturnal. The evidence for this
conclusion, which is at variance with the observations of other
workers, has been shown by Howard, Dyar and Knab to be very
inadequate and faulty. The danger of sleeping in an infected
place; and the comparative freedom from danger enjoyed by
persons who visit infected places only in the daytime, is thought
to be due to the fact that most of the mosquitoes obtain a meal
very early in the morning, just after daybreak. :

Breeding. — A édes calopus never lays eggs until it has had a
meal of blood and when water or moist surfaces are available.
According to recent experiments by Bacot a single male mosquito
may fertilize a number of females. Fertile eggs are usually

BREEDING OF AEDES CALOPUS 445

laid from four to seven days after a blood meal. The nearest
allies of this species are tree-hole breeders, but the yellow fever
mosquito has become domesticated to such an extent as to much
prefer a rain barrel or water-filled tin can in a garbage heap, or,
even better, a water-pitcher or flower-vase indoors. Churches
in Central America are usually well supplied with yellow fever
mosquitoes which breed in the holy-water fonts.

Fic. 203. <A yellow fever center in Panama in the pre-American days. (Drawn
from photo from Thompson.)

The eggs (Fig. 193C), up to 150 in number, are laid in several lots
at intervals of a few days, either on the surface of the water, or, as
is more common, on the edges of the container, or on a partially
submerged object, wherever a moist surface is presented and where
a slight elevation of the water will submerge them. The female
mosquitoes die a short time after the last batch of eggs is laid.
According to Bacot’s experiments the. promptness of hatching
depends on temperature and on whether the eggs have been kept
under moist or dry conditions. The eggs of this species retain
their vitality for several months when kept absolutely dry, but
they hatch more readily and with less mortality if kept moist.
When the eggs.are laid directly on the surface of water they ma-
ture less rapidly than when laid above the surface, probably on
account of the cooling effect of the water. Eggs laid on the
surface hatch in a minimum of two days, while those above it,
if later submerged, may hatch in less than 12 hours. According
to recent work by Atkin and Bacot, eggs will not hatch in sterile
water, but will hatch within a few hours after the introduction of
living bacteria. The larve (Fig. 204) thrive in either clean or foul

446 MOSQUITOES

water and even in brackish water, provided food material, in the
form of dead organic matter and the accompanying bacteria, is
present. Atkin and Bacot have recently shown that the food
consists almost, if not quite, exclusively of bacteria, and that
when the larve are present in large
numbers they exert a considera-
ble influence in the purification of
water. Often the larve are over-
looked, since they immediately
wriggle to the bottom of their
dwelling place when approached,
and hug the bottom so closely that
even if a barrel containing thousands
of them is turned over on its side,
about 80 per cent will stay in the -
little remaining water. The larve
feed exclusively on the bottom and °
can often be seen nibbling away
at a dead insect or bit of decaying
vegetation. With plenty of food
and at favorable temperatures the
larval existence may be completed
in four days, according to Bacot,
though it usually requires a longer
time than this, and may be drawn
out to two months or more. The
larve are not resistant to dry-

Lge ing, and die in a few hours in a

Fic. 204. Larva of yellow fever dry place, though capable of liy-
Chee Pe poe ee ing nearly two weeks on moist

ground.

The pup (Fig. 205) transform, under normal conditions, in a
day and a half or two days. The entire cycle from egg to adult
seldom takes place in less than nine or ten days, and probably
12 or 15 days is more usual under ordinary conditions. As has
been shown above, the period of development may be drawn out
over several months by unfavorable conditions. The adult mos-
quitoes may live for a considerable time, and apparently are
able to transmit yellow fever any time from 12 days after in-
fection to the end of their lives. Male mosquitoes ordinarily

HABITS OF AEDES CALOPUS 447

will not live beyond 50 days, but the females frequently live
under laboratory conditions for four months or more. Kind
of food, dryness of climate and facilities for laying eggs are among
the chief factors determining the length of life of these mosquitoes,
and, strange as it appears at first,
the length of life is shortest under
the most favorable conditions,
namely, plenty of blood for food,
plenty of moisture, and suitable
places for egg-laying.

The flight of the yellow fever
mosquito is strong but, like most
other mosquitoes, it seldom flies
long distances, usually not more
than a few hundred feet. Vessels
_lying half a mile from shore rarely
if ever are visited by these mosqui-
toes unless the latter are carried
from shore by lighters or boats. Fie. 205. Pupa of yellow fever

Owing to its domestic habits ee eee yeaa ee |
and its ability to “‘ stow away ”
the yellow fever mosquito has been, and annually is, widely
distributed over the world. As pointed out by Howard, Dyar and
Knab, its original home was very probably tropical America,
since the evidence points to the origin of yellow fever in the
West Indies and neighboring mainland, and it is inconceivable
that the parasite of this disease would have developed in any
other region than the original home of its obligatory host. The
permanent home of this mosquito is now almost the entire warm
portion of the world, wherever a temperature of 80° or more
is maintained for any length of time, and where freezing does not
occur. The once common occurrence and breeding of this mos-
quito during summer months in cities of the Atlantic Coast of
the United States and in other ports outside the frostless zones was
due to its importation on ships from such infested cities as New
Orleans, Havana and Rio de Janeiro. The cool nights and low
summer temperatures on the Pacific Coast of the United States
prevents its thriving there, in spite of the fact that it is still some-
times carried there on ships. Since the practical extermination
of this mosquito in most of the ports where it was once abundant

448 MOSQUITOES

its importation to other places has become a rare occurrence.
Since A édes calopus has a much wider range than has yellow fever
there is constant danger of the introduction of the disease into
places where it has not previously been known and where, due
to the non-immune condition of the people, it would become
a terrible scourge if once successfully introduced. For this
reason the yellow fever mosquito is fought as a public menace
in India, Australia and many of the South Sea Islands, where it
is frequently the most abundant mosquito.

Mosquitoes and Dengue

The relation of mosquitoes to‘'dengue or breakbone feyer was
first pointed out by Graham, of Beirut, in 1902, who performed
experiments which showed that this disease was not caught by —
close association with patients in the absence of mosquitoes,
whereas isolated men subjected to bites from mosquitoes which
had bitten dengue patients readily contracted the disease.
Other workers have adduced evidence in favor of the mosquito
transmission of the disease, and Ashburn and Craig in the Philip-
pines have shown that laboratory-bred mosquitoes, fed on dengue -
patients, could transmit the disease three days after the infective
meal. The nature of the disease and development of it in mos-
quitoes and man is discussed in Chap. X, pp. 186-187. It isa
disease which resembles a mild form of yellow fever, is seldom fatal,
and occurs in very sweeping and rapidly traveling epidemics.

Transmitting Species. — So far, only the tropical house mos-
quito, Culex quinquefasciatus (fatigans) and A édes calopus have
been shown to be capable of transmitting dengue. Circumstan-
tial evidence, such as distribution and epidemiology of the disease,
habits of the mosquitoes, etc., all point to C. quinquefasciatus as
being the most important species concerned. Aédes calopus
has repeatedly been suspected of transmitting the disease, es-
pecially in Australia, but conclusive evidence of this has been
brought forth only recently (1916) by Cleland, Bradley and
McDonald in Australia. .

C. quinquefasciatus is the common house mosquito of the
tropics, and very closely resembles the house mosquito of tem-
perate climates, C. pipiens, in both appearance and _ habits.
It is brown in color with a broad whitish band on each abdominal

MOSQUITOES AND FILARIA 449

segment. The thorax and legs are plain brown except for a pale
area at the bases of the legs.

This species is very common in houses in all thickly populated
parts of tropical and subtropical portions of the world, though
not so thoroughly “‘ domestic ’”’ as Aédes-calopus. In America
it becomes abundant in summer as far north as Washington and
St. Louis. It is strictly nocturnal and will bite in complete
- darkness, therefore its work supplements that of the yellow fever
mosquito, the latter taking the day shift, the former the night
shift. The house mosquito does not pursue man with as much
devilish cunning and perseverance as does Aédes calopus, and,
indeed, shows a very inferior grade of intelligence as compared
with it. There is reason to believe that it is primarily a perse-
cutor of birds and poultry, and attacks man only as a second
choice. C. quinquefasciatus breeds in almost any standing water
but apparently prefers artificial receptacles and is partial to filthy
water. The eggs, about 200 to 300 in number, are laid in rafts
as is the case with other members of the genus. The larve
(Fig. 196A), which hatch in from one to three days, have long
breathing tubes, and feed chiefly on microscopic organisms.
The length of time required for the mosquitoes to reach the adult
stage from the time the eggs are laid depends very largely on
temperature, food conditions, etc. The minimum period is
probably about five or six days.

Alcock remarks about this mosquito: “Apart from its prac-
tical importance, Culex fatigans (or Culex quinquefasciatus) has
a peculiar interest as being the living document of two discoveries
of the first magnitude in the history of medicine, namely, Sir

Patrick Manson’s discovery ... of the part played by mos-
quitoes in the life cycle of certain filarial blood-parasites, and
Sir Ronald Ross’s discovery ... of the necessary connection

between mosquitoes and certain Protozo6n blood-parasites. The
first discovery laid open a new world to Pathology; the second,
which is the outcome of the first, will affect the destiny of the
human race.”

Mosquitoes and Filaria

As intimated in the last paragraph above, the discovery by
Sir Patrick Manson in 1879 of the function of the mosquito as
an intermediate host of filarial worms, the larve of which live

450 | MOSQUITOES

in the blood, marked the beginning of a new era in medical
science; it was the first evidence of the development of germs
of human disease in the bodies of insects. An account of the
life cycle of filarial worms, including the development in the
bodies of mosquitoes, the means by which the worms are re-
turned to their primary hosts, and the effect of filarial infection
on man, will be found in Chap. XVII, pp. 299-306.

Not all species of filarial worms utilize mosquitoes as inter-
mediate hosts, a notable exception being the loa worm of Africa.
Four human species, Filaria bancrofti, F. philippinensis, F. per-
stans and F. juncea (demarquayt) are known, or thought, to be
nursed by mosquitoes. The last two named are not known to
have any pathogenic effects, but F. bancrofti is connected either
directly or indirectly with a number of human ailments (see
p. 306). F. philippinensis is closely allied to F. bancrofti, but -
differs in that it appears in the peripheral blood diurnally as well
as nocturnally, a habit which is supposed to be associated with
the diurnal habits of its usual intermediate host, Aédes pseudo-
scutellaris.

Although the successful development of filarial worms is not
limited to one particular species of mosquito or even to any
particular group of species, the development is not completed
equally well in all species. The tropical house mosquito, Culex
quinquefasciatus, is the species in which the worms apparently
develop most frequently with least fatality to either worms or
mosquitoes. In Fiji the development of the worms is more
regular and more rapid in A édes pseudoscutellaris than in any other
mosquito. In Aédes calopus, however, the development of the
worms is very slow, and they eventually degenerate in the tho-
racic muscles without reaching maturity. Many species of
Anopheles serve as suitable hosts, as do also some species of
Mansonia and other genera. In many species of mosquitoes
the filarial larve are digested, or else die in the course of their
development. On the other hand, there are some mosquitoes
which are very susceptible to the injury done by the worms,
especially in case of heavy infestation, and the mortality may
amount to a large per cent. Apparently the most critical time
for the mosquitoes is when the larve have penetrated into the
proboscis. This is a striking example of the almost universal
truth in parasitology, that the host in which the asexual cycle of a

MOSQUITOES AND DERMATOBIA 451

parasite is passed is less perfectly immune to the parasite, and
the parasite less perfectly adapted to the host, than is the case
between a parasite and the host in which it goes through the
mature sexual phase of its life history. In the case in hand
man may be looked upon as the disseminator of a deadly disease
among mosquitoes in much the same way that the mosquito
may be considered the disseminator of deadly human diseases
in the case of malaria and yellow fever.

Mosquitoes and Dermatobia

In many parts of tropical America where the man-infesting
botfly, Dermatobia hominis (see Chap. X XVII, pp. 513-515), is
found there has long been a belief among the natives that the
maggots of this fly, which develop under the skin of man and of
many other animals, are in some way the result of mosquito bites.
Inhabitants of some endemic regions, e.g., Trinidad, point to
mosquitoes as the cause of the skin maggots, and in some places
the larve are known as “ mosquito-worms.” Until recently
the scientific world looked upon these beliefs as mere superstition,
and gave them no further thought. In 1911, however, Dr.
Morales, of Guatemala, received a specimen of a mosquito sent
him as a mosquito “ carrier’ of Dermatobia, with eight relatively
large elliptical eggs glued by their posterior ends to its abdomen.
A few days later a larva emerged from one of the eggs, and was
induced to enter an abrasion in the skin of an attendant, where
it thrived so well that for the patient’s sake it was removed after
a little over six weeks and transplanted to the back of a rabbit.
Here it-continued its development and escaped, probably just
before pupation, exactly two months after the eggs were first
received. Dr. Morales was quite certain that the larva was
really a Dermatobia. In the same year Dr. Tovar of Caracas,
Venezuela, made similar discoveries, and is said to have caused
typical Dermatobia tumors by allowing an egg-laden mosquito
to bite a susceptible animal. From these tumors the larve
were obtained at the end of 11 days and from these larve the
adult flies were reared. Dr. Surcouf of Paris, Dr. Knab of the
United States, and Dr. Sambon of England have published ob-
servations of their own bearing on the réle of the mosquito in
transmitting Dermatobia infection. From these observations
one would be inclined to believe that, as expressed by Dr. Rin-

452 | MOSQUITOES

cones of Caracas, the mosquito is utilized by the Dermatobia fly
as an aeroplane for transporting her eggs or larve to a suitable
host for development, and we would have here, if true, one of
the strangest interrelations of animals in the whole realm of
nature, comparable, perhaps, with the manner in which certain
mites of the family Tyroglyphid assume a special traveling garb
and adhere to the appendages of flies to obtain transportation
to new feeding grounds (see pp. 339-340).

Dr. Neiva, of the Instituto Oswaldo Cruz, Brazil, does not
believe in the mosquito theory. He points out that in various
parts of tropical America not only mosquitoes, but also craneflies,
ichneumon-flies, certain large hairy flies and other insects are
accused of being Dermatobia carriers, though they could not
possibly serve in this capacity; that although Dermatobia is:
abundant throughout Brazil, and the mosquito Janthinosoma
lutzi, on which the eggs are found, also occurs there, yet no
specimen of this mosquito with these eggs has ever been found
there in spite of the great amount of mosquito collecting which
has been done in Brazil; that the observations of Dr. Tovar must
be at fault, since all observations on the development of the
larva are opposed to the possibility of an eleven-days-old specimen
being able to mature; that the eggs from a Janthinosoma figured
by Dr. Surcouf do not agree with the eggs obtained by dis-
secting adult female flies; that the fly is frequently seen pestering
cattle and horses, and that he himself has been persistently fol-
lowed by egg-containing females; that new-born children kept
indoors are very seldom infected, although the incriminated
mosquitoes, but not the flies, are common in houses; and that
dissected flies show the eggs to be in various states of develop-
ment, indicating their disposal singly or a very few at a time, at
intervals. Neiva’s contentions are further corroborated by the
fact that the mosquito theory is upheld by other observations,
so obviously inaccurate as to tempt one to look with doubt on
all of them. Dr. Zepeda, of Nicaragua, for instance (quoted by
Sambon), says he observed Dermatobia tumors developed two
days after bites by egg-bearing mosquitoes, and says that seven
days later the larva dropped out! Sambon believes that the
larvee of some other fly were confused with those of Dermatobia,
especially as Zepeda later obtained specimens of the screw-worm
from tumors following mosquito bites. ;

mero) AES oe = em, :

Nind ae FH

MOSQUITO BITES AND REMEDIES — 453

On the other hand, the widespread popular belief in the part
played by the mosquito, the fact that several observers have
independently observed similar phenomena, and the fact that
Dermatobia has been observed holding flies between its legs, and
has never been seen actually depositing its eggs on a host, make
it unwise to discard the mosquito theory as impossible. As
remarked by Sambon, this fly may have several ways of disposing
of its eggs, and the utilization of the mosquito and perhaps of
other insects as transports for them may well be one of these ways.

The mosquito involved, whenever determined, has been found
to be a species of Jan-
thinosoma; in the one
case where the species
was determined it was
found to be J. lutzi (Fig.

206). This is a large,
beautifully colored
mosquito, with flashes
of metallic violet and
sky blue on its thorax
and abdomen. It is #
said by Knab to be one
of the most blood-
thirsty of American
mosquitoes and is

found throughout trop- Fic. 206. Mosquito, Janthinosoma lutzi, with
ical America. The eggs, supposedly of Dermatobia hominis, attached
to abdomen. (After Sambon.)

larve breed almost ex-
clusively in rain puddles, the eggs being laid in dry depressions
on the forest floor which will become basins of water after a
tropical downpour of rain. The eggs hatch almost with the first
drop of rain, and mature so rapidly that adult insects may
emerge in four or five days. The larvee feed on particles of
organic matter, and are themselves fed upon by the larvee of the
closely allied genus of mosquitoes, Psorophora, which breed in the
same rain pools.

Mosquito Bites and Remedies for Them

Ag has been remarked before, the pain and irritation produced
by a mosquito bite is usually believed to be due to the injection

454 MOSQUITOES

of a bit of poisonous saliva into the wound made by the piercing
mouthparts of the insect. The susceptibility of some people to
the effect of mosquito poison is much greater than that of others.
The author has seen individuals on whom mosquito bites swelled
up like bee stings and were even more painful, whereas the author
himself has frequently been unaware of the fact that a mosquito
was biting him unless the insect was seen by him or was pointed
out by a less indifferent companion. Moreover, the effect of the
bites of different species of mosquitoes varies, so that while some
species may produce very little irritation others may prove un-
bearably annoying. Dr. Smith, of New Jersey, became prac-
tically immune to the bites of some of the salt marsh mosquitoes,
but was troubled by the house mosquito, Culex pipiens, and still
more so by Anopheles. The author has had similar experience,
and has found himself driven almost to frenzy by some species
and hardly annoyed at all by others. It is quite probable that
the complaints which are heard from visitors to the ocean resorts
of the New Jersey coast are due to the fact that these visitors
are fully susceptible to the poison of the salt marsh mosquitoes
whereas they may have become more or less immune to the
inland mosquitoes of their own districts. These facts clearly
indicate that there is a specific difference in the poison of different
kinds of mosquitoes, and Dr. Smith’s experiences show that
acquired immunity to one mosquito may give little or no relief
from another. |

There is a popular belief that if a mosquito is allowed to draw
his fill of blood, the bite is less painful and becomes less swollen
than if she is killed or driven away. This belief is to a large
extent true, the probable reason being that when the insect
is allowed to finish her meal, the droplet of poisonous saliva in-
jected into the wound is drawn back into the stomach of the
mosquito with the blood on which it acts.

Many different remedies have been recommended for mos-
quito bites. Ammonia, alcohol, glycerine, indigo, iodine, ether,
camphor, naphthaline (moth balls), cresol preparations, a 2%
per cent carbolic solution — all these and others have had their
adherents amongst entomologists, hunters, travelers and house-
wives. All of them probably have some alleviating effect, and
it is not unlikely that their effects may vary with different spe-
cies of mosquitoes and perhaps even with individuals. Dr.

PERSONAL PROTECTION 455

_ Howard found that moist soap rubbed on the bites was the most

satisfactory remedy in his own personal experience.

Probably no remedy or disinfectant, no matter how quickly
applied after an infected mosquito has been sucking blood, would
be effective in preventing infection with malaria, yellow fever
or dengue. Filaria and Dermatobia infections, however, could
probably be prevented in this manner, since it takes an ap-
preciable time for the larvee to enter the skin in the vicinity of the
wound.

Control and Extermination

The control of mosquitoes may be undertaken in the following
ways, in order of permanent usefulness: (1) personal protection
by the use of repellents on or near the person, or of protective
clothing; (2) the elimination and exclusion of mosquitoes from
dwellings; (3) the local destruction of larve by the use of
temporary “larvicides”; (4) the prevention of breeding by
obliterating breeding places or making them uninhabitable.

Personal Protection. — This method of dealing with mos-
quitoes has no permanent value whatever, and does nothing to
lessen the number of mosquitoes, but it is indispensible to the
hunter or visitor in mosquito-infested places. Concerning the
use of protective clothing, little need be said; the value of gloves,
veils, high boots, leggings, etc., is obvious.

The use of “ mosquito dope,” or ointments repellent to mos-
quitoes, on the exposed skin is a popular but usually disappoint-
ing safeguard against attacks by these insects. The number of
popular repellents for mosquitoes is as great, if not greater, than
the number of popular applications for the bites. Nearly all
of these are unquestionably effective while they last, but they
all have the disadvantage of losing their power by evaporation
in a short time, and therefore have to be renewed at frequent
intervals. Spirits of camphor, oil of pennyroyal, oil of pepper-
mint, lemon juice, vinegar, anise oil and oil of citronella are
all effective protectors while they last. Oil of citronella has
been most widely used in America. This mixed with an equal
amount by weight of spirits of camphor and half as much oil of
cedar is a mixture recommended by Dr. Howard, and one which
the author has used with good results. A few drops of this mix-
ture poured on a bath towel at the head of a bed, and a little

456 MOSQUITOES

rubbed on the face and hands if the mosquitoes are very per-
sistent, was found by Dr. Howard to last long enough through
the night to be effective against all mosquitoes except the yellow
fever species, A édes calopus, which begins its attacks at daybreak.

Elimination and Exclusion from Buildings. — The second
means of controlling mosquitoes, by eliminating and excluding
them from dwellings, is of more permanent value than the first,
and should never be omitted while the process of mosquito
extermination is under way.

One of the best methods of ridding houses of mosquitoes after
they are once in is fumigation, and this is also an indispensable
method of destroying hibernating mosquitoes in cellars, attics,
barns, etc. The substance used for fumigation must depend on
the kind of place to be fumigated, and on the conditions under

which it is done. The most thorough and certain method of —

fumigation, when the place to be fumigated can be vacated, is
by the generation of hydrocyanic acid gas. A less dangerous
and equally effective method, but one which is injurious to metals
and house furnishings is by the use of fumes of burning sulphur.
These methods of fumigation are described in Chap. XXII, pp.
383-386.

Fumigants which are not dangerous to human beings can be
used effectively against mosquitoes since these insects do not
require such penetrating fumes as are necessary to destroy
hiding parasites, as bedbugs and lice. Pyrethrum or Persian
insect powder, manufactured out of the dried flower heads of
certain species of chrysanthemums, is an effective fumigant of
this type; it can either be dusted into corners, blown into the
air of a room, or burned. Powdered jimson weed, Datura
stramonium, is recommended by Dr. Smith, eight ounces, mixed
with one-third its weight of niter or saltpeter to make it burn
more readily, being burned per 1000 cubic feet. ‘‘ Mimm’s
Culicide ” is a volatile liquid made of carbolic acid crystals and

gum camphor in equal parts by weight, which is effective against ©

mosquitoes, four ounces being volatilized by heating for every
1000 cubic feet of space. A fumigant which has come into great
favor in the last few years is cresyl; 75 grains to 35 cubic feet is
sufficient to kill all mosquitoes, and in this dilution it is not in-
jurious to man or other higher animals. It is not injurious
to metals or to household goods.

.
a
vu

ELIMINATION FROM BUILDINGS 457

In camps which are not mosquito proof, the only effective
means of obtaining comfort is by the use of smudges as described
for blackflies (p. 484).

Protection of houses against mosquitoes is almost a necessity
in many places. To a certain extent the construction of a house
affects the number of mosquitoes attracted to it. Light, airy
rooms with white walls are much less infested with mosquitoes
than are dark, damp houses. Ross says that houses decorated.
with curtains, pictures, stuffed chairs and similar “‘ barbarous ”
furnishings are entirely inappropriate for the tropics, and he
deplores especially the use of curtains since they “ check the
breeze which is so cooling to the inmates and so unpleasant for

_ mosquitoes.”’

The careful screening of houses or rooms is highly valuable,
especially in places where mosquito-borne diseases are prevalent.
Mosquito net or screen should never be less than 18 meshes to
the inch. Cloth net is more effective than wire, since mos-
quitoes cannot as readily force their way through, but nets with
thin threads should be used and should be stretched tightly in
order not to exclude the breeze in hot weather. The use of tight
canopies over beds is extensively practiced in southern United
States, especially in malarial districts, and these are very com-
mendable when kept in good repair. Most firms dealing in camp
outfits place on the market light folding frames covered with
mosquito netting for use when resting or sleeping out of doors
in mosquito-infested places. |

Usually a few mosquitoes find their way into screened rooms
in spite of the screens, through unnoticed crevices, opening of
doors and the like. These can usually be discovered and des-
troyed with a fly spanker, or, what is just as effective in case
spotting the walls with blood is to be avoided, by holding a cup
of kerosene directly under them. The mosquitoes are stunned
by the vapor and fall into the cup in a few seconds. Mosquito

traps have been found useful in some places, these contrivances

consisting merely of a box, dark colored inside, placed where it
will readily be found by mosquitoes and utilized as a hiding
place. The box is arranged so that the insects do not readily
find their way out and so that it can be fumigated easily.
Larvicides. — Far more effective and satisfactory in every
way as a method of coping with mosquitoes is their actual ex-

458 MOSQUITOES

termination, not necessarily in a whole continent or a whole
country, but in local places. Only comparatively recently has
the local extermination or even reduction of mosquitoes ceased
to be looked upon as too vast an operation to be undertaken.
Because ponds or marshes were known to exist, perhaps miles
away, the value of destruction of such breeding places as rain
barrels, tin cans full of water, cesspools and troughs was looked
upon as a mere drop in the bucket. Knowing as we do now that
in most cases every annoying mosquito which attacks us was
born and bred within 200 yards of where we meet her, the
local extermination of mosquitoes has taken on a very different
aspect. It is difficult for the uninitiated to realize that the
mosquitoes which make life miserable for him did not travel from
distant marshes and ponds but were probably bred in his own
backyard or in his own living room.

Wonderful results have been obtained by the destruction of
larve in their breeding places. This is accomplished either by
pouring into the water some substance which will form an emul-
sion, and will destroy the larvee when very dilute, or by pouring or
spraying some oil on the water which will spread out and form
a thin film over the whole surface. When the larve rise to obtain
air through their breathing. tubes or pores, the latter become
plugged by a tiny bit of oil, and the larve drown. It has recently
been pointed out by Lima, in Brazil, that the drowning is has-
tened by the coating of the body of the larve by the oil, especially
in Anopheles, so that air cannot be absorbed through the body
wall.

The oil film is the method most commonly employed, espe-
cially for use on a small scale. Except for wind-swept bodies of
water, ordinary petroleum is as cheap and efficient as any oil
that can be obtained. The oil film is so thin and light, however,
that it is blown aside by a high wind, and a considerable portion
of the water left uncovered. Different grades of oil can be used,
varying with conditions. The thick heavy grades do not readily
form a uniform film, especially if obstructed by water weeds,
whereas the very thin oils evaporate rapidly, and the film is easily
broken. Howard, Dyar and Knab recommend a grade known
as “light fuel oil” for ordinary use. These authors state that
about one ounce of petroleum to 15 square feet of water surface
gives satisfactory results, and produces a film which lasts for

PREVENTION OF BREEDING 459

ten days. Films of heavier oils or heavy and light oils mixed
last longer, and need be renewed only once in two, three or four
weeks, according to conditions. Thin oil will spread into a film
if simply poured on the surface, but heavier oils are best sprayed
on. In Africa mops made by tying kerosene-soaked cloths on
long sticks are used for spreading the oil and in Panama waste
cloth soaked in oil is placed where a slow flowing stream will
constantly take a thin film from it.

In the tropics the use of petroleum has often been found im-
practicable on account of the rapid evaporation, continued
heavy rains, and the interference made by the luxuriant and
rapid growth of water plants and alge and the formation of an
interfering scum from a combination of the oil and dead alge.
For this reason substances which are actively poisonous to the
larve and which form an emulsion in the water are used instead.
An almost ideal larvicide of this type is now made at Ancon,
C. Z., in enormous quantities. It is made of crude carbolic acid,
powdered resin and caustic soda, heated together to make a black
liquid resin soap which readily forms a milky emulsion with
water. It destroys Anopheles larve in 16 minutes in an emul-
sion of one part in 5000. It also kills larve in mud, and destroys
grass, alge and water weeds in which larve ordinarily hide.
In making the substance 150 gallons of crude carbolic acid are
heated to 100° C., 150 to 200 Ibs. of powdered resin stirred in,
30 Ibs. caustic soda added and the whole stirred and kept hot
until the black liquid soap is formed.

Prevention of Breeding, and Natural Enemies. — The most
valuable method of reducing mosquitoes, where practicable, is
to obliterate breeding places or to make them uninhabitable
for the larve. The first step in reducing mosquitoes is to see
that there are no flower-vases or other water receptacles serving
as aquaria for the larve, that there are no water-filled tin cans
in the garbage heap or that the roof or street gutters do not
hold standing water. Any rain barrels, cisterns, cesspools or
- gmall reservoirs which cannot be disposed of can be made harm-
less by screening. Pieces of low ground, temporary pools, ete.,
can usually be eliminated by draining.

The natural enemies of mosquito larve can often be exploited
successfully for destroying them. Dr. Smith found that one of
the most potent factors in the reduction of mosquitoes in the

460 MOSQUITOES

great tidal salt marshes of the New Jersey coast were the various
species of killifish. These fish abound wherever the marshes
are constantly flooded and push into places where there is barely
enough water to cover them, and are so active in destroying mos-

Se

beri!
o Wes

< il Maya

Fic. 207. One of the first places to clean up in a mosquito campaign. A
favorite breeding place for such annoying or dangerous species as the yellow fever
mosquito, Aédes calopus, the house mosquitoes, Culer pipiens and C. quinquefas-
ciatus, Anopheles quadrimaculatus, and others.

quito larve that the latter can exist only in high-lying or shut-in
portions of the marsh over which the tide only occasionally sweeps
and to which the “ killies’’? do not penetrate. Knowing the
value of killifish as destroyers of larvee, the problem of preventing
the marshes from producing countless mosquitoes resolves it-
self into so draining that the water on it either will be drawn
off at every low tide or will be constantly stocked with fish. A
number of workers have recently remarked on the folly of oiling
pools which could be stocked with fish, since the oil kills the
natural enemies of the larve and is not permanent. Instead it
is urged that fish be propagated in such pools. The water weeds,
however, should be removed and overhanging plants cut back
so that the fish can operate freely in their pursuit of larve. In
the case of swamps it is suggested that a permanent pond be
constructed at the lowest level and stocked with fish, and the
swamp drained into the pond.

A fresh-water fish of the same family as the killifish (Cyprino-
dontide) known as “ millions” (Girardinus peciloides) has been

NATURAL ENEMIES 461

found very efficient as a destroyer of mosquito larve and has
been extensively introduced into various parts of the tropics
from its home in Barbados and other West Indian Islands.
Except where other fish are present to prey upon it, this tiny

Fic. 208. Some good natural enemies of mosquitoes; A, common killifish,
Fundulus heteroclitus, of great value in brackish marshes; B, fresh-water killifish,
Fundulus diaphanus, valuable in fresh-water streams and ponds. 2 nat. size.
(After Jordan and Evermann.)

fish usually thrives wherever introduced, and carries with it a
noticeable diminution in mosquitoes. Other species of the same
family occur in various parts of the world and are almost in-
variably deadly enemies of mosquito larve.

Other natural enemies of the larve besides fish might well be
encouraged in ponds or reservoirs. The western newt or water-
dog, Notophthalmus (or Diemyctylus) torosus, which is abundant all
along the Pacific Coast of the United States, has been observed
to feed very largely on larve. In Oregon the author has ob-
served grassy pools, which were otherwise ideal breeding places
for mosquitoes but which contained numerous water-dogs, ab-
solutely free of larve, whereas other pools not a quarter of a
mile distant in which no newts were found were swarming with
larvee and pups. Recent experiments by the author, not yet
published, have demonstrated conclusively that this salamander
can be utilized successfully to keep mosquito larve out of such
receptacles as rain barrels, troughs, etc.

462 MOSQUITOES

Other efficient enemies are whirligig beetles (Gyrinide), pre-
daceous diving beetles and various aquatic predaceous larve, in-
cluding some species of mosquito larve. Among birds, ducks
have been quoted as efficient destroyers of mosquitoes and Dixon
of Pennsylvania recently demonstrated their ability to keep ponds
free of larvae; he believes the mallard duck surpasses any other
creature in the number of mosquito larve and pup which it can
destroy. As destroyers of adults the value of such birds as
swifts, nighthawks, swallows, ete., is well known. Bats, also,
have been exploited as mosquito destroyers. The erection of
“bat roosts’ for propagation of these animals has been tried in
Texas, and was found to reduce markedly the numbers of mos-
quitoes, and was financially profitable on account of the guano
which could be collected.

CHAPTER XXVI
OTHER BLOOD-SUCKING FLIES

Importance. — Although the mosquitoes hold the center of
the stage as regards importance as human parasites, there are
many other members of the order Diptera which affect the wel-
fare of the human race. From a medical point of view the
Diptera are far more important than all other arthropods put
together. Besides the mosquitoes, which we have seen are the
transmitters of at least four and probably five diseases, two of
which are of prime importance, the Diptera include the Phle-
botomus flies, which are known to be the sole disseminators of
phlebotomus or three-day fever, and are believed to be the
transmitters of verruga in Peru and of oriental sore in North
Africa and possibly other places; the tsetse flies, which are
transmitters and intermediate hosts for the trypanosomes of
sleeping sickness; the stable-fly and other biting allies of ‘the
housefly, which may carry the bacteria of anthrax and other
diseases from dead or dying animals to human beings; the gad-
flies or horseflies, one species of which is incriminated as the
transmitter of the African loa worm, and all of which may act
in the same capacity as stable-flies, to transmit bacteria mechani-
cally from the blood of a diseased animal to a healthy animal
or person; and the blackflies (Simuliide) and ‘ no-see-ums ”’
(Chironomid), which are sometimes terrible pests though not
known to be disease carriers. Besides these blood-sucking
species, the Diptera include also all the insects which live in the
human body as maggots, and also the housefly and allied species
which, though not properly to be considered parasites, are
~ nevertheless of incalculable importance as mechanical spreaders
of disease germs. »

General Structure of Diptera. — To understand the relations
of thesé numerous important insects and their classification,
we must make a brief survey of the characteristics and classi-

fication of the order Diptera. The whole order can usually be
463

464 OTHER BLOOD-SUCKING FLIES

distinguished readily from other insects by the fact that there
is only one pair of membranous wings, the second pair of wings
being represented only by an insignificant pair of knobbed
rodlike appendages known as halteres (Fig. 191, halt.). The
head is joined to the thorax by a very slender flexible neck. The
thorax itself consists of one mass on account of the fusion of its
three component parts, and the abdomen consists of from four
to nine visible segments and is terminated by the ovipositors
or egg-laying organs in the female, and by the copulatory organs
in the male. The head is provided with a pair of antenne, a
pair of maxillary palpi and a proboscis composed of or con-
taining the mouthparts. The antenne and also the palpi are of
considerable use in classification; the extent of the variations in
the antenne may be gathered from Fig. 211. The mouthparts
are profoundly modified in accordance with the habits of the
flies. In the botflies, in which the adults live only long enough.
to reproduce their kind, the mouthparts and even the mouth are
much degenerated; in the non-blood-sucking forms, such as the
common housefly, the mouthparts are more or less fused into a
fleshy proboscis which is used for lapping up dissolved foods;
in the blood-suckers, which are the forms that particularly in-
terest us here, the mouthparts are developed into an efficient
sucking and piercing apparatus. In some, e.g., mosquitoes
(Fig. 190) and horseflies (Fig. 225), the lower lip acts as a sheath
for the other parts which are fitted for piercing and sucking;
in others, e.g., the stable-fly, Stomoxys (Fig. 240), and the tsetse
flies, Glossina (Fig. 229), the lower lip itself forms a piercing organ,
and the epipharynx and hypopharynx form a sucking tube, the
mandibles and maxille being absent.

Life Histories. — All of the Diptera have a complete metamor-
phosis (see p. 329), and sometimes undergo a most profound
remodeling of the entire body during the usually short pupal
stage. The life history, beyond the fact that a complete meta-
morphosis occurs, varies within very wide limits. Most flies lay
eggs, but some, e.g., the screw-worm fly, Cochliomyia (or Chryso-
mya), and allied species, produce newly hatched larve or eggs
which are just at the point of hatching, while still others, e.g.,
the tsetse flies, Glossina, do not deposit their offspring until it
has undergone its whol¢ larval development and is ready to
pupate.

LARVZ AND PUPA OF DIPTERA 465

The larve of Diptera may be simple maggots with minute
heads and no appendages and capable of only limited squirm-
ing movements, ¢.g., the screw-worms (Fig. 250), or they may
be quite highly developed, active creatures, e.g., the larve of
mosquitoes, midges, etc. Many are aquatic, many others ter-
restrial; usually the eggs are laid in situations where the larvze
will find conditions suitable for their development, and the flies
often show such highly developed instincts in this respect that
itis hard not to credit them with actual forethought. The
pup of the Diptera also vary widely. In one great suborder,
Orthorrhapha, the pupa is protected only by its own hardened

Fig. 210. A, fly emerg-
ing from pupal case, show-

Fie. 209. Types of pupal ing bladder-like ptilinium
cases, showing manner of emer- (ptil.) by means of which
gence of adults. A, empty case the end of the case is
of blowfly, typical co-arctate - pushed off; B, face of fly
pupa of Cyclorrhapha; B, empty showing scar or lunule
case of mosquito, typical ob- (lun.) left by drying up of
tected pupa of Orthorrhapha. ptilinium. (After Alcock.)

cuticle, and is often capable of considerable activity; from this
“obtected ” type of pupa (Fig. 209B) the adult insect emerges
through a longitudinal slit along the back. In the other sub-
order, Cyclorrhapha, the pupa retains the hardened skin of the
larva as a protective covering or “ puparium,” and is usually
capable of very slight movement; from this “ co-arctate ” type
of pupa (Fig. 209A) the adult escapes by pushing off the anterior
end of the puparium with a hernia-like outgrowth on the front of
the head. This outgrowth, called the “ ptilinium ” (Fig. 210A),
shrinks after the fly has emerged, but leaves a permanent cres-
cent-shaped mark on the head known as the “ frontal lunule ”
(Fig. 210B) which embraces the bases of the antenne, and gives

466 OTHER BLOOD-SUCKING FLIES

a dependable clue to the early life of the insect. Adult flies are
usually not long lived, and often live only a few days, just long
enough to copulate and lay their eggs. Some species, however,
e.g., mosquitoes, may live for several months.
The order Diptera, as already indicated, is
ee divided into two great suborders, the Orthor-
rhapha and the Cyclorrhapha. The first order
| 6 includes those species which have a well de-
ps cc veloped larva with a distinct head, and an ob-
oe tected type of pupa. The second includes the
'< flies which have headless maggot-like larve and
D acoarctate type of pupa. In nearly all of these
the antenne are of the type shown in Fig. 211D
¢ and. These suborders are further divided into
ate ones sections or suborders and then into families, but
of antenne of Dip- for our purposes it is unnecessary to follow out
alte ee this classification. It will suffice to take up,
fly: C, gadfly (tab- family by family, those forms which are impor-
pene > gileel tant as blood-sucking parasites of man. The
mosquitoes are of such very great importance
that they deserve separate consideration and have been discussed
in a chapter by themselves (Chap. XXY).

Phlebotomus Flies

General Description. — Phlebotomus flies, otherwise known
as ‘‘ sandflies’’ or ‘“‘ owl-midges,”’ are minute mothlike midges
which are found in nearly all warm and tropical climates of the
world, with the exception of Australia and the East Indies. In
Australia (Queensland) they are represented by an allied fly
of the same family, Pericoma townsvillensis, which is said to be
a very severe biter, producing swellings which may last three
weeks. They belong to the family Psychodidz, which includes
a large number of species of flies found all over the world, nearly
all of which resemble tiny moths on account of their very hairy
bodies and mothlike pose. The latter characteristic, however,
is not shared by the genus Phlebotomus. The latter is the only
genus, except Pericoma, containing habitual blood-suckers with
a long proboscis; in all other members of the family the pro-
boscis is short and inconspicuous.

.
;
:

PHLEBOTOMUS FLIES 467

The phlebotomus flies (Fig. 212D) are small dull-colored in-
sects, usually yellowish or buff, slender in build, with hairy
body and very long and lanky legs. The hairy-veined wings
are narrow, somewhat the shape of mosquito wings, and are held
erect over the body when the insect is in repose. The wings are
quite remarkable for the inconspicuousness of the crossveins which
gives them the appearance of having nine or ten nearly parallel
longitudinal veins. The antenne are long, consisting of a series
of beadlike segments with whorls of hairs at the joints. The

Fic. 212. Life history of phlebotomus fly, Phlebotomus papatasii; A, egg;
B, larva; C, pupa; D, adult. A, x 80; B, C and D,x8. (After Newstead.)

relatively long proboscis is made up in practically the same way
as 1s that of a mosquito (see p. 426), except that the needle-like
organs project beyond the tip of the sheath made for them by
the labium or lower lip. These insects are usually less than
one-fifth of an inch in length and often not over one-eighth of
an inch; they can easily crawl through the meshes of an ordinary
mosquito net, and are therefore hard to avoid. Their bites are
very annoying and cause an amount of irritation which seems
quite out of proportion to the size of the insects. In most cases
it is only the female which sucks blood, but in some species the

468 OTHER BLOOD-SUCKING FLIES

male has a proboscis equally well fitted for piercing skin and
sucking blood, and the male of at least one African species is
known to bite as well as the female. Most if not all of the spe-
cies are nocturnal or become active at twilight only. In Corsica,
for instance, it is said to be very difficult to capture these midges
except for about one hour after sunset. During the daytime
they remain hidden away in dark corners, cellars, crevices of
rocks, ete.

Life History. (Fig. 212.) — Most species of Phlebotomus lay
their eggs in crevices of rocks, in damp cracks in shaded soil, on
moist rubbish, in crannies
or chinks in cement of dark
‘cellars, between boards in
privies and cesspools, and
in other similar situations.
Most species seem to show
a decided preference for
crevices in rocks, and find
ideal situations in ruins of
old stone buildings, crum-
bling rock fences, ete. In
Malta Captain Marett found

eB
ee Gi these insects breeding only
Xi in such places. In Peru,

he

i Eg tt (AM : according to Townsend, the
Fic. 213. An earthquake ruin in Sicily, universal type of fence, a
at ani shai breeding places for phle- + rueture of rubble and loose
| rock, provides ideal breed-
ing places for the species found there, whereas in Italy and
Sicily the earthquake ruins furnish equally ideal breeding places
for them (Fig. 213). The sandflies which occur in certain parts
of Egypt are believed to breed in damp cracks in the sandy soil,
since there seem to be no other suitable places.

The eggs are about 40 to 50 in number and are usually all laid
at approximately one time, being literally shot out by the female
to a distance several times the length of the abdomen. The
eggs are viscid and adhere to the surfaces with which they come
in contact; it would seem that the peculiar method of ejecting the
eggs is a protective adaptation, facilitating their deposition in
the farthest reach of a crevice where even the tiny insect itself

Ss —

LIFE HISTORY OF PHLEBOTOMUS FLIES 469

could not penetrate. The eggs are elongate and are of a dark,
shiny brown color, with fine surface markings which vary in
different species (Fig. 214).

The incubation in the case of the common Old World P.
papatasw requires from six to nine days under favorable con-
ditions, but the eggs are very susceptible to
external conditions, and die quickly if ex-
posed to sunlight or if not kept damp. The
larve (Fig. 212B) are tiny caterpillar-like
creatures with a relatively large head with
heavy jaws (Fig. 215), and with two pairs
of bristles on the last segment of the abdo-
men, one pair of which are sometimes nearly
as long as the body and are held erect and
spread out fanlike; in the newly hatched ye, 214. Egos of
larve there is only one pair of bristles. The phlebotomus flies; 4, P.
body is provided with numerous toothed ee. ie dente
spines which give it a rough appearance. X about 200. (After
These spines have recently been shown by ne
Howlett to differ in different species and, together with the rela-
tive length of the caudal bristles, to form good identification
marks. The whole length of the larva of P. papatasii when
full grown is less than one-fifth of an inch, and is therefore not so
large as an ordinary rice grain. It is
quite active in spite of the fact that it
has neither legs nor eyes; it progresses
in the manner of a caterpillar, holding
to a rock or board with the tip of the
abdomen while stretching the body, then
hiding with the doubled-under head while

drawing up the body again. It feeds on
ey eo decaying vegetable matter, and probably
tus larva. Much enlarged. also on moulds, etc. When exposed to
aoe ‘light the larva of P. papatasiz has the
peculiar habit of flicking itself off the surface on which it has
been resting. On approach of danger, Phlebotomus larve often
“ play ’possum ” and feign death.

The full development of the larve requires from three weeks
to two months or more, depending almost entirely on the tem-
perature. Larve which hatch at the beginning of cold weather

470 OTHER BLOOD-SUCKING FLIES

do not pupate until the following spring. When, after several
moults, they go into the resting pupal stage the last larval skin
with its caudal bristles remains adhering to the posterior end.
The pupa (Fig. 212C) is characterized by a very rough cuticle
over the thorax, but can be identified best by the adhering larval
skin. It is colored so much like its surroundings, and looks so
much like a tiny bit of amorphous matter, that it is very difficult
to find. In warm weather the adult insect emerges after from
six to ten days, but this is much prolonged by low temperatures.
The entire life cycle from the laying of the eggs to the emergence
of the adults may be passed through in a month in hot weather,
according to Howlett’s observations on an Indian species, though
it takes two months of more in cool weather. In Malta, accord-
ing to Newstead, the cycle takes about three months.
Phlebotomus and Disease. Phlebotomus Fever. — Although

sandflies have been accused of transmitting a number of human

diseases in various parts of the world, in most cases their actual
role has not been determined beyond doubt. The most im-
portant relation of sandflies to disease is in connection with a

relatively mild febrile disease sometimes known as three-days,.

fever, but more commonly known as phlebotomus fever or
papataci fever from the name of the transmitter, Phlebotomus
papatasi1. The nature of the disease and the réle of the sandfly
in carrying it is discussed in Chap. X, p. 188. As in the case
of many other insect-borne diseases, the relation of the insects
to the disease was suspected for a long time before the scientific
proof of it was made. It was not until 1908 that Doerr demon-
strated the part played by sandflies.

The principal species concerned in the transmission of phle-
botomus fever is P. papatasi, but it is possible that other species,
especially P. perniciosus and P. minutus, both of Mediterranean
countries, may also be involved, though as far as is known the

disease does not occur outside the range of the first-named species.

except. at Aden.

P. papatasw (Fig. 212D) is of medium size, reaching about one-
eighth of an inch in length, pale yellowish gray in color with
a dull red-brown stripe down the middle of the thorax and a spot
of the same color at either side. It is found in many parts of
southern Europe, North Africa and in southern Asia. It has
the typical habits of the genus, preferring to lay its eggs in

PHLEBOTOMUS FLIES AS DISEASE CARRIERS 471

crevices in damp cellars, in caves, cracks in broken walls, etc. In
Malta the life cycle of this species has been observed to take about
three months, but under ideal conditions it would probably be
shorter.

The adult fly, as observed in Malta, where it has been most
extensively studied, chooses caves, catacombs and other similar
places as its favorite localities. On still, warm nights it is com-
mon in houses, but rarely appears when there is a cool fresh breeze.
Some houses were found to be much more infested than others,
possibly due to the proximity of suitable breeding places and to
the lack of breezes. Newstead found that dark rooms on the
sheltered side of the first floor of a house were most likely to be
infested; only one individual was found on the second floor.
The distance which the adults travel is thought to be very short,
but they may be carried by public. conveyances, and infection
has been known to be transplanted long distances by flies carried
on coasting vessels.

Phlebotomus and Other Diseases. — Sandflies have frequently
been suspected of complicity in the spread of the parasites of
oriental sore, though no definite proof of this has ever been ~
brought out. Wenyon, from his study of oriental sore at Bag-
dad, believed that these flies, as well as certain other insects,
might easily be concerned in the spread of the infection, but he
did not have an opportunity to test his belief. Recently a
number of French workers in North Africa, including Laveran
and the Sergents, have advanced the theory that P. minutus
var. africanus is the carrier of the infection, and that certain
lizards or geckos of the region, Tarentola mauritanica, serve as a
reservoir for the disease. Parasites, closely resembling Leish-
man bodies which cause oriental sore, have been found in the
blood of geckos taken near Tunis, and it is well known that rep-
tiles are an important if not the prime source of food for the
various species of Phlebotomus, and P. minutus especially harasses
the North African gecko. Roubaud found a lizard in West
Africa which was covered with gorged females of this species
and in India P. minutus is said to prefer geckos to man as a
- source of food. It is interesting to note in this connection that
the forest workers in Paraguay, where the more serious American
type of leishmaniasis is found, believe the infection to be caused
by the bite of blood-sucking arthropods which have fed on snakes.

472 OTHER BLOOD-SUCKING FLIES

Phlebotomus minutus is a buff-colored sandfly. It is small, even
for a Phlebotomus; the female measures only about yy of an inch
in length and the male considerably less than this.

Other diseases with which Phlebotomus has been connected
are two which occur together in certain regions of the Peruvian
Andes, namely, Oroya fever and verruga peruviana (see Chap.
X, p. 178). These diseases, as pointed out elsewhere, have
long been confused, and even yet are held by some investigators
to be different phases of the same disease. Townsend, of the
U. S. Department of Agriculture, spent two years in Peru in-
vestigating the diseases (which he considers identical) and came
to the conclusion that Phlebotomus verrucarum is the transmitter,
basing his conclusions on the distribution and habits of the in-
sect, and on certain experiments which he undertook. The sand-
fly in question, which was discovered and named by Townsend,
is the only nocturnal insect which is closely limited in its dis-
tribution to approximately the same localities as is Oroya fever
and verruga, and it seems to be well established that the disease
is contracted at night. Townsend believes that he obtained proof
of the transmission of verruga, and obtained a typical breaking
out, by injecting into a dog the macerated bodies of insects which
had fed on a verruga patient, but his results have not been widely
accepted. If, as is now more generally believed, Oroya fever and
verruga are really distinct, then it is possible that P. verrucarum
may be the carrier of both diseases, or of either one or the other.
If this insect acts as a carrier for both diseases, which would be
a very unusual situation, this fact would explain the close limi- |
tation of the two diseases to nearly the same zones, and would
also explain the frequency with which the two infections occur
simultaneously or following each other. That oroya fever is an
insect-borne disease is almost certain, and it is quite likely that
the sandfly discovered by Townsend will be found to be the
carrier of it. Verruga, however, is a smallpox-like disease and
may be contagious rather than infective.

Phlebotomus verrucarum is a species of sandfly which breeds
principally in the damp recesses of the loose rubble fences which -
are so universally used in Peru, and probably feeds largely on a
species of lizard, Tropidurus peruvianus, which inhabits the same
rock fences. According to Townsend it requires for its life cycle
a fairly high total of summer heat and much moisture, with an

TRUE MIDGES (CHIRONOMIDA) 473

absence of night fogs and of low winter temperatures. The
adults will not live where there are continuous strong air currents,
These conditions limit the species closely to the deep-cut canyons
or “ quebradas”’ (Fig. 53), between 3000 and 8000 ft. elevation, on
the west face of the Andes. There is certainly a remarkable
agreement between this distribution and that of Oroya fever.

Control. — Sandflies are very difficult insects to deal with, both
on account of the small size of the adults and of the nature of
the breeding places.

The only precaution that can be employed to keep the adults
out of houses during warm weather is the use of repellents.
Spraying mosquito netting with some repelling substance, such as
odorous oils, e¢.g., anise oil, eucalyptus oil, etc., or with a weak
solution of formalin, or, in fact, with any of the repelling sub-
stances mentioned in connection with mosquitoes, serves to keep
the insects out as long as the odor lasts. The insects are attracted
toward a light, and are therefore usually very abundant in lighted
rooms on warm still nights. A gentle breeze or a current of air
from electric fans placed near the windows prevents their entrance
and, as has already been mentioned, upstairs rooms are practi-
cally immune. Personal protection can be obtained by appli-
cations of repellents. Townsend recommends equal parts anise
oil, eucalyptus oil and oil of turpentine in a boric acid ointment.

It is almost impossible to destroy sandflies in their early stages.
Townsend thinks that the elimination of rubble fences in Peru
would reduce their numbers, at least locally, but it would be
far from a simple problem to destroy all possible breeding places,
even within a very small radius. In Europe, where stone and
cement are more extensively used than in America, the problem
is still greater. The earthquake ruins of Sicily, as has been
mentioned before, give unlimited breeding places. The large
numbers of these insects in parts of Egypt where such places are
not available indicate that damp cracks in soil may be utilized
as breeding places, and it would be obviously impossible to
eliminate these or to treat them thoroughly.

True Midges (Chironomide)

General Account. — The family Chironomide comprises a
large number of species of small flies, sometimes almost micro-
scopic, found all over the world. The larger ones quite closely

474 OTHER BLOOD-SUCKING FLIES

resemble mosquitoes except for the absence of the long proboscis,
and the dancing flocks of these insects which can be seen over
pools or swamps on any summer day are usually taken for mos-
quitoes without question. As expressed by Riley and Johann-
sen, ‘‘ these midges, especially in spring or autumn, are often seen
in immense swarms arising like smoke over swamps, and pro-
ducing a humming noise which can be heard for a considerable
distance.’’ In such swamps the larve, most of which are aquatic
and live in the mud or amid aquatie vegetation, may be scooped
up, literally by the shovelful. Fortunately the great majority
of these insects are quite harmless, in fact, inasmuch as the
larve are an important food for young fishes, they are distinctly
beneficial. The blood-sucking species belong to the subfamily

Fic. 216. Life history of blood-sucking midge, Culicoides; A, adult male (C.
reticulatus), X 5; B, eggs (C. marium), x 18; C, larva (C. reticulatus), x 5; D,
pupa (C. marium), xX 10. (After Lutz.)

Ceratopogonine and are very small; only the females are known
to suck blood. They are well known to hunters and anglers and
other frequenters of the woods in most parts of the world. In
America they are usually called “ gnats” or ‘‘ punkies ”’ and in
the West are known as “‘ no-see-ums,” on account of their very
small size.

These insects (Fig. 216) can usually be distinguished from
allied insects by the peculiar venation of the wings, the first two
veins being very heavy while the others are indistinct. Though
the bodies, and sometimes to a slight degree the wings, are more
or less hairy the scales so characteristic of mosquitoes are ab-
sent. The proboscis is never long even in the blood-suckers,
and one is led to marvel at the irritation which can be inflicted
by such a small insect with such a small organ. . Usually midges

ja re

— sa ee phe s

>

re ee

LIFE HISTORY OF CHIRONOMIDS- 475

rest with the front legs elevated, though not all species have this

_habit. In most Chironomide the thorax of the adult insect

projects like a hood over the head, but in the subfamily Cera-
topogoninz, which alone interests us here, this is not the case,
and this negative characteristic is the best distinguishing mark
of the subfamily.

There are a number of genera and many species included in
this group of blood-suckers, but they fall naturally into two groups
according to the habits and structure of the larve. In one, of
which the principal genera are Ceratopogon and F orcipomyia,
the larve differ from all other Chironomide in being terrestrial,
living in damp places under bark, stones, moss, etc., and in being
covered with spines (Fig. 217). In the other group, of which the
principal genus is Culi-
coides, the larve are
orthodox in being

aquatic and unspined

3 : i Fig. 217. Larva of Forcipomyia specularis.
(Fig. 216C); a fen oe x 15. (After Malloch.)

cies are marine. Most
of the blood-sucking midges become active at dusk, but if dis-
turbed they will bite in the shade even on bright sunny days.
Life History. — The eggs of aquatic midges (Fig. 216B), sev-
eral hundred in number, are laid in water, either floating free or
moored to some object. Each one is covered with a gelatinous
envelope, and the eggs adhere in chains or in little masses, thus
resembling very diminutive bunches of frog or toad eggs. In
about six days, more in case of low temperature, the eggs hatch
into almost microscopic larve (Fig. 216C). The latter are worm-
like creatures practically without hairs or spines in the aquatic
species, but with conspicuous bristles in the terrestrial forms.
Usually the only hairs present are in a pair of tufts on the last
segment. In most midge larve there is a footlike outgrowth
on the first and last segments of the abdomen. The larve have

_ inconspicuous blood-gills for breathing in water, and therefore ©

do not need air as do mosquito larve. Most midge larve are
free-swimming, but some excavate tubes in mud and line them
with a salivary secretion which hardens on contact with water.
The food consists of microscopic plant and animal life. The
pupa (Fig. 216D) rather resembles that of a mosquito, except
that the abdomen is kept extended instead of curled under and

476 OTHER BLOOD-SUCKING FLIES

the pupa floats in a vertical position, breathing through tufts of
threadlike filaments which correspond to the breathing trumpets
of mosquitoes. In the terrestrial forms the pupa retains the
last larval skin hanging to its posterior end. The aquatic species
of the subfamily Ceratopogonine are peculiar in that the pupz
must reach a dry surface before the adult will emerge. Little
is known about the length of time required for the development
from egg to adult, but it is probably comparable with that re-
quired by mosquitoes — two weeks or less to a month or more,
according to temperature.

Annoyance. — The amount of annoyance which may be caused
by midges is sometimes very great. The writer will never for-
get his experiences with them in a
collecting and fishing trip in the
Cascade Mountains of Oregon.
The midge which proved itself
troublesome, a species of Culicoides
(Fig. 218), was very local in dis-
tribution, and always standing
pools of shallow water were found
in the near vicinity. The prox-
imity of such pools was invariably

Fie. 218. A “punky” or “no- proclaimed, towards evening, by
serum lieder, which is the eollection of great numbers of
the Cascade Mountains of Oregon. these insects on all exposed parts
eo of the body, each one so minute as
to be hardly visible, but in the aggregate sometimes giving the
arm or shirt sleeve a dark gray color. Each one is presently
the cause of an intensely itching spot. That the insects are
attracted by animal smells is evident from the following experi-
ence. The writer had shot a rabbit and was skinning it. Al-
most immediately after the animal was cut open and the smell
of the warm bowels exposed to the air the writer found himself
attacked by myriads of these insects, and was bitten to such
an extent as to be driven almost to a complete frenzy, until he
discovered that only a few yards from the opened animal he was
not attacked at all. The skinning of the rabbit was completed
in the welcome protection of a dense smoke.

Midges as Disease Carriers.— Only in one instance have
midges been accused of carrying disease. Two species of land-

CONTROL OF CHIRONOMIDS ATi

breeding midges, Forcipomyia ute and F. townsendi, have been
incriminated by Townsend as the carriers and intermediate hosts
of the protozoan parasite causing “uta”? in Peru. Uta (see
Chap. V, p. 86) is a form of leishmaniasis occurring on the
western face of the Andes. According to Townsend, Leishman
bodies are found in abundance in the digestive tract of these
midges, and injection into laboratory animals of serum contain-
ing the ground bodies of captured insects resulted in the forma-
tion of sores which Townsend regarded as uta, and from which
he obtained a few Leishman bodies. Two cases are cited, also, in
which uta sores developed following the bites of the midges, and
supposedly due to them. According to Townsend the infection
is evidently transmitted by contamination of the wound made by
the proboscis with infected excrement. That these insects are
really the transmitters of uta in man cannot be considered as
proved, but it must be regarded as a possibility. It should be
recalled that many insects have been accused of carrying Oriental
sore and allied diseases, among which are blackflies (Simulium),
sandflies (Phlebotomus), gadflies (Tabanide) and others, and it
is open to question whether any insect which harbors a Her-
petomonas in its gut may not be able to infect vertebrates if the
germs reach the blood. If so, these midges must be regarded as
conveyors of a Leishmania infection.

Little is known about these species of Forcipomyia, but it is
probable that their habits are similar to those of better known
species. In the North American species, the larve (Fig. 217)
are slender whitish worms about one-eighth of an inch in length
which live in damp places in moss and under bark, stones, etc.
The pupz are pale yellowish, later becoming brown.

Control. — The control of the aquatic biting midges is not
difficult, and can be accomplished in the same manner as can the
control of swamp-breeding mosquitoes, by draining, stocking with
natural enemies or oiling. It is improbable that these midges
breed to any extent in transient pools, for most of them, at least,
prefer pools of standing water, abundant in organic débris and
microscopic organisms. The terrestrial-breeding forms of For-
cipomyia and Ceratopogon, like the sandflies, are practically im-
possible to exterminate.

Much protection from the adults can be obtained by the use
of repellents as advised for mosquitoes and sandflies (see p. 455).

478 OTHER BLOOD-SUCKING FLIES

Blackflies or Buffalo Gnats

General Account. — The blackflies, as annoyers of domestic
animals and man, are among the most important of insect pests.

small,

The females are most insatiable blood-
suckers, and have been known to at-
tack cattle in such swarms as to kill
them; a Himalayan species, accord-
ing to Alcock, has been said to kill
even human beings in the same way.
These small insects, which constitute
the family Simuliide, are quite unlike
the other flies of the group to which
they belong. Instead of the usual
slender, long-legged, midgelike flies of
this group we have in the blackflies

robust, humpbacked creatures

with short legs and broad wings, rather

Fia. 219. Blackfly, Simulium resembling, in a general way, minia-

pecuarum. X 7. (After Riley.)

ture houseflies (Fig. 219). The an-

tenne are composed of 11 segments, but they are short and

stocky, and have no hairs at the
joints. The proboscis in the
female is short but heavy and
powerful, while in the male it
is poorly developed. The mouth-
parts are made up of the same
‘parts as in mosquitoes, but are
dagger-like instead of needle-
like (see Fig. 220). Most of the
northern species are black in
color, whence their name, but
some of the species are red-
dish brown or yellowish, and
they may be variously striped
and marked. The wings are
either clear or of a grayish or

Fic. 220. Mouthparts of blackfly,
Simulium; ant., antenna; ep., epiphar-
ynx; hyp., hypopharynx; lab., labium;
label., labellum; mand., mandible;
max., maxilla; max. p., maxillary pal-
pus. (After Mieace: )

yellowish color with the few

heavy veins near the anterior margin often distinctively
colored. Some of the species are not over one. mm. (gs of

ee ee ee

in number, by a number of

4

LIFE HISTORY OF BLACKFLIES 479

an inch) in length and the largest of them scarcely exceed one-
fifth of an inch. 2

Life History. — Unlike the mosquitoes and midges, blackflies
breed in running water and few streams flow too swiftly for
them. The eggs are laid in large masses, up to many thousands
females. The eggs (Fig. 221A), ‘te
which are elliptical and yellowish
and have a peculiar slimy coat-
ing, are deposited by some spe-
cies on leaves or blades of grass
which are occasionally licked by
running water, the weight of
the eggs sufficing to submerge
them; other species dart into
the water and deposit directly
on the slimy surfaces of sub-
merged stones or twigs. The
author found a favorite breed-
ing place of the blackflies in
the woods of Northern Ontario
(species undetermined) to be on
the slimy boards of old lumber
chutes over which water was
constantly flowing. It requires
at least a week for the eggs to
hatch.

’
\
k
Pi
Fi
x
ey
fs
bse
py
VA:
Uys

Fic. 221. Developmental stages of
blackflies. A, egg of Simulium venu-
stum; B, larva of S. bracteatum; C, pupa

The larva (Fig. 221B) as soon
as hatched attaches ‘itself by a
sucker at the posterior end of the
body to a stone or other sub-

(in pupal case) of S. venustum; all much
enlarged, not drawn to same scale;
an. g., anal gills; ant., antenna; dev. g.
fil., developing gil) filaments of pupa;
g. fil., gill filaments; m. f., mouth fans;

p. ¢., wallpocket-like pupal case; post.
s., posterior sucker. (A, after Meczni-
kow from Jobbins-Pomeroy, others
after Jobbins-Pomeroy.)

merged object. As expressed
by Alcock, “one of the most
characteristic attitudes of the
larva is to sit upright on the end of its tail,— to use the lan-
guage of the poets of the daily press, — with its mouth fans
standing out from its head like a pair of shaggy ears.” The
“mouth fans,’ which are very delicate and elegant, are used
for sweeping microscopic particles into ‘the mouth as they are
brought by the running water. The stump of a leg on the

480 OTHER BLOOD-SUCKING FLIES

first segment (Fig. 222 prol.) is used for creeping, in conjunction
with the posterior sucker, the larva looping along like a “‘ meas-
uring worm’”’; it is also of use in constructing the silken cocoon
from the secretions of the salivary glands. This single little
leg has a crown of tiny hooklets which make it possible for the
possessor to hold its ground even in a torrent of water. The
salivary glands referred to are quite
unlike those of other insects, in that
they extend clear back to the pos-
terior end of the body (Fig. 222, sal.
gl.). The fluid secreted hardens to
sik at once on exposure to water,
and is used not only in spinning the
cocoon, but also in spinning anchoring
threads and life-lines. According to
Malloch, the larva when disturbed
releases its hold and floats downstream,
holding by the stumpy leg to a silken
thread which is being spun out, and
by means of which the insect later
regains its former position. The
larve breathe by means of tiny gills
which can be projected through a slit
in the last segment of the abdomen
é; (Figs. 221 and 222, an. g.). The larve

Fic. 222. Larva of black- 2re mever found solitary, as would be
fly, Simulium venustum, side expected from the manner of laying
Pa : a= pon eggs; the author has seen the boards
dig. tr., digestive tract; m.f., on the bottom of a log chute com-
enti ae Ee ee pletely covered with mosslike patches
posterior sucker; sal. gl., sali- of these larve for areas of a square
vary and spinning gland. yar d or more.

After four or five weeks, in summer, the larve prepare to go
into the resting pupal stage, and spin for themselves a partial
cocoon which is variously shaped like a jelly glass, slipper, wall
pocket, etc., open at the upper end for the extrusion of the
branching gill filaments which are used as breathing organs (Fig.
221C). Some species simply spin a snarl of threads, the work
of a whole community, in the meshes of which the pupz exist in
a fair state of protection. The general form of the pupe can be

-
di Ghoauvtiinm _ a ie

_——_—_—_ | a

BLACKFLIES 481

seen in Fig. 223. The breathing filaments vary greatly in dif-
ferent species and may have from four to 60 branches.

The adults escape from the pup after from one to three
weeks through a slit in the back, and are carried safely to the
surface by a bubble of air which has been collecting inside the
old pupal skin. The adults are short lived and lay their eggs
soon after emergence. The whole life of a gen-
eration from egg to egg may be passed in from
six weeks to two months or more. Some spe-
cies have several generations a year but the
majority produce but a single brood a year.
The Canadian species already referred to is
seen only for a few weeks in May and early
June, during which time it is locally exces-
sively abundant. Most species are diurnal,
but the author found the Ontario species to
be most active from late afternoon until dark,
and again early in the morning. This species
will also bite readily at night in the presence of
artificial light.

The species of blackflies are numerous, but Be

; : : 2 Bie. - 223. - Pupa
are all included in the single genus Simulium, of blackfly, Simu-
with several subgenera which some workers ““™ jJenningsi, re-

moved from case;
elévate to the rank of true genera. Some ¢, eye; lc., leg
species do not attack man but viciously attack cases; br.f., breath-
: ‘ P ; ing filaments or gills;
various domestic animals. While on a collect- y. ¢. wing case.
ing trip in the Cascade Mountains of Oregon (After Jobbins-Pom-
the author found it necessary to keep the pack ae
animal picketed in the smoke of the camp fire constantly to pro-
tect the poor creature from the blackflies which congregated in
large numbers about his eyes and nose, yet neither the author nor
his companion was ever bitten by one of these flies. One of the
most troublesome species in the United States is S. pecuarum,
_ the famous buffalo gnat of the south central portion of the country.
This species was formerly more abundant than now, and was a
terrible scourge to mules and cattle. S. venustwm is one of the
most important molesters of man. It occurs over the greater
part of the eastern portion of North America.

Annoyance. —In the estimation of the author, no insect

scourge he has ever experienced is more terrible than an attack

482 OTHER BLOOD-SUCKING FLIES

of blackflies as he encountered them in Canada. From ae-
counts of other authors they must be equally terrible in other
places. King, for instance, states that in parts of Sudan (Don-
gola) a species known as the nimetti, Simulium griseicollis,
renders life a burden during the winter months. The famous
Columbacz fly, S. columbaczense, of southern Europe is said to
be a terrible pest, and there are instances of children having been
killed by it. My own experiences occurred in the woods of
Northern Ontario early in June. Upon arriving there I did not
recognize Dr. Munford of Cornell University, with whom I
had been quite intimate, until he spoke. He had been in the
region about a fortnight. His face, neck and arms were so swol-
len from blackfly bites as to completely alter his appearance.
The wrists were swollen until no constriction between hand and
forearm was present. That evening, having been told of the
manner in which deer came and stood in the water near the
outlet of the lake, a mile or so from camp, I went in a canoe to
watch them, being warned to tie my trouser legs tightly around
my shoes and my coat sleeves to my gloves, and to fit a veil
stretched from a broad-brimmed hat tightly around my neck.
No repellents were at hand. With some impatience (having been
bred among the mosquitoes of New Jersey) I submitted to these
precautions, though I was careless in carrying them out, and
made the trip to the outlet which is an old log chute, and the
breeding place of the flies. In spite of the precautions taken,
the blackflies, alighting on the veil in such numbers as to make
it difficult to see through it, managed to find vulnerable spots
in my armor. Unlike mosquitoes they alight and crawl; they
found their way up under the veil, between the buttons of shirt
and trousers, and through the cords at my wrists. In a few
minutes I was driven almost frantic and could hardly restrain
myself from diving into the lake to avoid the attacking flies, as
did the deer. Each bite, and before I got to the safe haven of a
dense smudge at camp I had hundreds of them, was only slightly
painful; the flies drilled a tiny hole which bled a drop or two, so
that the attacked parts of the body became completely smeared
with blood. But this was not the end. The bites next morning
were swollen, and itched somewhat; the swelling and irritation
grew constantly worse until the third night, when each bite
became the site of an oozing pimple. By this time the itching

CONTROL OF BLACKFLIES 483

was so intense that I was in agony all night and could not sleep.
Accompanying this there was a feeling of general ‘“ ennui”
and despondence with some fever, due, no doubt, to the action
of the poison injected by the numerous insects. Subsequent
attacks by the flies, though always far from pleasant, were not
so severe in their effects, a certain amount of immunity appar-
ently having been built up. On account of the slow develop-
ment of the symptoms it was my belief that possibly they were
due to the injection of a living organism. Stokes, however,
has shown that the effects of blackfly bites, essentially as de-
scribed above, can be reproduced by the injection of material
from preserved flies. An interesting suggestion is made by
Stokes that possibly the first bites of the flies sensitize the body
to the particular poison injected so that it reacts rather violently
to subsequent injections of it. This phenomenon, which is
known to occur in connection with many poisonous substances,
is a form of anaphylaxis (see p. 24). Possibly the rashes pro-
duced by mites, lice, etc., may also be due to such a reaction.

As yet blackflies are not known to be the carriers of any dis-
eases. A theory was rampant a few years ago that pellagra was
due to a protozoan transmitted by blackflies, but it is now gen-
erally held that this disease is due to an imperfect diet, or rather
to lack of the necessary assortment of substances in the diet,
and so is in no way connected.with blackflies or other insects.

Control. — Since blackflies breed in running water the methods
to be employed in their extermination are quite different from
those ordinarily used in the extermination of mosquitoes. One
of the measures most widely ‘used is the treatment of breeding
streams with phinotas oil, a poisonous oil which forms an emul-
sion in the water and slowly soaks through it. In concentrations
sufficient to destroy the larve, however, this oil is also destruc-
tive to fish. Often the breeding grounds of blackflies may be
locally destroyed or reduced by damming the stream at inter-
vals, leaving falls between, or in the case of small brooks by the
construction of underground channels or of a drain-pipe line.
The clearing away of roots and fallen logs from streams is often
of value, in that it removes surfaces on which the eggs are laid,
and obliterates the numerous small falls which are ideal for the
larve. In larger streams the cultivation of fishes, such as trout,
young bass, darters, etc., greatly reduces the number of black-

484 OTHER BLOOD-SUCKING FLIES

flies if it does not eliminate them entirely. In such cases care
should be taken that there are no small trickling streams which
are not readily reached by fish. In the author’s experience
streams which harbor large numbers of caddis worms, dragon-fly
larvee and other carnivorous aquatic insects do not breed black-
flies to any extent.

A considerable degree of protection from blackflies can be
obtained by the use of repellents such as are used for mosquitoes,
but their efficiency seems to be lost more quickly than in the case
of mosquitoes. Moreover the crawling habits of the flies must
be taken into account, and other parts of the body than those
which are directly exposed must be treated. Blackflies may be
driven from houses by fumigation with pyrethrum powder or by
any other fumigation method. In camp life the use of smudges
is indispensable. An efficient smudge which will last all night
can be made in an old bucket with a few holes punched near the
bottom. A small fire is started in this and then the bucket is
filled with partly wet, punky, decayed wood which will smoulder
slowly and produce a dense yellow smoke. Sleeping in the
presence of such a smoke is at first almost as unpleasant as are
attacks by mosquitoes and blackflies (the latter becoming active
only toward dawn) but one soon becomes accustomed to it,
and it has none of the terrible after-effects of an attack by the
flies. |

Gadflies (Tabanidz)

General Account. — Although primarily of importance as
blood-thirsty pests of domestic animals, the gadflies or horseflies
(Tabanidz) cannot be ignored as biters of human beings, es-
pecially as they have been shown to be implicated in the spread
of certain human diseases. The bites are painful, and sometimes
cause annoyance for several hours; not infrequently these bites,
which may bleed, subsequently become infected and give rise
to troublesome sores. The females alone are bloodsuckers, the
males living chiefly on plant juices. These flies, of which over
2500 species have been recorded, occur in every part of the world,
and in every sort of habitat where water or damp places are avail-
able for breeding purposes.

The gadflies are of large size and heavy build (Fig. 224A).
They are often beautifully colored in black, brown and orange

TABANIDS A485

tones, sometimes with brilliant green or green-marked eyes,
though in most species of temperate climates the huge eyes are
brown or black. The head is large, and in the male is almost.
entirely occupied by the eyes, which meet across the crown of
the head (Fig. 224B), though in the females a narrow space is

Fie. 224. Life history of a Tabanid, Tabanus kingi, a ‘‘seroot’”’ of Sudan. Ae
adult female, x 3; B, head of adult male, x 3; C, egg mass, laid in crevices of rock,
<x 5; D, larva, xX 23; EF, pupa, x 23.. (After King.)

left between them. The antenne are of characteristic shape
(Fig. 211C) varying somewhat in the different genera. The
mouthparts (Fig. 225) are almost exactly like those of the
blackflies on a large scale. The stabbing and cutting parts
are usually short, heavy and. powerful, though in one genus,
Pangonia, the proboscis is very long, enabling the fly to pierce
flesh and suck blood while hovering in the air and to pierce
even through thick clothing. Most of the species are very

\

486 OTHER BLOOD-SUCKING FLIES

deliberate and persistent in their feeding and are not easily dis-
turbed when they have begun to suck blood. The thorax is
relatively long, and the wings are large and expansive and usually
held at a broad angle to the body, as shown in Fig. 227. The
markings of the wings usually give the easiest means of identi-
fication of the genera. Of
the four most important
genera as human pests,
Tabanus (Fig. 224) is of
large size and has clear
or smoky wings, with no
spots or a few small scat-
Fic. 225. Mouthparts of a tabanid; hyp., tered OOS Pangonta

hypopharynx; lab., labium; label., labellum; (Fig. 226) also has clear
labr. ep., labrum-epipharynx; mand., mandible; or smoky wings but can

max., maxilla; max. p., maxillary palpus. pe distinea nee 7 ae
long proboscis; Hamatopota is of moderate size and has wings
with profuse scroll-like markings; and Chrysops, the species of
which are often small, even smaller than a housefly, has a con-
spicuous black band on
the wing (Fig. 227).
Life History.— All the
tabanids breed in water
or in damp places. The
eggs (Fig. 224C), several
hundred in number, are
laid in definitely shaped
masses on the leaves of
marsh or water plants,
on the leaves or twigs
of trees overhanging

water, or in crevices of fig. 226. A long-beaked tabanid, Pangonia

rocks along the sides of 7uppellit, of eastern Africa. X 2. (After Castel-
lani and Chalmers.)

streams. The eggs are
white when laid, but soon turn dark. They are deposited during
the summer and under favorable circumstances hatch in from five
to seven days. The newly hatched larve fall into the water or
to wet ground or decaying vegetation such as occurs around the
edges of marshes, in sphagnum bogs, in decaying logs, ete. The
larve (Fig. 224D) are cylindrical legless creatures, pointed at

fod

TABANIDS AND DISEASE A487

each end, and with a number of spines or warts on the body.
They are voracious feeders and prey upon various soft-bodied
animals which they find in the water or mud in which they live,
and are not averse to the practice of cannibalism if food is scarce.
The larve grow rapidly during the remainder of the summer, but
remain inactive and with little*or no growth during the winter.
In the spring they complete their development and creep out to
drier ground to pupate. The pupa (Fig. 224E) often resembles
the chrysalis of a butterfly in form. The adults of the species
of temperate climates emerge after two or three weeks, but King
states that tabanids in the Sudan exist as pup only six to eight
days. The whole life history of species of temperate climates
therefore occupies about a year, but it is shorter in tropical species,
in which there are probably several broods a year.

The adult flies are strictly diurnal, and are often active in the
clear sunlight of a summer day, though many forest-dwelling
forms, e.g., the deerflies, Chrysops, prefer shade. They do not
go in swarms as do many other biting insects but are usually
solitary in habit. On account of their powerful wings they are
sometimes found at considerable distances from their breeding
places. As remarked before, only the females are blood-suckers;
the males, and very probably the females to some extent also,
feed on plant juices, the dew of leaves which hold a little organic
matter in solution, excretions of insects, etc. Gadflies collect
near pools and skim over the surface of the water, the under side
of the body often touching the water. Portchinsky, in Russia,
has devised a means of trapping the flies, based on this habit
(see p. 489).

Tabanids and Disease. — Although tabanids are not known
to serve as the intermediate hosts of any disease-causing pro-
tozoans, they have been shown to be efficient as mechanical
disseminators of various disease germs, being especially dangerous
in this respect on account of their intermittent feeding. It is
quite common for them, having been disturbed while feeding on
one animal, to continue their meal on another.

Surra, an important disease of horses in southeastern Asia and
Madagascar, caused by a trypanosome, is transmitted in this
manner, and also El debab, a trypanosome disease of camels.
Other trypanosome diseases of animals, normally transmitted
by tsetse flies, can be transmitted experimentally by tabanids,

488 OTHER BLOOD-SUCKING FLIES

but only immediately after the infective feed. Human trypano-
some diseases have been suspected of being transmitted likewise,
but there is yet no proof that this takes place.

The most important disease disseminated by tabanids is an-
thrax. This is a bacterial disease to which nearly all herbivorous
animals and man are susceptible, and which is very destructive,.
sometimes killing over 75 per cent of its victims. The bacilli
which cause the disease gain entrance to the body either through
abrasions of the skin to the blood, through spores in the air to
the lungs, or through contaminated food to the intestine. The
bacilli have been found in the alimentary canal of tabanids
which have fed on dying or dead victims, and animals inoculated
with these bacilli died of anthrax. That these flies could trans-
mit the disease not only when crushed so that the contents of the
digestive tract could contaminate the wound, but also by their
bites, has been stated many times, and has recently been observed
in China under conditions which placed it beyond doubt. The
method of transmission is purely mechanical and probably oc-
curs only when a fly which has been feeding on a diseased animal
finishes its meal on a healthy animal or on a human being, the
disease germs adhering to the mouthparts long enough to be
transferred to the new animal. The stable-flies, Stomoxys, and
other biting flies which will attack two or more animals in quick
succession are equally as dangerous as anthrax carriers.

Tabanids have often been accused of causing diseases similar
to, if not identical with, oriental sore. In the intestines of vari-
ous tabanids there exist flagellate parasites belonging to the
genus Herpetomonas, and it is believed that if these should ac-
cidentally gain entrance to the flesh of a human being by contami-
nation of the puncture made by the host fly, they might assume
the form of Leishman bodies and multiply to a sufficient extent to
cause a local sore. Obviously such implanted parasites would
be permanently side-tracked, and would stand little chance of
ever being released by a fly of the species in which they nor-
mally live. Such a theory is proposed to explain the sporadic
cases of leishmaniasis of the skin which occur in Panama and
other places, and which are usually reported to develop at the
site of a horsefly bite. In Sao Paulo, Brazil, a form of leish-
maniasis is very common among forest workers, even in wild —
uninhabited regions. The fact that the disease is contracted

CONTROL OF TABANIDS 489

only by men who spend the day in the forest, and is most prevalent
in May and June, a time corresponding to the appearance of
many tabanids, points strongly to these insects as the carriers
of the infection, since they are the only diurnal insects exclusively
found in forest regions. The forest leishmaniasis of Paraguay
may also be due to tabanids.

In one other case a tabanid is implicated in the spread of a
disease. In the tropical jungles of Africa certain species of
Chrysops locally known as
mangrove flies, serve as in-
termediate hosts for filarial
worms. Leiper and other
investigators have found
that the larve of the loa
worm, Loa loa, which
swarm in the _ peripheral
blood of the host in the
daytime only, undergo
rapid development in sev- Fig. 227. <A deerfly, Chrysops callidus.
eral Chrysops, especially te
C. dimidiata and C. silacea, and probably also C. centurionis
(see p. 309). It is probable that other species of Chrysops,
including our own deerflies (Fig. 227), would be able to serve as
intermediate hosts for the worms, in which case there is danger
that this form of filarial disease, if introduced into America or
other countries, might become endemic.

Control. — Prevention of bites from tabanids, especially dur-
ing an epidemic of anthrax, or in places where diseases believed
to be transmitted by tabanids are prevalent, is an important mat-
ter. Practically the only means that can be employed is the
use of repellents, as for other insect pests (see p. 455). Accord-
ing to Herms, repellents efficient against tabanids usually con-
tain fish oil.

In a recent publication Portchinsky, a Russian entomologist,
having found that tabanids have the peculiar habit of skimming
over pools, touching the lower side of their bodies to the surface,
advised the conversion of such pools into traps by pouring oil
on them to produce a surface film, so that the insects would be
caught in it, and the spiracles (openings of the trachee through
which air is absorbed) closed up. In an experiment which he

490 OTHER BLOOD-SUCKING FLIES

performed in a pool with a surface of a little over a square yard,
he caught in five days 1260 male and 258 female Tabanus, and
416 male and 33 female Chrysops. This ‘‘ pool of death ”’ was
literally studded with ‘ floating islands of dead tabanids.”’
The flies are said to visit the pools even after sucking blood.
Portchinsky suggests the construction of traps of this nature in
pastures where tabanids are troublesome, fencing them in, of
course, to prevent the stock from getting access to them.

From the solitary nature of the flies, and the great variety of
breeding places which may be selected, it is obviously impossible,
in most cases, to exterminate tabanids during their early stages.
Natural enemies probably do much to limit their numbers;
fishes and large carnivorous aquatic insects prey upon the larve,
and birds and hornets on the adults. Hine describes seeing

bald-faced hornets, Vespa maculata, capture and cut to pieces .

horseflies which were too large for them to carry.

Tsetse Flies

Next to the mosquitoes the tsetse flies are the most important
of the biting flies. The history and destiny of the African con-
tinent has been and will be very largely controlled by these
insects. As far as their own biting power is concerned, tsetse
flies are of little importance; their bites are less painful than are
those of many other biting flies of similar size. It is in the réle of
carriers of trypanosome diseases that they gain their importance.
Not only the two or possibly three forms of human sleeping sick-
ness, but also a large number of deadly trypanosome diseases of
animals are transmitted by these insects. The native wild ani-
mals of Africa are largely immune to these diseases and serve as
a reservoir for them, but domestic animals and man succumb in
large numbers, in fact to such an extent that some parts of Africa
are uninhabitable, and in other parts it is impossible to keep
domestic animals of any kind. The abundant and varied wild

game of Africa, particularly the numerous species of antelopes, |

are the chief natural source of food for tsetse flies, and since the
flies serve as intermediate hosts for the trypanosomes harbored
by the wild game, it is obvious that when man or domestic ani-
mals are bitten by these flies they are in great danger of being
inoculated with one or more species of trypanosomes.

a ee a en ee ee ee ee Pee Pare Lee ee

TSETSE FLIES

491

General Form. — The tsetse flies (Fig. 228) are elongate, dark
brown or yellowish brown flies, some species no larger than an

ordinary housefly, others larger than
blowflies. They are- usually in-
cluded as an aberrant group of the
housefly family, Muscide, but from
other members of the family they
differ in a number of striking ways,
especially in the manner of repro-
duction, and in form of the larva.
They constitute the genus Glossina
which contains 15 species and has
no very close allies; some species
are of very wide distribution, while
others are local or very rare. Tsetses
can most easily be distinguished
from other flies by their position
when at rest (Fig. 228); their wings

Fig.
position.

228.

Tsetse fly in resting

x 4. (After Austen.)

are folded flat, one directly over the other, straight down the
back, like the blades of a pair of scissors, while the proboscis

Pie: . 229.
mouthparts of tsetse fly;
ant., antenna; ep., epi-

Head and

pharynx; hyp., hypo-
pharynx; palp., palpus;
lab., labium; label., label-
lum; sp., spiracle. (After
Alcock.)

projects horizontally in front of the head.
Beyond these characteristics there is noth-
ing strikingly distinctive about a tsetse fly,
and it is therefore difficult for anyone who
is not thoroughly familiar with it to identify
it on the wing. The darting manner of
flight and buzzing sound are said to be
quite diagnostic when one is once familiar
with them. When the flies are caught and
examined, however, there are a number of
good identification marks. Most charac-
teristic, perhaps, is the arrangement of
the mouthparts and antenne (Fig. 229).
The proboscis consists of a bulblike base
which is continued as a slender shaft, com-
posed of a grooved lower lip with two
needle-like puncturing organs within it, one

of which, the hypopharynx, contains a delicate tube for carrying

the salivary juices.

The proboscis proper is ensheathed in the

maxillary palpi which are so grooved as to conceal entirely the

492 OTHER BLOOD-SUCKING FLIES

mouthparts when the latter are not in use, and it is thus the palpi
alone that are seen when the long blunt-tipped proboscis is ob-
served. The characteristic form of the antennze is shown in
Fig. 229. The thorax is relatively large and
quadrangular, with a characteristic pattern
which is, however, inconspicuous in some
species. The abdomen may be nearly uniform
dark brown, or pale brown banded with a
dusky color. The male has a large oval swell-

ing on the under side of the last segment of

Fie. 230. Hypo- : ;
pygium of male the abdomen, the “ hypopygium ” (Fig. 230),
tsetse fly. (After which forms a good distinguishing mark be-
Alcock.)

tween the sexes.

Distribution, Habits, etc. — Tsetse flies, fortunately, are lim-
ited in their distribution to the middle portion of the African
continent from south of the Sahara Desert to the northern borders
of British South Africa (Fig.
231,=). One species occurs
in the southwestern corner
of Arabia. Tsetses are by
no means evenly distributed
over this great area, but are
limited locally to “fly-belts,”
chiefly along rivers and at
the edges of lakes. All the
factors which cause the
“patchy ” distribution of
tsetses are not known; there
are cases where close limita-
tion to certain areas cannot
be explained by any known Fig. 231. Approximate ranges of tsetse
requirements of the flies. flies. (Compiled from Austen.)
Different species vary in =... range of entire genus glossina
their choice of habitats; ») pti - rs pe i
Glossina palpalis (Fig. 236), .
the carrier of Gambian and Nigerian sleeping sickness, is
seldom found more than 30 yards from the edge of water
where a sandy bottom and overhanging vegetation is abun-
dant, though it follows animals and man for a few hundred
yards from such positions. This species is found only in shady

oS LLOE e
Oe LE AE AF LAF

HABITS OF TSETSE FLIES 493 —

places and where there is great humidity. Glossina morsi-
tans (Fig. 237), the fly which is particularly well known to big-
game hunters in Africa and is the carrier of Rhodesian sleeping
sickness, is less dependent on water, and in fact prefers a rather
hot and fairly dry climate. It is confined to open brushy country
with scattered trees, where there is a moderate amount of shade
for cover. It is never found either in dense forest or in open
grass land. Most other species of tsetses resemble one of these
two species in choice of habitats, though few if any are as inde-
pendent of water as is G. morsitans. | ,

Tsetses are diurnal in habits, but the time of activity varies
with the species. G. palpalis is most active during the middle
part of the day on bright days; G. tachinoides, on the other hand,
is especially hungry on dull days and early in the morning; G.
morsitans is active in the morning and afternoon, but usually
disappears at midday; G. brevipalpis and G. longipennis bite
in the early morning from sunrise until about 8 a.m. and in the
afternoon from 4 p.m. until some time after dark. Both the last-_
named species are attracted by lights at night, and enter lighted
railroad coaches passing through the “ fly-belts.”’ G. palpalis,
and probably other species, also, seldom rise more than a few feet
above the ground.

It has been the universal experience of collectors of tsetse
flies that the males outnumber the females, often to the extent of
ten or more to one. Yet it is a remarkable fact that when bred
in the laboratory, males and females are obtained in equal pro-
portions. Many different explanations for these apparently
contradictory facts have been proposed, but the most probable
is the one recently brought out by Lamborn, based on his ob-
servations on G. morsitans in Nyasaland. Lamborn has ob-
served that copulation takes place after a rough capture, and
that, in captivity at least, females even in an advanced state of
gestation are not exempt from the attacks of the males, although
this often results in abortion. In nature, therefore, the preg-
nant females would necessarily have to hide to avoid the males,
and so would be less likely to be caught by a casual collector.

Tsetses show marked preference for certain colors, being es-
pecially attracted to blacks or browns, and repelled by white.
The dark skin of negroes is selected in preference to pale skin to
such an extent that a white man is seldom troubled when ac-

494 OTHER BLOOD-SUCKING FLIES

companied by natives. Black or dark clothes are preferred to
light ones; khaki color, however, appears to be particularly
attractive to them. Moving objects seem to attract the flies,
and they are said to follow launches when moving, though they
leave them alone when quiet.

When biting, these flies spread apart their front legs, lower the
proboscis into the skin and begin to gorge. The abdomen of
an unfed tsetse is very
flat (Fig. 232A) but after
30 or 40 seconds of feed-
ing it becomes distended
like a balloon, some-
times containing over
twice the weight of the
fly in blood (Fig. 232B). |
The flies do not feed ex-
clusively on blood, but
also suck plant juices
and show definite, selec-
tive taste for various
fluids presented to them
under a membrane, according to experiments by Yorke and
Blacklock. Both warm- and cold-blooded animals are sucked,
but flies fed only on a cold-blooded animal (crocodile) never
produce offspring. It has been thought that perhaps water
fowl constitute an important article of diet for tsetses, but in
the case of Glossina morsitans, at least, birds’ blood proved
rather indigestible for them, and eften produced a clot in the
digestive tract, resulting in abortion in female flies. In the case
of such species as G. palpalis, however, bird blood may be more
easily digested, and the diurnal habits and close adherence to
the vicinity of water would argue in favor of subsistence on
water animals, in part at least. On the other hand, the habit of
many species of frequenting places where game animals come to
drink or browse and of feeding early in the morning and at even-
ing is apparently an adaptation to the habits of such hosts as
wild game animals. Examination of the stomach contents of
wild flies usually shows a preponderance of mammal blood, but
Carpenter, studying G. palpalis in Uganda, often found that a
large proportion of some collections of flies had fed on reptiles,

Fig. 232. Glossina morsitans before (A) and
after (B) feeding. x 4. (After Austen.)

LIFE HISTORY OF TSETSE FLIES ~ 495

especially on certain large lizards. Lloyd thinks that small mam-
mals and birds may be important sources of food for tsetses, for,
though these animals are usually able to avoid attacks by the
flies during their time of activity, many of the nocturnal species
hide during the day in the same places frequented
by the flies and would then be easy prey for
them.

Life History. — Tsetse flies differ from all

others of their family in their remarkable manner
of reproduction. Not only do they not lay eggs,
but the single developing larva is retained within
the body, being nourished by special glands on
the walls of the uterus. The larva is full grown
and occupies practically the entire swollen abdo-
men of the mother before it is born. The proc- Fic. 233. Newly
ess of giving birth to the larva is very rapid, eee, Paes
occupying only a very few minutes. As soon as lis. x 5. (After
born another larva begins its development, etc, Roux.)
In Glossina palpalis the first larva is born three or four weeks after
mating, immediately after emergence from the pupal case, and
another is born every nine or ten days providing the temperature
is around 75° or 80° F. and food is abundant.
There is little data on the total number of young
produced, but in one captive fly eight larva were
produced in 13 weeks and only one egg was found
left in the body. Pregnant flies often abort when
disturbed and cases are known in which the larvee
pupated within the abdomen of the mother, to
the destruction of both of them.

The larva (Fig. 233) is a yellowish white crea-

Fig. 234. Pupa ture, about one-third of an inch in length, with
of tsetse fly, Glos- ‘ :
sina palpalis. Xx a pair of dark knoblike protuberances at the pos-
5. (Partly after terior end of the body between which are the res-
Austen.) : 2 ; , : E

piratory openings. It immediately hides itself in
loose soil or under dead leaves in the place where it was deposited
by the mother, and transforms to a pupa (Fig. 234). The pupa-
tion takes place in the course of less than half an hour in soft dry
ground, and in an hour to an hour and a half in hard or damp
ground. After pupation the color begins to turn dark and in
four hours the pupa is a dark purplish brown color. It is shaped

496 OTHER BLOOD-SUCKING FLIES

more or less like a small olive, and has at the tip of the body the
blackish knobs which are so characteristic of the larval stage also.
The shape and size of the knobs and of the notch between them
are good distinguishing marks between species. The duration
of the pupal stage depends on the dryness of the soil, temperature,
exposure to sunlight, ete., and may occupy from 17 days to nearly
three months. In experiments made by Lloyd with Glossina
morsitans the pupal stage ranged from 23 days at 85° F. to 81 days
at 70°. Few adults emerged at temperatures below 70° or above
86°. Little is known about the reproductive season, but it is
probable that reproduction occurs only in the warm part of the
dry season in cool climates, but may occur to a varying degree
throughout the year in hot climates. f

The places selected for depositing the eggs vary somewhat
with the species, but all species select dry, loose’ soil in shaded,
protected spots, preferably in places where-a little sunlight will
penetrate for a short time each day and where scratching birds
cannot easily reach them. G. palpalis deposits under tree trunks
and at the foot of various species of trees, especially where a
dense thicket gives a protected spot. In Sierra Leone, Yorke
and Blacklock found numerous pupal cases at the foot of oil-
palms where the dense foliage of the lower limbs makes approach
difficult. G. morsitans is partial to cavities in trees or stumps,
or under logs or branches lying a few inches above the ground
(Fig. 235). The length of life of tsetses is probably less than a
year. Specimens have been kept in the laboratory for over eight
months.

Tsetse Flies and Disease. — As remarked before, the enormous
importance of tsetse flies lies in their réle as carriers of trypano-
somes. The effect of trypanosome diseases on domestic animals
in Africa has practieally excluded these aids to development and
civilization from some parts of that continent. The importance
of trypanosomes to man in Africa is discussed in Chap. VI. It
is sufficient here to repeat that sleeping sickness, which is the
final stage of trypanosome disease, is one of the most deadly, if
not the most deadly, disease known. Several types of the disease
are recognized; the most widespread Gambian disease is caused
by Trypanosoma gambiense and in nature is transmitted chiefly
if not exclusively by Glossina palpalis. The mild Nigerian form
of the disease is believed to be a mere variety of the Gambian

=~ st. _—

TSETSE FLIES AND SLEEPING SICKNESS 497

disease and is likewise transmitted by G. palpalis. Rhodesian
sleeping sickness, however, is transmitted by G. morsitans. It
is the belief of some workers that the Rhodesian parasite is a

Tis

Vf |e
hate
a)
/)

| ¢,
Ns iii)
GES

RN AMAL,
YEN
WY 2

Vt gf,

i:
—

_- “ fi
<_< Foo sa aS

Fic. 235. Typical breeding places of Glossina morsitans in Rhodesia. (From
photographs from Kinghorn and Yorke.)

mere strain of the trypanosome, 7’. brucei, which causes nagana
in animals and which also is transmitted by G. morsitans. The
development of the trypanosome in the flies and the mode of
transmission is discussed on p. 99.

498 OTHER BLOOD-SUCKING FLIES

Glossina palpalis (Fig. 236) is a large dark species with black-
ish brown abdomen and with gray thorax having indistinct brown
markings. This species is found over the whole of West Africa,
from the Senegal River to Angola, and east to the upper valley of
the Nile and the eastern shores of the central lakes (Fig. 231, \\\).
Its range is thus nearly coincident with that of Gambian sleeping
sickness. This species, more than any other except possibly
G. tachinoides, which occurs around the southern border of the
Sahara Desert, is dependent on the presence of water. Its natu-
ral range is said seldom to exceed 30 yards from the edge of water,
and the distance that it will follow animals or man is not more

Fie. 236. Glossina palpalis, carrier of Gambian and Nigerian sleeping sick-
ness. 4. (After Austen.)

than a few hundred yards. Muddy, reedy sloughs or swamps
are not frequented by this fly, but rather sandy- or gravelly-
banked streams with abundant overhanging vegetation. In
the rainy season the flies extend their range to headwaters which
are dry during the remainder of the year and retreat again with
the drying up of the water. It is feared that this species may
sometime bridge the short gape between the headwaters of the
Congo and the Zambesi, and become established along the latter
river and its tributaries, carrying sleeping sickness with it.

This fly probably feeds naturally on a number of different
animals. Wild game, especially the Situtunga antelope, is

a ee ae

GLOSSINA MORSITANS 499

utilized to a large extent, and the habitats of the flies imply that
they feed considerably on water animals. Crocodiles are said
by Koch to form the staple food on the shores of Lake Victoria
and water fowl are believed to be attacked also. This species fd
said, however, to thrive better on human blood than on any other.
Data concerning the life history has already been given.
Glossina morsitans (Fig. 237), carrier of many trypanosome
diseases of animals and of the newly arisen and still narrowly
limited Rhodesian sleeping sickness, is the most widely distrib-
uted species of tsetse fly, occurring all the way across Africa

Fig. 237. Glossina morsitans, carrier of Rhodesian sleeping sickness. x 4.
(After Austen.)

from Senegal to southern Sudan and Abyssinia on the north,
to northeastern Transvaal and Zululand on the south (Fig. 231,
\\\). This is also the best known species, and is the one which
has attracted to itself the attention of big-game hunters in Africa
for many years. It is slightly smaller than G. palpalis and much
lighter colored, with very inconspicuous markings on the gray
thorax, and with more or less distinct dark bands, not con-
tinuous across the middle line, on the buff colored abdomen.
As remarked elsewhere, G. morsitans is not confined to the im-
mediate vicinity of water, but prefers hot dry country, covered
with bush or scattered trees. In some places it is found at an

500 OTHER BLOOD-SUCKING FLIES

altitude of over 5000 feet, but usually occurs at much lower
levels. It feeds on the blood of almost any large mammal which
comes its way. It was long supposed that the fly was especially
dependent on the Cape buffalo, Bubalis caffer, as it undoubtedly
was before this animal was almost exterminated by rinderpest,
but the fly is certainly able to exist in the absence of the buffalo,
though often in less numbers than when the abundant food supply
was at hand. Baboons are said to be relished by the fly in some
parts of Africa.

Glossina morsitans, though most active in the morning and
late afternoon, sometimes bites at midday and even after dark,
especially on warm moonlight nights. The habit of following
moving objects is especially marked in this species, and some
observers state that flies have followed them several miles, fre-
quently alighting on the ground to rest, or on the person pursued,
often without attempting to bite.

The reproduction and choice of breeding places of this species
have already been mentioned.

Although G. palpalis is undoubtedly the normal transmitter
of Gambian sleeping sickness and G. morsitans of Rhodesian
sleeping sickness, they are not the only species which have been
found capable of transmitting these diseases, at least under labo-
ratory conditions. G. morsitans has been found to be able to
nurse Trypanosoma gambiense in some districts but not in others.
G. pallidipes, which resembles G. morsitans but is larger, and
confined to southeastern Africa, can be experimentally in-
fected also.

G. tachinoides is suspected of carrying sleeping sickness in parts
of Nigeria and Tegoland. This is one of the smallest species,
being about the size of a housefly. It has very distinct bands on
the abdomen, and is browner and darker than G. morsitans.
It is found around the southern edges of the Sahara Desert and
in southwestern Arabia. Its habitats are practically the same
as those of G. palpalis but it is active on dull days and early in
the morning when the latter species is quiet. It frequently
bites after dark, also, and in some places is said to be more
troublesome than mosquitoes.

Another species experimentally able to transmit human
trypanosomes, 7’. gambiense, is G. brevipalpis, of South Central
and East Africa. This is a large species found in abundant

CONTROL OF TSETSE FLIES 501

shade, in bush mixed with creepers and young trees near water
courses. Its counterpart in the more northern parts of East
Africa is Glossina longipennis, a large warm-brown species with
indistinct markings. G. brevipalpis is said to be desirous of
feeding only before 8.00 a.m. and after 4.00 P.M. In the middle
of the day it hides under leaves or grass blades near the ground,
so that its presence would never be suspected.

To sum up it may be said that while there is much variation
in the susceptibility of different species of tsetses to different
trypanosome infections, so that one or a few species come to
serve as the usual transmitters of any particular trypanosome,
yet other species cannot be definitely excluded as carriers with-
out extended experimentation. Even in the case of natural.
carriers of a particular trypanosome, a very small per cent of
flies are found naturally infected, and not more than a few per
cent can be infected experimentally. Moreover it is evident
that a single species of fly shows marked differences in recep-
tivity to infection in different parts of the range. The re-
fractory nature of some West African races of G. palpalis prob-
ably accounts for the absence of sleeping sickness in Dahomey
and neighboring states. It is probable that climatic conditions
and food habits play a leading part in determining susceptibility
of flies to trypanosome infections.

Control. — Attacks of tsetse flies can be avoided to some ex-
tent by the use of the usual insect repellents (see p. 455), by
fly-proof clothing or veils, and by wearing white clothes. When
it is necessary to travel through fly-infested places where sleeping
sickness occurs, all of such measures should be adopted, or,
better still, the fly-belts should be passed through in the dark-
ness of night when the insects are inactive. Railroad trains and
steamboats passing through fly-belts should be protected by
fly-proof screens; this expedient is adopted in many parts of
Africa at the present time.

Extermination of tsetses on a large scale is a very difficult
matter, but locally it is quite feasible. There are probably
factors influencing the distribution of the flies which are still
unknown, and which may be turned to account in destroying
them.

Clearing away of brush along fly-infested streams in the case
of such species as G. palpalis and G. tachinoides, which are closely

502 OTHER BLOOD-SUCKING FLIES

confined to patches of brush along water courses, is the most
valuable measure in connection with their local destruction.
As said before, these flies seldom go over 50 yards from such
brushy borders of streams except when following prey, in which
case they may go several hundred yards. If brush is cleared
away and low branches of trees cut out for a distance of 30
yards from the edge of water in the vicinity of fords, villages,
washing places, etc., the flies quickly disappear, and do not re-
appear as long as the cleared area is kept clear. The effective-
ness of this method of extermination has been demonstrated
especially well by the Portuguese Sleeping Sickness Commission
on the Island of Principe where tsetse flies were almost, though
not entirely, exterminated in a four years’ campaign. In ad-
dition to clearing margins of bodies of water, the beds of the
water courses were straightened and leveled to make the clear-
ing easier, and forests were completely cleared away on a large
scale where they seemed to harbor tsetses. In addition some of
the men employed in these operations wore on their backs black
cloths smeared with sticky bird-lime, thus being converted
into active traps for capturing flies. Nearly half a million flies
were thus caught, and the number caught daily gave a good in-
dex to the effectiveness of the preventive measures being used,
and must of itself have been a supplementary means of destruc-
tion which was of value. The eradication of Glossina morsi-
tans is a much more difficult problem, since its habitats, though
sharply confined to “ belts,” are not so closely limited to the
edge of water, and are therefore more difficult to clear. Since,
however, the areas occupied are usually not over a few square
miles at the most, complete deforestation of such areas when
near villages or highways would often be feasible.

The destruction of pupz of tsetse flies by natural enemies
undoubtedly aids in limiting their numbers, but the instinct
which leads tsetses to deposit their offspring where birds cannot
scratch gives the pup a high degree of immunity to this class
of natural enemies and to artificial means of destruction. The
newly deposited larve are covered by a slimy secretion which
apparently protects them against the attacks of the ants which
almost always abound in the tsetse breeding places. The pu-
pe are attacked by parasitic insects (Fig. 238), but apparently
not to a sufficient extent to seriously reduce their numbers.

—_— ee

a ae

oe ee be ee i RA ew ee

CONTROL OF TSETSE FLIES 503

However, five species of Hymenoptera and two of Diptera are
known to parasitize the pupz of tsetse flies. It is possible that
some of these insects could be successfully exploited. The
adults of G. morsitans are attacked, according to Lamborn, by
a species of dragon-fly, Orthetrum chrysostigma,
which persistently pursues them and diligently
searches the vicinity of men and animals for
them. Elimination of breeding places is the
only feasible method for exterminating tsetses
in their early stages.

Constructive measures should follow the de-
structive ones, such measures, for instance, as eg
the cultivation of unfavorable plants and en- case Ga Gok
couragement of natural enemies. Following are as a showing
summarized briefly the methods of fighting of a small an,
tsetses advised by Bagshawe: pes age ee .

(a) clearing of fly-infested brush, and its re-
placement by citronella grass or other plants noxious, or at least
not favorable, to the flies;

(6) filling up, straightening out and draining of pools and
water courses where possible;

(c) destruction of main food animals, if found feasible and
possible. (The wholesale destruction of wild game is not ad-
_ vised by Bagshawe.)

(d) encouragement and introduction of natural enemies, and
investigation of food habits of possible enemies among birds
and bats. The black drongo, Dicrurus ater, and the small bee
eater, Melittophagus meridionalis, are known to feed on the
adult flies.

(e) collection and destruction of pupe or adult flies. This .
can be facilitated by creating artificial sites for depositing lar-
vee to which the flies will be attracted. Natives in Sudan arc
said to use gourds filled with blood for capturing flies to be
turned loose to torture the stock of enemy tribes. Other traps _
have been devised also, among which should be mentioned the
black bird-lime cloths already described as being used on the
Island of Principe.

Some workers have advocated the wholesale destruction of
wild game animals in parts of Africa where deadly trypanosome
diseases occur, in the hope that in this way the natural reservoirs

504 OTHER BLOOD-SUCKING FLIES

of the disease could be destroyed, and that the tsetse flies would
disappear if their main source of food were cut off.

Domestic animals are, however, quite as suitable for tsetse
flies to feed upon as are wild game and there is ample reason to
believe that the flies would be able to subsist on small forest
mammals, birds, crocodiles, etc., in the absence of other food.
Even if all the wild game were destroyed, and domestic animals
excluded for many years, enough flies would survive to reéstab-
lish the scourge with the subsequent introduction of domestic
animals. The destruction of the rich and varied, and indeed
unique, wild life of Africa is a measure so radical, so contrary
to our present growing determination to save the irreplaceable
handiworks of nature, and, to be sure, so inhuman, that it cannot
be advocated or even tolerated until absolutely proved to be an
effective, and the only effective measure.

Stable-Flies (Stomoxys) and Their Allies

Belonging to the family Muscide in company with the house-
flies, blowflies and tsetse flies, are a number of other biting flies,
most important of which are the stable-flies, Stomoxys, especially

S

i f

OG

————__ f le Le

SSS
See aie AL < ae = a4

5:

‘ j Hy ie

Fic. 239. Stable-fly, Stomorys calcitrans. 5.

the common species, S. calcitrans (Fig. 239), which makes itself
annoying and often dangerous in nearly every part of the world.
It is chiefly a persecutor of domestic animals, but is very willing
to attack man when opportunity is offered.

The stable-fly in general appearance so closely resembles the
housefly, Musca domestica, as often to be mistaken for it, whence

—_—

ee SS ee ‘=

——s

ae et ek

r= %

STABLE-FLIES 505

the frequent statement that houseflies sometimes bite. They
differ, however, in several ways. The stable-fly is more robust,
browner in color, rests with the wings spread at a broader angle,
and has a narrow, pointed shining-black proboscis (Fig. 240)
which is quite different from the blunt fleshy proboscis of the
housefly.

The mouthparts (Fig. 240) differ from those of many other
biting flies in that the lower lip, which usually merely forms a
sheath for the piercing mouthparts,
is itself a piercing organ. It is bent
at nearly right angles under the head
so that it projects straight forward,
being, therefore, fixed to the head
like a bayonet to a rifle. The short
basal segment is movable and mus-
cular, and is used to manipulate the
proboscis itself. The latter has at
its tip rasplike spines which aid in
perforating the skin of the host. ¢; ise Cee
Inside the’ groove in the lower lip is ant., antenna; ar., arista of an-
the labrum and hypopharynx which [yinich: cpinhiryns: BvD hype
together form a sucking tube. The lum; max. p., maxillary palpus.
maxillary palpi, which form enclosing Cae se
sheaths for the proboscis in tsetse flies, are less than half the
length of the proboscis in Stomozys.

The stable-fly is commonly believed to breed in manure, and
gains its name from the frequency with which it is found about
stables, presumably having been bred in manure. As a matter
of fact, the presence of stable-flies about stables is due to the
presence there of animals — horses, cattle, etc., — on which they
feed. The breeding place which is most preferred is moist,
decaying straw or rotting vegetable matter. According to Herms,
the very best breeding places are afforded by the left-over hay,
alfalfa or grain in the bottoms of, or underneath, out-of-door
feed troughs in connection with dairies. In this soggy, fermented
material practically pure cultures of Stomoxys larve may be ob-
tained. , :

The eggs of Stomoxys (Fig. 241) are banana-shaped white
objects about one mm. in length, curved on one side and flat
on the other, with a groove on the flat side. They are de-

506 OTHER BLOOD-SUCKING FLIES

posited, sometimes deep in the decaying material selected, in
small batches of from two to half a dozen, until from 25 to 50 or
more are laid; there are a number of such depositions made by a
single fly during her life. The eggs hatch in from two to five
days, usually three, into whitish,
almost transparent footless mag-
gots (Fig. 242A) very similar to
those of the housefly, but easily
distinguishable by the position of
the posterior stigmal plates (see
Fig. 243). The larve mature in a
minimum of from 12 days to over
two months, usually in about 15 to
20 days, and crawl into drier por-
tions of the breeding material to
Keoruncye eilsiiven: 30. “Now Pune The pupe (Fig. 242B) are
eggs natural size in upper corner. olive-shaped, chestnut-colored ob-
oe Sere jects, one-fourth of an inch in
length. With favorable temperatures the adult fly emerges in
-from six to ten days, but this period may be much prolonged
by cold weather. The shortest time in which
a stable-fly may develop from the time of
egg-laying is about three weeks, and this is
extended under conditions which are not
ideal. According to Herms’ experiments,
the average length of life of stable-flies is
about 20 days. They sometimes live several
months, however.

There are several other genera and species
of the family Muscide which sometimes
bite man, but none of them are habitual :
feeders on human blood, and they are hardly ic. 249. “Lacon tl
worthy of special consideration. They all and pupa (B) of stable-
resemble Stomoxys in general appearance, Ay Ore
though some, notably the common hornfly,
Hematobia serrata (or Lyperosia irritans), are much smaller. Their
life histories are in general like that of Stomozys, though there is
some variation as regards choice of breeding places. Manure of
various kinds is selected by some species, as it is by the house-
fly, much more than in the case of the stable-flies.

Fie. 241. Eggs of stable-fly,

STABLE-FLIES AND DISEASE 507

Stomoxys and Disease. — Like the tabanids, the stable-flies
are intermittent feeders, 7.e., they frequently leave one animal
in the course of a meal if disturbed, to finish feeding on another.
For this reason they are of importance in mechanically trans-
mitting blood diseases.

It has been shown that the trypanosome of sleeping sickness,
T. gambiense, can be transmitted by interrupted feeding, and a
few years ago Macfie showed that the Nigerian strain of the
parasite could go through at least part of its development in the
gut of the black stable-fly, Stomozxys nigra (see p. 98).

More serious than this is the relation of stable-flies to anthrax
(see p. 488). This fatal disease of domestic animals and man is
caused by bacteria which live long enough on or in the proboscis
of stable-flies to be readily transmitted by them within an hour
or two after an infective feed. The biting flies of this or other
species which congregate to feed on sick or dying animals must
be looked upon as a serious source of danger. Other diseases,
such as foot-and-mouth disease, to which both animals and man
are susceptible, may presumably be transmitted in like manner
by these flies, though no proof of it has yet appeared.

In 1912 and 1913 several American workers, among them Dr.
M. J. Rosenau, of the U. 8. Public Health Service, adduced the
theory that the stable-fly, Stomorys calcitrans, was responsible
for the transmission of infantile paralysis, and the theory was
apparently supported by some facts in the epidemiology of the
disease (though contradicted by others), and by carefully con-
ducted experiments. In subsequent experiments, however, by
the same and other workers, the results have been uniformly
negative, and in the meantime much data has been collected to
show that this terrible disease, which reached unprecedented
proportions in New York City and vicinity during the past year
and terrorized the entire United States, is transmitted by con-
_tagion, and not through the agency of any particular insects.
It cannot be said that the disease is never transmitted by biting
flies, or by ordinary houseflies, but that insects are not the main
or even important factors in the spread of the disease is now a
fairly well-established fact.

Control. — Control of the stable-flies and of allied species of
biting flies depends almost entirely on the elimination of their
favorite breeding places. In the case of Stomozys, which is the

508 OTHER BLOOD-SUCKING FLIES

most important of this group of biting flies, preventive measures
are fairly easy. The drying out, burning, or burying of waste
vegetable matter, such as piles of weeds, wet hay, lawn clippings,
waste vegetable matter in garbage heaps, etc., eliminate the main
breeding places. Poorly constructed hay stacks, around which
there is a good deal of loose hay which becomes soggy and de-
cays, are breeding centers for the flies. Stacks, when needed,
should be constructed with evenly rounded top and vertical sides;
but a better way, when possible, is to bale hay or straw and store
it in dry places. Manure especially when mixed with straw is
utilized by stable-flies in lieu of better breeding places, but the
principal manure-breeder is the housefly, Musca domestica. Ac-
cording to recent work by the U. 8. Department of Agriculture,
manure can be treated in such a way as to destroy the young
stages of stable-flies and houseflies without injuring its fertilizing
value. A mixture of ten oz. of borax and 12 oz. of crude calcium
borate (colemanite) is applied to ten cubic feet (eight bushels)
of manure, the manure being then sprinkled with two or three
gallons of water. A still better substance to apply is hellebore

powder, one-half lb. in ten gallons of water to eight bushels of

manure. An excessive quantity of the powder has no injurious
action on the fertilizing power of the manure, as has an excess of
borax.

oe eee ee ee Eee eee eee eee ee CCU

CHAPTER XXVII
FLY MAGGOTS AND MYIASIS

General Account. — Disgusting as it may seem, the human
body is attacked not only by the numerous adult flies discussed
in the last chapter, but is subject to attacks or invasion by the
maggots or larval stages of some species of flies. Such an in-
festation by fly maggots is commonly known as myiasis, intestinal
myiasis being the presence of fly larve in the intestine, cutaneous
myiasis in the skin, etc.

_ All of the maggots which habitually or occasionally parasitize
man belong to the order Diptera, and to the suborder Orthor-
rhapha, in which the larve have very small and indistinct heads,
and the pup are inactive oval bodies from which the adults emerge
by pushing off one end, like a cap (see p. 465 and Fig. 209A).

Most cases of myiasis are caused by flies quite closely allied
to houseflies, and this famous transporter of germs and filth is
itself occasionally guilty. The identification of maggots is often
a difficult matter and is sometimes impossible without rearing
the adult insect. Larve of the botfly family, Gstridz, are of
various shapes, but seldom taper evenly from the posterior to the
anterior end; the body has a leathery covering and is armed
with girdles of thornlike spines. Larve of the genus Fannia
(Fig. 253) are flattened, and have very: characteristic fleshy
processes along their sides. Nearly all other maggots causing
myiasis are cylindrical, whitish, footless creatures, tapering from
the broad posterior end to the small head, and are difficult to
identify. The chief characteristics used for distinguishing them
are the number and form of the mouth hooks (see Fig. 251),
and the nature of the respiratory openings at the posterior end
of the abdomen. These openings consist of two “ stigmal plates,”
hardened, yellowish, eyelike spots, in which are three slits or
openings, with sometimes a button-like mark at their base.
The relative position of the stigmal plates to each other and to the
surface of the larva, and the form of the slits; whether straight,
curved or wavy, and whether vertical or oblique, are some of

509

510 FLY MAGGOTS AND MYIASIS

the characters used in distinguishing genera and species of fly
maggots. A few typical forms are shown in Fig. 248.

It is more convenient to consider the different types of myiasis
according to the way in which the larve attack the body or ac-
cording to parts affected than according to the families and genera
to which the flies belong. We may divide the various flies

Muscina stabulans(x78)

VAY,

Cochliomyia macetiaria(xs50)

SQ

Sarcophagq sarraceniae-(x 50)

Gastrophilus sp?25)

Oestrus ovis (430)
Fic. 243. Posterior stigmata and breathing pores of various maggots. Note

distance apart of opposite stigmal plates, form and position of spiracles, pres-
ence or absence of button, etc.

causing myiasis into four groups: (a) those in which the larve live
outside the body and suck blood by puncturing the skin, (6)
those in which the larve develop under the skin; (c) those in
which the eggs or young larve are deposited in wounds or in
natural cavities of the body, such as the nose, ears and vagina;
and (d) those which live in or pass through the intestine or uri-
nary passages.

CONGO FLOOR MAGGOT 511

Blood-Sucking Maggots

A number of species of flies allied to the blowflies are known to
deposit their offspring in the nests of birds, where the maggots
attach themselves to the nestlings and suck blood. The only
species of fly in which the larva sucks blood by puncturing the
skin of man, however, is the Congo floor maggot, Aucheromyia
luteola (Fig. 244), found throughout tropical Africa south of the
Sahara Desert. Its range closely coincides with that of the

Fra. 244. Congo floor maggot and adult female fly, Aucheromyia luteola.
A, x3; B, x 4. (After Manson.)

Negro and Bantu races of men; it does not occur in countries
inhabited by Arabs and Berbers.

The adult fly (Fig. 244A) resembles the blowfly, to which it is
nearly related. The color, however, is different, being a dirty
yellowish brown with the tip of the abdomen rusty black. . This
fly can usually be observed in shady places about human habi-
tations, preferring the vicinity of latrines; it feeds principally
on rotting fruits and on excrement. The female lays her eggs
during the daytime in dust or débris in shady places, especially

512 FLY MAGGOTS AND MYIASIS

on the floors of native huts. The fly is said by Roubaud to make
a furrow in the dust with her abdomen while running on the
ground, feeling for breaks or cracks in which to deposit her eggs.
Having found such a spot she forces her abdomen into it and
deposits usually a single egg, then seeks a new crack, deposits
another egg, ete., until the whole number of from 30 to 80 eggs
has been disposed of. The eggs, the development of which is
favored by dry surroundings, hatch in a few days. Within four
or five hours after emergence the larve are ready to suck blood if
opportunity presents itself, but they are able to live nearly a
‘ month without food, remaining buried an inch or so in the dust
of floors. They can always be collected by digging with the point
of a knife in cracks in the earth under sleeping mats. Roubaud
collected 100 larve in half an hour, many of them filled with
blood, in a hut where a dozen children slept.

The maggots (lig. 244B) are dirty-white creatures, much
wrinkled in appearance, but otherwise quite like the larve of
houseflies. The tapering anterior end of the body is provided
with a pair of black hooks to aid in piercing the skin of the host,
and has retractile sucking mouthparts. The thick leathery skin
and the position in a crack in the ground protects the larva from
injury when stepped on by the bare feet of the natives. The
body is beset with rings of spines which aid in the wriggling
method of locomotion. The maggots are inactive in the day-
time, but come forth at night to suck the blood of sleepers, biting
them usually on the side of the body next to the ground. The
bites are less irritating than those of mosquitoes, and according
to Roubaud the bites of 20 larve at once produced no inflam-
mation or itching.

Under ideal conditions the larve pass through two moults and
go into the pupal stage in 15 days, but this may be extended to
about two and one-half months under unfavorable conditions,
such as low temperature and irregular food supply. The pupal
stage lasts about 11 days. The adults do not begin laying eggs
until about two weeks after emergence. The whole life cycle,
therefore, from egg to egg, is about one and one-half months
under favorable conditions.

The Congo floor maggot is not known to attack any animals
but man in nature, though a closely allied maggot, Cheromyia,
lives in the burrows of the wart hog and other hairless mam-

CUTANEOUS MYIASIS 513

mals. Its bite is more painful to man than is that of the normal
human parasite.

The attacks of the floor maggot can very easily be avoided by
sleeping on mats or beds raised just a few inches from the ground.

Maggots Under the Skin

There are several species of flies in which the larve develop
under the human skin, like “ warbles”’ in cattle, but they are
found only in Africa and in tropical America. The African
species are closely related to the blowflies and fleshflies, whereas
the American species, of which there is usually believed to be
but a single one, is a true botfly, closely allied to the ox warble.

Fie. 245. Adult of South American skin maggot, Dermatobia hominis. x 2.
(After Castellani and Chalmers.)

Dermatobia. — The American species, sometimes called the
human botfly, Dermatobia hominis (Fig. 245), is found through-
out tropical America from Mexico to northern Argentina. Its
larve develop not only in man but also in many other animals,
as dogs, cattle, mules, hogs, etc. In certain parts of South
America the hides of cattle become so riddled with the perfora-
tions made by these bots that they are rendered quite worthless.
The infestation in man is contracted chiefly in forest regions, and
apparently very seldom in houses, a fact which possibly accounts
for the greater degree to which dogs are parasitized by it than are
cats, and men than women or young children.

The adult fly (Fig. 245) is about the size of a blowfly (half an
inch in length) with face and legs yellowish, thorax bluish black
with a grayish bloom, and the abdomen a beautiful metallic

514 FLY MAGGOTS AND MYIASIS

violet blue. The mouthparts are not fitted for piercing flesh,
and there is no “ stinger’’ at the posterior end of the body to
drill a hole for depositing the eggs. Evidently, therefore, the
many accounts which one can find of the fly’s biting or sting-
ing at the time the eggs are deposited are faulty.

The manner in which the larve gain access to the skin of their
hosts is at present a much-disputed question. A recently ad-
vanced theory, and one which is looked upon with much favor
by many scientists is that the female fly captures a certain species
of mosquito, glues her eggs to the under side of the abdomen
of this insect (see Fig. 206), and
trusts it to carry the eggs to the
body of some animal on which
it feeds. The eggs adhere to the
body of this animal and hatch
almost immediately into tiny
maggots which at once bore
under the skin. Fora discussion
of the origin and details of the
mosquito transmission theory
and objections to it, the reader
is referred to Chap. XXV, p. 451.
Other theories are that the fly
deposits its eggs, ready to hatch,
directly on the skin; on clothing

w ; while not being worn, as does
gon Be casbuth American ‘kin mae the African skin maggot fly; oF
view, extended; B, ventral view. x on foliage along paths where
a ac a passing animals are likely to
brush against the leaves. It is possible that, as is the case with
- some other botflies, different methods of disposing of the eggs
may be used according to circumstances.

However the larve may reach their host, they immediately
enter the skin, probably through a pore, and begin their growth,
ultimately reaching a length of half or three-quarters of an inch
(Fig. 246). The anterior end of the larva is broad and is pro-
vided with double rows of thorn-shaped spines; the posterior end
is constricted, especially in fully-developed larve, and does not
possess spines. As the larva develops, a sort of boil or cyst forms
about it, opening to the surface of the skin by a little pore. This

A
“
ry

i Hae
NY ee phy)
tt

CUTANEOUS BOTS 6

is plugged by the posterior end of the maggot, and used for ob-
taining air. At intervals these warble-like boils give rise to the
most excruciating pain, due, no doubt, to a turning over or
moving about of the spiny larva in its close quarters.

There are very conflicting records of the time required for the
larve to reach maturity, but it seems probable that at least a
month or six weeks is usually occupied. When mature the larve
voluntarily leave their host and fall to the ground to pupate.
They transform into the adult form in the course of several weeks.

The swellings under the skin occupied by human botflies, as
remarked before, are very painful at intervals, while at other
times they are entirely painless. As the larva matures, a puslike
material exudes from the open end of the “ boil,” containing,
no doubt, the excretions of the maggot. After the worm has
evacuated its cyst or has been removed the wounds sometimes
become infected, and may even result in blood poisoning and
death.

The method usually employed to remove the maggots is to
apply tobacco juice or tobacco ashes to the infested spots, thus
killing the worms and making their extraction easy. Another
method used by natives in some parts of South America is to tie
a piece of fat tightly over the entrance to the boil. The larva,
deprived of air, works its way out into the fat, being thus induced
to extract itself. A much more satisfactory method of dealing
with the worms is to kill them with an injection of weak carbolic
acid, mercuric bichloride, or some other poisonous substance,
then enlarge the entrance to the cyst with a sharp clean knife
and remove the body of the worm. A washing of the wound
with a weak carbolic or lysol solution, followed by an antiseptic
dressing, obviates any danger of subsequent infection. The
wound heals quickly but leaves a scar.

Other Bots. — Other botflies occasionally infest man and cause
cutaneous myiasis. The common warble-flies of cattle, Hypo-
derma lineata and H. bovis (Fig. 247), have been recorded as oc-
curring in the skin or flesh of human beings and there is one fatal
case on record where an ox warble caused an ulceration in the
back part of the lower jaw of a boy six years old. Ox warbles
usually gain access to the tissue under the skin of cattle in an in-
direct way, the hairy bee-like flies depositing their eggs on hairs
of cattle where they will be licked off. As soon as licked the

516 FLY MAGGOTS AND MYIASIS

eggs hatch, and the larve burrow out through the wall of the
cesophagus, migrate through whatever tissues they may find in
their path, and ultimately reach a position just under the skin,
usually on the back, where they finish their development. Occa-
sionally the larve penetrate the skin directly, but the indirect

Fig. 247. Larva of Hypoderma bovis; A, posterior view; B, lateral
view. X 2.

method is the usual one. Recent investigations indicate that the
two species differ somewhat in this respect. In Russia the horse
botfly, Gastrophilus hemorrhoidalis, which normally develops
in the stomach of the horse, occasionally lives under the human
skin.

African Skin Maggots. — The commonest species of maggot
which develops in the human skin in Africa is the “‘ ver du Cayor,”
the larva of the tumbu fly,
Cordylobia anthropophaga.
This fly belongs to the same
family as blowflies and
houseflies. It is widespread
throughout Africa, from
Senegal and Khartoum to
the Transvaal. To quote
from Fuller, ‘‘ There is no
é . ill the flesh is heir to among

Fic. 248. Adult female of African skin the vicissitudes of life in
mee camel, auteaneptear- ® South Africa, which is more

offensive than parasitism
by (this insect).’”’ Man is not the main host of the larve of this
fly, but he suffers in common with a large number of wild and
domesticated animals, especially domestic dogs.

The adult fly (Fig. 248) is about the size of a blowfly (half an
inch long), and is brown in color. The thorax is rusty to yellow-
ish brown with indistinct dusky stripes, the abdomen pale brown,
a little darker toward its tip, and with two dusky bands. Ex-

AFRICAN SKIN MAGGOT 57

actly where the fly deposits its eggs or newly hatched maggots is
not quite certain. According to some observations the living
larve are deposited directly on the skin and immediately bore
their way in, while according to others the eggs or young larve
are laid on the hair, on clothing which has been hung out, on
soiled bed-clothes of children, etc. There is good reason to
believe that the fly when about to lay eggs is attracted by fresh
animal smells, such as perspiration, fresh excrement, etc., when
these occur on the skin or on fabrics. The heads of infants,
especially if not kept perfectly clean, are favorite places for the
flies to deposit their offspring, and cases are on
record in which 20 or 30 maggots were taken
from the scalp of a child under six months old.
Woolen clothing, if smelling of perspiration,
is almost sure to become infested with the
maggots when hung out in an exposed place,
and it is dangerous to put on such clothing
where the fly is abundant. Roubaud, in ex-
periments with this fly, induced a specimen to
lay 150 eggs on the walls of a glass vessel and
on rotten fruit, and obtained infestation of a:
guinea-pig with 15 larve hatched apart from
the host. That in some cases, at least, the eggs
hatch before being deposited is evident from
the fact that living maggots can sometimes be
squeezed out of the bodies of the flies, and it is , F'- 249. African
skin maggot, Cordy-
quite probable that the fly normally produces jobia anthropophaga,
living young. The maggots are usually most Me panes B,
abundant in the southern summer (January to
March), especially in March. It is probable that there are not
more than two or three generations a year, all of them during the
summer, the rest of the year being spent in the adult stage.

The maggots (Fig. 249) are said to bore into the skin rapidly
with active flapping movements and without causing any pain.
As pointed out by Fuller it would endanger the life of the species
if in entering the skin it excited its victim to dislodge it. Even
if, as is probably often the case, the larva enters the skin during
sleep, unless quite painless the host would probably wake and
scratch it out, especially in the case of wild animals which must
always sleep with an ear and an eye open, so to speak. As many

518 FLY MAGGOTS AND MYIASIS

as 300 maggots have been taken from the skin of a puppy, and
it is not unusual for 20 or more to be present at once in a human
being. They come to rest just under the surface of the skin,
where they give rise in a few days to an inflamed boil, the in-

flammation being due to the movements of the spiny worm, and .

to the presence of toxic excretions. As in the case of Dermatobia,
an opening is left to the surface of the skin from which the larva
_ obtains air through the spiracles at the posterior end of the body.
In some cases very little discomfort is felt from the maggots,
but in other cases an intense pain is caused at intervals.

The larva is a fat, creamy-white maggot which reaches a
length of half an inch when full grown. It is bluntly pointed
at the anterior end but broad at the posterior end. The body
is thickly covered with minute dark brown spines, each one re-
curved like a rose thorn.

Maturity is reached in about two weeks or less from the time
the infestation occurs, though usually the time is underestimated,
due to the fact that the larva is not noticed during the early part
of its existence in the skin. When fully developed the larva
voluntarily leaves its host and falls to. the ground to pupate.
The pupa is of the usual barrel-shaped form characteristic of
the group of flies to which this species belongs. It is a little
less than half an inch in length, at first of a light rusty color,
later turning dark purplish brown. The adult insect emerges
from the pupal case in about two weeks.

Preventive measures against the fly consist to some extent in
personal cleanliness, since it is doubtful if the flies will deposit
their offspring except on surfaces smelling of perspiration or other
body excretions. Infants seem to be especially subject to attack,
and should, therefore, be kept scrupulously clean. Since the
larva of the fly lives readily in many domestic and wild animals,
its extermination is hardly possible. In some parts of Africa,
notably in Natal, the worm becomes abundant for several
seasons, and then disappears for a number of years. The reason
for this is not understood.

A closely allied fly, C. rodhaini, occurs in the damp equatorial
forests of Africa, attacking thin-skinned animals such as an-
telopes and rodents, and occasionally man. Dogs, cattle and
other thick-skinned animals are immune. The female of this
species may deposit over 500 eggs, which hatch in from two to

SCREW-WORM o19

four days. The mature larva, which closely resembles that of
C. anthropophaga, leaves the host in from 12 to 15 days, buries
itself to a depth of several inches in the ground, and pupates.
If a little moisture is present, the transformation into the adult
occurs in a little over three weeks. About two months is required
for the whole life cycle of this fly.

Myiasis of Wounds and of Natural Cavities of the Body

A large number of flies, all of them related to the blowflies and
houseflies, occasionally deposit their eggs or newly hatched
larve in neglected wounds when offensive discharges are exuding
from them. In severe cases infestations with maggots of these
flies may lead to a most horrible and loathesome death.

The instinct of the female flies of all the species implicated is
to deposit offspring in places from which the odor of meat or of
decaying animal matter is emanating, regardless of where the
place may be. This instinct is, of course, of the highest. value
to the species, since the larve live upon the substances from which
such smells arise. It is an instinct analogous to that which
causes a mosquito to lay its eggs in water, or a horsefly to oviposit
in objects overhanging water —an unknowing but accurate
intuition on the part of the parent to provide for the welfare of
its young.

Screw-worm. — One of the most important species in this
connection is the American screw-worm fly, Cochhomyia (or
Chrysomyia) macellaria, which occurs throughout America from
Canada to Patagonia, though abundant only in warm countries.

The adult fly (Fig. 250A) is a handsome insect, slightly larger
than a housefly, of a metallic blue-green color with three dark
stripes on the thorax. It belongs to the family Muscidx, and
to the same section as the ordinary blowflies. The adults con-
gregate about carcasses of dead animals on which they ordinarily
deposit their offspring and on which the larvee feed. Records
differ as to whether the eggs hatch within the body of the parent
or after being deposited, and it is probable that during the early
part of the season and in cool climates the eggs are deposited,
while under other circumstances the living maggots are born.
The number produced by a single fly may be several hundreds,
but they are deposited with amazing rapidity. The maggots

520 FLY MAGGOTS AND MYIASIS

(Fig. 250B) are white, footless creatures, provided with a pair
of stout hooks near the mouth, and with bands of minute spines
which give them a screwlike appearance, whence they derive
their name. Eating away at flesh and even bone, they develop
rapidly to a length of about half an inch, and maturity may be
reached in three days,
though four or five days is
usually required. When
fully developed the larva
leaves its feeding grounds
and buries itself in loose
earth nearby, where it
pupates in two or three
days. The pupe are
brown in color, and shaped
somewhat like olives. After
four days or more in the
pupal case the adult insect
emerges, climbs up on
nearby herbage and rests in
a characteristic position

with the head down. The

Fie. 250. Screw-worm fly, Cochliomyia (or 3 ,
Chrysomyia) macellaria, adult and maggot. whole life cycle occuples
x 3. (Adult after Castellani and Chalmers, from nine days to two
larva after Blanchard.)

weeks or more.

As remarked before, the female screw-worm fly, about to re-
produce, is attracted to any animal smell and frequently finds a
suitable place for egg-laying in exposed wounds, or in the nose or
ears of people sleeping out doors, especially in case of foul-smell-
ing catarrh. Sometimes the flies select recently vacated Der- ©
matobia nests, boils, sores, etc., for the young to develop in. As
soon as hatched the maggots begin eating their way into the
tissues with which they are in contact, using their strong man-
dibles as nippers for cutting flesh and even bone. From the
ear they may make their way into the inner ear, completely de-
stroying the auditory apparatus. From the nose they penetrate
to the pharynx, frontal sinus, the eye-ball, and even the brain,
occasionally doing such extensive damage as to cause death.
Usually an abundant discharge of pus and scraps of tissue, in-
tense pain, and delirium accompany the infestation. A severe

MYIASIS OF WOUNDS 524

case which occurred in Kansas, reported by Professor Snow,
was substantially as follows: The victim had been suffering
from nasal catarrh and was subject to offensive discharges. On
August 22 he complained of a peculiar sensation at the base of
the nose, followed by violent sneezing, and later by excruciating
pain in the region of the forehead back of the nose. On the 24th
there was a profuse discharge of offensive matter from nose and
mouth with a subsidence of pain, the discharge continuing three
days and amounting to 16 ounces, becoming almost pure pus with
particles of bone, blood, etc., in it. The odor was very offensive,
and coughing and fever developed, together with difficulty in
speech and swallowing. At this time a maggot dropped from
the nose, giving the first inkling of what the trouble was. The
worms continued to drop from the nostrils and mouth, burrowing
from under the soft palate and covering of the hard palate.
The palate was completely honeycombed, and in places patches
as large as a dime were entirely destroyed. The estimated
number of maggots which escaped during 48 hours was over 300.
The whole of the soft palate was destroyed by this time, and
the patient died four days after the emergence of the last worm.

Other Species. — Although the screw-worm is the species most
thoroughly addicted to breeding in wounds and natural cavities
of the human body, it is by no means alone in this nefarious
habit. The beautifully colored green-bottle fly, Lucilia cesar,
and other species of Lucilia have this habit, and the common
blowflies, Calliphora vomitoria and C. erythrocephala, are sometimes
implicated. These ubiquitous pests are said to have been a
great torment to wounded soldiers in the Civil War. The red-
headed blowfly, C. erythrocephala, is recorded in one case as
having flown into the nostril of a woman to deposit its eggs.
A week later over 100 maggots passed out from nose and mouth,
leaving the nasal cavities and palate in a horribly mutilated
condition. Of the fleshflies, which are related to the Muscide,
but are placed in a separate family, Sarcophagide, many, and
possibly all, will at least occasionally breed in wounds or natural
cavities of living bodies.

A particularly troublesome species in Europe, especially in
Russia, where it is almost as much of a scourge as is the screw-
worm in America, is the fleshfly, Wohlfartia magnifica. In
Russia during hot weather this fly attacks the nose, ears, mouth,

o22 FLY MAGGOTS AND MYIASIS

sores, wounds of any kind, or even the eyes, of human beings.
In one case 70 maggots were extracted from one eye after about
this many had already escaped and been thrown away. This
fly, unlike most of its allies, is said to attack only living animals.
The larve are unusually resistant to substances which readily
kill other insects; they will survive two hours in 95 per cent

Fie. 251. Larva of fleshfly, Sarcophaga; A, side view of larva; B, posterior
view showing posterior spiracles in depression; C, anterior spiracle, marked ‘‘sp.”’
in Fig. A; D, skeleton of pharynx, with mouth hooks. (After Riley and Johannsen.)

alcohol, and ten minutes in turpentine or pure hydrochloric acid.
This species is said to be a great pest in war, where it causes
myiasis in the wounds of soldiers. In France it is said to add
much to the sufferings of wounded men.

Other fleshflies occasionally deposit their eggs on living animals
or human beings. Sarcophaga carnaria is particularly likely to
deposit eggs or larve in the vagina when it has: access to it.
As in the case of the flies mentioned above, this species will
readily attack the nose or ears, especially if there is a foul-smell-
ing catarrhal discharge flowing from it, and will infest inflamed
or diseased eyes, sometimes nesting in large numbers under the
eyelids and eating away the cornea.

The fleshflies are mainly gray in color, with longitudinal dark
stripes on the thorax and a checkered abdomen which is change-
able in varying lights. In summer the smell of decaying flesh
will invariably attract them. The checkered abdomen and the
broad angle at which the wings are held serve to distinguish
them from other gray flies. Their life history is essentially the
same as that of the screw-worm fly.

Another fly which must be mentioned in this connection is
the sheep head-maggot, @strus ovis, a species of botfly. It

INTESTINAL MYIASIS 523

normally lays its eggs in the nostrils of sheep, from which place
the maggots burrow into various parts of the head. In Algeria
it is said to lay its eggs while flying without alighting, upon
the eyes, nostrils and lips of shepherds, especially those whose
breath smells of fresh sheep or goat cheese. It somewhat re-
sembles a housefly, but is larger and of a warmer brown color.
Its mouthparts are deficient to such an extent that the fly is
incapable of feeding, its only instincts being those connected
with the reproduction of its kind.

Treatment.— The danger arising from attacks of screw-
worms and flies of similar habits is that the infestation is often
not discovered until too late. Even when one is aware of an
attack by the fly, it is not always possible to drive it away soon
enough to prevent the eggs or maggots from being deposited.
The larve should be removed as speedily as possible since they
may do a great deal of damage in a very short time. Usually
the maggots may be induced to release their hold and to fall
out by douching the infested part of the body with a 20 per cent
solution of chloroform in sweet milk, or with a carbolic or lysol
wash. Even salt water is often effective in removing the mag-
gots and should be used if no better wash is at hand. Maggots
in the ear, if outside the ear drum, should be removed by means
of water or milk saturated with chloroform, but if they have
already pierced the ear drum, surgery will probably be necessary.
Often where infections are two or three days old surgery must be
resorted to and the larve removed by means of curved forceps.
Frequent antiseptic washes prevent the injuries made by the
maggots from becoming infected with bacteria.

Myiasis of the Intestine

There are a number of species of fly maggots which may ac-
cidentally be taken into the intestine of man and cause trouble
there. To quote from Banks, ‘‘ When we consider that these
dipterous larve occur in decaying fruits and vegetables and in
fresh and cooked meats; that the blowfly, for example, will
deposit on meats in a pantry; that other maggots occur in cheese,
oleomargarine, etc., and that pies and puddings in restaurants are
accessible and suitable to them, it can readily be seen that a
great number of maggots must be swallowed by persons each year,

’

524 FLY MAGGOTS AND MYIASIS

and mostly without any serious consequences.” Banks gives the
following quotation from Walsh, — ‘“‘ Taking everything into con-
sideration, we doubt whether, out of 10,000 cases where the larvee
of two-winged flies have existed in considerable numbers in the
human intestines, more than one single case has been recorded
in print by competent entomological authority for the edification
of the world.”

Botflies. — There are some flies of the botfly family, stride,
which as larve habitually parasitize the digestive tracts. of horses
and other domesticated animals, and are especially adapted in
habits and structure for such a larval life.
They occasionally, though rarely, occur in
man. The horse botfly, Gastrophilus equi,
for instance, lays its eggs (Fig. 252) on the
hairs of horses in spots where they are likely
to be licked. The moisture and rubbing
of the horse’s tongue cause the eggs to
hatch at once, and the new larve, adhering
to the tongue, make their way to the
stomach and intestine where they attach
themselves and develop to full-grown spiny
larve, three-quarters of an inch in length.
In the following spring the larve let go their

: : hold, pass out with the faces of their host

Fic. 252. Egg of : : .
horse botfly, Gastro: and pupate in the ground. Obviously it
philus equi, attached egyuld be only by a series of unusual cir-
to hair; gr., groove for 7
cementing to hair; op., Cumstances that these larve could gain access
operculum. (After to the human stomach, yet a number of cases
Collinge.)

have been recorded.

Fannia Larve.— A much more common occurrence in man
is infection of the intestine with larve of various species of house-
frequenting flies, especially the lesser housefly, Fannia canicu-
laris, and the latrine fly, F. scalaris. The former species is very
common in houses both in Europe and America. It closely
resembles the housefly but is smaller, and appears earlier in the
spring. The peculiar manner of flight, a sudden dart followed by
a hovering, is very characteristic and a good means of identifica-
tion. This fly is frequently observed hovering about chandeliers
hanging near the center of rooms. The eggs are oval, white
objects and are laid in decaying vegetable and animal matter

F
|
|

FANNIA LARVE 525

and sometimes in excrement. The occasional presence of eggs
in partially decayed vegetables, as in decayed lettuce leaves
rotten fruit, etc., probably accounts for the not uncommon ie
pearance of the larve in the human intestine, although the eggs
may also be laid in or near the anus of people using unsanitary
privies, whence the larve work their way up into the large in-
testine. The larve (Fig. 253) are very different from those of
houseflies and blowflies, being broad and flattened, about one-

Fig. 253. Larvex of Fannia scalaris (left) and Fannia canicularis (right). x 8.
(After Hewitt.)

fourth of an inch in length when full grown, brown in color,
with rows of spiny processes to which adhere particles of dirt
and filth. The latrine fly, F. scalaris, is very similar to the
species described above, but is larger and differs in minor details
of form and habits. It prefers excrement, especially human
excrement, on which to deposit its eggs, and has gained its com-
mon name from its frequent presence about privies and latrines.
The author has found larve of this species very abundant in
chicken manure. The adult has the same darting and hovering

526 FLY MAGGOTS AND MYIASIS

manner of flight as its close relative, F. canicularis. The larve
(Fig. 253) differ from those of the latter species in the form and
arrangement of spines. Several cases are on record in which
Fannia larvee were passed in the feces intermittently for a num-
ber of years, often accompanied by a chronic disorder of the
intestine. It is probable in these cases that repeated reinfections
occur, though it may be conceived that the complete life history
of the fly could be passed within the intestine of the host. The
probability of this seems rather remote.

Other Species. — Another common cause of intestinal myiasis
is the larvae of the cheesefly, Piophila casei, popularly called
“ cheese-skippers’”’ (Fig. 254). These
larvee often occur in abundance in old
cheese, and also in ham, bacon and other
foods. It is thought by some people that
their presence in cheese is an indication
of particularly good cheese! These mag-
gots resemble diminutive housefly larva,
but have two mouth hooks like the blow-
fly maggots, whereas the housefly larve

have a single median one. Probably in
alge! orn Mc 9 on many cases the cheese - skippers pass
x 3. (After Graham- through the intestine without doing much
pena Riley and damage, but they sometimes attack the

mucous membranes, causing bleeding sores
which may become infected and ultimately lead to ulceration.
Severe pain in the abdomen, headache and vertigo have been
known to be caused by these larve in the intestine.

There is one case on record of the infection of a Chinaman
with the fleshfly, Sarcophaga fuscicauda. He passed about 50
larve in each stool for eight days. Occasional infection of the
intestine with maggots of other species of flies has been recorded,
but the instances are so rare as to be of interest only as ab-
normal occurrences.

The powerful resistance of fly maggots to substances which
would quickly destroy other animals makes it possible for many
species to pass through the stomach safely if accidentally swal-
lowed either as eggs or young worms. As said before experi-
ments show that the larve of the fleshfly, Wohlfartia magnifica,
can survive two hours in 95 per cent alcohol, and ten minutes in

;
}
|
|

To i. Pe ae

a on
ee ia ee

EFFECTS OF INTESTINAL MYIASIS 527

pure hydrochloric acid or turpentine. It is a little wonder, then,
that fly maggots are not destroyed by the 0.2 per cent hydro-
chloric acid of the stomach or by the other digestive juices.

Effects. — The effects of fly larve in the intestine are extremely
variable, depending on the heaviness of the infection, the species
of flies, and on individual susceptibility. There are many cases
where the presence of the larve in freshly passed stools is the
first indication of their having existed in the intestine, and it is
practically certain that the majority of infections are never known
or suspected. |

On the other hand more or less serious symptoms may be
caused by intestinal myiasis. The presence of Fannia larve or
of cheese-skippers in the digestive tract often gives rise to tem-
porary intestinal disturbances, such as loss of appetite, vomit-
ing, general malaise, abdominal pains, diarrhea, constipation and
intestinal bleeding. Sometimes headache and vertigo indicate
the absorption of toxic substances secreted by the maggots or
their entrance to the blood circulation through the wounds.
Four cases of death from intestinal myiasis have been recorded,
and it is probable that appendicitis may sometimes be caused
through injury to the walls of the appendix by fly larve which
start sores leading to ulceration. Those maggots which pass
directly through the digestive tract, feeding only on food sub-
stances with which they come in contact en route, do little or
no harm to the temporary host. Those larve, however, which
attack the living tissues lining the stomach and intestine are the
cause of the symptoms named above. Even the maggots of
the housefly, Musca domestica, have been known to damage the
walls of the digestive tract. In a case which occurred in the
Philippines, the walls of the stomach were extensively eaten away
by larve of this common fly, and 20 or 30 maggots were obtained
by means of a stomach pump. A liver abscess which was not due
to the usual amebic infection accompanied this case, but whether
due directly or indirectly to the myiasis can only be conjectured.

Fly maggots can usually be expelled readily by means of
purges and doses of the drugs which are used for intestinal worms
(see p. 237). The chief danger from infection, as in other forms
of myiasis, lies in the fact that the presence of the maggots is
usually not even suspected until much of their damage has been
done. Prevention, of course, consists principally in care as to

528 FLY MAGGOTS AND MYIASIS

what is eaten, especially in regard to such foods as raw vegetables
and partly decayed fruits.

Myiasis of Urinary Passages.— Myiasis of the urinary pas-
sages, both urethra and bladder, is a rare but occasional occur-
rence. ‘The flies implicated are usually the lesser housefly, Fannia
canicularis, and the closely allied latrine fly, F. scalaris, which
have already been described in connection with intestinal myiasis.
In most cases infection occurs from eggs laid near the external
opening of the urethra, the larve working their way up into this
tube and even into the bladder; apparently they need very little
oxygen. Contamination is favored by sleeping without covers
in hot weather, so that flies have free access to the anal and
genital region. The larvae, when escaping, are said to be able to
project themselves with a flicking motion to a distance of from
12 to 20 inches.

SOURCES OF INFORMATION

The following list of ‘ sources of information” includes only
those periodicals which are at least partly devoted to parasitology
and preventive medicine, or which frequently contain important
articles on these subjects, and those books which cover the entire
subject or parts of it in a comprehensive manner. Books which
are out of date and have been superceded by newer ones are not
included. Most of the books listed contain more or less extensive
bibliographies which should be of great assistance to anyone who
desires to pursue any phase of the subject of human parasitology
beyond the hallway to which this book may lead him.

PERIODICALS
United States and Canada

Amer. Journ. Publ. Health, New York, 1911-

Amer. Journ. Trop. Diseases and Prev. Med., New Orleans, 1913-1915,
(Merged with New Orleans Med. and Surg. Journ.).

Exper. Sta. Bull. (Contains synopses of interest in sections on “ Economic
Zoology and Entomology ” and “ Veterinary Medicine.’’)

Harvard School Trop. Med., Rep. (one issued), 1913-

Index Medicus, Washington, 1879-

Journ. Amer. Med. Assoc., Chicago, 1883- (Contains references to all current
medical literature, and reviews of much of it.)

Journ. Canad. Med. Assoc., Toronto, 1911-

Journ. Cutaneous Diseases, Boston, 1882- (Continuation of ‘‘ Journ. Cutaneous
and Venereal Diseases.’’)

Journ. Econ. Ent., Concord, 1908-

Journ. Exper. Med., New York, 1896-

Journ. Inf. Diseases, Chicago.

Journ. Med. Research, Boston, 1901-

Journ. Parasitology, Urbana, 1914-

New Orleans Med. and Surg. Journ., 1844-

Publ. Internat. Health Comm., Rockefeller Foundation, New York.

Publ. Rockefeller San. Comm. for Eradication Hookworm Disease. Wash- —
ington.

U.S. Bur. Animal Industry, Bull.; Washington.

U. S. Bur. Ent., Bull., Washington.

U.S. Dep’t Agr., Bull., Washington.

U. 8. Naval Med. Bull., Washington.

U. S. War Dep’t Bull., Washington.
529

530 SOURCES OF INFORMATION

South America

Brazil Medico, Rio de Janiero, Brazil, 1887-
Cronica Medica, Lima, Peru, I884—-
Mem. do Inst. Oswaldo Cruz, Maguinhos, Rio de Janiero, Brazil, 1909-

Great Britain

Ann. Trop. Med. and Parasitology, Liverpool, 1907-

Brit. Med. Journ., London, 1857-—

Bull. Entom. Research, London, 1910-

Journ. Econ. Biology, London, 1906-

Journ. Hyg., Cambridge, 1901-

Journ. London School Trop. Med., London, 1911-1913

Journ. Royal Army Med. Corps, London, 1903-

Journ. Trop. Med. and Hyg., London, 1898-

Lancet, London, 1823-

Memoirs, Liverpool School Trop. Med.

Parasitology, Cambridge, 1908-

Quarterly Journ. Micr. Science, London.

Rep. Sleeping Sickness Comm. Roy. Soc., London, 1903-

Review Applied Entom., Ser. B (Med. and Vet.), London, 1913-
(Contains reviews of al! important work on medical and veterinary
entomology.)

Sleeping Sickness Bull., London, 1908-1912

Trans. Soc. Trop. Med. and Hyg., London, 1907-

Trop. Diseases Bull., London, 1913-

(Contains reviews of all important work on tropical diseases, including
nearly all work on protozoan parasites and on helminthology.)

France

Ann. d’hyg. et de med., Paris, 1898-

Ann. de l’institute Pasteur, Paris, 1887-

Arch. de parasitologie, Paris, 1898-

Bull. de la soc. de path. exotique, Paris, 1908-

Bull. Sci. de la France et de la Belgique, 1888—
Comp.-Rend. de la soe. de biol., Paris, 1849—
Comp.-Rend. des seances de l’acad. des sci. Paris, 1835-
Revue de med. et d’Hygiéne tropicales, Paris, 1904—

Germany and Austria

Arch. fiir Protistenkunde, Jena, 1902-

Arch. fiir Schiffs- und Tropen-Hyg., Leipzig, 1897-

Bibliographica Zoologica.

Centralblatt fiir Bakt. und Parasitologie, 1 abt., Orig. und Ref., Jena, 1887-
(Ref. contains references and reviews of many articles dealing with in-
fectious diseases.)

PERIODICALS 531

Deutsche Med. Wochenschrift, Berlin, 1875-
Wiener Klinische Wochenschrift, Vienna, 1888-
Zeitschr. fiir Hyg. und Infektionskrank., Leipzig, 1886-

Italy
Annali d’Igiene, Rome, 1895-
Malaria e Malattie dei Paesi Caldi, Rome, 1910-
Malariologia, Rome, 1908-
Policlinico, Rome, 1893-
Pediatria, Naples, 1893-

Portugal
Arch. de hyg. e path. exot., Lisbon, 1905—

_ Asia

China Med. Journ., Shanghai, 1887- (Contains bimonthly, beginning 1916,
“Japanese Medical Literature,” a review in English of current Japanese
medical work, also issued separately.)

Ind. Journ. Med. Research, Calcutta, 1913-

Ind. Med. Gazette, Calcutta.

Philip. Journ. Sci., Ser. B (Trop. Med.), Manila, 1906-

Proc. All India San. Conferences.

Sci. Mem. by Officers Med. and San. Dep’t of Gov’t of In dia, Calcutta.

Africa

Arch. de l’inst. Pasteur, Tunis, 1906-
Nyasaland Sleeping Sickness Diary, Zomba, 1908-
Rep. Wellcome Research Lab., Khartoum, 1906-

Australia

Australian Inst. Trop. Med., Collected Papers, Townsville, 1914-

BOOKS
General

Bolduan, C. F., and Koopman, J. Immune Sera, 5th ed., 206 pp., 9 figs.,
New York, 1917.

Braun, M., anp Lunn, M. Handbook of Practical Parasitology (trans-
lated from German by L. Forster), vii + 208 pp., ill., 1910.

Brawn, M. Die Tierischen Parasiten des Menschen, 5th ed. Part 1, Natur-
geschichte, 560 pp., 407 figs., Wurzburg, 1915. Part 2 by Siebert, O., to
appear later.

BreInt, ANTON. The Distribution and Spread of Disease in the East;
Protozoa and Disease; The Influence of Climate, Disease and Sur-
roundings on the White Race Living in the Tropics (Stewart Lectures
of Univ. of Melbourne) 31 pp., Melbourne, 1914.

Soe SOURCES OF INFORMATION

Brunet, E. Precis de parasitologie, xxviii + 1011 pp., Paris, 1913.

CASTELLANI, A., AND CHaLmers, A. J. A Manual of Tropical Medicine,
xxv +1242 pp., num. figs., London and New York, 1914.

Fantuam, H. B., StepHens, J. W. W., anp THEosatp, F. V. The Animal
Parasites of Man (partly adapted from Braun’s ‘‘Die Tierischen Para-
siten des Menschen), xxvii + 900 pp., London, 1916.

La.oy, L. Parasitisme et mutualisme dans la nature, 284 pp., 82 figs.,
Paris, 1906.

Levuckart, R. Die Parasiten des Menschen und die von ihnen herruhrenden
Krankheiten, 2nd ed., (also English translation), Leipzig and Heidel-
berg, 1886-1889.

Manson, Patrick. Tropical Diseases, 5th ed., xxiv + 937 pp., 239 figs.,
16 pls., London and New York, 1914.

Mense. Handbuch der Tropenkrankheiten, Band I, 1905

NrEuMANN, R. O., anpD Mayer, M. Atlas und Lehrbuch wichtiger tierischer
Parasiten und ihrer Uebertriger. Vol. IX of Lehman’s Medizinische
Atlanten, vi + 580 pp., 45 pls., 237 figs., Munich, 1914.

Neveu-Lemarire, M. Precis de parasitologie humaine, parasites vegetaux
et animaux, 4th ed., Paris, 1911.

SurpLtey, A. E. The Minor Horrors of War, 184 pp., London, 1915.

ZINSSNER, H. Infection and Resistance, xili + 546 pp., ill., New York, 1914.

Protozoélogy and Helminthology

Boycr, R. Yellow Fever and Its Prevention, 396 pp., London, 1911.

Brurto pa Costa, B. F., Santa Anna, J. F., pos Santos, A. C., and pp ARANJO
Atvares, M. G. Sleeping Sickness, a Record of Four Years’ War
Against it in the Island of Principe (Trans. from Portuguese by Wyllie,
J. A.), xii + 261 pp., ill., London, 1916.

Ca.kins, Gary N. Protozodlogy, ix + 349 pp., 125 ill., New York, 1909.

Ciark, J. J. Protozoa and Disease, 4 vols., London and New York, 1903-
1916.

Craic, C. F. The Malarial Fevers, Hemoglobinuric Fever and the Blood
Protozoa of Man, New York, 1909.

Dortern, F. Lehrbuch der Protozoenkunde, 3rd ed., xii + 1043 pp., 951

figs., Jena, 1911.

FantTHAM, H. B., AnD Porter, A. Some Minute Animal Parasites, 319 pp.,
56 figs., London, 1914.

Ko.uie, W., AND WASSERMAN, E. von. Handbuch der Pathogenen Mikro-
organismen, 2nd ed., Band VII (Protozoa), 1039 pp., 121 figs., 20 pls.,
and Band VIII (Worms and Obscure Organisms), 1109 pp., 372 figs., 22
pls., 1913.

LAVERAN, A., AND MeEsniL, F. Trypanosomes et Trypanosomiases (1904 ed.
trans. to English by D. N. Nabarro), Paris and Chicago, 1912.

Looss, A. The Anatomy and Life History of Ankylostoma duodenale, 451
pp., 19 pls., Cairo, 1908.

MacNzat, W. J. Pathogenic Micro-organisms, xxi + 462 pp., 213 ill., Phila-
delphia, 1914.

BOOKS 533

Mincutn, A. E. An Introduction to the Study of the Protozoa, xi + 517
pp., London, 1912.

Puiuuips, L. P. Ameebiasis and the Dysenteries, xi +147 pp., London, 1915.

ProwaZEK, 8. von. Taschenbuch der Mikroscopischen Technik der Protis-
ten-untersuchungen, Leipzig, 1909.

Handbuch der Pathogenen Protozoen, in 6 Lief., in all 878 pp., 24 pls., 310

figs., Leipzig, 1912-1914.

Ross, R. The Prevention of Malaria, xx + 669 pp., London, 1910.

Sravusu, C. Trichinosis, Wiesbaden, 1909.

STEPHENS, J. W., AND CurisToPHERS, 8.R. The Practical Study of Malaria
and Other Blood Parasites, ix + 414 + xiv pp., 6 pls., ill., London, 1908.

Tuimm, C. A. Bibliography of Trypanosomiasis. Issued under the Direc-
tion of the Honorary Managing Committee of the Sleeping Sickness
Bureau, London, 1909.

Medical Entomology

Aucock, A. Entomology for Medical Offices, xx + 347 pp., 136 figs., Lon-
don, 1911.

AusTEN, E. African Blood-sucking Flies, British Mus. Publ., London, 1909.
A handbook of the Tsetse Flies, British Mus. Publ., x +110 pp., 24
figs., 10 pls., London, 1911. !

Boyce, R. W. Mosquito or Man? The Conquest of the Tropical World,
xvi + 267 pp., 44 pls., New York, 1909.

Doane, R. W. Insects and Disease, xiv + 227 pp., New York, 1910.

GRAHAM Situ, G. 8S. Flies in Relation to Disease (Non-Blood-Sucking
Flies), xiv + 292 pp., Cambridge, 1913. .

Heeu, E. Notice sur les glossines ou téstsés, 148 pp., 29 figs., London, 1915.

Herms, W.B. Medical and Veterinary Entomology, xii + 393 pp., 228 figs.,
New York, 1915.

Hinpis, E. Flies and Disease (Blood-Sucking Flies), 414 pp., ill., Cambridge,
1914.

Howarp, L. O., Dyar, I., anp Knas, F. The Mosquitoes of North and
Central America and the West Indies, Carnegie Inst. Publ., 4 vols.,
520 + 1064 pp., 14 +150 pls., Washington, 1913-1917.

LePrince, J. A., AND OrrensTEIN, A. J. Mosquito Control in Panama, with
Introduction by L. O. Howard, xvii + 335 pp., 100 ill., New York, 1916.

Norra, G. H. F., Warsurton, C., Coorsr, W. F., and Rostinsov, L. E.
Ticks; a Monograph of the Ixodoidea, Parts 1 to 3, Cambridge, 1908-1915.

Patron, W. S., AnD Crace, F. W. A Textbook of Medical Entomology,
764 pp., London. 1913.

Riney, W. A., AND JOHANNSEN, O. A. A Handbook of Medical Entomology,
ix + 348 pp., 174 figs., Ithaca, 1915.

Russet, H. The Flea, 125 pp., 9 figs., Cambridge, 1913.

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INDEX

Abyssinia, relapsing fever, 44; tape-
worm infections, 240; Ornitho-
dorus savignyi, 361, 368, 369.

Acanthaspis sulcipes, and endemic
goitre in Africa, 382.

Acanthocephala, 199; 283-285.

Acanthocheilonema perstans, see Fi-
laria perstans.

Acarina, 324; 331-333;
mites.

Acid, resistance of maggots to, 522.

Acne, relation of Demodex to, 347.

Adaptations, of parasites and hosts,
14-15.

Aden, phlebotomus fever outside
range of Phlebotomus papatasii,
470.

Aédes, intermediate host of Filaria
bancrofti, 301.

calopus, and yellow fever, 184, 443;
443-448; extermination in Loui-
siana, 185; and dengue, 186, 448;
time of activity, 436, 444; food
preferences, 436; description,
443-444; habits, 444; breeding,
444-447; habits of larve, 446;
flight and distribution, 447-448.

pseudoscutellaris, intermediate host
of Filaria, 301, 450.

sollicitans, migrations, 435.

spenceri, habits, 436.

Africa, relapsing fever, 42, 43; yaws,
63; spirochztal bronchitis, 71;
kala-azar, 77; importance of
sleeping sickness, 93; distribu-
tion of Trypanosoma gambiense
and T. rhodesiense, 98; malaria,
147-148; blackwater fever, 161;
yellow fever, 182; Schistosoma
hematobium, 212; Schistosoma
mansoni, 217; Gastrodiscoides in

see also

horses, 229; Watsonius watsoni,
229; Hymenolepis nana, 242;
Tenia africana, 245; Dibothrio-
cephalus latus, 246; Sparganum
mansoni, 252; Necator ameri-
canus, 255; Physaloptera mor-
dens, 282; Ternidens deminutus,
283; (sophagostomum apio-
stomum, 283; ZZ. stephanostomum,
283; Filaria perstans, 307-308;
Loa loa, 308, 489; Chrysops with
larval filarie, 310, 489; Oncho-
cerca volvulus, 310; Dracunculus
medinensis, 311; aquatic leeches,
317; tick paralysis, 358-359;
Ornithodorus moubata, 360; Ar-
gas reflexus, 364; Otiobius még-
nint, 365; Amblyomma hebreum,
367; Cimex hemipterus, 373;
Triatoma rubrofasciatus, 381;
Acanthaspis sulcipes, 382; Xenop-
sylla, 417; chigger, 419; malaria-
carrying Anopheles, 441; oil
films for mosquito larve, 459;
Phlebotomus papatasii, 470, 471;
tsetse flies, 490, 492; Glossina
morsitans, 493, 499; Glossina
palpalis, 498; other species of
Glossina, 500-501; destruction
of wild game, 503-504; blood-
sucking maggots, 511-513; skin
maggots, 513, 516-519.

African relapsing fever, relation of
ticks to, 8, 43-46; importance,
42; transmission, 43-44, 360-
361; in Persia, 44; severity, 47.

African skin maggot, see Cordylobia
anthropophaga.

Agglutination, 21; of trypanosomes,
102-103.

AGRAMONTE, C. A., 184, 448.

535

536

Akamushi, see Leptus akamushi.

AKASHI, 244.

Aucock, A., 433, 449, 478.

Alcohol, in prevention of filarial in-
fection, 307; for red-bug rash,
336; resistance of maggots to,
522, 526.

Alcresta ipecac, for Balantidium in-
fections, 127; for amebic dys-
entery, 135-136; for amebic
infections of mouth, 146.

Algeria, relapsing fever transmission,
44; infantile kala-azar, 82; sheep
head-maggot, 522-523.

Alum, for fleas, 421.

Amblyomma, 366.

cajennense, 367.
hebreum, 367.

Amebe, cultivation, 9; encysted, in
Egypt, 34; 128-146; classifica-
tion, 128-130; and dysentery,
131-134; effect of emetin on,
135; of mouth, 139-146.

Amebic dysentery, in United States,
6; 130-137; importance, 130;
parasites of, 132-134; course of,
134; treatment, 135-136; pre-
vention, 136-137.

America, relapsing fever, 42, 43;
origin of syphilis, 48; importa-
tion of yaws, 63; possibility of
kala-azar, 77; introduction of
sleeping sickness, 93; yellow
fever, 182-183; Schistosoma man-
soni, 217; Hymenolepis nana,
242; introduction of Necator
americanus, 255; hosts of tri-
china, 288; Demodex follicu-
lorum, 347; Amblyomma cajen-
nense, 367; original home of
Aédes calopus, 447; Culex quin-
quefasciatus, 449; Janthinosoma
lutzt, 453; oil of citronella as
repellent for mosquitoes, 455;
Chironomide, 474; skin mag-
gots, 513-516; screw-worm, 519;
Fannia, 524. See also various
geographic subdivisions.

INDEX

American hookworm, see WNecator
americanus.

American Hookworm Commission,
use of thymol, 263; work of, 268.

American leishmaniasis, see Es-
pundia.

American Red Cross, work in Serbia,
378, 398.

American Yellow Fever Commission,
7-8, 184, 443.

Ammonia, for red-bug rash, 335; for’
body lice, 402.

Ameba, 131.
Anaphylatoxin, 23-25.
Anaphylaxis, 23-25; specific, 24;

treatment, 25.
Ancon, manufacture of larvicide, 459.
Ancylostoma duodenale, distribution,
255; description, 255-257.
ceylanicum, 255.
ANDERSON, J. F., 8, 397.
Andes, uta, 86; Oroya fever, 178,
472; Phlebotomus verrucarum, 473.
Animal experimentation, 10-11.
Anise oil, for body lice, 401; for mos-
quitoes, 455; for phlebotomus
flies, 473.
Anisol, for body lice, 401.
Annelida, 199-200; 315; relation to
arthropods, 323; see also Leeches.
Anopheles, malaria-carrying species,
157-158, 438, 439-441; cessation
of breeding and _ subtropical
malaria, 162; number necessary
to propagate malaria, 165; inter-
mediate host of Filaria bancrofti,
301, 450; palpi, 426; eggs, 429;
larve, 431, 442; time of activity,
435, 437; identification, 438—
439; habits, 441-443; variable
ability of species to transmit
different kinds of malaria, 439;
effect of oil on larve, 458; effect
of larvicide, 459.
albimanus, and malaria in tropical
America, 439.
argyrotarsus, and malaria in tropi-
cal America, 441.

INDEX

bancrofti, and malaria in Australia,
441.

bifurcatus, hibernation, 441.

braziliensis, habits, 441.

costalis, and malaria in Africa, 441.

crucians, relation to various types
of malaria, 439.

culicifacies, and malaria in India,
441.

cruzi, habits, 442.

eisent, habits, 441-442.

funesta, and malaria in Africa, 441.

listoni, and malaria in India, 441;_

in China and Japan, 441.

ludlowi, habits, 442.

maculipennis, and malaria in
Europe, 441.

malefactor, not a malaria carrier,
158, 434.

punctipennis, development of Leish-
mania donovani in, 78; relation
to certain types of malaria, 439.

quadrimaculatus, resistance of Plas-
modium vivax to low tempera-
tures in, 156; carrier of certain
types of malaria, 439; develop-
ment, 442..

sinensis, and malaria in China and
Japan, 441.

stephensi, and malaria in India, 441.

umbrosus, and malaria in Malay
countries, 441; habits, 441.

willmori, and malaria in Malay
countries, 441; habits, 441.

Anoplura, characteristics, 330, 388;
see also Lice.

Antelope, host of Tenia saginata, 240;
host of tsetse flies, 490; host of
Cordylobia rodhaini, 518.

Anthelmintics, 270.

Anthrax, and tabanids, 488;
stable-flies, 488, 507.

Antibodies, 21; duration, 22.

Antigen, 22.

Antimony, metallic, in kala-azar, 81;
see also Tartar emetic.

Antitoxin, 21.

Anti-vivisectionists, 10-11.

and

537

Apes, hosts of Trypanosoma cruzi, 112;
relation of intestinal worms to
typhoid in, 204.

Aphthomonas infestans, and foot-and-
mouth disease, 76, 195.

Aphthous fever, see Foot-and-mouth
disease.

Aponomma, 366.

Appendicitis, relation of intestinal
worms to, 204; and intestinal
myiasis, 527.

Arabia, oriental sore, 85; Ornitho-
dorus savignyt, 361; tsetse flies,
492, 500.

Arachnida, 324.

Aradide, 383.

AraGAo, H. pEB., 73, 130.

Archi-annelida, 199.

Arctomys bobac, and plague in Man-
churia, 413.

Argas miniatus, see A. persicus.

persicus, and relapsing fever, 45,
361; importance, 364; control,
369.

reflexus, 364.

Argaside, egg-laying habits, 355;
general characteristics, 356-357;
important species, 364-366.

Argentina, trypanosomes in T'ria-
toma, 108, 112, 381; dengue, 186;
Tetranychus molestissimus, 341.

Armadillo, host of Trypanosoma
cruzi, 112; and Triatoma genicu-
lata, 380-381.

Arsenical dip, to remove ticks from
domestic animals, 368.

Arthropoda, 322-330; importance,
322; rdle in disseminating
disease, 7-8, 322-323; relation-
ships, 323-324; classification,
324-325.

Ascaris, nutriment absorbed, 202;
toxins, 202-203; 273-276; de-
scription, 273; life history, 274-
275; symptoms, 276; treatment,
276.

lumbricoides, 274.

marginata, see Toxascaris limbata.

038

mystax, see Belascaris catt.
suilla, 274.

Ascaride, 282.

AsHBURN, P. M., 301, 448.

Asia, oriental sore, 84; blackwater
fever, 161; dengue, 186; kedani,
192; Schistosoma hematobium,
212; Clonorchis sinensis, 224;
Yokagawa yokayawa, 228; Hete-
rophyes heterophyes, 228; Fas-
ciolopsis buski, 229; Hymeno-
lepis nana, 242; Necator ameri-
canus, 255; Filaria bancrofti, 299;
Dracunculus medinensis, 311;
Porocephalus moniliformis, 351;
Cimex hemipterus, 373; Tria-
toma rubrofasciata, 381; Xenop-
sylla, 417; Phlebotomus, 470;
surra, 487.

Asopia farinalis, intermediate host of
Hymenolepis diminuta, 244.

Assam, eradication of kala-azar, 82.

Astacus japonicus, intermediate host
of lung fluke in Korea, 222.

Ateles, host of Pediculus, 389.

ATtxIn, E. E., 445, 446.

Atoxyl, discovery, 8; for trypano-
somes, 105.

Aucheromyia luteola, 511-513; de-
seription, 511; life history, 511-
512; maggots, 512; avoidance
of, 513.

Australia, Aédes calopus carrier of
dengue, 186; hydatids, 247, 249;
Filaria bancrofti, 299; land
leeches, 319-320; tick paraly-
sis, 358-359; malaria-carrying
Anopheles, 441; Aédes calopus,
448; transmission of dengue, 448;
Pericoma townsvillensis, 466.

Austria, relapsing fever, 43; typhus,
398.

Auto-salvarsanized serum, for syphilis
of nervous system, 57; for sleep-
ing sickness, 106.

Axopodia, 31.

Axostyle, 32.

INDEX

Baboon, host of Trichostrongylus in-
stabilis, 282; fed upon by tsetse
flies, 500.

Bacillus coli, 204.

icteroides, and yellow fever, 184.
pestis, discovery, 411.

Bacot, A. W., 375, 376, 391, 393, 395,
409, 412, 444, 445, 446.

Bacteria, distinguished from Protozoa,
27; relation to trachoma, 194;
relation to diseases of obscure
nature, 195; and _ intestinal
worms, 204; relation to filarial
diseases, 305-306; food of Aédes
calopus, 446.

Bacterium tularense, transmitted by
fleas, 413.

Badger, host of Pulex irritans, 414.

Bagdad, oriental sore, 85, 88, 471.

BaGcsHAaweE, A. G., 503.

Bane, P. H., 303.

Baking soda, for mites, 335, 339.

Balanitis, cause of, 70; treatment, 71.

Balantidial dysentery, 129.

Balantidium coli, discovery, 7, 37;
115; 126-127; description, 126;
pathogenicity, treatment and
prevention, 127.

Balkans, relapsing fever, 43, 45.

Balsam of Peru, for itch, 346.

Baltic countries, Dibothriocephalus
latus in, 246.

Bancrort, TH., 7.

Banks, N., 333, 339, 523, 524.

Barbados, home of “millions,” 461.

Barbeiro, see T'riatoma megista.

Bartow, N., 117, 187, 139, 281.

Barton, 179.

Bartonella bacilliformis,
181; 360.

Basal granule, 30.

BasILB, C., 84. .

Bass, C. C., 9, 149, 164.

Bats, Cimex in, 372, 375; trypano-
some disease of, carried by Comex
pipistrelli, 378; natural enemies
of mosquitoes, 462; natural
enemies of tsetse flies, 503.

168; 179-

INDEX

Bayon, H., 378.

BEAUPERTHOUY, L. D., 322.

Bedbugs, and relapsing fever, 45, 46;
378; and kala-azar, 77-78, 377;
and Leishmania infantum, 83;
and oriental sore, 86, 377-378;
and Trypanosoma cruzi, 112, 378,
370; 371-379; general structure,
371; odor, 371-372; species,
372-373; habits, 373-375; effect
of bites, 374; hosts, 374-375;
life history, 375-376; and disease,
376-379; and bubonic plague,
378-379; remedies and preven-
tion, 383; fumigation of, 385-386.

Bee eater, natural enemy of tsetse
flies, 503.

Beef tapeworm, see Tenia saginata.

Beetles, intermediate hosts of Hy-
menolepis diminuta, 244; hosts
of Gigantorhynchus hirudinaceus,
284; natural enemies of mos-
quitoes, 462.

Belascaris cati, 282.

Belgium, T'ydeus molestus, 341.

Bello Herizonte, eradication of
Chagas’ disease, 114.

Beta-naphthol, for Giardia infections,
125; for hookworm infections,
264; ointment for itch, 346.

Béte rouge, 335, 336.

Bi-flagellate Protozoa, of intestine,
117-118.

BiLHarzZ, Tu., 7.

Biliary fever, of horses, 168.

Binucleata, 30.

Bird lice, see Mallophaga.

Birds, hosts of Cimex, 372;
prey of Culex quinquefasciatus,
449; as food for tsetse flies, 494,
495; natural enemies of tsetse
flies, 503; blood-sucking mag-
gots in nests of, 511.

BisHopp, F. C., 422.

Bismuth salicylate, for Giardia in-
fections, 125.

Bismuth subnitrate, for amebic dys-
entery, 135.

chief .

539

Biting flies, see Flies, blood-sucking.

Black corsair, see Melanolestes picipes.

Black drongo, natural enemy of tsetse
flies, 503.

Blackflies, and espundia, 92; mouth-
parts, 327, 478; 478-484; de-
scription, 478-479; life history,
479-481; annoyance, 481-483;
and disease, 483; control, 483-
484.

Blackheads, relation of Demodezx to,
347.

BLACKLOCK, B., 494, 496.

Black sickness, see Kala-azar.

Black vomit, in yellow fever, 185.

Blackwater fever, 161-162.

Bladderworms, types of, 235; dam-
age done by, 236-237.

beef bladderworms, see Cysticercus
bovis.

pork bladderworms, see Cysticer-
cus cellulose.

Blanfordia, host of Schistosoma ja-
ponicum, 219.

Blepharoplast, 29;
basal body.

Blood, immunity reactions, 20-22;
relation to anaphylaxis, 23-24.

Blood corpuscles, white, see Leuco-
cytes.

Blood flukes, discovery, 7, 8; 211-
220; relation of sexes, 211, 212;
possibility of introduction into
United States, 219-220. See
also Schistosoma.

Bloodsuckers, see Leeches.

Blowflies, maggots parasitic on birds,
aad

Bodo, 115; 117-118.

Bolivia, oriental sore, 87.

Bombay, relapsing fever, 43.

Bont tick, see Amblyomma hebreum.

Borax, and calcium borate for treat-
ing manure, 508.

Botflies, mouth parts, 464; in human
skin, 513-516; and _ intestinal
mylasis, 524.

see also Para-

040

Bozzo.o, C., 8.

BRADLEY, B., 448.

Braun, M., 36.

Brazil, yaws, 63; kala-azar, 77;
espundia, 90, 488; trypanoso-
miasis, 94, 108-114; bug-proof
houses, 114; Trichomonas patho-
genic, 121; Endameba brazilien-
sis, 180; hookworm disease, 255;
(sophagostomum stephanosto-
mum thomast, 283; Filartia ma-
galhaesi, 308; Triatoma, 380-
381; Anopheles cruzi, habits,
442; Dermatobia and mosquitoes,
452.

Breakbone fever, see Dengue.

BREINL, A., 73.

British Columbia, tick paralysis, 358-
359; Dermacentor venustus, 363.

British Guiana, Sparganum mansoni,
252; hookworm disease, 262;
filarial infections, 308.

British Isles, see Great Britain.

British Plague Commission, 411, 412.

British Royal Commission on Vene-
real Diseases, report, 50, 58,
59-60. .

Bronchitis, caused by spirochetes, 71.

Broce, BD. 7, 98, 108.

Brunet, E., 83.
Buba braziliensis, 89.
Bubalis caffer, host of Glossina

morsitans, 500.

Bubonic plague, see Plague.

Buenaventura, yellow fever in, 183.

Buffalo, host of Glossina morsitans.

Buffalo gnats, see Blackflies.

Bugs, see Hemiptera.

Bulgaria, typhus in, 398.

Bullinus contortus and B. dybowskit,
intermediate hosts of Schisto-
soma in Egypt, 214, 215, 217.

Bursa, of hookworms, 256.

Butter, on clothing to prevent lousi-
ness, 402.

Cachexia, malarial, 161, 162; treat-
ment, 164.

INDEX

Cairo, prevention of Schistosoma in-
fections, 216.

Calabar swellings, 309.

CaLANDRUCCIO, S., 284.

Calcium borate, and borax for treat-
ing manure, 508.

California, hookworm in mines, 262;
hookworm introduced by Hin-
dus, 268; Dermacentor occiden-
talis, 358, 363; Ornithodorus
coriaceus, 364-365; plague in
ground squirrels, 411; Pulex
irritans, 415; Ceratophyllus acu-
tus, 418.

Ca.xins, G. N., 33, 129.

Calliphora vomitoria, cause of myiasis,
521.

erythrocephala, cause of myiasis,
521.

Calomel, for Giardia infections, 125.

Camel, and oriental sore, 86; host of
Trichostrongylus instabilis, 282;
host of Ornithodorus savignyi,
361; el debab, 487.

Camphor, for red-bug rash, 336;
repellent for mosquitoes, 455.

Canada, blackflies, 479, 481, 482.

Capitulum, of ticks, 354.

Carapatos, see Ornithodorus moubata
and O. turicata.

Carbolic acid, for head lice, 401; to —
remove Dermatobiafromskin, 515.

Carbon bisulphide, fumigation, 386;
for fumigation of body lice, 401,
402.

Carpenter, G. D. H., 494.

Carrier, definition, 19, 21.

Carrion, D., 178.

Carrion’s fever, see Oroya fever.

CaRROLL, J., 184, 443.

CasTELLANI, A., 121, 307, 340.

Castor oil, for Giardia infections, 125;
in treatment of hookworm in-
fections, 264.

Cats, and infantile kala-azar, 82;
hosts of Opisthorchis, 225; Dipy-
lidium caninum, 245; fewer
parasites than dogs, 266; tri-

INDEX

china, 288; Notedres cati, 348;
and bedbugs, 375; fleas, 416-

417; Echidnophaga gallinacea,
420; destruction of fleas on,
422-423.

Cattle, hosts of spotted fever tick,
191; Paramphistomum cervi, 229;
Tenia saginata, 240; hydatids,
248, 250; hosts of Dermacentor
venustus, 363; hosts of stable-
flies, 505; Dermatobia in, 513;
warble-flies, 515-516.

Central America, relapsing fever, 46;

trypanosomes in Triatoma, 108, .

112, 380-381; use of shoes, 265;
work of Hookworm Commission,
268; béte rouge, 335; Ornitho-
dorus, 361; Triatoma, 379, 380,
381; other Reduviide, 382;
chiggers, 418, 419; Anopheles
eisent, habits, 441; yellow fever
mosquitoes breeding in _holy-
water fonts, 445.
Centrosome, in Protozoa, see Basal
granule.
Ceratophyllus, cysticercoids in, 243;
and plague, 412.
acutus, and plague, 413, 418.
fasciatus, life history, 409; habits,
etc., 417-418.
galline, 417.
silantiewi, and plague, 413.
Ceratopogon, 475, 477.
Ceratopogonine, 474, 475, 476.
Cercaria, 210.
Cercomonas, 115, 117-118.
Cerebrospinal fluid, spirochetes in,
49, 57; trypanosomes in, 104;
trichina in, 290.
Cerebrospinal meningitis, animal ex-
perimentation with, 10.
Cerodon rupestris, host of Triatoma
chagasi, 381. ;
Cestoda, 198; see also Tapeworms.
Ceylon, Necator americanus, 259;
beta-naphthol used for hook-
worm infections, 264; land-
leeches, 319; copra itch, 340.

541

Chetopoda, 199.
Cuaaas, C., 8, 94, 110, 111, 112.
Chagas’ disease, 108-114; course of,

113-114; treatment and _ pre-
vention, 114.

Chancre, 54.

Chaparro amargosa, for intestinal
amebe, 136.

Cheesefly, see Piophila caset.

Cheese-skipper, see Piophila casei.

Chelicerze, of Acarina, 331; of ticks,354.

Chenopodium, oil of, for amebic dys-
entery, 136; for intestinal flukes,
230; for tapeworms, 237; for
hookworms, 263-264; specific
action, 270; for Ascaris, 270,
276; for whipworms, 277; for
pinworms, 279.

Chicken mite, 341.

Chickens, and bedbugs, 375; and
Triatoma, 379; Ceratophyllus gal-
line, 417; LEchidnophaga galli-
nacea, 420.

Chigger, see Dermatophilus penetrans
and Harvest mites.

Chigoe, see Dermatophilus penetrans.

China, relapsing fever, 43; syphilis,
50; kala-azar, 77; Trichomonas
pathogenic, 121; Schistosoma
mansoni, 218; lung flukes, 220;
human liver flukes, 224; Yoka-
gawa yokagawa, 228; use of
shoes, 265; rat fleas, 417;
malaria-carrying Anopheles, 441;
transmission of anthrax by taba-
nids, 488.

Chinese fluke, see Clonorchis sinensis.

Chironomide, and uta, 86, 477; 473-
477; description, 473-475; habits,
475; life history, 475-476; an-
noyance, 476; as disease carriers,
476-477; control, 477.

Chlamydophrys stercorea, 129.

Chlamydozoa, 170, 192-194.

Chloroform, for hookworm _infec-
tions, 264; as an anthelmintic,
270-272; in milk for myiasis of
nose, ear, etc., 523.

042

Chlorosis, 255.

Cheromyia, 512-513.

CHRISTIANSEN, E., 124.

Chromidia, 28.

Chrysomyia, see Cochliomyia.

Chrysops, and Loa loa, 309-310, 486,

487, 489; trap for, 490.
centurtonis, 489.
dimidiata, 489.
silacea, 489.

Chyluria, filarial, 305.

Cilia, 30.

Cihata, cilia in, 30; 35; 36; human

parasites, 126.

Cimex, 371, 372; see also Bedbugs.

hemipterus, and kala-azar, 77-78,
377; characteristics, 372-373.
lectularius, characteristics, 372-

373; hosts, 374-375.
pipistrelli, 378.
rotundatus, see C. hemipterus.

Cimicide, characteristics, 371.

Cinchona, see Quinine.

Cinchonization, see Quininization.

Cirri, 30.

Cirrus pouch, 232.

Citellus beecheyi, and plague, 413.

Citronella, oil of, repellent for mos-

quitoes, 455.

Civet cats, hosts of Ancylostoma cey-

lanicum, 255.

Civil War, fly maggots in, 521.

CuaRKB, F. C., 414.

CLELAND, J. B., 448.

Clonorchis endemicus, = sinensis, 225.
sinensis, discovery, 7; 224-225;
life history, 226.

Cnidosporidia, 36.

Cocaine, for leeches, 318.

Coccidians, 168; 170-173; life his-

tory, 170-172; in man, 172-173.

Coccidium seebert, 174.

Coccoid bodies in spirochetes, 39.

Cochliomyia macellaria, in espundia

sores, 90; egg-laying, 464, 519;
519-521; description, 519; ef-
fects, 520-521; treatment, 523.

Cockle bur, mites on, 341.

INDEX

Cockroach, and Davainea madagas-
cariensis, 244; and Hormorhyn-
chus moniliformis, 284.

Cenurus, 235.

Cold storage, effect on bladder-
worms, 238; on trichina, 295; on
Clonorchis larvee, 227.

Colemanite, and borax for treating
manure, 508.

Colombia, relapsing fever, 46; spiro-
chetal bronchitis, 71; Balan-
tidium infections, 127; yellow
fever, 185; hookworm disease,
254.

Columbacz fly, 482.

Combs, on fleas, 404, 408.

Compulsory notification, of venereal
disease, 60.

Cone-nose, see T'riatoma.

Congo, rubber industry and sleeping
sickness, 107.

Congo floor maggot, see Avuchero-
myta luteola.

Contractile vacuole, 31.

Copra itch, 340.

Cordylobia anthropophaga, 6516-18;
deposition of eggs, 517; develop-
ment of maggot and life history,
518; prevention, 518.

rodhaini, 518-519. —

Corethra, 425.

Corethrine, 437.

CoRNWALL, 377, 378.

Corrosive sublimate, see Mercuric
chloride.

Corsica, phlebotomus flies, 468.

Coyote, host of Opisthorchis pseudo-
felineus, 225.

Crabs, relation to lung flukes, 8, 222—
223.

Craae, F. W., 374, 416.

Craia, C. F., 137, 148, 301, 448.

Craigia, 35; 129; 130; and craigiasis,
137-139.

hominis, 137; life history, 138-139.
migrans, 137; life history, 139.
Craigiasis, 137-139.
Craneflies, allied to mosquitoes, 425.

INDEX

CRAWLEY, H., 176. .

Crayfish, possible host of lung flukes,
223.

Creolin, for removal of ticks, 367; for
fumigation, 386; to destroy
fleas, 422-423.

Cresol, for killing Schistosoma cer-
carie in water, 217; for body
lice, 402; for chiggers, 420.

Cresyl, for fumigation, 386; for fumi-
gation of mosquitoes, 456.

Crithidia, 75; stage of trypanosome,
95-96.

Crocodiles, fed on by tsetse flies, 494,
499.

CRUICKSHANK, J. A., 306.

Crustacea, first intermediate host of
Dibothriocephalus latus, 246; 324;
see also Crabs, Shrimp, Cyclops.

Ctenidia, 404, 408.

Ctenocephalus canis, and infantile
kala-azar, 83, 413; life cycle,
410; and Dipylidium caninum,
414; habits, etc., 416-417.

felis, life cycle, 409; habits, etc.,
416-417. .

Culex, intermediate host of Filaria
bancrofti, 301; and bird malaria,
438.

fatigans, see C. quinquefasciatus.
pipiens, resemblance of C. quinque-
fasciatus to, 448.
quinquefasciatus, and dengue, 186,
448; and Filaria bancrofti, 301;
description, etc., 448-449.
territans, 434.

Culicide, characteristics, 425.

Culicine, 437.

Culicini, 437.

Culicoides, habits of larve, 475; an-
noyance, 476.

Cultivation, of animal parasites, 9.

Cyclasterion scarlatine, 194.

Cyclops, and guinea-worm, 312, 313-
314.

Cyclorrhapha, 465, 466.

Cyprinodontidz, natural enemies of
mosquitoes, 460.

043

Cysticercoid, nature of, 235.
Cysticercus, nature of, 235.
bovis, thermal death point, 237-
238; effect of cold storage, 238;
description, 240.
cellulose, thermal death point, 237—
238; effect of cold storage, 238;
description, 241; hosts, 241-
242; in man, 251. ~
Cytopyge, 31.
Cytoryctes variole, 170.
Cytostome, 31.

Dahomey, absence of sleeping sick-
ness in, 501.

Da Marta, A., 92.

Darina, 8., 129, 175.

Darwin, Cuas., 4, 381.

Dasypus novemcinctus, host of Try-
panosoma cruzi, 112.

Datura stramonium, for fumigation
of mosquitoes, 456.

Davainea madagascariensis, 244.

formosana, 244.

Deer, host of Pulex irritans, 414.

Deerfly, see Chrysops.

Dexruir, P. H., 23-25.

Demarquay, J. N,, 7.

Demodecide, 333, 346.

~ Demodex folliculorum, 346-348; life

history, 347; and leprosy, 347.
Dengue, relation of mosquitoes to, 8,
187, 448-449; parasites. of, 169,
186; 186-187; confusion with
Phlebotomus fever, 186; pre-
vention, 187.
De Raapt, O. L. E., 399, 417.
Dermacentor, 366.
andersoni, see D. venustus.
occidentalis, effects of bite, 358-
359, 366; possible transmitter
of spotted fever, 363, 366-367.
variabilis, 367. |
venustus, transmission of spotted
fever, 189-190; and tick paral-
ysis, 358; description, 361-363.
Dermanyssus galline, 341.

044

Dermatobia hominis, and mosquitoes,
451-458, 514; objections to
mosquito-transmission theory,
452; transmitting mosquitoes,
453; 513-515; description, 513-
514; manner of reaching host,
514; effects, 514-515.

Dermatophilus penetrans, 418-420.

De Sitva, P., 83.

Dibothriocephalide, larve of, 235;
characteristics, 239; important
species of, 245-247; Sparganuwm
larva of, 251. ©

Dibothriocephalus latus, 246-247.

cordatus, 247.

Dicrurus ater, natural enemy of tsetse
flies, 503.

Diemyctylus torosus, natural enemy
of mosquitoes, 461.

Dioctophyme renale, 200.

Diplogonoporus grandis, 247.

Diplozoa, 26.

Diptera, 326; characteristics, 330;
425; 463-464; importance, 463;
general structure, 463-464; life
histories, 464-466; classifica-
tion, 466; parasites on tsetse fly
pup, 503; and myiasis, 509.

Dipylidium caninum, 245; and fleas,
414, 415, 417.

Dirt-eating, in hookworm disease,
262.

Diseases, conquest of, 2; ignorance
of, .4; causation by germs, 6;
transmission by arthropods, 7-8,
322-3238.

Disinfection, of mosquito bites, 307;
of tick bites, 367; to eradicate
lousiness, 402-403.

Dizxa, 425.

Dixon, 8. G., 462.

Doang, R. W., 414.

Dorrr, R., 470.

Dog flea, see Ctenocephalus canis.

‘Dogs, and infantile kala-azar, 82, 83;
and oriental sore, 86; Trypano-
soma gambiense in, 108; host of
Trypanosoma cruzi, 112; sus-

INDEX

ceptible to lung fluke infections,
220; host of Clonorchis sinensis,
224; host of Opisthorchis, 225;
Dipylidium caninum, 245; host
of Dibothriocephalus cordatus, 247;
Echinococcus granulosus, 247, 248,
250-251; hosts of Ancylostoma
ceylanicum, 255; more parasites
than cats, 266; trichina, 288;
Demodex, 347; Linguatula rhina-
ria, 349-350; Dermacentor vari-
abilis, 367; and bedbugs, 375;
inability of human lice to draw
blood from, 393; host of Pulex
irritans, 414; fleas, 416-417;
Echidnophaga_ gallinacea, 420;
destruction of fleas on, 422;
Dermatobia in, 513; Cordylobia
anthropophaga in, 518.

Dog ticks, see Dermacentor variabilis
and Ixodes ricinus.

Dongola, blackflies in, 482.

Donova\, C., 7, 74, 377.

Dracunculus medinensis, 311-314;
distribution, 311; life history,
312-313; extraction and pre-
vention, 314.

Dragon-flies, natural enemy of tsetse
flies, 503.

Dusint, A., 7.

Ducks, natural enemies of mosqui-
toes, 462.

Dumdum fever, see Kala-azar.

Dutcuer, B. H., 305.

Durron;,.J. 1., 7, 8, 339:

Dwarf tapeworm, see Hymenolepis
nana.

Dyar, I., 429, 437, 444, 447, 458.

Dysentery, types of, 131; réle of
amebe, 131-132.

Dysentery ameba, see Hndameba
histolytica. |

Dysodius lunatus, 382-383.

Ear tick, see Otiobius mégnini.

East Coast fever, of cattle, 168.

East Indies, gangosa, 64; blackwater
fever, 161; land-leeches, 319;

INDEX

Porocephalus moniliformis, 351;
Anopheles in coral reef pools,
442.

Echidnophaga gallinacea, 420.

Echinorhynchus hominis, 284.

moniliformis, 284.

Echinococcus granulosus, 236; 24T-
2651; distribution, 247; adult
and life history, 248; develop-
ment of hydatids, 248-249; other
species of Echinococcus, 249;
prevention, 250-251.

Echinostomum tlocanum, 228-229.

malayanum, 229.

Ectoplasm, 29.

Ecuador, yellow fever, 183: fone
worm disease, 262.

Education, present need, 3-4;
cerning sex hygiene, 62;
cerning sanitation, 268-269.

Eelworms, see Ascaris.

Egypt, amebe in sand, 128; Schisto-
soma hematobium, 212, 216-217;
Heterophyes heterophyes, 228;

con-
con-

Paramphistomum cervi, 229; Spar-

ganum mansoni, 252; hookworm
disease, 255; work of Hookworm
Commission, 268; Trichostron-
gylus instabilis, 282; Xenopsylla
,cheopis, 417; brecdine places of
Phlebotomus, 468, 473.
Exueiicu, P., 8, 47, 49, 56.
Eimeria, in man, 172-173.
stiede, in man, 172.

El debab, 487.

Elephantiasis, 304-305; relation of
bacteria to, 305-306; treatment,
306; and Onchocerca volvulus in
Congo, 311.

Elephantoid fever, 305.

Elk, host of Dermacentor venustus.
363.

Eus, A. W. M., 57.

El Marg, Schistosoma hematobium,
P12, 214.

Emetin, discovery, 8; not effective
for Giardia, 125; for Balanti-
dium infections, 127; nature of,

545

_ 185; effects on amebe, 135; for
craigiasis, 139; effect on pyor-
rhea, 143, 144, 145-146; effect on
goitre, 144.

Emrticu, W., 136.

Encapsulation, 20-21;
291.

Encystment, 34.

Endameba, in jaw lesion, 121, 129;
species, 129-130.

braziliensis, 130.

buccalis, see E.. gingivalis.

coli, 129-130; harmlessness, 131,
132; compared with EF. histoly-
tica, 135.

confusa, 141.

gingwalis, 130; 139-146; relation
to pyorrhea, 140, 142-144; de-
scription, 140-141; compared
with E. histolytica, 141; relation
to tonsilitis, 144; relation to ~
goitre, 144-145.

histolytica, 115; 129; and amebic
dysentery, 131, 132-134; life
history, 132-133; compared with
E. coli, 135; compared with
E. gingivalis, 141.

kartulisi, 141.

mortinatalium, 130.

muris, 137.

tetragena, = histolytica, 132.

urogenitalis, 130.

Endomixis, 33-34.

Endoplasm, 29.

Endotoxins, 24.

Entameba, see Endameba.

Eosinophiles, increase with worm in-
fections, 203.

Epimys norvegicus,

of trichina,

and plague in

Europe, 411.
rattus, and plague in Europe,
411.

Epipharynx, 326.

Epsom salts, see Magnesium sulphate.

ErRpMANN,-R., 175.

Eriocheir japonicus, intermediate host
of lung fluke, 222.

EscomEL, P., 117, 122, 125.

546

Kspundia, 89-92; distribution, 89;
parasites, 89; skin sores, 89;
mucous membrane ulcerations,
90; treatment, 91-92; preven-
tion, 92.

Ether, for body lice, 401.

Eucalyptus, oil of, for hookworm in-
fections, 264; for body lice, 401;
for fleas, 422; for phlebotomus
flies, 473.

Eupodide, 333, 341. '

Europe, plague in, 2, 411; relapsing
fever, 42, 44, 378; introduction
of syphilis, 48; infectious jaun-
dice, 65; blackwater fever, 161;
dengue, 186; Opisthorchis feli-

neus, 225; Hymenolepis nana, 242;

hookworm disease, 255; An-
cylostoma duodenale, 255; hook-
worm in miners, 265; trichina,
287, 288; Filaria bancrofti, 299;
Hemopis, 317; red-bugs, 336;
Norwegian itch, 343; Demodex
folliculorum, 347; Linguatula
rhinaria, 350; Argas reflexus,
364; Ixodes ricinus, 367; typhus,
398; origin of Pulezx irritans, 414;
Ceratophyllus sp., 417, malaria-
carrying Anopheles, 441; Phle-
botomus papatasti, 470; control
of Phlebotomus, 473; Columbacz
fly, 482; Wohlfartia magnifica,
521-522; Fannia, 524. See also
geographic subdivisions.

European War, typhus in, 2, 398;
infectious jaundice, 68; amebic
dysentery, 131.

Eustrongylus gigas, see Dioctophyme
renale.

Evans, J.S8., 144.

Ewine, H. E., 332.

Feces, search for parasite eggs in,
272.

Fannia, characteristics of larvee, 509;
and intestinal myiasis, 524-526;
effects of myiasis caused by, 527.

canicularis, and intestinal myiasis,

INDEX

524-526; and myiasis of urinary
passages, 528.

scalaris, and intestinal myiasis,
524-526; and myiasis of urinary
passages, 528.

FantuaM, H. B., 39, 102, 174.

Farmers, responsibility for trichini-
asis, 296.

Fasciola hepatica, discovery of life
cycle, 7; life history, 208-210;
in man, 224.

Fasciolopsis buski, 229.

Fibrolysin, in elephantiasis, 307.

Fiji Islands, yaws in, 63; Filaria
bancrofti, 301.

Filaria, discovery, 7, 298; relation of
mosquitoes to, 7, 301-303, 449-
451;:298-314; prevalence, 298-
299.

bancrofti, 299-307; distribution,
299; life history, 299-303; peri-
odicity, 300-301; cycle in mos-
quitoes, 301-303, 450; trans-
mission, 303; pathogenic effects,
303-306; treatment for, 306-
307; prevention, 307.

-demarquaii, see F. juncea.

juncea, 308, 450.

loa, see Loa loa.

magalhaesi, 308.

perstans, 301, 450.

philippinensis, 307-308, 450.

Filarial diseases, 303-306; elephanti-
asis, 304-305; chyluria, 305; re-
lation of bacteria to, 305-306;
treatment, 306-307; prevention,
307.

FINOCCHIARO, F., 72.

Fish, intermediate hosts of Clonorchis
sinensis, 226; of Opisthorchis,
226-227; of Dibothriocephalide,
245; of Dibothriocephalus latus,
246; relation to Sparganum
mansoni, 252; relation to Spar-
ganum proliferum, 253.

_ Fish oil, repellent for tabanids, 489.

Fish tapeworm, see Dibothriocephalus
latus.

INDEX

Flagellata, flagella in, 29, 35, 36.

Flagellates, chlorophyll-bearing, 27;
of blood-sucking insects in verte-
brates, 74, 75.

Flagellum, 29.

Flame cells, 197.

Flatworms, 196-198.

Fleas, and infantile kala-azar, 83,

413; intermediate hosts of Di- —

pylidium caninum, 245, 414;
fumigation, 386, 421; general
structure, 404-407;
tion, 407; identification, 408;
life history, 408-410; habits,
410; and disease, 410-414; and
plague, 410-413; and typhus,
414; human flea, 414-415; dog
and cat fleas, 83, 416-417; rat
and squirrel fleas, 417-418; chig-
gers, 418-420; sticktight flea,

420-421; prevention, 421-423;
traps, 421.
Fleshflies, and Sarcosporidia, 175;

and myiasis of wounds, 521-522;
description, 522; and intestinal
myiasis, 526-527.

FLEXNER, S., 10.

Flies, see also Diptera.

blood-sucking, mouthparts, 327,
464; importance, 463; see also
various groups and species.

non-blood-sucking, and _ oriental
sore, 86; and espundia, 92; rédle
in transmission of Giardia, 125;
and tapeworm eggs, 240; mouth-
parts, 327, 464.

Flood fever, see Kedani.

Florida, prevention of malaria by
screening, 167; Sparganum proli-
ferum, 252-253.

Flukes, 206-225; general anatomy,
206-207; reproduction, 207; life
history, 207-210; parasitic habi-
tats, 211; see also Blood flukes,
Lung flukes, Liver flukes, Intesti-
nal flukes.

Fiury, F., 202, 290, 293.

Fly-belts, 106, 492-493.

classifica-.-

547

Foot-and-mouth disease, parasite of,
76, 169.

Forcipomyia, and uta, 86;
A75, 477.

townsendi, and uta, 86, 477.
ute, and uta, 86, 477.

Forpe, R. M., 7.

Formaldehyde, for fumigation, 386;
to destroy flea eggs, 421; to
repel phlebotomus flies, 473.

Formalin, see Formaldehyde.

Formosa, lung flukes, 220, 222;
Yokagawa yokagawa, 228; Da-
vainea formosana, 244; aquatic
leeches, 317.

Fostmr, W. D.,263, 264, 270, 272, 276.

FouRNIER, 50.

Fowl tick, see Argas persicus.

FRACASTORIO, G., 6.

Frambesia, see Yaws.

France, amebic dysentery, 131; Wohl-
fartia magnifica, 522.

FRANKEL, S., 402.

French Guiana, Onchocerca, 310.

French Yellow Fever Commission,
444.

Fricks, L. D., 190.

Frontal lunule, 465.

Roman Cb 1G oly.

Fumigation, for ticks, 369; hydro-
cyanic acid, 383-386; sulphur,
386; carbon bisulphide, 386;
cresyl, 386; formaldehyde, 386;
for fleas, 421; for mosquitoes,
456.

Furakl, K., 69, 73.

habits,

Gadflies, see Tabanide.

Gallipoli, Giardia, in soldiers from,
123, 125; Coccidian infections,
172.

Galyl, substitute for salvarsan, 65.

Gamaside, see Parasitide.

Gangosa, 64.

Gasoline, for bugs, 383.

Gastrodiscoides hominis, 229.

Gastrophilus equi, 524.

hemorrhoidalis, 516.

048

Gatrs, Dr. H., 253.
Gecko, Algerian, and oriental sore,

86, 471.

Geese, host of Holothyrus coccinella,
341.

Geographic distribution, of para-
sites, 18-19.

GERLACH, A. C., 345.

Germany, multilocular hydatids, 249;
trichina, 286; Linguatula_ rhi-
naria in man, 350; louse pre-
vention, 402-403.

Giardia, 115, 123-125; description,
123; multiplication, 123-124;
pathogenicity and _ treatment,
125; réle of flies in transmission,
125.

intestinalis, 123-125.
muris, 124.
Gibraltar, relapsing fever, 47.
Gigantorhynchus hirudinaceus, 284.
gigas, 284.

Ginyu; A. A., 162.

Giraffe, host of Tenia saginata, 240.

Girardinus peciloides, natural enemy
of mosquitoes, 460-461.

GIRAuLT, A. A., 376.

Glossina, 491-492;
flies.

brevipalpus, time of activity, 493,

501; and human trypanosomes,

500.

longipennis, time of activity, 493,
501.

morsitans, and Trypanosoma rho-
desiense, 98, 101, 497; distribu-
tion, 98; fly-belts, 106, 492-493;
499-500; time of activity, 493,
500; habits, 493; food, 494, 500;
duration of pupal period, 496;
breeding places, 496; and nagana,
497; distribution, 499; de-
scription, 499; and Trypano-
soma gambiense, 500; control,
501; attacked .by dragon-flies,
503.

pallidipes, and Trypanosoma gam-
biense, 500.

see also Tsetse

INDEX,

palpalis, and Trypanosoma gam-
biense, 98-101, 496-497, 501;
fly-belts, 106, 492-493, 498;
time of activity, 493; food, 494;
498-499; life history, 495; breed-
ing places, 496; distribution,
498; description, 498; control,
501.

tachinoides, time of activity, 493,
498; and sleeping sickness, 500;
habitats, 500; control, 501.

Glyciphagus, 340.

buski, 340.

Gnats, see Chironomidz.

Goats, hosts of Linguatula rhinaria,
349.

Goitre, caused by Trypanosoma cruzi,
114; caused by Endameba gin-
givalis, 144-145; transmitted by
Acanthaspis sulcipes, 382.

GOLDBERGER, J., 8, 339, 397.

GONDER, R., 34.

GonzALEs, E., 217.

Goopgy, T., 119, 120.

Gorgas, W. C., 166.

Gorilla, host of Necator americanus,
255; host of CMsophagostomum
stephanostomum, 283.

GRAHAM, H., 8, 448.

Grain mites, see Tyroglyphide.

GrassI, B., 284.

Grayback, see Pediculus humanus.

Great Britain, syphilis in, 50.

Greece, downfall due to malaria, 147.

Greenland, Dibothriocephalus corda-
tus, 247.

Grocers’ itch, 340.

GROLL, 293.

Ground itch, 259, 260.

Guam, gangosa, 64.

Guarnieri bodies, in smallpox, 192.

Guayaquil, yellow fever in, 183.

Guinea-pigs, for experimentation, 10;
immunization against infectious
jaundice, 68; host of Trypano-
soma cruzi, 112, 378, 381; sus-
ceptible to trichina, 288; and
plague, 413.

INDEX

Guinea-worm, see Dracunculus medi-
nensis.

Gumma, 54.

Gyrinide, and mosquitoes, 462.

Haptey, P., 121.

» Haxcket, E., 27.

Hemadipsa ceylonica, 319.

japonica, 320.

Hemaphysalis, 366.

Hematobia serrata, 506.

Hematopinus ventricosus, inability to
draw human blood, 393.

Hematopota, 486.

Hemoflagellata, 75.

Hemopis, 316, 317.

HaGier, 378.

Hat, M. C., 263, 264, 270-272, 276.

Hau, H. C., 393, 394.

Haltere, 464. : :

Haplosporidia, Rhinosporidium mem-
ber of, 173.

Harvard School of Tropical Medi-
cine, South American expedition,
on uta, 86; on Oroya fever, 178,
179, 180, 181.

Harvest mites, 333-337; life history,
334; annoyance, 335; species,
336; and kedani, 191, 336-337.

Havana, reduction of malaria, 166;
reduction of yellow fever, 183,
185.

Hawai, introduction of mosquitoes,
435.

Head-maggot, of sheep, see strus
ovis.

Hellebore, for treating manure, 508.

Hemiptera, mouthparts, 326; di-
gestive tract, 327-328; char-
acteristics, 330, 370.

Heros, W.B., 364, 365, 489, 505, 506.

Herrick, W. W., 293.

Herrick, G. W., 335, 384, 385, 387.

Herpetomonas, stage of Leishmania,
74; species, 75; relationships,
75; in blood in leishmaniasis, 75;
developed from Leishmania do-
novani in bedbugs, 78; in Anoph-

Hogs,

549

eles punctipennis, 78; stage of
trypanosomes, 95-96; in taban-
ids, 488.
ctenocephali,
azar, 83.
Heterophyes heterophyes, 228.
Heteroptera, 370.
Hine, J. S., 490.
Hippobosca canina, and leishmaniasis
of dogs, 86.
Hirudinea, 199-200; see also Leeches.
Hirudo, 316.
History of parasitology, 6-13.
Trypanosoma gambiense in,
108; and human intestinal Pro-
tozoa, 116; and Balantidium
coli, 127; Paragonimus kellicotti,
220; Gastrodiscoides hominis, 229;
Fasciolopsis buski, 229; Tenia
solium, 240-241; Ascaris, 274,
275; trichina, 286, 287, 288, 292,
296; Ornithodorus turicata, 361;
Dermatophilus penetrans, 418;
Dermatobia in, 513.
Holothyrus coccinella, 341.
Honduras, craigiasis, 137; Strongy-
loides, 281.
Hooke, 387.
Hookworms, economic importance of,
3, 254, 262-263; in immigrants,
5; discovery, 7; toxins, 203, 261;
254-269; history, 254-255; local
names, 254-255; distribution,
255; description of species, 255—
257; life history, 257-260; eggs,
258; mode of infection, 259-
260; disease, 260-263; dirt-
eating, 262; treatment, 263-264;
prevention, 264-265; sanitation,
265-269.
American, see Necator americanus.
Old World, see Ancylostoma duo-
denale.
Hoplopsyllus anomalus, and plague,
413.
Hormorhynchus clarki, 284-285.
moniliformis, 284.
Horseflies, see Tabanide.

and infantile kala-

500

Horsehair snakes, popular supersti-
tion, 4; see Nematomorpha.

Horse leech, 316.

Horses, and oriental sore, 86; spotted
fever tick, 191, 363; Gastrodis-
coides, 229; leeches, 317, 319;
Ornithodorus savignyt, 361; Otio-
bius mégnint, 365; surra, 487;
hosts of stable-flies, 505; hosts of
Gastrophilus hemorrhoidalis, 516.

Housefly, see Musca domestica.

House mosquito, of tropics, see Culex
quinquefasciatus; of temperate
zones, see Culex pipiens.

Howarp, L. O., 148, 429, 437, 442,
444, 447, 455, 458.

How ett, F. M., 469, 470.

Hung, 81.

Hyalomma, 366.

Hydatids, nature of, 235, 247-251;
distribution, 247; life history of
Echinococcus, 248; development,
248-249; multilocular, 249; ef-
fects on host, 250; prevention,
250-251.

Hydrocyanic acid, for fumigation, of
bedbugs, 383, 385; method, 383-—
385; effectiveness, 385-386; for

fleas, 421.
Hydrogen peroxide, for balanitis,
. (ae

Hydrophobia, see Rabies.
Hymenolepis, prevention, 238;
ticercoids in fleas, 414.

diminuta, 244.
murina, 242.
nana, discovery, 7; oil of cheno-
podium for, 237; prevention,
238; 242-244.
nana fraterna, 242.
Hymenoptera, parasites of tsetse fly
pup, 503. ;
Hypoderma bovis, 515-516.
lineata, 515-516.
Hypopharynx, 326.
Hypopus, 339-340.
Hypopygium, 492.
Hypostome, 354.

cys-

INDEX

Iceland, hydatids, 247, 249, 250.

Ichneumon flies, and Dermatobia,
452.

Ichthyol, for microfilarize, 306; in
ointment for chiggers, 420.

Idaho, spotted fever, 189.

{poy G5:

Toma, J., 2525 258:

Illinois, Hormorhynchus clarki, 285.

Immunity, natural, 19-22; artificial,
22-23; passive, 22; of Protozoa
to drugs, 34-35; in relapsing
fever, 47; in infantile kala-azar,
84; in oriental sore, 87; in
Rhodesian sleeping sickness, 94;
reactions among trypanosomes,
96-97; in malaria, 162-163;
in yellow fever, 185; in dengue,
187; in phlebotomus fever, 188;
in trichiniasis, 294-295.

Immunization, history, 8-9; in re-
lapsing fever, 47; in infectious
jaundice, 68; in oriental sore,
88; against trypanosomes, 106.

Immunology, development of, 9.

Inaba, R., 65.

India, plague in, 3, 411; relapsing
fever, 42, 43, 44; kala-azar, 77;
oriental sore, 85; malaria, 147;
fulminant malaria, 163; Rhino-

_ sporidium, 173; dengue, 186;
phlebotomus fever, 188; Clonor-
chis sinensis, 224; Gastrodis-
coides hominis, 229; Tenia sa-
ginata and dung-eating habits of
cattle, 240; hookworm disease,
262; use of shoes, 265; land-
leeches, 319-320; Rhizoglyphus
buski, 340; Ornithodorus sa-
vignyi, 361; bedbugs and kala-
azar, 377; cat flea, 416; chigger,
420; malaria-carrying Anopheles,
441; Aédes calopus, 448; Phle-
botomus minutus, 471; black-
flies, 478.

Indian bedbug, see Cimex hemipterus.

Infantile kala-azar, 82-84; distribu-
tion, 82; transmission, 82-83,

INDEX

413, 417; course of, 84; treat-
ment, 84; prevention, 84.

Infantile paralysis, 195; and stable-
flies, 507.

Infectious jaundice, 65; course of,
65-66; mode of infection, 67;
in rats, 67-68; treatment, 68;
prevention, 68-69.

Infusoria, see Ciliata.

Insanity, relation of syphilis to, 53, 54.

Insects, 325-330; general character-
istics, 325; mouthparts, 325-
327; general anatomy, 327-329;
life history, 329-330; classifica-
tion, 330.

Intestinal flukes, 228-230; life his-
tory, 230.

Intestinal Protozoa, 115-127; of
man and animals, 115, 117;
encystment, 115-116; specific
hosts, 116; geographic distribu-
tion, 116; pathogenic effects,
116-117; prevalence, 116; bi-
flagellate species, 117-118; multi-
flagellate species, 118-125, cili-
ates, 126-127; effects on progress
of school children, 266-267.

Intestinal worms, entrance and exit
from host, 201; effects on host,
201-204; nutriment absorbed
by, 202; toxic effects, 202-203;
infection of wounds made by,
203-204; effects on progress of
school children, 266-267; round
worms, 270-272; selection of
drug for treatment, 270; search
for eggs, 272; prevention, 266-
269, 272; see also various species.

Iodine, for Trichomonas infections, 122.

Ipecac, and amebic dysentery, 135;
for craigiasis, 139.

Island of Principe, extermination of
sleeping sickness, 108, 502.

Ismailia, reduction of malaria, 165.

Isospora, in man, 172, 173.

Italy, infantile kala-azar, 84; ful-
minant malaria, 163; reduction
of malaria, 165; phlebotomus

dol

fever, 188; Hymenolepis nana,
242; Hormorhynchus monilifor-
mis, 284; Pediculoides, 338;
breeding places of phlebotomus
flies, 468.

Itch, 342, 344-345; Norwegian, 343;
treatment, 345-346; prevention,
346.

Itch mites, 342-346; description,
342-343; life history, 343-344;
disease caused by, 344-345;
treatment, 345-346; prevention,
346.

IruRBE, J., 217.

Ixodes, habits, 356;
366.

holocyclus, and tick paralysis, 359.
pilosus, and tick paralysis, 359.
ricinus, 367.

Ixodide, egg-laying habits, 355;
general characteristics, 356-357;
important species, 366-367; key
to genera, 366.

characteristics,

Janthinosoma lutzi, carrier of Der-
matobia, 453.

Japan, relapsing fever, 438; infectious -
jaundice, 65, 67; kedani, 191;
Schistosoma japonicum, 218, 219;
lung flukes, 220, 223; human
liver flukes, 224, 225, 227;
Yokagawa yokagawa, 228; Hetero-
phyes heterophyes, 228; Davainea
formosana, 244; Dibothriocepha-
lus latus, 246; Diplogonoporus
grandis, 247; Sparganum man-
soni, 252; Sparganum prolife-
rum, 252-253; Trichostrongylus
orientalis, 282; land-leeches,
319-320; kedani mite, 336-337;
rat flea, 417; malaria-carrying
Anopheles, 441.

Japanese flood fever, see Kedani.

Java, malaria in children and adults,
162; lice and plague, 399-400;
Xenopsylla, 417.

JENNER, E., 4, 9.

Jigger, see Dermatophilus penetrans.

502

Jimson weed, for mosquitoes, 456.
JOHANNSEN, C, A., 339, 474.

Jouns, F. M., 9, 149.

JoHNSON (Mrs.), see Lawson, Mary

Kabure, relation to Schistosoma ja-
ponicum, 218.

Kala-azar, 77-82; distribution, 77;
transmission, 77-79, 377; human
cycle of parasite, 79; course of,
80; mortality, 81; treatment,
81; prevention, 81-82; see also
Infantile kala-azar.

KANEKO, R., 69.

Kansas, screw-worm, 521.

Katajama, see Blanfordia.

Kedani, and Piroplasmata, 168; rela-
tion to spotted fever, 189, 191-
192.

Kedani mite, see Leptus akamushi.

Keren, W. W., 10.

Ketioce; V. L., 389.

Kerosene, see Petroleum.

Killifish, natural enemies of mos-
quitoes, 460-461.

Kinetonucleus, see Parabasal body.

Kine, A. F. A., 149.

Kine, H. H., 482, 487.

Kine, W. V., 156.

Kine, W. W., 368.

Kincuorn, A., 100.

Kissing, and syphilis, 51; and amebic
infections of mouth, 146.

Kissing bugs, 382.

KueEIng, F. K., 310.

Knas, F., 429, 485, 486, 437, 444,
447, 451, 453, 458.

Kospayasul, H., 226, 227.

Koca, R., 8, 9, 162, 499.

Koror, C. A., 112, 119, 124, 381.

Korea, lung flukes, 222; Clonorchis
sinensis, 224; Yokagawa yoka-
gawa, 228.

Kouuaain, N. M., 442.

Labella, of mosquitoes, 427.
Labial palpi, 325.

Labium, 325.

Labrum, 325.

INDEX

Labrum-epipharynx, 326.

Lamblia, see Giardia.

LamMpBorn, W. A., 493, 503.

Land-leeches, 319-321.

LANING, 218.

Larvicides, 457-459.

LaAvERAN, A., 7, 148, 471.

Laverania malarie, see Plasmodium
falciparum.

Lawson, Mary R.., 150.

Lazear, J. W., 184, 443.

Leeches, 315-321; general anatomy,
315-316; importance as para-
sites, 315, 316-317; intermediate
hosts of trypanosomes, 317; in
nose and throat, 317-318; land-
leeches, 319-321.

LEEUWENHOEK, A. VAN, 6, 37, 391.

Lerper, R. T., 8, 218, 216, 217, 219;
224, 228, 229, 267, 310.

LrIsHMANn, W. B., 7, 48, 74.

Leishman bodies, see Leishmania.

Leishmania, T4-92; discovery, 7, 74;
transformations in insects, 74;
species, 75, 76; relationships,
75; diseases, 76; and kala-azar,
77-82, 377; and infantile kala-
azar, 82-84; and oriental sore,
84-88, 377-378; of uta, 86;
stage of trypanosomes, 95.

americana, 76, 89; and espundia,
89-92.

braziliensis, see L. americana.

donovani, discovery, 7, 74; culti-
vation, 9, 76, 78; development
in bedbugs, 77-78; in Anopheles
punctipennis, 78; human cycle,
79; distribution in body, 80.

infantum, 76; infantile kala-azar,
82-84.

tropica, 76; in oriental sores, 85;
transmission, 85-86.

Leishmaniasis, in Panama, 74-75;
origin from insect flagellates, 75;
see also Kala-azar, Oriental
Sore and Espundia.

Lemon juice, for land-leeches, 319;
repellent for mosquitoes, 455.

INDEX

Leprosy, spread by bedbugs, 379.
Leptomonas, see Herpetomonas.
Leptospira, 67.

Leptus, 336; see also Harvest mites.
akamushi, and kedani, 191, 333.
americanus, 336.
autumnalis, 336.
trritans, 336.

LEUCKART, R., 7, 202.

Leucocytes or white blood corpuscles,

prey on parasites, 20.

Lice, intermediate hosts of Dipylid-
tum caninum, 245; fumigation,
386, 387-403; importance, 387;
general structure, 388-389; hu-
man species, 389; specificity of

.action of salivary juice, 393;
lice and disease, 397-400; and
typhus, 8, 378, 397-399; and

relapsing fever, 44-46, 378, 399;
and bubonic plague, 399-400;

_ and syphilis, 400; dispersal, 400;
prevention, 400-403; control in
war, 402-403; body louse, see
Pediculus humanus; head louse,
see Pediculus capitis; crab-louse,
see Phthirius pubis.

Life histories of parasites, discoveries
Of, 7.

Lima, A. C., 458.

Inmnea, host of Fasciola hepatica,
208; host of Schistosoma japoni-
cum, 219; occurrence in United
States, 220.

Limnatis nilotica, 316; in nose and
mouth, 317-318.

Innguatula rhinaria, 349-350.

Linguatulina, 333, 348-351.

Linstow, O. F., von, 245.

Liston, W. G., 411.

Liver abscess, sequel of amebic dys-
entery, 134; in a case of myiasis,
527. ;

Liver flukes, of sheep, goats, etc.,
208-210, 224; human, 224-228;
symptoms, 227; prevention,
227-228.

Livineston, D., 360.

503

Llama, host of Tenia saginata, 240.

Luoyp, L., 495, 496.

Loa loa, 308-310; and Chrysops, 489.

London, copra itch, 340.

Looss, A., 258.

Loscu, F., 7.

Louisiana, extermination of Aédes
calopus and yellow fever, 185.

Louse-mite, see Pediculoides ventri-
cosus.

Lucilia, 521.

cesar, 521.

Luetin test, for syphilis, 55.

Lung flukes, relation of crabs to, 8,
220-224; distribution, 220; re-
lation to host, 220-221; life
history, 221-223; mode of in-
fection, 223; prevention, 223-

224.
Lunule, frontal, 465.
Morz, A. 217.

Lymphangitis, in filarial disease, 305.

Twncey K. M.,. 117; 120): 137.

Lyon, H., 409.

Lyperosia irritans,
serrata.

Lysol, in prevention of filarial infec-
tions, 307; for chiggers, 420.

see Hematobia

’ MacConneEt., J. F. P., 7.

McCuttocg, Miss I., 112, 381.

McDona tp, W., 448.

Macrig, J. W. Scort, 98, 507.

MacGrecor, W., 7.

Mackie, F. P., 81.

McNaveuton, J. G., 306.

MacNeEat, W. J., 9, 10.

Macronucleus, 28.

Macrostoma mesnili, 122-123.

Madagascar, T'riatoma rubrofasciata,
381; surra, 487.

Maggots, in espundia sores, 90; and
myiasis, 509-528; characteris-
tics, 509-510; blood-sucking,
511-513; under skin, 513-519;
in wounds and natural cavities
of body, 519-523; in intestine,
523-528; in urinary passages,

504

528; resistance to reagents, 522,
526-527.

Magnesium sulphate, in treatment of
amebic dysentery, 136.

Malaria, in Panama, 2; importance

of, 5, 147-148; relation of mos-

quitoes to, 7, 149, 157-159;

147-167; prevalence of, 148;

history, 148-149; parasites of,

149-150; occurrence of attacks

of ague, 153; quotidian, 153;

numbers of parasites, 153; ben-

nign vs. malignant, 156; propa-

gation, 157-159; latent, 158;

effect of weakening of host, 158-

159; course of, tertian and

quartan, 159-161; sstivo-au-

tumnal, 161; immunity, 162-163;

tropical vs. subtropical, 162;

carriers, 162, 165, 438-443; ful-

minant, 163; treatment, 163-

164; prevention, 164-167; num-

ber of mosquitoes necessary to

propagate, 165.

Malarial parasites, see Plasmodium.

Malay bug, see Triatoma rubrofas-
cata.

Malay States, kedani or pseudo-
typhus, 192; Echinostomum, 228;
malaria-carrying Anopheles, 441;
habits of Anopheles, 441.

Malcceur, 254.

Mal de boca, cause of, 70-71.

Mal d’estomac, 254.

Male fern, for tapeworms, 237; for
hookworms, 264; for pinworms,
279.

Mattocg, J. R., 480.

Mallophaga, compared with Ano-
plura, 388.

Matmsten, P. H., 7, 37.

Malpighian tubules, 328.

Malta, phlebotomus flies, 468, 470, 471.

Manaos, reduction of yellow fever,
183, 185...

Manchuria, plague, 413.

Mandibles, of insects, 325.

Mange, 342.

INDEX

Mangrove fly, see Chrysops.

Manila, Balantidium infections, 127;
amebic dysentery, 130; Echino-
stomum tlocanum, 229; Tenia
philippina, 245.

Manson, Sir P., 7, 47, 80, 162, 298,
301, 305, 309, 322, 449.

Mansonia, habits of larvae, 431; host
of Filaria, 450.

Manure, treatment to prevent fly-
breeding, 508.

Marett, P. J., 468.

Margaropus annulatus, 12; life his-
tory, 356, 366; extermination,
368.

Martatt, C. L., 373, d7a,a008

Marmot, host of Hormorhynchus
montliformis, 284; and plague
in Manchuria, 413.

Marriage, syphilis and, 60-61.

Masterman, EK. W. G., 317, 318.

Mastigameba, 35.

Mastigophora, see Flagellata.

Mauritius, Holothyrus coccinella, 341;
trypanosomes in Triatoma rubro-
fasciata, 381.

Maxilla, 325.

Maxillary palpi, 325.

Mayflies, life history, 329.

‘ Mealworm, intermediate host of Hy-

menolepis diminuta, 244.

Measles, human, 169, 195; beef, 240;
pork, 241.

Meat, fitness for food when diseased,
296-297.

Meat inspection, 286;
trichiniasis, 295-296.

Medical entomology, beginning of,
7; summary, 322-323.

Mediterranean countries, infantile
kala-azar, 82; oriental sore, 84,
85; dengue, 186; phlebotomus
fever, 188; Schistosoma hema-
tobium, 212; Limnatis nilotica,
317; phlebotomus flies, 470.

Megarhinus, 437.

Melania, host of lung fluke, 221; of
Clonorchis sinensis, 226.

relation to

INDEX

libertina, and Paragonimus ringeri,
221; and Clonorchis sinensis, 226.
Melanolestes, 382.
picipes, 382.

Melittophagus meridionalis, and tsetse
flies, 503.

Membranelles, 30.

Mercurial ointment, for crab lice, 401.

Mereuric chloride (corrosive subli-
mate), for syphilis, 56; for rat-
bite fever, 70; for guinea-worm,
314; for destroying flea eggs,
421; to remove Dermatobia from
skin, 515.

Mesozoa, 27.

Metamorphoses, of insects, 329.

Metastrongylus apri, 200.

Metazoa vs. Protozoa, 26-27.

Methylene blue, for Trichomonas in-
fections, 121; for Balantidiwm
infections, 127.

Mexico, relapsing fever, 46; amebic
dysentery, 130, 136; tlalsahuate,
335; Ornithodorus, 361, 365;
Otiobius mégnini, 365; distribu-
tion of lice, 394; lice and typhus,
396, 397.

Miana tick or bug, see Argas persicus.

Mice, and infantile kala-azar, 82;
hosts of human intestinal Pro-
tozoa, 116; spread of Sarco-
sporidia among, 175; Sarcocystis
muris, 176; and kedani mite,
191; experimental infection with
Schistosoma, 217, 219; Hymeno-
lepis nana and diminuta, 242-

244; and bedbugs, 375; Hor-
morhynchus moniliformis, 284;
trichina, 288, 296; occasional

hosts of Pulex irritans, 414.
Microfilaria, discovery, 7, 299-300;
periodicity, 301; effect of drugs
on, 306.
bancrofti, 299-300; periodicity,
301; effect of drugs on, 306;
comparison with mf. loa, 309.
juncea, 308.
loa, 309.

509

perstans, 308. -
volvulus, 311.

Micromys montebelloi, host of kedani
mite, 191, 336.

Micronucleus, 28.

MipptetTon, W. S., 144.

Midges, see Chironomide.

Mieutano, L., 72.

Miller’s itch, caused by Pediculoides,
338.

“Millions,” natural enemy of mos-
quitoes, 460-461.

Mimm’s culicide, 456.

Minas Geraés, Triatoma megista, 380.

Miner’s itch, see Hookworm.

Mines, hookworm in, 262, 265.

Miracidium, 208.

Mites, and kedani, 191; general
account, 331-332; life history,
332; parasitism, 332-333; fami-
lies containing parasites, 333;
toxic effects of salivary juices,
337; see also various species.

Mirzmatn, M. B., 405.

Mryarrei, K., 218, 219, 222.

Moco, host of Triatoma chagasi, 381.

Mongols, possibly result of syphilis,

53.

Monkeys, for experimentation, 10;
relapsing fever, 43, 47; and in-
fantile kala-azar, 82; and es-
pundia, 89; susceptible to Schis-
tosoma infections, 215; Tri-
churis trichiura, 277; hosts of
Ternidens deminutus, 283; Ciso-
phagostomum apiostomum, 283;
probable host of Msophagos-
tomum stephanostomum thomasi,
283; and plague, 413.

Montana, spotted fever, 189; Poro-
cephalus in man, 351.

Moratgs, R., 451.

Moscow, transmission of relapsing
fever,378; habits of Anopheles,442.

Mosquitoes, and espundia, 92; and
Oroya fever, 181; mouthparts,
327, 426-427; fumigation, 386,

_ 456; 424-462; importance, 424;

506

general structure, 425-428; dis-
eases carried by, 424; relation-
ships, 425; sexes distinguished,
426; life history, 428-433; habits
of adults, 433-4384; habitats, 434;
migration, 434-435; time of
activity, 435-436; food habits,
436; hibernation, 486; length
of life, 486-437; classification,
437; effect of bites, 453; reme-
dies for bites, 454-455; personal
protection, 455-456; elimination
and exclusion from buildings,
456-457; larvicides, 457-459;
prevention of breeding, 459;
natural enemies, 459-462;
and malaria, discovery, 7; develop-
ment of Plasmodium falciparum
in, 154-156; malaria carriers,
157-159, 438-441; number neces-
sary to propagate malaria, 165;
habits of Anopheles, 441-443;
and yellow fever, discovery, 7, 443;
transmitting species, 443-448;
and Filaria, discovery, 7, 298,
449; development of Filaria
bancrofti in, 301-303, 450-451;
as transmitting species, 450-451;
and dengue, discovery, 8, 448; 187;
transmitting species, 448-449;
and Dermatobia, 451-453, 514;
objections to mosquito trans-
mission theory, 452; transmit-
ting species, 453.

Mosquito-worm, 451.

Mould, cause of kedani, 192.

Mouth, spirochetes in, 70; Tri-
chomonas in, 119; amebz in,
139-146.

Mouth ameba, see Endameba gin-
givalis.

Mouthparts of insects, 325-327.

Mule, host of Dermatobia, 513.

Murray, C. H., 371, 372, 374, 375.

Musca domestica, changed attitude
towards, 3; stable-flies mistaken
for, 504; breeds in manure, 508;
and intestinal myiasis, 527.

INDEX

Muscide, includes tsetse flies, 491;
stable-flies, 504; other blood-
suckers, 506; screw-worm, 519;
other species causing myiasis of
wounds, 521.

Muserave, W. E., 221.

Myiasis, 509-528; definition, 509;
flies causing, 509; classification,
510; by blood-sucking maggots,
511-513; of skin, 513-519; of
wounds and natural cavities of

body, 519-523; of intestine,
523-528; of urinary passages,
528.

Myoneme, 31.

Myriapoda, 324-325.
Mycxococcidium stegomyie, and yellow
fever, 184.

Nagana, 108, 497.

Nageayo, M., 192, 337.

Naxaaawa, K., 8, 221, 222, 223.

Naphthaline, for intestinal fluke in-
fections, 230; for body lice, 401,
402; to eliminate fleas, 421, 422-
423.

Nasal polypus, 173-174.

Natal, hookworm quarantine, 268;
Cordylobia anthropophaga, 518.

N CI, for lice, 402.

Nebraska, Tenia confusa, 245.

Necator americanus, distribution, 255;
description, 255-257; see also
Hookworms.

Negri bodies, 170, 194.

Negroes, syphilis among, 51; im-
munity to malaria, 163.

Netva, A., 381, 452.

Nematoda, 198; intestinal, 270-272,
282; see also various species.

Nematomorpha, 199.

Nemathelminthes, 198-199; intes-
tinal forms, 270-272; see also
various species.

Nemertinea, 198.

Neosalvarsan, for syphilis, 57; to
prevent trypanosome infection,
107.

INDEX

Nephridia, 199.

Neuroryctes hydrophobie, 170, 194.

New Jersey, ecologic groups of mos-
quitoes, 434; migrations of salt
marsh mosquitoes, 435; control
of salt marsh mosquitoes, 459-
460.

New Orleans, plague in, 2, 411;
yellow fever, 183.

NeEwstTEaD, R., 470, 471.

Newt, natural enemy of mosquitoes,
461.

New York, amebz in school children,
144-145; invasion by mosqui-
toes, 435...

Nicnots, H. J., 54.

Nico.u, W., 267.

NIcoLueE, C. N., 8, 44, 397, 399.

Nigeria, sleeping sickness, 98, 102,
104; transmission of sleeping
sickness, 500.

Nighthawk, natural enemy of mos-
quitoes, 462.

Night-soil, use in oriental countries,
227-228, 267.

Nimetti, 482.

Nit, 391.

Nocucut, H., 9, 67.

Noma, cause of, 70; treatment, 71.

North America, infectious jaundice,
65; tick paralysis, 358; Der-
macentor variabilis, 367; Reduvii-
dee, 382; typhus, 398; mosquito
scourge, 424; malaria-carrying
Anopheles, 439; blackflies, 481.

No-see-um, 474.

Notedres cati, 343.

Notophthalmus torosus, natural enemy
of mosquitoes, 461.

Novy, F. G., 9, 23-25.

Norrat., G. H. F., 34.

Nymph, 329, 332.

OBERMEIER, O., 7, 43. :

Odocoileus columbianus,
trritans, 414.

(Estridz, characteristics of larve,
509; and intestinal myiasis, 524.

and Pulex

507

strus ovis, and myiasis, 522-523.
(sophagostomum apiostomum, 283.
brumpti, see 2. apiostomum.
stephanostomum thomasi, 283.
Ogeata, M., 192.

Oil, poured in ears to remove Otio-

bius mégnini, 366; for removal
of ticks, 367; film to destroy
mosquito larve, 458, 460; film to
trap tabanids, 489-490.

Oxupa, K., 69.

Onchocerca volvulus, 310-311.

Ontario, blackflies, 479, 481, 482.

Onychophora, 324.

Opilaggo, 255.

Opisthorchis felineus, 225.

noverca, 225.
- pseudofelineus, 225.

Opsonin, 20.

Oregon, trichina, 292; tick paralysis,
358-359; Dermacentor occiden-
talis, 363; Notophthalmus torosus
and mosquitoes, 461; Culicoides,
476; blackflies, 481.

Oregon State Board of Health, corre-
spondence concerning venereal
diseases, 59.

Organelles, 29-32.

Oriental sore, 84-88; distribution,
84-85; transmission, 85-86, 377-
378, 477, 488; susceptible ani-
mals, 86; course of, 86-88;
treatment, 88; prevention, 88.

Ornithodorus, effect of bites, 361, 364.

coriaceus, effect of bites, 364-365.

mégnini, see Otiobius mégnint.

moubata, and relapsing fever, 43-
44, 360-361; control, 369.

savignyi, and relapsing fever, 44,
361; control, 369.

talaje, and relapsing fever, 46, 361;
habits, 361; control, 369.

tholosani, and relapsing fever, 44,
Sol.

turicata, and relapsing fever, 46,
361; severity of attacks, 361;
control, 369.

508

Oroya fever, 168, 176-181; history,
176; distribution, 176; con-
fusion with other diseases, 177;
course of, 179; parasite of, 179-
181; transmission, 181, 360.

Orthetrum chrysostigma, preys on
tsetse flies, 503.

Orthorrhapha, pups, 465, 466; and
myiasis, 509.

OSLER, Sir W., 49.

Osvumt, S., 69.

Otiobius mégnini, 365-366.

Owl midges, see Phlebotomus flies.

Oxyuris vermicularis, nutriment ab-
sorbed, 202; 277-279.

Pajaroéllo, 364.
Palestine, leeches in nose and mouth,
317-318.
Palpi, of insects, 325; of acarina, 331.
Panama, French failure and Ameri-
can success, 2; Leishmania sores,
74-75, 488; malaria and the
Canal, 149; non-malarial Anoph-
eles, 158; reduction of malaria,
166; malaria-proof houses, 166;
yellow fever during French opera-
tions, 185; reduction of yellow
fever, 185; dengue, 186; oil
films for mosquitoes, 459.
Pangonia, 485, 486.
Papataci fever, see Phlebotomus
fever.
Parabasal body, 29-30.
Paragonimus, 220-224; see also Lung
flukes.
kellicotti, 220, 223.
ringert, 220-224.
westermant, see P. ringert.
Paraguay, rattlesnakes and espundia,
92, 471.
Paralysis, general, result of syphilis,
53, 54; from tick bites, 358-359.
Parameba, see Craigia.
Paramecium, old age, 33.
Paramphistomum cervi, 229.
Paraplasma flavigenum, and yellow
fever, 184.

INDEX

Parasites, discoveries ‘of, 7; life his-
tories discovered, 8; definition,
12; kinds of, 12-13; effects of
parasitism on, 14; effects on
hosts, 15-17; modes of infection
and transmission, 17; geograph-
ic distribution, 18-19; effects
of temperature, 19; immunity
to, 19-22; introduction to virgin
territory, 20; relation to inter-
mediate and to final hosts, 450-
451.

Parasitic diseases, history of treat-
ment of, 8.

Parasitide, 333, 341.

Parasitism, degrees of, 12; effects on
parasites, 14; origin among
mites, 332-333.

Parasitology, importance of, 5; his-
tory of, 6-11.

Paratyphoid, confused with Oroya
fever, 178.

Paris, syphilis in, 50.

Pasteur, L., 7, 9, 20.

Patagonia, Filaria bancrofti, 299.

Parton, W.S., 77, 377, 416.

PEACOCK, 7.

Pediculoides ventricosus, 337-339.

Pediculus, hosts, 389.

capitis, 389; compared with P.
humanus, 389-390, 394-395, 394—
396; habitat, 395; life history,
395; effects of bites, 395-396;
and typhus, 397; and relapsing
fever, 399; and bubonic plague,
399-400; dispersal, 400; reme-
dies, 401.

corporis, see P. humanus.

humanus, 389-394; compared with
P. capitis, 389-390, 394-395;
and disease, 390, 397-400; habi-
tat, 390; life history, 391-393;
habits, 393-394; effects of bites,
394; and typhus, 397-398; and
relapsing fever, 399; and plague,
399-400; dispersal, 400; eradi-
cation, 401-403.

vestimenti, see P. humanus.

INDEX

Pedipalpi, 331.

Pellagra, and blackflies, 483.

Pelletririne, for tapeworm infections,
237.

Pennyroyal, oil of, repellent for fleas,
422; for mosquitoes, 455.

PENSCHKE, 420.

Peppermint, oil of,
mosquitoes, 455.

Pericoma townsvillensis, 466.

Peripatus, 324.

Persia, African relapsing fever, 44;
oriental sore, 85, 86; Ornitho-
dorus tholosani, 361; Argas persi-
cus, 364.

Persian insect powder,
thrum insect powder.

Peru, uta, 86; oriental sore, 87;
Trichomonas pathogenic, 121;
Oroya fever, 176, 181, 472; lung
fluke, 224; breeding places of
phlebotomus flies, 468; Phle-
botomus verrucarum, 472, 473.

Petroleum, for removal of ticks, 367;
for bugs, 383; emulsion for head
lice, 401; for body lice, 401, 402;
for chigger wounds, 420; for
mosquitoes, 457; for mosquito
larvee, 458.

Phalangomyia debilis,
fever, 181.

Philemon, 320.

Philippine Islands, amebic dysen-
tery, 130; craigiasis, 137; dengue,
186; kedani, 191; Schistosoma
japonicum, 218; lung flukes, 220,
221; human liver flukes, 224;
Echinostomum ilocanum, 228;
Tenia solium, 241; Hsophagosto-
mum apiostomum, 283; Anopheles
ludlowi, habits, 442; Musca do-
mestica and intestinal myiasis,
527.

Phinotas oil, for blackflies, 483.

Phlebotomus, and oriental sore, 86,
471; and Oroya fever, 181, 472-
473; and phlebotomus fever,
188, 470-471; 463; 466-473;

repellent for

see Pyre-

and Oroya

509

general description, 466-468; life
history, 468-470; and diseases,
470-473; control, 473.
perniciosus, and phlebotomus fever,
470. :
minutus, and oriental sore, 86, 471;
and phlebotomus fever, 470;
habits, 471; description, 472.
minutus, var. africanus, and orien-
tal sore, 86, 471.
papatasii, and phlebotomus fever,
188, 470; life history, 469; de-
scription, habits, etc., 470-471.
verrucarum, and Oroya fever and
verruga peruviana, 181, 472-
473.

Phlebotomus fever, parasites of, 169,
188.

Phthirius, hosts, 389.
inguinalis, see P. pubis.
pubis, 389, 396-397;

400; remedies, 401.

Physaloptera mordens, 282.

Physopsts africana, intermediate host
of Schistosoma haematobium in
South Africa, 215.

Pigeon, Argas reflexus, 364.

Pinworm, see Oxyuris vermicularis.

Prophila casei, and intestinal myiasis,
526, 527.

Piroplasmata, 27, 168; Bartonella a
member of, 180-181; and
spotted fever, 168; and kedani,
192; transmission by ticks, 168,
181, 360.

Pito bug, 382.

Plague, in Europe, 2, 411; in United
States, 2, 411; in India, 3, 411;
and bedbugs, 378; and lice, 399-

dispersal,

400; and fleas, 410-413; and
rats, 411.

Planorbis, occurrence in United
States, 220.

boissyi, intermediate host of Schisto-
soma mansoni in Egypt, 214, 217.

guadelupensis, intermediate host of
Schistosoma mansoni in Ven-
ezuela, 217.

560

olivaceus, intermediate host of
Schistosomamansontin Brazil,217.

Plasmodium, discovery, 7; cultiva-
tion, 9; 35; 149-159; species,
°149-150; life history, human
cycle, 150-154; relation to red
blood corpuscles, 150-151; mos-
quito cycle, 154-156; effects of
temperature on development in
mosquito, 156.

falciparum, 150-156; life history,
human cycle, 150-154; clogging
of capillaries, 152; sporulation,
152-153; numbers in blood, 153;
crescents, 154; mosquito cycle,
154-156; resistance to low tem-
peratures, 156.

malarie, 150; description, 157.

vivax, 150; resistance to low tem-
peratures, 156; description, 156.

Platyhelminthes, 196-198.

Puienciz, M. A., 6.

Plerocercoid, nature of, 235.

Puiny, 372:

Protz, H., 169, 397.

Poliomyelitis, acute anterior, see In-
fantile paralysis.

Pork, measly, 241; trichina in, 286,
287, 292; killing of trichina in,
295; imspection, 295-296; fit-
ness for food, 296-297.

Pork tapeworm, see Tenia solium.

Porocephalus armillatus, 350-351.

crotali, 351.
moniliformis, 351.

Portcuinsky, I. A., 487, 489, 490.

Porter, A., 123.

Porto Rico, hookworm disease, 262;
unsanitary conditions, 266.
Portuguese Sleeping Sickness Com-
mission, extermination of sleep-
ing sickness on Island of Prin-
cipe, 108; eradication of tsetse

flies, 502.

Potamon dehaanii, intermediate host

of lung flukes, 222.
obtusipes, intermediate host of lung
fluke, 222.

INDEX

Potassium cyanide, for hydrocyanic
acid fumigation, 384.

Potassium permanganate, for tropical
ulcer, 72.

Potassium sulphide, to destroy fleas,
422.

Precipitins, 21.

Paicn, JD: 377.

PRIESTLEY, H., 73.

Privies, lack of, in warm countries,
266.

Proglottid, 232.

Prostitution, and syphilis, 61; munic-
ipal control of, 61-62.

Protista, 27.

Protozoa, vs. Metazoa, 26-27; vs. -

bacteria, 27; structure, 28-29;
organelles, 29-32; nutrition, 32;
reproduction, 32-34; life cycle,
33-34; immunity to drugs, 34-
35; classification, 35-36; im-
portance, 37; discovery, 37.

Protozodlogy, importance of, 37.

Prowazekia, 115; 117-118.

Prowazek’s bodies, 194.

Pseudopodia, 29.

Pseudotyphus, 191-192.

Psorophora, larve prey on Janthino-
soma larve, 453.

Psychodide, 466.

Ptilinium, 465.

Pulex irritans, jumping power, 405; .

identification, 408; egg-laying
habits, 408; life cycle, 410; and
plague, 412; and infantile kala-
azar, 413; and Dipylidiwm can-
inum, 414; habits, etc., 414-
415.

Pulicide, 407.

Punkies, see Chironomide.

Puparium, 465.

Pygidium, 404.

Pygiopsylla ahale, 417.

Pyorrhea, 140-146; importance, 140;
relation of amebe to, 142-144;
relation of bacteria to, 143-144;
prevention and treatment, 145-
146.

INDEX

Pyrethrum insect powder, for ticks,
369; for mosquitoes, 456.
Python, host of Porocephalus, 350,
see.

Quack doctors, 4; and syphilis, 56.

Queensland, hookworm disease, 262.

Quinine, discovery and history, 8;
for malaria, 163-164, 167.

~ Quininization, and prevention of
malaria, 165, 166.

Quiros, D., 419, 420.

Rabbits, Eimeria stiede of, in man,
172; susceptible to trichina, 288;
Linguatula rhinaria, 349; and
bedbugs, 375; Echidnophaga gal-
linacea, 420.

Rabies, 169; parasite of, 170, 194.

Ransom, B. H., 238, 243, 286, 287,
292, 294, 295.

Rasahus, 382.

Rat-bite fever, 69; cause of, 69-70;
treatment, 70.

Rats, relapsing fever immunization,
47; reservoir of infectious jJaun-
dice, 67-68; and infantile kala-
azar, 82; development of T'ry-
panosoma rhodesiense in, 97;
hosts of human intestinal
Protozoa, 116; and amebic dys-
entery, 137; and Hymenolepis
nana, 242-244; Hymenolepis di-
minuta, 244; development of
Ascaris in, 274-275; Hormo-
rhynchus moniliformis, 284; rela-
tion to trichiniasis, 287, 288, 296;
and bedbugs, 375; occasional

hosts of Pulex irritans, 414;
fleas, 417-418; Echidnophaga
gallinacea, 420.

Rattlesnakes, Porocephalus crotali,
351.

Redbugs, see Harvest mites.

Rept, F., 6.

Redia, 208-210.
Red spider, 340.
Reduviide, 379.

561

Reduvius, 382.

REED, W., 184, 443.

Relapsing fever, 42-48; distribution,
42; spirochetes of, 42, 46; trans-
mission, 43-46, 378, 399; nature
of, 46-47; mortality, 47; treat--
ment, 47; prevention, 47-48;
development in lice, 399.

Repellents, for fleas, 423; for mos-
quitoes, 455; for phlebotomus
flies, 473; for chironomids, 477;
for tabanids, 489; for tsetse flies,
501.

Reptiles, reservoirs of Leishmanian
diseases, 471; fed on by tsetse
flies, 494.

Réunion, trypanosomes in Triatoma
rubrofasciata, 381.

Rhinosporidium, 168; 173-174.

kinealyi, 173.

Rhipicephalus, 366.

Rhizoglyphus parasiticus, 340.

Rhizopoda, see Sarcodina.

Rhodesia, sleeping sickness, 94.

Rhodnius prolixus, 382.

Rhynchoprion, see Dermatophilus.

Rhynchota, see Hemiptera.

Ricketts, H. T., 8, 189, 397.

Rickettsia prowazeki, and typhus, 169.

RipEwoon, W. G., 409.

Rigg’s disease, see Pyorrhea.

Ritey, W. V., 339, 474.

Rincongs, G., 451-452.

Rio de Janeiro, reduction of yellow
fever, 183, 185; Triatoma vitti-
ceps, 381.

RoBERTSON, Miss, 99.

RocwHa-Lima, H., 169.

RocKEFELLER, J. D., 268.

Rockefeller Institute, 10.

Rocky Mountain spotted fever, see
Spotted fever.

Rodents, hosts of Trypanosoma cruzi,
112, 114; and spotted fever, 190,
191, 369; susceptible to Schisto-
soma infections, 215; hosts of
immature stages of Dermacentor
venustus, 362-363; and Tria-

562

toma, 380-381; plague trans-
mitted by lice, 399; hosts of
Cordylobia anthropophaga, 518.

RoceErs, L., 8, 9, 81, 377.

Rosenauv, M. J., 48, 507.

Ross, Sir R., 7, 147, 148, 149, 156,
158, 164, 165, 449, 457.

RovuBaup, E., 471, 512, 517.

Rougets, 336.

Roundworms, see Nemathelminthes.

Russia, relapsing fever, 43, 45; Dibo-
thriocephalus latus, 246; Gigan-
torhynchus hirudinaceus in man,
284; typhus, 398; Gastrophilus
hemorrhoidalis in man, 516;
Wohlfartia magnifica, 521-522.

Sabethini, 437.

Salicylic acid, in ointment for chig-
gers, 420.

Salt, enema for amebic dysentery,
135; to destroy hookworm larve,
267.

Salt water, for myiasis of nose, ears,
etc., 523.

Salvarsan, discovery, 8, 49; for re-
lapsing fever, 47; for syphilis,
56-57; for yaws, 64; for infec-
tious jaundice, 68; for rat-bite
fever, 70; for Vincent’s angina
and noma, 71; for tropical ulcer,
72; for trypanosomes, 105, 107;
for Balantidium infections, 127;
for Schistosoma infections, 215.

Salvarsan copper, to prevent tryp-
anosome infections, 107.

SALZMAN, F., 294.

SamBon, L. W., 350, 351, 451, 452,

453.

Samoa, periodicity of Filaria ban-
crofti, 301.

Sand flea, see Dermatophilus pene-
trans.

Sandflies, see Phlebotomus flies.

San Francisco, plague in, 2; anti-rat
campaign, 411.

Sanitation, and syphilis, 61; and
prevention of amebic dysentery,

INDEX

136-137; relation to intestinal
parasites, 265-269; effect on
school children’s progress, 266—
267; necessity for practical
demonstrations, 268-269.
Santonin, for intestinal fluke infec-
tions, 230; for Ascaris infec-
tions, 276.
Sao Paulo, Triatoma sordida, 381.
Sarcocystin, toxin from Sarcosporidia
spores, 175.
Sarcocystis muris, sexual phenomena,
176.
tenella bubalis, in Indian buffaloes,
176.
Sarcodina, pseudopodia in, 29, 36,
129.
Sarcophaga fuscicauda and intestinal
myiasis, 526.
magnifica, see Wohlfartia magnifica.
Sarcophagide, 521. .
Sarcopsyllide, 407, 418, 420.
Sarcoptes, 342-346.
scabiei, 342-346.
scabiet crustose, 343, 345.
Sarcoptide, 333, 342.
Sarcosporidia, 168, 174-176; in man,
L7G:
SAVARELLI, 184.
Scabies, 342.
Scarlet fever, 169, 194. -
ScHAUDINN, F., 7, 49, 428.
Schistosoma, discovery, 7; life history
discovered, 8, 211-212; see also
Blood flukes.
hematobium, 212-217; distribu-
tion, 212; relation to host, 212;
pathogenic effects, 213; life his-
tory, 213-215; treatment, 215—
216; prevention, 216-217.
japonicum, 218-219; symptoms of
infection, 218; life history, 219.
mansoni, 217-218.
ScuHroepEr, O., 6.
ScHUEFFNER, W., 192.
ScHULZE, 6.
ScHWANN, 6.
Scolex, 231.

INDEX

Screening, for mosquitoes, 457.

Screw-worm, see Cochliomyia macel-
laria.

Scutum, of ticks, 354.

Seal, host of Dibothriocephalus cor-
datus, 247.

Seattle, plague in, 411.

Seed ticks, 355.

SEIDELIN, H., 184.

Seviarps, A. W., 131, 134.

Serbia, relapsing fever, 45, 378, 399;
typhus, 398.

SERGENT, E., 471.

Sesarma dehaani, intermediate host
of lung flukes, 222.

Seven-days’ fever, see Dengue.

Shanghai, Clonorchis sinensis, 225.

Sheep, liver fluke, 208-210; Param-
phistomum cervi, 229; hydatids,
248; host of Trichostrongylus in-
stabilis, 282; Linguatula rhina-
ria, 349; tick paralysis, 358-
359; grazing to destroy ticks,
369; head maggot, 523.

SHIPLEY, A. E., 204.

Shrimp, host of Fasciolopsis buski,
229.

‘Siberia, Opisthorchis felines in man,
225.

Sicily, breeding places of phleboto-
mus flies, 468, 473.

Stxora, H., 391, 392, 393, 394.
Silver, organic compounds of, for
Balantidium infections, 127.
Silver nitrate, for Vincent’s angina

and noma, 71.
Simultide, 478-484.
Simulium, 481.
columbaczense, 482.
griseicollis, 482.
pecuarum, 481.
venustum, 481.
Siphonaptera, characteristics,
404.
Situtunga antelope, reservoir for
sleeping sickness trypanosomes,
107; host of Glossina palpalis,
498.

330,

563

Skunk, host of Pulex irritans, 414.

Sleeping sickness, importance, 93;
Rhodesian, 94, 97, 103; Gam-
bian, 97, 103; Nigerian, 98, 103,
104; 98-108; transmission, 98-
99, 490, 496-501; course of, 103-
104; treatment, 104-106; pre-
vention, 106-108; animal reser-
voirs, 107, 503-504.

Smallpox, 169; parasite of, 170, 192-
194.

Smitu, A. J., 144.

Smit, J. B., 434, 435, 441, 456, 459.

Smudge, for mosquitoes, 457; for
blackflies, 484.

Snails, intermediate hosts of flukes,
208, 210; of Schistosoma, 214,
215, 216, 217, 219-220.

Snakes, possible reservoirs of Letsh-
mania, 92, 471.

Snow, F. H., 521.

Snow, W. F., 58.

Soap, in treatment of itch, 345.

Sodium fluoride, for fleas, 421-422.

Somaliland, relapsing fever, 44.

Sources of Information, periodicals,
529-531; books, 531-533.

South Africa, blood-fluke infections
in British soldiers, 213; inter-
mediate host of Schistosoma
hematobium, 215.

South America, oriental sore, 85; uta,
86; espundia, 89; trypanosomi-
asis (Chagas’ disease), 94, 108;
Coccidium seeberi, 174; dengue,
186; use of shoes, 265; Filaria
perstans, 308; Filaria juncea,
308; land-leeches, Cimex hemip-
terus, 373; Triatoma, 379-381;
Rhodnius prolixus, 382; Dy-
sodius lunatus, 382-383; Der-

- matobia in cattle, 513.

South Sea Islands, Filaria bancrofti,
301; prevalence of elephanti-
asis, 305; Aédes calopus, 448.

SPAGNOLIO, G., 83.

SPALLANZANT, A., 6.

Sparganum, 247; 261-2653.

564

mansoni, 251-252.
proliferum, 252-253.

Spinose ear tick, see Otiobtus mégnint.

Spiny-headed worms, see Acantho-
cephala.

Spiracles, of insects, 328; of ticks,
354.

Spirocheta, see Spirochetes.

balanitidis, 41.

bronchialis, transmission, 40, 41;
cause of bronchitis, 71.

buccalis, 40; pathogenicity, 70-71.

carteri, 42; in bedbugs, 378.

dentium, 40.

duttoni, 42.

exanthematotyphi, 73.

icterohemorrhagie, 41; 66-67; mode
of infection, 67.

morsus muris, 69.

nodosa, see Sp. icterohemorrhagie.

novyt, 42.

obermeiert, see Sp. recurrentis.

orventalis, 41.

pallida, discovery, 7, 41, 49, 52.

pertenuis, 41, 63.

recurrentis, discovery, 7, 43; de-
scription, 52; distribution in
body, 52.

refringens, 52.

schaudinni, 41, 72.

vincenti, 41.

Spirochetes, cultivation, 9; 38-73;
relationships, 38; multiplica-
tion, 39; granule shedding, 39;
and disease, 40-42, 73; localiza-
tion, 41; and relapsing fever,
42-48; and syphilis, 48-62; and

yaws, 63-65; and _ infectious
jaundice, 65-69; and rat-bite
fever, 69-70; and _ Vincent’s

angina, 70; and noma, 70; and
balanitis, 70; and mal-de-boca,
70; and bronchitis, 71; and
tropical ulcer, 72; and ulcerat-
ing granuloma, 72-73; trans-
mission by ticks, 360.

Spleen rate, and prevalence of ma-
laria, 161.

INDEX

Sporocyst, 208.

Sporozoa, 35, 36; and human disease,
149, 168.

Spotted fever, relation of ticks to,
8, 190, 361-363; and Piroplas-
mata, 168; 189-191; distribu-
tion, 189; parasite of, 190;
course of, 190; reservoirs, 190-
191; control, 191.

Spotted fever group of diseases, 189.

Spotted fever tick, see Dermacentor
venustus.

Squirrels, hosts of Hormorhynchus
clarki, 285; hosts of immature
stages of Dermacentor venustus,
362; and plague, 411, 413; fleas,
418.

Stable-flies, see Stomozxys.

STANLEY, and spread of sleeping
sickness, 93.

Staten Island, reduction of malaria,
166.

STAUBLI, C., 290.

STAUFFACHER, H., 76, 195.

Stegomyia, see Aédes.

fasciatus, see Aédes calopus.

STEPHENS, J. W. W., 282.

Stephensport, quininization, 164-165.

Sterilization, of blood against tryp-
anosomes, 107.

Stewart, F. H., 274, 275.

Sticktight flea, see Echidnophaga gal-
linacea, 420.

Stigmal plates, of maggots, 509-510.

Stites, C. W., 116, 125, 242, 252,
254, 266, 296, 297, 400.

Stoxss, J. H., 483.

Stomoxys, transmission of T'rypano-
soma gambiense, 98, 507; rela-
tion to Onchocerca volvulus, 311; |
mouthparts, 327, 464, 505;
transmission of anthrax, 488,
507; 504-508; general descrip-
tion, 504-505; life history, 505-
506; and disease, 507; control,
507-508.

calcitrans, 504;
paralysis, 507.

and _ infantile

INDEX

nigra, and Trypanosoma gambiense,
98, 507.

Streptothrix, and rat-bite fever, 70.

STRICKLAND, C., 409, 410, 417.

‘Srrone, R. M., 86, 178, 179, 180.

Strongyloides stercoralis, 279-282; life
history, 280-281; symptoms,
281-282.

Strongylus, see Trichostrongylus.

Sudan, spirochetal bronchitis, 71;
kala-azar, 77; Simulium, 482;
tabanids, 487; methods of cap-
turing tsetse flies, 503.

Sulphur, for mites, 335, 339, 341, 346,
348; for fumigation, 383, 386;
for lice, 401.

Sulphur ointment, for itch, 346.

Sulphuric acid, for hydrocyanic acid
fumigation, 384.

Sumatra, pseudo-typhus or kedani,
191; land-leeches, 319, 320.

Surcour, M. J., 451, 452.

Surra, 99, 487. -

Suzux1, M., 219.

Swallows, .bugs on, 374; natural
enemies of mosquitoes, 462.

SWELLENGREBEL, N. H., 417.

Swezy, O., 119.

Swirt, H. F., 57.

Swift-Ellis treatment, for syphilis
of nervous system, 57.

Swifts, natural enemies of mos-
_quitoes, 462.

Switzerland, Dibothriocephalus latus,
246.

Syphilis, importance of, 3; history,
48-49; prevalence, 49-51; trans-
mission, 51-52; spirochetes of,
52; course of, 53-55; congenital,
53; malignant, 55; diagnosis,
55-56; treatment, 56-58; stand-
ard of cure, 57-58; prevention,
58-63; exclusion from hospitals,
58; free diagnosis and treatment,
59; compulsory notification, 60;
relation to yaws, 63; and Enda-
meba mortinatalium, 130; pos-

565

sible spread by bedbugs, 379;
by lice, 400.

Syria, oriental sore, 85;
epidemic, 398.

typhus

Tabanide, and leishmaniasis, 75,
488; and espundia, 92, 488-489;
mouthparts, 327, 485; 484-490;
general account, 484-486; life
history, 486-487; and disease,
487-489; transmission of surra
and el debab, 487; and human -
trypanosomiasis, 488; and an-
thrax, 488; and loa worms, 489;
control, 489-490.

Tabanus, 486; trap for, 490.

Tabardillo, see Typhus fever.

Tenia africana, 245.

confusa, 245.

philippina, 245.

saginata, discovery of life history,
7; nutrition absorbed, 202; de-
scription, 239-240; life history,
240.

soltum, 240-242;
man, 251.

Teeniide, 238; important species of,
239-245.

TAKAKI, F., 69.

Tampan, see Ornithodorus moubata,

TAniGcucuHl, T., 69.

Tapeworms, 231-253; general struc-
ture, 231-233; reproduction, 233-
234; life history, 234-235; dam-
age to host, 236-237; treatment,
237; prevention, 237-238; im-
portant species, Tzeniidz, 239-
245; Dibothriocephalide, 245-
247; larval tapeworms of man,
247-253.

African, see Tenia africana.
beef, see Tenia saginata.

dog, see Dipylidium caninum.
dwarf, see Hymenolepis nana.
fish, see Dibothriocephalus latus.
pork, see Tenia solium.

Tarentola mauritanica, and oriental
sore, 86, 471.

cysticercus in

566 INDEX
Tarsonemide, 333; 337. history, 3855-357; effects of
Tartar emetic, discovery, 8; for bites, 357-358; tick paralysis,

ulcerating granuloma, 73; for
kala-azar, 81; for infantile kala-
azar, 84; for oriental sore, 88;
for espundia, 91-92; for tryp-
anosomes of sleeping sickness,
105; for Chagas’ disease, 114.

Tauts, M:, 107.

Teeth, pyorrhea cause of loss of, 140;
amebz among, 140, 142-144.

- Temperature, limiting factor in dis-
tribution of parasites, 19.

TENNENT, J. E., 319.

Ternidens deminutus, 283.

Tetramitus, see Macrostoma.

Tetranychide, 333; 340.

Tetranychus molestissimus, 341.

telarius, 341.

Texas, Sparganum mansoni, 252;
propagation of bats to destroy
mosquitoes, 462.

Texas fever, caused by Piroplasmata,
168, 180, 360.

Texas fever tick, see Margaropus
annulatus.

THEOBALD, F. V., 437.

Tuiézk, J., 310.

Tuomas, W., 8.
Three-days’ fever, see Phlebotomus
fever.

Thymobenzene, for Schistosoma in-
fections, 215.

Thymol, discovery, 8; for intestinal
flukes, 230; for tapeworms, 237;
danger from, 237; for hook-
worms, 263; for pinworms, 279;
for microfilariz, 306.

Thysanura, direct life history, 329.

Tick-bite fever, 367.

Tick fever, see African relapsing
fever.

Tick paralysis, 358-359.

Ticks, and espundia, 92; transmitters
of Piroplasmata, 168, 181, 360;
and kedani, 194, 360; 352-369;
importance, 352; general anat-
omy, 352-354; habits, 354; life

358-359; and disease, 359-360;
and relapsing fever, discovery, 8;
43-44; 352; transmitting species,
360-361; and spotted fever,
discovery, 8; transmission, 189-
190, 352; transmitting species,
361-363; troublesome.Argaside,
364-366; troublesome Ixodide,
366-367; treatment of bites, 367;
removal, 367; prevention, 368-
369. :

Tipulide, mosquitoes allied to, 425.

Tlalsahuate, 335.

Tobacco, for leeches, 318, 319; to
remove Dermatobia from. skin,
515.

Topp, J. L., 8, 359.

Togoland, transmitter of sleeping
sickness in, 500.

Tongue-worms, 348-351; general ac-
count, 348; life history, 348-
349; species found in man, 349-
351.

Tonkin, relapsing fever epidemic, 47.

Tonsilitis, relation of Endameba gin-
givalis to, 144.

Torres, M., 111, 380.

Tovar, N., 451, 452.

Townsenp, C. H. T., 86, 181, 468,
472, 473.

Toxascaris limbata, 282.

Toxins, 16-17; from spores of Sar-
cosporidia, 175; from intestinal
worms, 202-203; from tape-
worms, 236; from Dhibothrio-
cephalus latus, 247; from hook-
worms, 261; from maggots in
intestine, 527.

Trachee, of Arachnida, 324; of
insects, 325, 328; of Acarina,
332.

Trachoma, 169; 194.

Trematoda, 197-198; see also Flukes.

. Trench diarrhea, 131.

Treponema pallida, see Spirocheta
pallida.

INDEX

Triatoma, relation to Trypanosoma
cruzi, 8, 108, 110-112, 380-381;
houses proof against, 114, 370;
379-382; habits and life history,
379.

chagasi, infected with trypano-
somes, 381.

dimidiata, infected with trypano-
somes, 381.

geniculata, and Trypanosoma cruzi,
112, 380-381.

infestans, infected with trypano-
somes, 381.

megista, and Trypanosoma cruzi,
110-112; habits and life history,
380.

protracta, and Trypanosoma. tria-
tome, 112, 379, 381.

rubrofasciata, and Trypanosoma
cruzi, 112, 381; and kala-azar,
377, 382; possible carrier of
trypanosome disease in Mauri-
tius and Réunion, 381.

sanguisuga, 110, 379.

sordida, infected with trypano-

somes, 381.
vitticeps, infected with trypano-
somes, 381.
Trichina worms, see _ T'richinella
spiralis.

Trichinella spiralis, discovery, 7;
286-297; history, 286; preva-
lence, 286-288; life history, 288-
292; hosts, 288; reproduction,
289;- distribution in body of
‘host, 290; formation of cysts,
291; trichiniasis, 292-294; treat-
ment, 294-295; prevention, 295-
297; effects of cold storage and
heat, 295; meat inspection for,
295-296.

- Trichiniasis, prevalence, 286-288;
course of, 292-294; treatment,
294-295; prevention, 295-297.

Trichinosis, see Trichiniasis.

Trichoma, 396.

Trichomonas, 115; 118-122; in vagina,
119; in mouth, 119; descrip-

567

tion, 119; multiplication and
encystment, 120; pathogenicity,

121; treatment of infections,
121.
buccalis, 119.

intestinalis, 118-122.

vaginalis, 119.
Trichostrongylus, 282-283.

instabilis, 282.

ortentalis, 282.

subtilis, see T. instabilis.

Trichuris trichiura, 276-277.

Trinidad, mosquitoes thought to
transmit Dermatobia.

Triodontophorus, see Ternidens.

Trombidiide, see Harvest mites.

Trombidium, and kedani, 191.

akamushi, 336.
holosericeum, 336.

Tropical sloughing phagedena, 72.

Tropical ulcer, 72.

Tropidurus peruvianus, host of Phle-
botomus verrucarum, 472.

Trypanoplasma, 117.

Trypanosoma, relation of tsetse flies
to, 7, 490, 496-497, 500-501;
cultivation, 9; immunity to
drugs, 34, 105-106; develop-
mental stages, 75, 96-97; 93-
114; importance, 93-94; de-
scription of, 94-95; hosts, 96;
identification of species, 96-
97; species pathogenic to man,
97; and sleeping sickness, 98-
108; spores, 102; granule-shed-
ding, 103; agglutination, 103;
and Chagas’ disease, 108-114;
and leeches, 317; carried by
Cimex pipistrelli, 378; possible
cause of disease in Mauritius
and Réunion, 381-382.

brucei, relation to Rhodesian sleep-
ing sickness, 108, 497.

cruzi, relation of Triatoma to, 8,
108, 380-381; and Chagas’ dis-
ease, 108-114; distribution, 108;
human cycle, 109-110; life cycle
in Triatoma, 110-113; other in-

568

termediate hosts, 112, 378; ver-
tebrate hosts, 112.

gambiense, discovery, 7; direct trans-
mission, 34, 97; 98-108; trans-
mission, 98-99, 496; distribution,
98; life cycle in fly, 99-101; life
cycle in man, 101-103; spores,
102; granule-shedding, 103; ag-
glutination, 103; and drugs, 105-
106; transmitting species, 496-
501; relation of stable-flies to,
98, 507.

lewisi, immunity to drugs, 105.

nigeriense, 98; and stable-flies, 98,
507. ;

rhodesiense, 97; distribution, 98;
and sleeping sickness, 98-108;
pathogenicity and relation to 7.
brucei, 107-108; and drugs, 106;
transmitting species, 98, 497,
499-501.

triatome, 112, 381.

Trypanosome fever, 103-104.

Tsetse flies, relation to trypanosomes,
7, 98-101, 496-497, 500-501;
relation to Onchocerca volvulus,
311; mouthparts, 327, 464, 491;
reproduction, 464, 495; 490-504;
importance, 490; general account,
491-492; distribution, 492;
habits, 493-495; life history,
495-496; and disease, 496-501;
control, 501-504.

Tsutsugamushi, see Leptus akamusht.

Tuberculosis, possible spread by bed-
bugs, 379.

“szTumbu fly, see Cordylobia anthro-

pophaga.
Tunis, Leishmania in gecko, 86.
Tunnel disease, see Hookworm.
TuNNICLIFF, R., 70.
Tuntun, see Hookworm.
Turbellaria, 197.
Turkeys, Trichomonas pathogenic in,
121.
Turpentine, to keep away ticks, 368;

for bugs, 383; oil of, for body lice, ,

401; resistance of maggots to, 522.

INDEX

Tydeus molestus, 341.

Typhoid, relation of intestinal worms
to, in apes, 204.

Typhus, in European War, 2, 398;
relation of lice to, 8, 397-399;
cause of, 73, 169, 195, 397; epi-
demics, 398-399; and fleas, 414.

Tyroglyphide, 333; 339-340.

Tyroglyphus, 340.

longior, 340.
longior castellanii, 340.

Uganda, sleeping sickness, 93; fishing
industry and sleeping sickness,
106-107; Filaria perstans, 308.

Ulcerating granuloma, 72-73.

Undulating membrane, 30.

United States, plague in, 2, 411;
syphilis in, 3; hookworm in
immigrants, - 5, 268; amebic
dysentery, 6, 131; relapsing
fever, 43; syphilis, 50; possibility
of kala-azar, 77; prevalence of
intestinal Protozoa in South, 116;
Trichomonas pathogenic, 121;
craigiasis, 137; malaria, 147-
148, 163; blackwater fever, 161;
swamp land and malaria, 166;
yellow fever, 183; dengue, 186;
spotted fever, 189-191; possi-
bility of introduction of blood
flukes, 220; Paragonimus kelli-
cotti, 220, 223; Opisthorchis
pseudofelineus, 225; Paramphis-
tomum in cattle, 229; Tenia
solium, 240; Hymenolepis nana,
242; Hymenolepis diminuta, 244;
Dibothriocephalus latus, 246; hy-
datids, 247; hookworm, 254,
255, 262, 263, 268; privies, 266;
prevalence of trichina in hogs,
286, 287; prevalence of trichina
in man, 287; Filaria bancrofti,
299; red-bugs, 336; Pedicu-
loides, 338; Norwegian itch, 343;
economic importance of ticks,
352; tick paralysis, 358; Der-
macentor venustus, 363; Otiobius

INDEX

mégnini, 365; Triatoma, 379,
381; kissing bugs, 382; plague-
like disease transmitted by fleas,
413; Pulex irritans, 415; Cteno-
cephalus canis, 416; Ceratophyl-
lus, 418; Echidnophaga galli-
nacea, 420; Aédes calopus, 447;
Culex quinquefasciatus, 449; mos-
quito canopies, 457; Notoph-
thalmus torosus natural enemy of
mosquitoes, 461; blackflies, 481;
infantile paralysis, 507.

United States Army, syphilis in, 50.

United States Bureau of Animal
Industry, experiments with tri-
china, 295.

United States Bureau of Entomology,
508.

Uranotenia, palpi, 426.

Uruguay, dengue, 186; Tetranychus
molestissimus, 341.

Uta, 86; 87; 88; 477.

Vaccination, 4; broad meaning of, 22;
in treatment of hookworm dis-
ease, 263.

Vaccine or cowpox, 194.

Vahlkampfia, 129.

lobospinosa, 130.

VAN DEN BRANDEN, F., 107.

VAULLEGEARD, A., 202.

VEDpDER, E. B., 8, 50.

Venezuela, Schistosoma mansoni, 217;
Rhodnius prolixus, 382.

Vera Cruz, amebic dysentery, 130,
136; malaria, 166.

Ver-du-cayor, see Cordylobia anthro-
pophaga.

Vermes, 196.

Verruga peruviana, 169; relation to
Oroya fever, 178, 195; and
Phlebotomus verrucarum, 472.

Vespa maculata, natural enemy of
tabanids, 490.

Vianna, G., 8, 73, 81, 109.

Vincent’s angina, cause of, 70; treat-
ment, 71.

Vinchuca, see Triatoma infestans.

569

Vinegar, effect on Clonorchis cercarie,
227; and kerosene for lice, 402;
repellent for mosquitoes, 455.

Von Duscu, 6.

Von Ezporr, H., 148.

Von Linstow, see Linsrow, von.

WaLKER, E. L., 131, 134, 136.

Wa .iace, A., 320.

Watsu, B. D., 524.

Warbles, see Hypoderma.

Warp, H. B., 245, 285.

Wart hog, host of Cheromyia, 512.

Washington, D. C., dispersal of lice
in family wash, 401; develop-
ment of Anopheles quadrimacu-
latus, 442.

WASSERMANN, A. VON, 49.

Wassermann reaction, 49; 50; 55-56.

Water-dogs, natural enemies of mos-
quitoes, 461.

Watsonius watsoni, 229.

Weil’s Disease, see Infectious jaun-
dice.

WEINBERG, M., 204.

WEINLAND, D. F., 7.

Wenyon, C. M., 85, 118, 123, 124,
125, 172, 471.

Western Australia, compulsory noti-
fication of syphilis, 60.

West Indies, dengue, 186; Schisto-
soma mansoni, 217; hookworm
disease, 254; Necator americanus,
255; work of Hookworm Com-
mission, 268; Filaria perstans,
308; béte rouge, 335; Cimex |
hemipterus, 373; chigger, 419;
origin of yellow fever, 447; home
of ‘“‘millions,” 461.

West Point, syphilis at, 51.

Whipworm, see Trichuris trichiura.

WuiTmars3#, P. L., 305.

WILp_ER, R. M., 8, 397.

Wild game, extermination to eradi-
cate sleeping sickness, 107; and
control of spotted fever in United
States, 191; hosts of Dermacen-

i og
Z 31D Le qo
7 Lip Sa
Be ad
070 INDEX é os

tor venustus, 363; hosts of tsetse
flies, 490, 498.

Witiiams, ANNA, 144, 194.

Wohlfartia magnifica, 521-522.

Woodrats, host of Triatoma protracta,
112.

Woodtick, see Dermacentor.

Worcester, D. C., 320.

Worms, 196-205; classification, 196;
flatworms in general, 196-198;
roundworms in general, 198-199;
annelids in general, 199-200;
parasitic habitats, 200; °. life
history and modes of infection,
200-201; effects of parasitism,
201-204; nutriment absorbed,
202; toxic effects, 202; infection
of wounds made by, 204; rela-
tion to appendicitis, 204; diag-
nosis, 201; eggs of, 205. See
also Intestinal worms and various
species.

Wrigglers, 431.

Wricat, R. E., 306.

Wyeomyia smithii, hibernation, 436.

Xanthium macrocarpum, mites on
leaves of, 341.

Xenopsylla cheopis, identification,
408; and plague, 411, 412;
intermediate host of Hymeno-
lepis, 414; distinguished from

|=

Pulex irritans, 415; habits, etc.,
417. , .

X-ray, for ulcerating granuloma, 73;

for Schistosoma infections, 215.

Yaximorr, W. L., 377.

Yaws, 63-65; distribution, 63; spiro-
chetes of, 63; course of, 63;
treatment, 64-65; prevention, 65.

Yellow fever, in Panama, 2; relation
of mosquitoes to, 7, 443; para-
site of, 169, 184; 182-186; distri-
bution, 182-183; course of, 184—-
185; treatment and prevention,
185; transmitting mosquito, 443-
448.

Yellow fever group of parasites, 169,
182.

Yellow fever mosquito, see Aédes
calopus.

YeERSIN, A., 411.

Yokagawa yokagawa, 228.

YorkxkE, W., 100, 494, 496.

YOSHIDA, 222, 223.

Yquitos, reduction of yellow fever,
185.

Zambezi, danger of spread of Glossina
palpalis to, 498.

Zebu, possible intermediate host of
Tenia africana, 245.

ZENKER, F. A. VON, 7.

ZEPEDA, P., 452,

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