4.3 J. 7

STATE DOCUMENTS

THE MONTANA

STATE BOARD

OF

ENTOMOLOGY

EIGHTH BIENNIAL
REPORT

1929 - 1930

Montana Stale Library

THE MONTANA

STATE BOARD

OF

ENTOMOLOGY

EIGHTH BIENNIAL
REPORT

1929 - 1930

Digitized by the Internet Archive

in 2010 with funding from

IVIontana State Library

http://www.archive.org/details/biennialre19291930mont

MONTANA STATE BOARD OF ENTOMOLOGY

W. F, Cogswell, M. D., Secretary State Board of Health,
Chairman, Helena, Montana.

"W. J. Butler, D. V, S., State Veterinary Surgeon,
Member, Helena, Montana.

E, A. CooLEY, B. Sc., State Entomologist,
Secretary, Bozeman, Montana.

LETTER OF TRANSMITTAL

Bozeman, Montana, January 6, 1930.

To His Excellency, John E. Erickson,
Governor of Montana,
Helena, Montana.

My dear Sir:

The services of the ex-officio Montana State Board of Entomology have
continued without interruption since 1913. There has been no change in the
personnel of the Board. There has been a determined effort to bring spotted
fever under control and real progress has been made, for what has been done
will not have to be done over again. At the same time, spotted fever is spread-
ing in Montana and in other western states and at the present time is far
more of a problem than it was when the Board of Entomology took up its
duties. It is now recognized both in Montana and other western states that
the problems of Eocky Mountain spotted fever, tularaemia and tick paralysis,
all of which are produced by the wood tick of this region, are not problems for
Montana alone but apply as well in some twelve other states. Accordingly, in
recent months an effort has been made to turn the entire research program of
the Board of Entomology over to the United States Public Health Service. It
is proposed also to turn over the Hamilton Laboratory to them. This laboratory
would thereby become the headquarters for the study of tick-borne diseases in
the western states, and the expense of the research work would be borne by the
Federal Government.

It has been necessary for the Board of Entomology to ask for a continu-
ance of the present appropriation for it is not at all assured that the program
to turn over the work to the Government will go through. In case the plan does
carry, the appropriation will be expended only in so far as it applies to "con-
trol work" which has to be distinguished from the research work. It will be
necessary for the Board of Entomolog;v- to continue its control progr;un, which
includes the destruction of rodents, the dipping of livestock and enforcement
of quarantines until such time as a more suitalsle method of controlling ticks or
spotted fever has been discovered.

It is recommended that this report be published as the Eighth Biennial.
Eeport of the Montana State Board of Entomology.

Most respectfully,

E. A. COOLEY, Secretary.

CONTENTS

Page

Activities in 1929-1930 7

Summary for 1929-1930 7

Cooperation with the United States Public Health Service 9

Organization and Personnel 11

Rocky Mountain Spotted Fever Outside of Montana 12

Proposal to Surrender the Board's Research Work to the

United States Government 13

Review of Tick Parasite Work for 1929-1930 16

Recovery of Tick Parasites from Nature 16

Rate of Multiplication of Parasites 17

Rate of Multiplication of Ticks 18

Correlation of Habits 19

Rate of Dispersion of Parasites 19

Influence of Climate 19

Parasitism of Larvae and Nymphae 21

Possibility of Transmitting Diseases by Tick Parasites 22

Tick Parasites in Africa 23

A Summary of Parasite Liberations 26

Present Status of the Use of Vaccine 36

A Review of Dipping and Quarantines 38

Control Work 40

STATE BOARD OF ENTOMOLOGY

ACTIVITIES IN 1929-1930

The activities of the Montana State Board of Entomology during the
Biennium now closing may be summarized as follows:

1. Continuation of the plan of informal cooperation with the Bureau of
the Public Health Service.

2. Continuation of the tick parasite project.

3. Continuation of the dipping of domestic animals and of the killing
of rodents by poisoning in the control districts in the Bitter Boot Valley.

4. Promotion of a plan to turn over the entire work of the Board, except-
ing "control work," to the United States Government.

SUMMARY FOR 1929-1930

The Montana State Board of Entomology created by the Thirteenth Legis-
lative Assembly in 1913, has made a continuous and determined effort to
bring the wood tick (Dermacentor andersoni Stiles) and the human disease,
Eocky Mountain Spotted Fever, under control. The Act creating the Board
made the Secretary of the State Board of Health, the State Veterinary Surgeon
and the State Entomologist ex officio the members to constitute the Board.
During this period of eighteen years there has been no change in the personnel
of the Board, and the three members have given much time and thought to
the work. To a certain extent also the resources of the three separate depart-
ments of Service in the State have been brought to bear on the joint problem
assigned to them.

When the Avork was started by the Board it was little realized that it
would be so long-drawn out, although it was understood at the first that the
problem was a complicated one. Now, after these years of labor, it becomes
necessary to say quite frankly that the problem is far from being solved, and
Eocky Mountain Spotted Fever is still a real public health problem in Montana,
and meantime it has both spread and been recognized far and wide in Western
United States and is now a problem in at least thirteen separate states.

At the same time it is very gratifying to state that real progress has been
made. Previous to the creation of the Board of Entomology, Eicketts alone and
McCalla and Brereton working together, publishing simultaneously, had shown
that the wood tick does in fact transmit Eocky Mountain Spotted Fever to
man, as had been suspected by Wilson and Cho-wning; and the State Ento-
mologist of Montana and the U. S. Bureau of Entomology had worked out
the biology of the wood tick with fair completeness. The high points of ac-
complishment since the Board's work began are: the naming and describing
of the organism of the disease by Wolbach; the discovery and quantity manu-
facturing of the Spencer-Parker vaccine; and the starting of a definite tick
parasite project. These few high points of progress do not at all adequately

8 EIGHTH BIENNIAL REPORT

cover the accomplishmeuts. A tremendous volume of work, more arduous and
dangerous than the world will ever know, has been done by such men as
Eieketts, McClintic, Fricks, Wolbach, Noguehi, Spencer, Parker and others,
including a long list of associates and assistants, and the aggregate of their
accomplishments has gone far toward accomplishing the desired solution. In
a very complicated problem like the present one, it is only natural that a
■considerable portion of the results of well laid out researches should be of
only intermediate value leading gradually toward the fiual end desired, namely,
the eradication or complete control of the disease. These secondary results are
of great scientific interest and many valuable publications have resulted. Not
the least of these results have been the contributions made by Parker and
Spencer of the Public Health Ser^•ice staff at Hamilton, to our knowledge of
tularaemia and tick paralysis, two other definite human diseases communicated
to man by the bite of the same tick. All or most of this preliminary work was
necessary and will not have to be done over again.

These studies have been made in a new field of knowledge where there
was very little in the published results of previous workers to guide new
workers, and to a remarkable degree, particularly in recent years, each new
discovery made has appeared to complicate the problem rather than to simplify
it, with the result that the workers have been continually finding it necessary
to set up ncAV studies and experiments. They could easily become hopelessly
confused and ineffective in their further efforts, were it not for the fact
that they are tlioroughly trained, much experienced and held by a rare devotion
to the work.

STATE BOARD OP ENTOMOI^OGY

THE COOPERATION WITH THE UNITED
STATES PUBLIC HEALTH SERVICE

Since the earliest years of the investigations of Eocky Mountain Spotted
Fever the United States Public Health Service has taken an active part. The
reader is referred to the Seventh Eeport, in which, on page 69, is a short
review of this subject written by Doctor W. F. Cogswell. For most of the
period since the Board of Entomology was organized the Public Health Service
has had a research worker, or a research organization, stationed in Montana
for the study of this disease. Thus, in 1913, when the Board began its labors,
Doctor L. D. Fricks began his studies with headquarters at Victor, and con-
tinued until 1917. In 1921 Doctor E. E. Parker, who previously had been em-
ployed by the Board of Entomology, was taken over by the Public Health
Service and a larger laboratory was established near Hamilton. In the spring
of 1922 he was joined by Doctor E. E. Spencer who had been detailed in
charge of the Eocky Mountain Spotted Fever studies. Doctor Spencer there-
after divided his time between the Service's field station at Hamilton and the
Hygienic Laboratory in Washington until September, 1928, when he was as-
signed to duty at the latter institution. During this period, there was the
closest cooperation between Doctor Spencer and Doctor Parker, and in 1930
there appeared a very valuable publication from the Public Health Service
giving the results of over six years of joint research d). These contributions, of
which the most important was the Spencer-Parker vaccine, have been of the
greatest value. Though now stationed at Washington, Doctor Spencer continues
to maintain an active interest in, and is still devoting a part of his time to,
spotted fever studies.

Doctor Parker, who served under the Board of Entomology from 1915 to
1921, and who has since been with the United States Public Health Service,
and is now directing its operations at Hamilton, has without doubt spent
more time in the study of Eocky Mountain Spotted Fever than any other man.
A tremendous worker, with extraordinary capacity for orderly detail and with
unfailing devotion and enthusiasm, he has accomplished much. During his
continuance in Montana he has been lone author of eighteen scientific papers
on Eocky Mountain Spotted Fever and closely related subjects, and of twenty-
five in joint authorships, principally with Doctor Spencer. In addition to these
he has written alone thirty-one scientific articles on other subjects in ento-
mology, or a total of seventy-four titles while working in Montana.

We have referred to our plan of cooperation as being an informal one.
In recent years the Board of Entomology has devoted its attention and funds
mainly to the tick parasite work, the destruction of rodents, and tlie dipping of
domestic animals. The Public Healtli Service has its own program of work
which includes the production of the Spencer-Parker vaccine on a rather large
scale, and researches in the laboratory and in the field. The Spencer-Parker

(1) Spencer, R. R. and Parker, R. R. Studies on Rocky Mountain Spotted Fever. Hygienic
Laboratory Bulletin No. 154, January, 1930.

10 EIGHTH BIENNIAL REPORT

vaccine has been supplied to the other western states as well as to Montana.
The Board of Entomology and the representatives of the Public Health Service
have had frequent conferences, and throughout the history of the cooperation
there lias been the freest possible exchange of ideas.

It is only natural that this branch of a Government Institution should
engage to some extent in other lines of work closely related to the spotted
fever problem and even more natural and necessary that work should be done
an other states as well as in Montana. The whole project has grown greatly in
recent years, and the Montana Laboratory has quite unavoidably become the
headqujirtors for the Government work on Eocky Mountain Spotted Fever and
other tiek-borne diseases in the Western United States.

While on duty in these studies in Montana the following became accident-
ally infected Avith Rocky Mountain Spotted Fever and made the supreme
sacrifice :

Doctor Thomas B. McClintic

Doctor Arthur H. McCray

William E. Gittinger

George H. Cowan

LeRoy Kerlee

All of these excepting Kerlee died before the Spencer-Parker vaccine was dis-
covered. Since tlie days of vaccination there have been at the Hamilton Lab-
oratory eight vaccinated cases of spotted fever contracted by accident, which
have recovered. Before the days of vaccination all laboratory cases died. In
addition to these must be mentioned eleven laboratory cases of tularaemia, all
of which recovered.

And yet the work goes on.

What shall we say of the some twenty-five workers who, fully appreciating
the dangers incident to the daily routine, still continue at a rate of compen-
sation not higher than the gain in other kinds of work in which these dangers
are lacking. We may say, at least, that idealism and the spirit of sacrifice for
the general good have not died out.

STATE BOARD OF EXTOMOI.OGY 11

ORGANIZATION AND PERSONNEL

THE STATE BOARD OF ENTOMOLOGY

Doctor W. F. Cogswell, Secretary, State Board of Health, Helena, Chairman.
Doctor W. J. Butler, State Veterinary Surgeon, Helena.

Professor E. A. Cooley, State Entomologist, Bozeman, Secretary, and in Charge
of Tick Parasite work.

Staff of the Board of Entomology

Hamilton, Montana
Mr. F. J. O'Donncll, Field Agent.
Mr. Glen M. Kohls, Assistant Entomologist.
Mr. Fred A. Morton, Assistant Entomologist.

(For a period of 3 months in 1930.)
^Ir. Harley Sargent, Field Assistant.
Mr. Nick Kramis, Laboratory Attendant.
Mr. Carl Larson, Laboratory Attendant.

(For a period of 3 months in 1930.)
Miss Marie W. Symington, Clerk.
Mr. P, M. Gillis, Janitor.

Field Crews on Rodent Control in 1930

Mr. F. P. Mcrritt, Supervisor.
Mr. Lloyd Merritt, Supervisor.
Mr., E. O. Everson, Supervisor.
Sixteen Field men.

UNITED STATES PUBLIC HEALTH SERVICE

Hamilton, Montana

(As of December, 1930)

Doctor R. R. Parker, Special Expert, Officer in Charge.

Doctor C. B. Philip, Associate Entomologist.

Doctor G. E. Davis, Bacteriologist.

Doctor Herbert Hayward, A. A. Surgeon.

Mr. Wm. M. Jellison, Assistant Bacteriologist (Resigned).

Mr. T. M. Sheehy, Senior Clerk.

Miss Selma C. Helvik, Typist.

Mrs. Ruth Romney, Typist.

Mr. E. W. Malone, Laboratory Assistant.

Mr. A. E. Whitcomb, Laboratory Assistant.

Mr. J. D. Kerlee, Laboratory Assistant.

Mr. F. B. Thrailkill, Field Assistant.

Mr. W. S. Willey, Field Assistant.

Mr. M. L. Nolan, Laboratory Attendant.

Mr. W. T. Smith, Laboratory Attendant.

Mr. P. M. Gillis, Janitor.

In addition to the above there have been employed by the Public Health
Service a number of temporary employees for such special services as Drafts-
man, Meteorological Observer, Seamstress, Field Assistant, Laboratory Assist-
ant and Laboratory Attendant.

12 EIGHTH BIENNIAL REPORT

ROCKY MOUNTAIN SPOTTED FEVER
OUTSIDE OF MONTANA

Eocky Mountain Spotted Fever is not a public health problem of Montana
alone. The same may be said of tularaemia and tick paralysis, a little under-
stood malady generally affecting children, and always ending fatally unless
the tick is found and removed. The wood tick of this region is, in part, re-
sponsible for tularaemia and wholly responsible for tick paralysis. It has been
known for many years that spotted fever is present in other states, notably in
Idaho, Wyoming, Nevada, Oregon, and Utah, but its geographic distribution
and the number of cases were not known. In recent years Doctor R. R. Parker,
of the Public Health Service, has given careful attention to tracing out the
records of cases of Rocky Mountain Spotted Fever in the Western States and
has added very much to our knowledge of this subject. It is evident that in
many localities the disease had existed for many years before its identity was
recognized by practicing physicians. There is evidence also that the disease
has been actually spreading to new areas. We know more about the epidemi-
ology of spotted fever in Montana than in any other state for we have given
extended attention to the subject in this state. Before the year 1914, cases had
been reported only from three endemic areas in Montana, occupying parts of
Ravalli, Missoula, Granite and Carbon counties, two of these areas being close
together in Western Montana and one in an isolated position in Eastern Mon-
tana, across the Continental Divide but continuous Avith infected areas in
Wyoming. In 1914 reports of cases began to come in from all over Montana
and in every year since, the reports have continued until now we have had
cases in 39 of the 56 counties of the state. There is evidence also that the
disease is becoming increasingly virulent in some localities. During 1930 it
was reported that in a certain restricted locality in Idaho which had been
developed as a place for summer camping and recreation, there had been
seven cases and five deaths this year alone. This is to be contrasted with the
previous figures frojn Idaho showing a death rate of only 4.86 per cent (as
computed by Maxey, 1908).

From unpublished work of Doctor Parker, of the United States Public
Health Service, there is reason to believe that Rocky Mountain Spotted Fever
has stepped across the boundary of the territory in which quite a different
tick occurs. This other tick, "The Eastern Dog Tick" (Dennacentor variabilis
Banks), occurs all over the eastern half of the United States, the western limit
of continuous distribution being along a line extending from a point on the
Mexican boundary, a little west of the southern point of Texas, northward to
the Canadian boundary near the state line between Montana and North Dakota.
This tick is also found in California and southern Oregon. If the disease has
established itself in the Eastern Dog Tick and if it continues to spread east-
ward it may, unless stopped, eventually involve some, at least, of the more
densely populated eastern and southern United States.

STATE BOARD OF ENTOMOLOGY 13

PROPOSAL TO SURRENDER THE BOARD'S RESEARCH WORK
TO THE UNITED STATES GOVERNMENT

Under authority from the State of Montana, the three members of the
State Board of Entomology attended the meeting of the "Western Branch of
the American Public Health Association held in Salt Lake in June, 1930. It
had become apparent that while for many years the State of Montana had
been engaged in studies on Eocky Mountain Spotted Fever and had expended
some $300,000, the time had arrived when the other states in the Western
United States should take an active part in the studies and particularly in the
use of tick parasites. The board had no very definite progi-am in mind at this
time but it did suggest to the meeting that a Eocky Mountain Spotted Fever
Committee be named. Accordingly, the following committee was constituted:

Doctor Wm. C. Hassler, President, Western Branch, American Public
Health Association.

Doctor F. W. Almond, Idaho, State Health Advisor.

Doctor Albert B. Tonkin, Wyoming, President State Board of Health.

Doctor A. U. Simpson, Washington, Epidemiologist, State Board of Health.

Doctor W. F. Cogswell, Montana, Secretary State Board of Health.

Doctor W. M. Dickie, California, Secretary State Board of Health.

Doctor E. J. Stroud, Arizona, Secretary State Board of Health.

At a meeting of the Board of Entomology held at Hamilton on August 6,
1930, further attention to the general welfare of the work was given. It was
apparent that Eocky Mountain Spotted Fever is spreading and is not a local
problem affecting Montana alone, and that the expense of maintaining the
work has become a burden to Montana. It was further apparent that it was
only natural to turn the research program over to the United States Govern-
ment. Accordingly, the following resolutions were unanimously adopted :

Whereas, The State of Montana took the initiative in the serious study of
Eocky Mountain Spotted Fever and has erected a Laboratory especially de-
signed for the study of this and other tick-borne diseases and has expended
approximately three hundred thousand dollars in these studies, and

Whereas, With the growth and development of the work the problem has
become an interstate problem affecting at least thirteen states (Washington,
Oregon, Idaho, California, Nevada, Montana, North Dakota, South Dakota,
Nebraska, Wyoming, Colorado, Utah and New Mexico), and

Whereas, The other affected states, in the past, depended on Montana
and have not expended funds in researches in Eocky Mountain Sjjotted Fever
and, while recognizing the desirability of centralizing the work at some one
headquarters, it would be impossible for the several states to expend funds
outside their own boundaries and erect a centralizing agency of their own, and

Whereas, The United States Public Health Service, beginning in 1903
and continuing to the present time, and more especially in recent years, has
made very valuable contributions to our knowledge of Eocky Mountain Spotted
Fever and other tick-borne infections, and

Whereas, The United States Public Health Service has originated and is
now manufacturing an effective vaccine for Eocky Mountain Spotted Fever,
the demand for which is very rapidly increasing in the several affected states,
and

Whereas, This vaccine is the only vaccine in the world made from ticks
or insects, and because of the peculiar and special circumstances can never
be made by any of the large biological houses, and

Whereas, The United States Public Health Service, in view of all the
circumstances, is the logical centralizing agency for the future conduct and

14 EIGHTH BIENNIAL, REPORT

developing of the research work in Rocky Mountain Spotted Fever and other
tick-borne diseases in the several states in the West which are concerned in this
problem, now

Therefore, Be It Resolved that the Montana State Board of Entomology
unanimously recommends to the Surgeon General of the United States Public
Health Service:

1. That the Service establish a branch laboratory in Montana for continu-
ing the researches on Rocky Mountain Spotted Fever and for such
other purposes as they may think desirable.

2. That they take over from the State of Montana the present laboratory.

3. That they enlarge the present laboratory facilities.

4. That they establish in connection with the laboratory, at some point
on the west side of the Bitter Root River, a field station or experi-
mental farm where larger animals may be infested with ticks and
where infected ticks may be reared for the production of the Spencer-
Parker vaccine.

5. That they take over all the branches of the spotted fever researches,
including the tick parasite work, but not including control work (such
as rodent destruction, dipping of domestic animals, quarantine, etc.).

On September 24, 1930, the Rocky Mountain Spotted Fever committee
mentioned above met with the Board of Entomology at Hamilton and made a
careful study of the research and control work in progress, and discussed the
entire situation. This committee adopted resolutions for later presentation to
the American Public Health Association, as reported below. This committee
also adopted the following resolutions:

Be It Resolved that this committee takes this opportunity to express at
this time the appreciation of our separate states, for the unselfish efforts of
the tax payers of the State of Montana through their law-making bodies and
the Montana State Board of Entomology and the Montana State Board of
Health, in the expenditure of consideral)le money and work in the study and
control of Rocky Mountain Spotted Fever, out of which great benefit has
accrued to our separate states and for which we are, and should be, truly
grateful; and

Be It Further Resolved that this committee expresses its appreciation of
the persistence of the members of the Montana State Board of Entomology
and Montana State Board of Health, over the period of these years in laboring
on this problem in the face of repeated discouragements, for out of this un-
selfish work and devotion to the cause has come much of our progress that
has now been made with regard to the acliievements in control of this disease.

The Chairman and the Secretary of the Board of Entomology were present
at the Annual Meeting of the American Public Health Association held at
Fort Worth, Texas, October 27-30, 1930, for the purpose of further promoting
the plan to turn the work over to the United States Government. A very
ready response was met with from this very large body of health workers from
all over the United States, Canada and Mexico. Some two thousand health
workers were present. The following resolutions presented by the Western
Branch were unanimously adopted:

Whereas, For the past twenty-eight years the State of Montana has been
actively engaged in the study and control of Rocky Mountain Spotted Fever
and other tick-borne diseases at an expenditure of approximately $300,000,
and in 1928 erected a new and modern Laboratory at Hamilton, Montana, at
a cost of $60,000 without financial aid from the other infected States; and

Whereas, The Bureau of the Public Health Service, cooperating with the
State of Montana, lias discovered and is making an effective vaccine from a

STATE BOARD OF ENTOMOLOGY 15

liighly virulent local strain of ticks and with enlarged facilities could increase
the production of this vaccine to meet the growing demand ; and

Whereas, The Montana State Board of Entomology is engaged in the
use of imported tick parasites and believes that the use of such parasites
offers the most practical and most promising method of control of ticks; and

Whereas, The problem of ticks and of the human diseases which they
transmit is not a local one affecting Montana only, but affects as well the
following States: Washington, Oregon, Idaho, Colorado, Wyoming, Utah, Cali-
fornia, and Nevada, and is threatening the adjoining states of North Dakota,
South Dakota, Nebraska and New Mexico, and is a potential menace to all
of the States of the Union ; and

Whereas, The Public Health Service has for many years been engaged in
the study of this group of tick-borne diseases; and

Whereas, It is the expressed desire of the State of Montana that this
work be turned over to the Bureau of the Public Health Service ;

Therefore, Be It Besolved that the Surgeon General of the Bureau of the
Public Health Service be requested to take over and assume full control of
investigations of tick-borne human diseases and of the control of ticks by
parasites ; and

Be It Further Besolved that Congress be requested to pass an Act author-
izing the Bureau of the Public Health Service to take over the Laboratory
located at Hamilton, Montana, and extend the scope of the work as may be
deemed necessary by the Surgeon General of the Public Health Service.

From the foregoing it is evident it is the wish and the recommendation
of the Board of Entomology to turn over the Board's work excepting "con-
trol" and including the tick parasite work, along with the laboratory at
Hamilton owned by the State of Montana, to the National Institute of Health
which was set up by the Ransdell Bill of Congress passed in May, 1930. If an
Act of the Montana Legislature is required, it is recommended that such an
Act be passed.

THE FUTURE OF THE BOARD OF ENTOMOLOGY

It is necessary to consider what is to be the future of the Board of
Entomolog}' in case the United States Government takes over the entire re-
search program. The logical, and in fact the necessary line of division to be
made is between "research" and "control." The further research work on
spotted fever and related subjects and on tick parasites is going to be neces-
sarily expensive and at the same time the results will be applicable at once
iu many other states, and, perhaps to the whole of the United States. The
control work includes the killing of rodents, the dipping of domestic animals,
the control of the movements of domestic animals by State quarantine laws
and otherwise, and such other similar projects as the research program may
bring to light. It is quite possible that the several states may find it necessary
to modify their game laws. All such projects aimed directly at control should
be under state rather than national supervision.

The Montana State Board of Entomology should be continued, provided
this plan carries, though it will not need as large an appropriation as in the
past.

Again, the State of Montana, provided the government does take over the
research and parasite work, will find it to its own advantage to maintain what
may be termed a contact organization for conferences with the government
representatives. The Board of Entomology will serve this purpose in Montana.
Other states may find it desirable to establish such contact organizations.

16 KIGHTH BIENNIAL REPORT

REVIEW OF TICK PARASITE WORK
FOR 1929 AND 1930

By E. A. CooLEY

SUMMARY

The work of the Montana State Board of Entomology in the attempt to
colonize the French Tick Parasite, Ixodipliagus caucurtei DuB., during the
biennium now closing, has been conducted in much the same manner as pre-
viously. Parasites have been used in quantity, and have been liberated in
selected localities in both western and eastern Montana. Experiments and ob-
servations have been made to determine if the parasites are surviving our
severe winters and attacking the wood tick. Other studies have been made in
the field and in the laboratory intended to make the parasite f)roject more
effective, and to determine if the parasites are capable of carrying diseases
from tick to tick.

QUANTITY REARING OF PARASITES AND TICKS

The rearing of parasites has been continued, the same methods being used
as reported in the Seventh Biennial Eeport (see p. 32, "Quantity Production
of Tick Parasites," by Fred A. Morton). The numbers of parasites have been
greatly increased, however, and it is planned that the annual production in
1931 will be increased at least three-fold.

In order to grow the parasites it is first necessary to grow the ticks on
which, or in which to feed them, and since it is essential that only non-infected
ticks be used, it is necessary to take great pains that the tick stocks shall not
become infected viath any disease. Formerly we bought fully fed female ticks
from farmers living in regions of the state supposed to be free of both spotted
fever and tularaemia. Some infection crept in, however, making it necessary
to discard a considerable portion of the stocks and since that time the complete
work of rearing the ticks has been done in the laboratory. The unfed, ' ' flat, ' '
adult ticks are fed on rabbits and the fully engorged females are recovered
and stored in one of the thermal cabinets at a temperature of 38 to 45 degrees
F. Mr. Kolils has found that the fed females can be stored without loss, thus
making it possible to do this part of the year's routine at a time when other
work is less pressing. A remarkable development is the skill with which Mr.
Kohls and Mr. Morton are able to hold living stocks of both ticks and para-
sites in all stages in the thermal cabinets.

In another part of this Eeport will be found a paper by Mr. Kohls, de-
tailing the parasite liberation.

Recovery of Parasites from Nature

It is of mucli importance to know whether the parasites which have been
li1)erated have attacked the wood tick in nature. During the season of 1929,
without making any extended effort to get information on this point, some
living ground squirrels and chipmunks were captured in a parasite liberation
area, taken to the laboratory and held in cages until the attached ticks had

STATE BOARD OF ENTOMOLOGY 17

completed their feeding. In some of the ticks, parasites developed showing
that they had survived the winter and attacked the ticks.

In the season of 1930 ground squirrels and chipmunks were captured in
the Lick Creek area but instead of taking them to the laboratory they were
held in cages in an improvised rearing room in a tent in the field. When the
ticks had completed feeding and were recovered, they were taken to the
laboratory and held under observation. A total of 133 rodents were trapped in
the Lick Creek area and these yielded 199 nymphae. The trapping was done
from June 10 to July 30, which embraces a considerable portion of the season
for active nymphae.

It is necessary to report that no parasites were recovered in 1930. The
failure to demonstrate the presence of parasites in the Lick Creek area in 1930,
on first thought, may be taken to mean either that the preceding winter had
killed off the hibernating insects or that the parasites are not attacking the
tick in a state of nature. Either of these may be true, of course, but it is yet
too early to draw any conclusions. As related above, parasites were recovered
the year before but we now consider that finding to be a piece of rare good
fortune. The question is of the greatest interest, and for this reason some
other facts should be mentioned.

It is entirely possible that the parasites are present in a living condition
but that we have failed to recover them merely because they have dispersed
so rapidly that capturing a few animals within the liberation area could
scarcely be expected to yield any of them. We have placed out overwintering
experiments in both eastern and western Montana every winter since we began
the parasite program and have found a percentage of the parasites alive each
spring in both ends of the state. Furthermore, we are using as stock, parasites
that have been reared from such parasites as have survived one or more
winters in the out-of-doors. It is a well known fact that immediately following
the introduction of a new insect, the numbers present are so small as to
easily escape detection. Tlie speed with which an introduced parasite can
multiply to numbers sufficient to overcome the host insect, or to be detected,
will depend on many factors. Some of these are the following: (1) the rapidity
with which the parasites are able to multiply and overtake the host; (2) the
rapidity with which the host can multiply and so escape being overcome; (3)
the correlation between the habits or seasonal histories of the parasite and the
host; (4) the rate of dispersal of the parasites; and (5) the climate.

Rate of Multiplication of Parasites

It has not been possible to obtain as yet any reliable information on the
rate of increase of the parasites in nature. All such studies on this parasite
are expensive and the results elusive.

To obtain information on the ratio between males and females in the
parasites, the computations shown below were made.

P^r^i^f Per Cent

<-ounted Males Females Females

173 65 108 62.5

216 75 141 65.3

276 83 193 70.0

320 9.5 225 70.4

Average 318 667 67.0

It is thus shown that the females predominate in the ratio of 67 to 33.

18 EIGHTH BIENNIAL REPORT

Experiments were eouducted by Mr. Kohls for the purpose of determining
the number of offspring of one parasite under laboratory conditions. Female
parasites were placed in tubes with unfed nymphae and allowed to remain for
twenty-four hours. The nymphae were then caged in rabbits' ears to prevent
loss of ticks and when recovered were watched for parasitism. The results of
tliis experiment are tabulated below.

Parasitized

Total

A

verage

Number of

Lot

Females

Nymphs

Parasites

Parasites

Nymphs

Per Cent

No.

Used

Obtained

Obtained

Pel

• Nymph

Fed

Parasitized

1

1

7

32

4.5

73

9.5

2

1

2

14

7.0

81

2.4

3

1

14

90

6.4

79

17.7

4

2

3

18

6.0

21

14.2

5

2

19

132

6.9

49

38.7

It will be observed that the numbers of offspring produced by individual
females is not large but it must be borne in mind that the conditions of the
experiment are wholly artificial. The parasites were exposed to flat nymphae
in a tube instead of to feeding nymphae on a host animal. It is doubtful if
it will be possible ever to get truly reliable data on the potential rate of
increase, though the actual rate of increase may be approximated by trapping
animals in nature and determining the percentage of parasitized ticks. Even
these results will be influenced by the high rate of dispersal discussed below.

In this connection it should be mentioned that even when, in the labora-
tory, the parasites are confined in bags with the ticks feeding on ral)l)its or
other animals, a large number of ticks escape being parasitized. In the table
above it will be seen that the per cent parasitized ranged from 2.4 to 38.7.
Again it is to be remembered that the conditions are unnatural and we cannot
say what the rate would be in a state of nature. The present writer had
previously crushed the ovaries under a microscope and shown that the number
of eggs is enormous. It was quite impossible to count them.

Rate of Multiplication of the Tick

The factors influencing the multiplication of ticks are very complex and
cannot be discussed at length in this place. In such a locality as the mountains
surrounding the Bitter Eoot Valley where the ticks have been present for a
great many years, probably since long before white man arrived, and have
had opportunity to increase to their maximum numbers, it may be said that
a. state of balance has been reached. In such a state there is a certain unknown
average rate of tick poi)ulatiou per square mile. Through the years, while
there are more ticks in some seasons than in others, it may be said that there
are so many ticks per square mile, and the numbers have an average constant.
To one who has given attention to the wood tick, it is easily understood that
there must be very powerful factors at work which tend to kill off the ticks in
tlie course of their development from the egg stage to the adult stage. Many
are killed by heat, cold, desiccation and by failure to find a host. The same
is true in a large measure of all ticks. Through natural selection ticks have
adapted themselves for survival by producing a large numljer of eggs. More
must make the start since the chances are so small that any one individual
making the start will ever reach maturity and reproduce. The eggs from five
females recently counted showed numbers to be 5196, 6820, 8574, 7971, and
3361. The average of these five counts is 6384.5 which may be taken as repre-

STATE BOARD OF ENTOMOLOGY 19

senting approximately the offspring of one pair of ticks. A count of both
male and female ticks in a mixed lot of 1118 ticks showed that there were
558 males and 560 females. We may therefore reason that in a balanced state
such as is mentioned above, the chances are as 1 to 3192.25 that any one
egg laid will ever reach the adult condition and reproduce.

If ticks are introduced into a new locality it will take time for them to
reach their maximum abundance or establish a balance. Similarly, if parasites
are liberated in a balanced tick community, the balance is upset. It is
readily seen that the rate of multiplication of the ticks in a balanced com-
munity will be different from that in an unbalanced one, and that the rate
at which the parasite population will overtake the tick population will be
affected. In a balanced community of ticks where parasites tend to reduce
the numbers of ticks, the ticks will tend both to increase because of greater
natural opportunity to multiply, and to decrease because decimated by the
parasites, and the speed with which the parasites can overtake the ticks will
depend upon their relative powers of multiplication.

Correlation of Habits

One of the factors affecting the rate of multiplication of tlie parasite is
the correlation between the habits, or seasonal histories, of the ticks and of
the parasites. We have shown that the adult parasites will lay their eggs in
both larval and nymphal ticks as they are feeding on their host animals. It
would be desirable that the adult parasites appear in their maximum numbers
at the same season of the year when the appropriate stages of the tick aj-e
out in greatest abundance. We are accumulating information on these points
in different parts of the state, and cannot state at the present time how
favorable the correlation factor will be.

Rate of Dispersion of Parasites

Quite naturally the parasites tend to scatter or disperse from the locality
in which they are at first planted. This will affect them favorably as regards
their rate of multiplication, for by scattering they may increase their food
supply. This same dispersion, however, will tend to prolong the time required
for the numbers of the parasites to overtake the numbers of the ticks in the
locality where the parasites are first planted. The parasites will tend to dis-
perse more rapidly because the ticks on which they feed are carried on the
hosts of the ticks (rodents chiefly) and will naturally tend to scatter as far
as the animals may go in their ordinary movements and migrations.

Influence of Climate

The climate of Montana has a bearing on the probability of success with
the tick parasites, not only as affecting the survival of the hibernating insects
in the winter but as governing the number of generations of the parasites
that may take place in one season.

Tests to determine if the parasites can survive our winters have been
made each year since the work on parasites was started in 1926. These tests
have been made in western, central and eastern Montana, and it has been
found that a large percentage of the parasites survive our winters.

A considerable amount of work has been done to determine the responses
of both the tick in various stages and the pai-asite, to controlled temperature

20

EIGHTH BIEXNIAL REPORT

Figure 1. Circles show where Ixodiphagus and Hunterellvs have been
found in the world. Squares show where attempts have been made to colonize
Ixodiphagus caucurtei DuB.

STATE BOARD OF ENTOMOLOGY 21

in thermal cabinets. The detailed results will be published at another time. We
have shown that at optimum temperatures of approximately 21 degrees C. the
parasites will pass through the cycle from the egg to the adult in about 45
days. It has been shown further that colder temperature retards development
greatly. This has been shown both in thermal cabinet tests and field tests.
In field tests, parasites placed out in nature from May 14 to July 2, or over
a period of 49 days, produced adults emerging during a period of 16 days
from August 13 to August 29. Those placed out May 14 produced adults in
91 days, while those placed out July 2 produced adults in 55 days. It is thus
apparent that the summer temperatures in the Bitter Eoot Valley are not
far from optimum but that those of the spring months are far below optimum.
As nearly as we can determine at the present time, we may expect one genera-
tion of parasites in Montana's climate under ordinary circumstances, though
in exceptional seasons there may be two generations.

It is highly desirable to determine the effects of such climates as those
of southern Idaho and Utah.

The accompanying map of the world will indicate by circles all of tlie
localities where parasites of the genus Ixodiphagus have been collected. The
squares indicate where attempts have been made to establish the parasite
artificially. It will be seen that Ixodiphagus has been taken in a wide range
of climates.

Parasitism of Larvae and Nymphae Compared

It has been shown elsewhere<i) that the adult parasites lay their eggs in
engorged larvae as well as in engorging nymphae. Further information on
this subject was obtained through experiments conducted at the Hamilton
laboratory. The work of rearing was done by Mr. Glen M. Kohls.

On February 3, 1930, four rabbits were infested with larvae of D. arider-
soni Stiles and on February 5 the same four animals were infested with
nymphae. Adult parasites were released on the animals on February 6, at
room temperature, and each animal was tied in a separate "infesting bag"
of muslin, 12 by 18 inches. The animals were kept in these bags for 24 hours
after the parasites had been released.

There were recovered 7000 fed larvae and 980 fed nymphae from these
four rabbits. The fed nymphae were held at 22 degrees C. and watched for
development of parasites. By March 11, the parasitized nymphae could all be
detected and it was determined that the fed nymphae were 80.9 per cent
parasitized.

The fed larvae were held at 22 degrees C. for a period of two months
beginning February 8, when they were placed in a "longevity tube" in the
tick yard out-of-doors. On June 13, about four months after the date of
parasitizing, the resulting flat nymphae were placed on a rabbit for feeding.
There were recovered after feeding 212 engorged nymphae which were placed
at 22 degrees C. to allow the parasites to mature. On July 24, 126 parasitized
nymphae, or 59.4 per cent of the fed nymphae, were recovered. It should be
noted that it is possible that the long holding of the nymphae may have
reduced the percentage of ticks in which the parasites matured. However, it
was desired to introduce this condition into the experiment because nymphae
normally pass the winter before obtaining their next feed.

<1) Cooley, R. A. and Kohls, G. M. Science, p. 656, 1928.

22 KIGHTH BIENXIAT^ REPORT

Thus, under these laboratoiy conditions there were recovered of ticks
parasitized as larvae, 59.4 per cent and of ticks parasitized as nymphae, 80.9
per cent.

The previous paper had shown not only that the parasites will lay eggs
on fed larvae, but that the resulting flat nymphae could be held for mouths,
after which the parasites would develop if the nymphae were allowed to feed.
These later results indicated that parasites in the presence of both larvae and
nymphae will lay eggs iu both. These findings are of much interest and may
be of much practical importance. The tick passes the winter in both the
nymphal and adult condition. It is possible that in a state of nature the
parasites will lay eggs in lioth larvae and nymphae, and if so, this greatly
increases our chances for the parasite to pass the winter successfully. There
are involved in the problem, among other things, the following questions: (1)
In this northern climate will the parasites pass the winter in sufficient numbers
to maintain a progressive advance in population? (2) Will the adult parasites,
in a state of nature, be alnoad and ready to lay eggs when the ticks in the
proper stages are available? The advantage of having the parasites lay eggs
in both larvae and nymphae ticks is apparent when we remember that the flat
nymphs are a normal stage for passing the winter and realize that this will
insure a brood of parasites to start in their active development as soon as the
parasitized flat nymphae Ijegin to feed.

It is of much interest also to report that Mr. Morton has found that in
laboratory experiments the parasites will attack the Eabbit Tick, Hoemaphy-
salis leporis-palustris Pack. This is a fairly common species in Montana as
well as in most of the United States. We believe this to be to our advantage
for the habits of the rabbit tick are different from those of the wood tick,
and the parasites Avill bo given an added opportunity to lay eggs.

The Possibility of Transmitting Tick-Borne Diseases by
Tick Parasites

Early in the work with tick parasites the possibility was foreseen that
the parasites might contract the organisms of spotted fever or tularaemia
and pass them on from tick to tick. The possibility is, of course, remote, Init
in view of its importance careful attention has been given to the point.

It is known that infected nymphs occur in nature and such nymphs run
as great a chance of becoming parasitized as any others. It is of interest to
know whether parasites maturing in infected nymphs are capable of transmit-
ting a living virus to ticks that they later parasitize. The parasitized nymph
will die but there exists the possibility that the parasitized nymph, if infected
by the egg of the parasite, may infect the rodent before it dies from the
parasite, and so pass on the disease to the rodent which, in turn might infect
other ticks.

With the assistance of Doctor B. E. Parker experiments were outlined to
determine if such transmission of spotted fever or tularaemia was possible,
and Mr. Kohls was asked to carry out the experiments. The experiments with
tularaemia have been completed and indicate clearly that there is no danger
of transmitting or spreading this disease through the agency of the parasites.
The experiments with spotted fever were begun in December, 1929, but they
failed in each instance because of an inability at the time to get a supply of
nymphae in which the infection could be positively demonstrated, and because

STATE BOARD OF ENTOMOLOGY. 23

also of an intercurrent infection in the guinea pigs, making it impossible to
reliably interpret the results. These experiments will be resumed at a latter
time, and when completed will be published in detail along with those on
tularaemia.

It should be added that because of the remote possibility of spreading
spotted fever by the parasites, the Board of Entomology is using only such
methods of parasite liberation as are absolutely safe. It is desirable to use
other methods of liberation as soon as it can be demonstrated that they are
equally safe.

TICK PARASITES IN AFRICA

The Secretary of the Board of Entomology went to Africa in March, 1928,
for the purpose of searching for new parasites of ticks. A report on the work
in Africa was prepared as far as possible immediately on returning in March,
1929, but the completion of the report has been delayed until the some 750
different lots of ticks can be identified by a specialist. The ticks were sent
to a world authority on ticks but on account of the large number to be studied
and because of some perplexing questions of identity which came up in the
course of the studies, it has been impossible for this specialist to make his
report. As soon as the identifications are received, the report on the African
studies will be completed and published.

It is unwise to attempt even to summarize the results of the African
venture now because the findings will be influenced by the tick identifications.
We may, however, in the briefest way, state the following:

Ixodiphagus was rediscovered near Pretoria, Transvaal, and for the first
time we had an opportunity to study the activities of a colony of these para-
sites attacking a tick (Hyalomma aegytium Linn.) in a state of nature. Some
new facts were obtained. Some other species of ticks collected in the im-
mediate vicinity were not parasitized.

A few days after I sailed from Durban, having completed my work in
South Africa, Doctor G. A. H. Bedford, Entomologist in the Division of
Veterinary Services of the Department of Agriculture, of the Union of South
Africa, discovered two living specimens of a species of chalcid in a bag in
which he had held a hedgehog for the purpose of feeding ticks. In a letter
dated November 2, 1930, Doctor Bedford, in writing of this incident, stated:

"I found the specimens at Onderstepoort in a cage in which I had a
hedgehog infested with Haemaphysalis cooleyi, on November G, 1928. The cage
was enclosed in a bag witli a small opening at the side, and the parasites were
found on the sides of the bag. At first I thought they might be parasites of
a larva feeding on green forage, but when I remembered that the hedgehog
was only fed on bread and milk I immediately came to the conclusion that
they were probably tick parasites. The day I collected the specimens I placed
them in n tube with one nymph of 77. leachi and one engorged female of
B. evertsi. The following day, on the 7th, one male was found dead. Each
morning of the 8th, 9th and 10th, the female parasite was observed ovipositing
in the female E. evertsi. On the 10th the parasite was transferred to another
tube containing one female 0. moubata, 3 engorged females E. evertsi, one
engorged female B. decoloratus and one engorged female A. liehraeum. The
parasite was not observed to lay eggs in any of these ticks and died on the
12th. -The female E. evertsi in which the eggs were laid, looked very sick for
a long time, Init eventually recovered and laid a normal number of eggs. The
other adults Inid normally and showed no signs of infection. The nymph of
H. leachi was placed on a rabbit to feed and was lost. The parasite did not
appear to be at all interested in this tick,"

24 EIGHTH BIENNIAL, REPORT

The specimens received from Doctor Bedford were sent to Mr. A. B.
Gahan, of the United States National Museum, who determined them as
Mormoniella vitripennis (Walker). This insect is a common parasite of blow-
flies, which it attacks apparently in the pupa stage. It appears that the insects
captured by Doctor Bedford are not a tick parasite at all, though it is difficult
to explain their association with the hedgehog, and also that when the female
was confined with ticks she repeatedly inserted her ovipositor in a tick.

In a letter from Doctor Bedford dated June 10, 1929, the following state-
ment was made:

"Dr. Kobinson, Cooper's Parasitologist, came out from England a short
time ago and spent several days with me at Onderstepoort. He informed me
that several years ago he received some engorged females of the bont tick
(Amblyomma hehraeum) from the Cape Province, and that chalcids had
hatched from some of them when he received them. He sent some of the chal-
cids to the British Museum to be identified, but they were unable to do so.
I showed him some chalcids, and he said that they were much larger than
Ixodiphagus caucurtel and were slightly larger than the new parasite I found,
also of a different color. He has promised to send me some si^ecimens when
he returns to England. There is no use in my trying to get any specimens
now as the bout tick is only found here during the summer months. In two
or three months ' time I will write to Veterinary Officers in the Cape and ask
them to send me all the engorged females of A. hehraeum they can collect."

A letter was addressed to Doctor Eobinson in England for the purpose of
getting further information on this very important subject, and the following
reply was received:

"THE COOPER TECHNICAL BUREAU

(Affiliated with Cooper, MacDonald & Robertson, Ltd.)

47, Russell Square, London, W.C.T.
11th November, 1930.
Dr. R. A. Cooley,

State of Montana Board of Entomology
Bitter Root Valley Field Station,
Bozeman, Montana. U.S.A.
Dear Sir:

I beg to acknowledge the receipt of your letter dated the 31st October,
1930.

I regret to say that I have not been able to find the single example of the
fly which was derived from parasitized specimens of Amblyomma hehraeum.
The material in question was collected at Gonubie Park, East London, South
Africa, in 1909, by W. F. Cooper. The fly, a small chalcid, was sent to the
British Museum (Natural History) for determination, but, to the best of my
recollection was returned to Mr. Cooper with the observation that it was an
undescribed species. Nothing further was done about the matter.

On making a search for the specimen of the fly, I came across a tube
containing the dried and shrivelled remains of parasitized examples of
Amblyomma hehraeum (females) which I am sending to you. If I can find
the fly, I will send that to you also.

I am very sorry that I have not been able to be more helpful to you.
Yours very faithfully,
LER/KK (Signed) L. E. Robinson."

From the foregoing it appears to be clearly evident that there is a para-
site of adult ticks in South Africa which attacks Amblyomma hehraeum. The

STATE BOARD OF EXTOMOLOGY 25

specimens of old dead ticks received from Doctor Eobiuson, along with his
letter, were carefully examined in the hope that there might be found some
fragments of chalcids among them, or that there might be dead specimens in
some of the ticks. This search resulted in nothing of value.

While in camp some thirty miles from Pretoria, South Africa, on Septem-
ber 1, 1928, in examining hares which were shot after dark the day previous,
a small Hymenopterous insect was seen. In opening the ear of a hare this
insect ran to the edge of the ear and flew immediately. I had only a very
hasty view of the insect and cannot say positively, but believe that it belonged
to the family Chalcididae. The insect came from a hare which was one of two
tied in a bag the night before. It undoubtedly was on one of the hares when
bagged. A sketch of the insect was made from memory immediately. In the
same ear was one well engorged nymph and two other partly engorged
nymphae of Hyalomma aegyptium Linn. These ticks were kept alone and
watched but no parasites developed. It should be stated, however, that if the
one resulting adult tick had been allowed to feed, it is possible that parasites
might have been found but I did not have the facilities for this experiment.
Realizing the possible importance of the observation, a special effort was made
to capture some of the same insects again. Special cages were made and
laboratory rabbits were infested with ticks of a common species ( Bhipicephalus
appendiculalus Newn.) in the nymphal stage and placed one each in six cages,
which were planted in the locality where the one supposed parasite specimen
had been taken. These rabbits were left out and visited twice daily for three
days and then taken to the laboratory in town. The ticks were recovered as
they dropped but no parasites were discovered.

26 VJGHTU BIENNIAL REPORT

A SUMMARY OF PARASITE LIBERATIONS

By

Glen M. Kohls, Assistant Entomologist, Montana State Board of Entomology

This paper summarizes all liberations of the French tick parasite,
Ixodiphagus caucurtei du Buysson, by the State Board of Entomology from
1927 to 1930, in an attempt to control the Eocky Mountain Spotted Fever tick,
Dermacentor andersoni Stiles.

In the selection of regions for parasite liberation the Board has received
aid from a number of sources. For particular assistance an expression of grati-
tude is due to Doctor E. E. Parker, Special Expert, U. S. Public Health
Service, for his advice and counsel on various phases of the work and to
Doctor A. F. Baldwin of Miles City and Doctor N. B. Smith of Billings, rep-
resentatives of the State Livestock Sanitary Board, who were ready at all
times to render assistance to the work in Eastern Montana in every possible
way. Mr. F. A. Morton, under the direction of Professor E. A. Cooley, spent
the summer months of 1929 and 1930 studying tick and rodent host popula-
tions in Eastern Montana in regard to parasite liberations and secured much
information of value to the work in the future.

The methods which may lie used in parasite Ulceration are briefly as
follows :

(a) Adult parasites for liberation are reared to maturity in the labor-
atory. Upon emergence from the nymphs in which they developed, the parasites
are collected in cotton stoppered glass tubes and transported to the field in
cold thermos jars. At the site selected for planting, the parasites are released
from the glass tubes, and they immediately begin to search for ticks in which
to lay their eggs.

(b) Native rodents are captured in regions in which tick-borne disease
is not known to exist and brought alive to the laboratory. Here they are in-
fested with nymphal ticks. Parasites are allowed to attack the feeding ticks,
and before the ticks have fed to repletion and dropped, the animals are taken
to the field and liberated in the region where colonization of the parasite is
desired. This method is the most "natural" means of parasite colonization,
and when the areas of liberation are not too distant from the laboratory to
render impractical the transi^ort of animals, its use effects an economy in time
and labor. The disadvantage of the method is the fact that all of the ticks
feeding on the animals are not parasitized and killed. Some will develop into
adult ticks which will be planted among the parasites. If any of the laboratory
ticks are infected, this method of parasite liberation may be a means of
introducing the infection in nature in regions where it had not previously
existed, though the possibility is exceedingly small.

(c) Engorged nymphs containing parasites in the egg, larval or pupal
stage are placed either in closed wire gauze tubes or in glass tubes open at
both ends over which wire gauze is attached. The mesli in the wire gauze is
large enough to permit the escape of the parasites yet retain any ticks that
might have escaped parasitism. These tubes containing the parasitized nymphs

STATE BOARD OF ENTOMOLOGY 27

are taken to the field and placed in mice and rat runs and in and around the
runs and nests of other rodents that might harbor stages of the ticks attacked
by the parasite. Often times and especially when the liberations are made in
mountain rat habitats, cloth or cotton is attached to the tubes to attract the
animals and have them carry the tubes to their nests.

(d) In some regions, more especially in Eastern Montana, where in view
of the hot dry weather parasites might fail to emerge due to desiccation of
the uymphal shell of the tick, engorged nymphs are often placed in a device
that maintains more than atmospheric humidity in the immediate vicinity of
the nymphs. Glass tubes are drawn out so that a bore of about 1 mm. remains
in one end, the other end being cotton plugged. The plugged end is inserted
into a cork which is fitted on a l"x5" shell vial filled with water. The para-
sitized nymphs are put into the glass tube and are thus submitted to a certain
humidity as the water evaporates and passes through the chamber of the tube
containing the nymphs. Parasites emerging from the nymphs escape through
the small opening at the upper end of the tube.

(e) Nymphs containing parasites in the egg, larval or pupal stage are
scattered broadcast around ground squirrel holes, mice holes, pack rat homes,
in thickets inhabited by rabbits and other likely places Avhere emerging para-
sites would have opportunity to find ticks.

Map 2 shows the general regions in whicli parasite plantings have been
made.

For convenience in reference, parasite liberations are placed in two
groups which refer roughly to the regions of liberation. Liberations that
were made in the Bitter Eoot Valley or immediate vicinity and at Helena are
termed Western Montana liberations. Those made elsewhere are termed Eastern
Montana liberations. Western Montana liberations include the areas of O'Brien
Creek, Lolo Canyon, Sheafman Creek, Blodgett Canyon, Roaring Lion Canyon,
Lick Creek, and Lake Como on the west side of the Bitter Eoot Valley, Willow
Creek on the east side and Helena. Eastern Montana liberations include those
made at or near Bozeman, Edgar, Musselshell, Forsyth, Miles City, Jordan
and Selway.

Western Montana Liberations.

O 'Brien Creek Area. The O 'Brien Creek area is located at the extreme
north end of the Bitter Root Valley and about o miles southwest of Missoula.
The sites of parasite liberation flank the road for a distance of about a
mile beginning al:)out a half mile from Graves' Ranch at the upper end of
the road. A number of cases of spotted fever have originated in this area,
and because of its proximity to a large center of population, it is desirable
that parasites be colonized here as soon as possible. Parasites have been
released here in considerable numbers during the past three years.
Tick Parasite Liberations — O'Brien Creek, 193S-1930
June 15, 4,000; June 29, 4,800; July 13, 9,600; October 6, 32,000

Season Total— 1928 50,400

May 14, 8,098; June 4, 24,438; June 27, 22,208; July 9, 38,960;

July 19, 3,440; October 16, 19,110 ,,^„ ,

' ' ' ' ' ' Season Total— 1929 116,254

June 26, 46,500 ; October 30, 38,780

' ' ' ' Season Total— 1930 85,280

GRAND TOTAL 251,934

28

EIGHTH BIENNIAL REPORT

STATE BOARD OF ENTOMOLOGY 29

LoLO Canyon Area. The Lolo Canyon area is located about 15 miles west
of the town of Lolo. The sites of liberation are: (1) near the junction of
Bear Creek with Lolo Creek and (2) near the junction of Graves Creek with
Lolo Creek. Lolo Canyon has long been known as an infected region and a
number of cases of spotted fever have originated here. Although the resident
population is scant, a large number of people travel through this region to
Lolo Hot Springs, and if it were not for the potential danger of ticks, this
section of the country undoubtedly would become a favorite recreation ground.

Tick Parasite Liberations — Lolo Canyon, 192S-1930
October 6, 30,000

Season Total— 1928 30,000

tober 16,

July 4, 19,000; October 30, 28,980

June 4, 27,313; July 3, 12,400; October 16, 15,190

Season Total— 1929 54,903

Season Total— 1930 47,980

GRAND TOTAL 132,883

Sheafman Creek Area. The Sheafman Creek liberation area is located
four miles west and two miles north of the town of Woodside. Few ticks were
found here at the time parasites were liberated. Due to the comparative in-
accessibility of the area only one liberation was made.

Tich Parasite Liberation — Sheafman Creek, 1929

May 31, 13,396

Season and Grand Total 13,396

Blodgett Area. Blodgett Canyon opens into the valley four miles west
and one mile north of Hamilton and extends west about 10 miles to summit of
the Bitter Root Mountains. At a point about three miles from the divide,
the Canyon widens to form a mountain meadow of approximately 10 acres in
area. Here Columbian ground squirrels are found in numbers along with
mice, mountain rats, chipmunks and other rodents. This isolated region with
its abundant and varied rodent fauna, located in the heart of the "tick
country," should prove very favorable area for parasite colonization. One
liberation was made here July 11, 1930.

The region bordering the north rim of the Canyon near its mouth has
been a site of parasite liberation in 1929 and 1930. Mountain goats are
found here during the spring months and probably feed most of the female
ticks dropped in this region. Since a comparatively high percentage of ticks
originating in goat country are infected with Rocky Mountain Spotted Fever,
it is desirable that parasite colonies be established in this area.

A third site of liberation is the territory in the vicinity of the mouth of
the Canyon. It was here that parasites were first released in Montana in
1927. Rodent control work carried on by the Board of Entomology has so
reduced the rodent population at this location that ticks are comparatively not
abundant.

30 EIGHTH BIEXXIAL, REPORT

Tick Parasite Liberations — Blodget 1927-1930
May 1, 500 ; June 20, 1,000 ; June 28, 1,500

Season Total— 1927 3,000

May 22, 250; May 29, 2,680; July 10, 7,200; November, 32,000

Season Total— 1928 42,130

June 1, 14,575; June 8, 7,591; June 29, 18,500; Oct. 22, 14,700

Season Total— 1929 55,366

May 15, 54,200; June 10, 33,660; July 11, 50,400; Oct. 23, 40,000

Season Total— 1930 178,260

GEAND TOTAL 278,756

EoARiNG Lion Area. This area is located in the mouth of Eoaring Lion
Canyon, four miles south and three miles west of Hamilton.

Ticlc Parasite Liberations — Boaring Lion, 1930
June 24, 35,120 ; July 3, 35,000 ; October 28, 38,780

Season and Grand Total 108,900

Lick Creek Area. This area is located one mile south and four miles
west of the Conio post office in the southern portion of the valley. It is quite
isolated and possesses a ground squirrel and tick population above that of
other parasite liberation areas in the Bitter Eoot Valley. Other rodents found
in this area include pine squirrels, chipmunks, mice and mountain rats. These
animals are hosts for the greater portion of the immature tick stages, while
cattle, deer, elk and other large animals that frequent the salt licks provide
hosts for the adult ticks. Of Western Montana areas this area is considered the
most favorable for parasite colonization.

Ticlc Parasite Liberations — Lich Creek, 1928-1930
June 22, 2,400 ; July 20, 4,800 ; October 18, 75,000

Season Total— 1928 82,200

May 28, 10,110; June 7, 4,524; June 25, 10,300; July 16, 37,044;
October 8, 14,700

Season Total— 1929 76,678

June 16, 22,000 ; July 19, 42,000 ; July 1, 28,380 ; July 24, 15,200 ;
October 27, 58,000

Season Total— 1930 165,580

GEAND TOTAL 324,458

Lake Como Area. This area includes the territory immediately south of
the Lick Creek area and extends to the east end of the lake. Due to the fact
that the lake vicinity is becoming a favorite outing place, the eradication
of the ticks, which are quite abundant, is particularly desirable. Parasite
liberations were made in considerable volume in this area in 1928 and 1929.
In 1930 it was felt that tick control measures affording more immediate
results should be employed. Eodent poisoning work was intensified with the
result that rodents became very scare, and it was deemed inadvisable to place
parasites in this area this season.

Tick Parasite Liberations — Lake Como, 1928-1929
May 24, 250; June 7, 4,920; June 22, 1,600; July 6, 2,400;
October 18, 25,000

Season Total — 1928 34,170

May 25, 8,477; June 7, 3,744; July 2, 23,147; July 13, 27,398;
July 23, 2,491 ; October 8, 9,800

Season Total— 1929 75,157

GEAND TOTAL 109,327

STATE BOARD OF ENTOMOLOGY 31

Willow Creek Area. This area is located eight miles east and 2 miles
south of Corvallis ou the east side of the valley. Parasites were planted here
primarily for the purpose of establishing an experimental colony for com-
parison with colonies on the west side of the valley.

Tick Parasite Liberations — Willow Creek, 1930
June 28, 14,400; July 16, 13,600

Season and Grand Total 28,000

Helena Area. Parasites have been released at three sites in the Helena
area, (1) Mount Helena, (2) Nelson Gulch, located about four miles from
Helena on the Priest Pass road, and (3) in the vicinity of an abandoned
mine about one-half mile south of Uuionville. Because this area is apparently
less well adapted to colonization than certain other regions, the number of
parasites released here has been somewhat restricted.

Tick Parasite Liberations — Helena Area, 1928-1930
April 30, 1,400; June 5, 710; October 3, 15,000

Season Total— 1928 17,100

July 1, 3,500

Season Total— 1929 3,500

June 3, 7,800; July 26, 43,960

Season Total— 1930 50,760

GEAND TOTAL 71,360

Eastern Montana Liberations.

BozEMAN Area. This area is situated in and near the mouth of Owl
Canyon, about five miles northeast of Bozeman. Ticks are usually quite abun-
dant and from this standpoint and others, this area is a desirable one for
parasite colonization. However, due to a limited supply of parasites, the
distribution of parasites at this area has been very limited.

Tick Parasite Liberations — Bozeman Area, 1928
Juuc 2, 1,120; June 9, 700; October 2, 14,000

Season and Grand Total 15,820

Edgar Area. This area is located in Box Canyon, about five miles east
of Edgar, and is the most westerly lilieratiou area in the sagebrush country
typical of a large portion of Eastern Montana. This type of country is charac-
terized by sagebrush covered plains or low hills cut through at intervals by
shallow but abrupt canyons. The canyons are often sparsely wooded with
alders and cottonwoods and are dry most of the year, but during the spring
thaw or after heavy rainstorms the run-off carried by the channels may be-
come torrential in character. Erosion is rapid, and rocks that are loosened
from the sides of the canyons and rolled down form refuge for cottontail
rabbits, clnpmuuks and mice. These animals are the principal hosts for im-
mature stages of D. andersoni. The adult ticks are fed by domestic range
animals and by jackrabbits. Parasites have been released in Box Canyon as
shoAvii in the following table:

Tick Parasite Liberations — Edgar Area, 1928-1930
April 22, 336; May 9. 840; May 21, 280; July 16, 644: August
20, 700; September 23, 20,000

Season Total— 1928 22,800

June 6, 3,360; July 2, 5,600; September 21, 19,600

Season Total— 1929 28,560

June 6, 11,000; July 3, 60,000; July 26, 10,000; Sept. 19, 7,000

Season Total— 1930 88,000

GEAND TOTAL 139,360

32 • EIGHTH BIENNIAL REPORT

Forsyth Area. This area is located in the vicinity of the Howard ranch,
about 15 miles south of Forsyth. The site of liberation is around a group of
abandoned farm buildings bordered by a prairie dog town on one side and
by sagebrush covered prairie on the other. Ticks are not numerous here, and
the value of the place as a site for parasite colonization is doubtful.

Ticl- Parasite Liberations — Forsyth Area, 1928-1930
May 28, 210; May 23, 280; July 16, 644; August 20, 700;
September 24, 15,000

Season Total— 1928 16,834

June 6, 3,360; July 1, 3,500; September 18, 19,600

Season Total— 1929 26,460

June 9, 11,000; July 7, 33,600; July 30, 16,400; Sept. 21, 7,000

Season Total— 1030 68,000

GEAND TOTAL 111,294

Miles City Area. This area is located about 18 miles northwest of
Miles City, on the Sunday Creek road in typical sagebrush country. Although
the tick population in the immediate ^'icinity of the site of parasite liberations
is apparently quite scant, the area as a whole is located in a region in which
ticks are quite prevalent on range stock and in which cases of spotted fever
have originated.

Tick Parasite Liberations — Miles City Area, 1928-1930
April 21, 336; May 8, 420; May 23, 140; June 1, 700; June 16,
3,500; July 15, 644; August 24, 700; September 25, 18,000

Season Total— 1928 24,440

June 6, 3,360; July 4, 4,200; September 19, 19,600

Season Total— 1929 27,160

June 16, 32,000; July 10, 101,600; July 30, 17,600; September
21, 7,000

Season Total— 1930 158,200

GEAND TOTAL 209,800

SeIiWay Liberation Area. This area is located near Selway in the

Custer National Forest. The first parasite liberation in this area was made

this year at the request of residents of the district who reported the presence

of ticks in considerable abundance.

TicTc Parasite Liberation — Selway Area, 1930
August 14, 29,600

Season and Grand Total— 1930 29,600

Jordan Area. This area is located near an old shack in an uncultivated

section about three miles west of Jordan. The remoteness of this area from

the other sites of parasite colonization has limited parasite plantings to but

one liberation made in 1928.

Tich Parasite Liberation — Jordan Area, 1928
June 2, 700

Season and Grand Total— 1928 700

Musselshell Area. The Musselshell area represents a type of country
quite different from that of other parasite liberation areas east of Bozeman.
It is located in the Bull Mountains about five miles southeast of the town
of Musselshell. The region is one of low hills of sandstone outcrop, eroded
to form coulees, the edges of which support a conifer growth consisting
chiefly of bull pine. It is in these coulees that ticks are most abundant; the

STATE BOARD OF ENTOMOLOGY

33

principal hosts for the immature stages being chipmunks and cottontail
rabbits. Livestock and jackrabbits serve as hosts for the adult ticks. Eesults
of field studies conducted in 1929 and 1930 indicate the superiority of this
area over other liberation areas in Eastern Montana from the standpoint of
parasite colonization.

Tick Parasite Liberations — Musselshell Area, 1938-1930
May 7, 420 ; May 22, 280 ; June 15, 2,700 ; July 4, 2,532 ; July 16,
644; August 15, 560; August 20, 700; September 26, 40,000

Season Total— 1928
July 6, 3,500 ; September 20, 39,200

Season Total— 1929
June 24, 17,200; June 25, 18,000; July 19, 18,000; July 22,
9,000; September 20, 14,000

Season Total— 1930

GRAND TOTAL

The estimated number of parasites released per year
and Eastern Montana is shown below:

47,836
42,700

76,200

166,736
in both Western

Western
Year Montana

1927 3,000

1928 238,900

1929 391,654

1930 614,000

Eastern
Montana

145,530
128,380
471,760

GRAND TOTAL

Estimated

Total
Parasites

3,000

384,430

520,034

1,085,760

1,993,224

During the 1929 season confined parasitized nymphs were placed in several
liberation areas at the time of the parasite liberations. The confined nymphs
were then e-xaniined at regular intervals throughout the summer in order to
determine the progress of development and the approximate date of emergence
of the parasites in the liberated material. From these observations it was
learned that active engorged parasitized nymphs liberated during the 49 -days
from May 14 to July 2 produced adult parasites that emerged during the
period of 16 days from August 13 to August 29. The number of days required
for the parasites to reach maturity ranged from 91 days for the parasitized
nymphs released on May 14 to 55 days for those released on July 2. These
observations indicate that, because of the more rapid development at summer
temperatures, parasites liberated in the egg stage in active, engorged nymphs
during May, June, and the early part of July tend to attain maturity and
emerge at about tlie same date, i.e. from the middle to the latter part of
August.

Attempts to determine if the parasite has become established in nature
have been made in two liberation areas : Lick Creek in 1929 and 1930 and
O'Brien Creek in 1930. Due to the scarcity of nymph hosts the number of
nymphs secured from the latter named area was too limited to yield data of
significance.

Briefly stated, the methods used in attempting to recover parasites in
nature were as follows : Engorged nymphs from nature were secured by trap-
ping rodents, principally ground squirrels, in the liberation areas and holding
them alive in an improvised rearing room in the field until the ticks that

34 EIGHTH BIENNIAL REPORT

were feeding upon them when captured had completed their engorgement and
dropped. Eodents were secured by trapping rather than shooting for two
reasons: first, the shooting of rodents on a limited area would soon reduce
their population to such an extent that they would be very difficult to secure
in any number and second, the number of nymphs in the engorged state as
required by the parasite for its development is small as compared to the number
in the flat or partially engorged state found on the host animals at any one
time. By taking the animals alive, all the ticks found on them are given an
opi^ortunity to complete their feeding, with the result that the number of
fed nymphs secured from each animal is materially increased. Furthermore,
after the ticks have been recovered, the animals are released back on the
areas so that the rodent abundance is not materially affected.

Rodents that were released were marked with numbered leg bands to
avoid their being retaken before sufficient time had elapsed to permit their
becoming reinfested with ticks in nature. In order to avoid the possibility of
taking nymphs that were parasitized by parasites released that season, para-
site liberation was either Avithheld until the recovery work was completed for
the season, or liberation was confined to immature parasites that would not
attain maturity l^efore that time. Engorged nymphs that were secured were
taken to the laboratory where they were held at 22° C. and observed for signs
of parasitism.

Parasites were first released in the Lick Creek area on June 22, 1928.
Attempts to recover parasites were begun on June 7, 1929, and from that
date to July 23, 1929, 250 engorged nymphs were secured from 108 ground
squirrels. Upon incubation it was found that 14 of the nymphs were parasitized.

In 1930 recovery work began June 10 and was continued until July 30.
A total of 139 rodents were captured yielding 209 engorged nymphs. Six
ground squirrels yielding 10 nymphs were taken in the O 'Brien Creek area.
None of the nymphs were parasitized.

STATE BOARD OF ENTOMOLOGY

35

36 EIGHTH BIENNIAL REPORT

PRESENT STATUS OF THE USE OF PUBLIC HEALTH VACCINE
FOR ROCKY MOUNTAIN SPOTTED FEVER"

By

E. E. Parker, Special Expert, United States Fublic Health Service

The Public Health Service vaccine for the prevention of Eocky Mountain
Spotted Fever has been in use for six years. A brief summary of the first
four years' use was published in the Seventh Biennial Eeport of the Montana
State Board of Entomology*^), and a more detailed account has appeared in a
recent bulletin of the Hygienic Laboratory(3). From the results of a two year
test (1926 and 1927) made in southern Idaho against the mildest type of the
disease and another test against the most virulent type, which had been in
progress for four years in the Bitter Eoot Valley in western Montana, the
following conclusions were expressed, — that against the milder types of infec-
tion the vaccine usually afforded full or nearly full protection, while against
the highly virulent type the degi'ee of protection was usually sufficient to
cause a marked amelioration of the customary very severe symptoms and to
insure the recovery of most cases.

No further test was deemed necessary so far as the mild types were con-
cerned, but additional data seemed desirable in regard to efficacy against the
virulent type. Therefore, complete record keeping in the Bitter Eoot Valley
has been continued and will likely be extended over at least a further two years.
The full six years' data for this valley (1925 to 1930) show that since the
beginning of the test 3,57S persons have been vaccinated, of which nine have
received vaccine 6 times, (i.e., in six different years), 64 five times, 143 four
times, 257 three times, 555 twice, and 2,550 have been vaccinated once. During
this test period 46 persons have become infected with the highly fatal local
strains. Of these, 30 cases Avere in nonvaecinated persons and 16 among those
vaccinated. Of the 30 nonvaecinated cases, 22 died; of the 16 vaccinated only
three. The death rate in the former group was 73.33, in the latter 18.75, thus
showing a marked reduction in mortality in favor of the vaccinated cases.
These six years' data, and the additional opportunity which has been afforded
during the past two years to observe comparatively the clinical course of in-
fection in vaccinated and nonvaecinated persons suggest no reason to modify
the conclusions previously stated regarding the value of the vaccine for use
against highly virulent strains.

Only one authentic case of Eocky Mountain Spotted Fever has been re-
ported in a vaccinated person in the much more extensive areas in which the
milder types of infection predominate. This case occurred in the Idaho test
area in 1927 and has been previously noted. The use of the vaccine against
the milder types has become more and more widespread and the number of

(1) Contribution from the Rocky Mountain Spotted Fever Laboratory of the U. S. Public
Health Service at Hamilton, Montana.

(2) Parker, R. R. Vaccination against Rocky Mountain Spotted Fever. Montana State
Board Ent. ; 7th Bien. Rept., pp. 68-69 ; Jan., 1929.

(3) Parker, R. R. and Spencer, R. R. Studies in Rocky Mountain Spotted Fever. Results
of four years' human vaccination. U. S. Pub. Hlth. Serv. ; Hyg. Lab. Bull. No. 154,
pp. 72-103 ; Jan., 1930.

STATE BOARD OF ENTOMOLOGY 37

persons vaccinated has markedly increased each year. The total now exceeds
16,000. Full protection against mild strains may usually be expected.

The data from the Bitter Eoot Valley test indicate that the duration of
protection in the average individual does not exceed one tick season. The
period varies in individuals, however, and for some may be quite short. Vac-
cination each year, therefore, is desirable.

The vaccine has been employed without apparent benefit in the treatment
of several of the severe Bitter Eoot Valley cases. Similar results have followed
its experimental use in guinea pigs infected with strains from this locality.
In fact, it was not certain that it was not harmful, and these observations
have been interpreted as indicating that the vaccine has no tlierapeutic value.
Its employment as a therapeutic agent, therefore, has not been recommended.
In spite of this, however, a considerable number of physicians have thus used
it, but particularly in sections where the milder types prevail. Some of the
physicians concerned have felt that there was a quite definite favorable result,
with amelioration of symptoms, shortening of the febrile period, and more
rapid convalescence. Nearly all have thought that there was some beneficial
effect. The number of doses, the amount, and the time at which administered
have been arbitrary and variable. For the time being at least, these reports
must certainly be accepted with reservation. At the same time, it should be
stated that drugs which, like the vaccine, have proved valueless or even harmful
when used in cases infected with Bitter Eoot Valley strains, have been em-
ployed with supposed good effect in milder infections, at least there have
been no apparent ill effects. Therefore, it would be unwise to condemn the
vaccine for therapeutic use in milder infections, because of the observations
made in the Bitter Eoot Valley. However, the considerable range of virulence
manifested by cases even in these areas of usually mild infections and the fact
that recovery is usual, no matter what line of treatment is pursued, will make
it exceedingly difficult to draw reliable conclusions, particularly since the
actual number of cases involved is relatively small. Certainly no evidence has
thus far been brought forward to justify a recommendation for its use, and
it is felt that in very severe cases it might prove harmful.

On the other hand, accumulating evidence does appear to justify the
statement that persons who have been tick-bitten could advisedly be vaccinated
as soon thereafter as possible. In case the tick concerned is infected, the data
indicates that such vaccination may result in a considerable modification and
shortening of the course of infection. Physicians are therefore being advised
to bear this point in mind. However, it is far more probable that vaccination
when used under these circumstances will be of most value in areas where the
cases are milder and the incubation period is a week or longer. There is
some evidence of possible value, however, against the more virulent types.

Each year there has been an increasing demand for the vaccine and it
lias been necessary to increase production accordingly. The amount manu-
factured was doubled in 1929 and again in 1930 and it is expected that pro-
duction for 1931 will increase in about the same ratio. It is now being used
in all the Pacific coast and Eocky Mountain states except Arizona, and there
is a moderate demand in South Dakota and Nebraska. The heaviest call is
from Montana, Wyoming, Idaho, and Oregon, the last named state using the
most in 1930.

38 EIGHTH BIENNIAI^ REPORT

Tlie vaccine is prepared solely by the Public Health Service. It is dis-
tributed to physicians without charge and it is expected that only a nominal
charge will be made for administration. Application for same should be
addressed to the Officer in Charge, United States Public Health Service,
Hamilton, Montana.

REVIEW OF DIPPING AND QUARANTINES

By W. J. Butler

In 1913, when the Montana State Board of Entomology was created, one
of the questions that presented itself was ' ' How are we to control the spread
of spotted fever?"

The Board realized that it could not prevent or even retard the movement
of wild animals and wild birds that might be carriers of one or more stages
of the tick Dermacentor andersoni Stiles. It could, however, prevent the move-
ment of domestic livestock out of infested areas. In order to prevent mechanical
carrying of ticks by domestic livestock from dangerously infested tick areas,
the Board established quarantines, restricting the movement of livestock out
of infested areas during the tick season, March 1st to July 15th, unless
dipped under official supervision or the ticks removed by hand picking and
the animals examined and passed upon and released by an official representa-
tive of the Board of Entomology.

The Board also required in addition to rodent control by poisoning, trap-
ping or shooting, that all domestic livestock in quarantine areas would have
to be dipped in an arsenical solution under official supervision for the removal
of ticks at periodical intervals. Dairy cows were exempt from this dipping
provided the owners kept them free from ticks by hand picking or spraying
with an arsenic pine tar solution containing 22/100 of 1% arsenic trioxide.
The board also provided that a close quarantine of all domestic animals in
the quarantine areas including driving horses, mules and oxen be placed upon
animals and premises of all persons who refused or failed to bring their
animals to the vat for dipping or who failed to remove ticks by hand picking
or spraying.

Dipping vats were constructed by the Board of Entomology at strategic
points in the quarantined areas. The dipping solution was made by the
official representative of the Board of Entomology and was kept at proper
standard by chemical tests. The board also employed men to assist in bringing
in and supervising the dipping of domestic livestock in the quarantined areas.

Under the laws of Montana it was a simple matter to restrict the move-
ment of domestic livestock out of any quarantine area. The laws of this state
provide that before cattle or horses may be shipped or trailed out of a county
for sale they must have a brand inspection. Brand inspectors Avere requested
not to issue a brand certificate until the animals had been found free from
ticks. A happy condition exists in the Bitter Koot Valley in that the Brand
Inspector is a veterinarian commissioned as a Deputy State Veterinary Sur-
geon and also as a representative of the Board of Entomologj' for the in-
spection of livestock going out of the quarantined areas.

STATE BOARD OF ENTOMOLOGY 39

I think it safely may be said that since the creation of the State Board
of Entomology that there has been no movement of domestic livestock out
of the Bitter Eoot Valley carrying infected ticks. Certainly if any domestic
livestock carried ticks out of the Bitter Boot Valley, it was an exception and
this exception could not in any possible manner account for the wide spread
of spotted fever in the State of Montana or other western states.

The dipping of domestic livestock in infested areas has a definite place in
tick control. Unfortunately, dipping under Montana conditions will never
eradicate the tick Dennacentor andersoni. Late snow storms, and inclement
weather during the early spring prohibits the periodic dipping of all live-
stock in the infested area. Eange, foothill and semi-range conditions make
it impossible to gather all animals and have them at a dipping vat at a
specified periodic time. However, inasmuch as rodent control cannot be suc-
cessfully practiced in the foothill country where wild animal life meets with
domestic animal life, it naturally follows that dipping will do more good in
such districts, although the amount of good that it does in such districts is
questionable. Wild life travels at night time. There are innumerable animals
that cross the border line and drift into the semi-cultivated lands during
the night periods carrying with them an abundance of some stage of tick life
that they have picked up in the wild animal country. In these overlapping
districts control of any kind, unless it be by tick parasites is difficult in the
extreme.

In such districts and in the mountain fortresses of wild animal life, our
main hope and in fact, the only salvation that we can see at this time in
controlling tick life is by tick parasites.

That domestic livestock grazing in infested areas are a potential danger
in the spread of spotted fever as well as other tick-borne diseases is mani-
fested by the fact that during the tick season, considerable numbers of ticks
are found on domestic animals in such areas. Mr. Prank O'Donnell reports
that he personally removed 474 ticks from one range steer. In one bunch of
ten head of cattle, he removed 1268 ticks or an average of 126.8 ticks per
animal. From one horse he removed 331 adult ticks. In a band of these horses
he removed 1055 ticks or an average of 175.8 ticks per annimal. Dr. H. P. "Wood
of the Bureau of Entomology in 1913 reports removing 212 ticks from 20
head of sheep or an average of 35.3 ticks per animal.

It is not to be presumed for one minute that every one of these ticks
was an infected tick, but it is reasonable to presume that some of these ticks
at least, were carriers of spotted fever or tularaemia. If the Montana State
Board of Entomology had not been created and had not required the dipping
or hand treating or hand picking of animals for the removal of ticks in in-
fested areas and had not restricted the movement of domestic livestock from
infested areas, it is not difficult to conceive that the spotted fever question
would have been a much more serious one at the present time in Montana, as
well as some of our sister states.

That there is some factor in the spread of spotted fever other than the
mechanical transfer of an infected tick from one area to another by domestic
livestock or wild animal life, cannot be discounted. We cannot conceive that
wild animal life or domestic animal life has caused the tremendous spread of

40 EIGHTH BIENNIAL REPORT

spotted fever that has taken place in the last fifteen years. Whether spotted
fever is a disease of the tick itself or an animal disease and whether or not
the viruleucy of the virus of spotted fever is increased by climate or food,
or by environment has not been determined.

We must concede that the preponderance of evidence is in favor of some
such contention, nevertheless it cannot be denied that infected ticks may be
carried from one area to another by wild animal life and wild bird life as
well as by domestic animal life. Therefore, in the control of tick life, the
destruction of rodents and the dipping or hand picking of domestic animals
cannot be discounted and should not be discontinued, unless and until a tick
parasite is found that will overwinter in our country and that will prove
itself a natural destructive parasite to the spotted fever tick.

CONTROL WORK: ROCKY MOUNTAIN SPOTTED FEVER CONTROL

DISTRICTS, BITTER ROOT VALLEY, FOR THE

BIENNIUM ENDING DECEMBER 31, 1930

By

F. J. O'DoNNELL, Field Agent, Montana State Board of Entomology

During the biennium now closing, the tick control work in the Bitter Eoot
Valley has been carried on with only minor changes in the methods adopted
several years ago, as described by the writer in the Sixth Biennial Eeport.
Previous methods were supplemented by tick dragging over a small area at the
eastern end of Lake Como. Our efforts were, therefore, mainly directed toward
rodent extermination and stock dipping as means of reducing the numbers
of ticks.

KoDENT Control: Table I summarizes the rodent control work in both
Ravalli and Missoula Counties. The average cost per acre is based on the
actual cost of the material used and the necessary labor required to do the
field work; administrative costs are not included. Figures for 1927 and 1928
have been included for comparison. It will be noted that there was a larger
area (17,454.25 acres) treated in 1929 than in 1930. This was due largely
to unfavorable weather conditions in 1930. However, the total acreage for
1927-28 as compared with the total for 1929-30 shows an increase of 76,568.03
acres for the latter period, which can be also attributed to weather conditions.
During the 1927-28 biennium there was considerable rainfall during the active
rodent season, which prevented carrying out the full program.

STATE BOARD OF EXTOMOI.OGY

41

STATE BOARD OF ENTOMOLOGY

SUMMARY COLUMBIAN GROUND SQUIRREL CONTROL,

RAVALLI AND MISSOULA COUNTIES

Table I

RAVALLI COUNTY CONTROL DISTRICTS

Year

Poisoned
Once
Acres

Poisoned Grain Calcium
Twice Poison Cyanide
Acres I Quarts Pounds

Labor
Hours

Average

Cost Per

Acre for

Treatment

■*1927

1 i
86,093.40 48,131.121 5.910.75 2.15.'; 00

6.968.83
7,421.92
7,433.42
7,561.50

.0340

*1928

91,851.50 21,514.00 5,700.00
99,161.26 54,536.39 5,569.00
91.440.90 45.3.^2.50 4.8.';0.7R

2,137.50
2,411.00
4,575.00

.0417

*1929 . .. .

0309

*1930

0366

1

MISSOULA COUNTY CONTROL DISTRICTS

1927 .

55,650.00
72,310.00
82,040.00
85,220.00

56,823.00
51,580.00
53,250.00
49,490.00

1,874.50
1,898.00
1,992.50
1,835.00

575.00
309.00
563.00
686.00

4,154.50
4,058.50
3.995.50
4,085.50

.0203

1928

.0177

1929

.0165

1930

.0168

U. S. Lands and National Forest

1927
1928
1929
1930

4,200.00

8,160.00

7,680.00

10,225.00

80.00

400. 00|

1,400.00)

1,580.00

220.66
657.83
214.33
623 . 00

.03108
.0481
.0194
.0332

*U. S. Lands and National Forest Included.

The average cost of $0.0252 per acre during the last two years is some-
what lower than for the preceding two years when it was $0.0284. This de-
crease was effected despite the increased use of calcium cyanide, the initial
cost of which is much higher than that of poisoned grain and involves an
increase of about 100% in the labor charge for distribution. There was also
an increase in the more intensive work in the brushy foothill areas where
more time is required to locate the rodent burrows, thus incurring a higher
labor charge for the acreage treated.

A considerable amount of intensive rodent extermination work was done
on the National Forest reserve along the north and south shores at the
eastern end of Lake Como. During the past two or three seasons this area has
become quite popular as a camping grounds for fishing and picnicking parties.
This was formerly a known spotted fever area, although there have been no
cases reported from there in recent years. A total of 18 cases have been re-
ported since 1893, the last case occurring in 1924, However, it was felt ad-
visable to make an especial effort to exterminate immature tick hosts and to
reduce tick infestation as much as possible. A field man was, therefore, em-
ployed to devote his entire time to rodent destruction and tick dragging in
this area. Three thousand eight hundred and twenty-five acres were treated
requiring 199 hours' time, 117 hours of which were employed in the distribu-

42 EIGHTH BIENNIAL REPORT

tion of both poison grain and calcium cyanide and in shooting and otherwise
destroying rodents. Eighty-two hours were spent in tick dragging. All. of
the favorite camping sites, roads, trails and gopher colonies were dragged
for ticks. Eight thousand five hundred and seventy-five adult ticks were thus
collected and delivered at the laboratory. Funds permitting intensive control
work will be continued in this area for at least another season.

Eodent control in both Missoula and Eavalli Counties has again been very
satisfactory. A personal survey by the writer of all the districts late in May,
1929, and again early in June, 1930, showed a marked decrease in the rodent
population as compared with the number of rodents noted in May and June,
1924 and 1925.

On May 22, 1924, on an inspection trip made by automobile from Hamil-
ton to Missoula over the main west side highway, a distance of about 52 miles,
at an average speed of about 30 miles per hour, 87 rodents were counted — 82
ground squirrels, one rabbit and four chipmunks.

On May 29, 1930, on a trij) made over the same route at approximately
the same rate of speed and under similar weather conditions, only five rodents
were seen — three ground squirrels and two chipmunks.

On a 22-mile auto trip and about 5 miles on foot in the Florence and
Lolo districts on June 2, 1924, 107 rodents were counted — four cottontail
rabbits, 12 chipmunks, two pine squirrels, eight ground hogs and 81 ground
squirrels. One June 1, 1930, the same ground was covered under practically
the same conditions and only two chipmunks, one pine squirrel and eight
ground squirrels were seen. Inspections in other control districts have shown
similar satisfactory results.

While these observations may not be an accurate index of the rodent
destruction accomplished in the control districts as a whole, they do neverthe-
less indicate the effective results obtained by systematic and persistent rodent
control work over a period of years.

As stated previously, rodent control work has been very satisfactory. This
applies, however, only to valley and foothill areas where, up to the present
time, the greater portion of the work has been done. It is recognized, however,
that this work will have to be continued from year to year in order to main-
tain present conditions because of the continual inward movement of rodents,
which, in tlie nature of the case, come principally from the mountain slopes and
canyons to the west which are heavily infested with both rodents and ticks.

Until adequate funds are made available to carry on intensive control
work for a number of years in the canyons and in the brushy foothill areas,
in addition to a continuance of the work in the valley areas, there can be but
little hope of securing permanent results in the control districts as a whole.
This is one reason why effective tick parasites are so desirable.

Dipping. Stock dipping during the present biennium was somewhat more
successful than during the preceding two years. A total of 2588 farm animals
were dipped during 1929 and 1930 as compared with 2073 during 1927 and
1928. This number could be greatly increased if there were more vats available.
This point has been frequently emphasized in previous reports. At present
there are only four vats in use, one each in the Florence, Victor, Stevensville
and Hamilton districts. There should be at least two vats in each of these

STATE BOARD OF ENTOMOLOGY

43

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44 EIGHTH BIENNIAL REPORT

districts as well as oue in the Gold Creek district, two in the Darby district
and three in the Missoula county district.

Stock dipping is a valuable accessory control measure and is popular with
a large majority of the stockmen and farmers, but we cannot expect to ac-
complish the maximum results obtainable by this method of control until we
have equipment and field crews sufficient to carry out a full and complete
program.

Stock Poisoning. The loss of farm animals from rodent baits has in the
past been the source of more or less friction between this office and the stock
owners. Forty-one cases have been investigated during the past seven years
and a settlement was made of 20 of these cases. However, with the increased
use of calcium cyanide and the greater care exercised in the distribution of
rodent baits, stock poisoning was entirely eliminated during the past three
years.

Our relations Avith the County Commissioners of both Eavalli and Missoula
counties have been very satisfactory. We have been given such financial assist-
ance as we requested from them and have had their hearty support at all
times.

We also wish to acknowledge the cooperation and assistance which we
have received from the State Board of Health and the State Livestock Sanitary
Board for the laboratory work they so kindly did for us.

The accompanying graph has been prepared to show the incidence of
spotted fever in the older control districts from 1913 to 1930 inclusive. The
data from which this graph was made includes only those cases which have
occurred in the Florence, Stcvonsville, Victor, Hamilton and Gold Creek dis-
tricts in Eavalli county, as the control work has been more or less continuous
over this area for the past IS years.

The average number of cases per year for tlie period covered by the
graph is 2.83 as compared with 3.06 which was the yearly average for this
area up to and including 1928. The marked decrease of spotted fever in these
districts is probably due primarily to rodent destruction and the resultant and
very marked decrease in tick abundance.

There are other important factors, however, which have had some influence
in controlling the disease. Many of the residents in the districts have received
the Spencer-Parker vaccine and also, greater care is exercised by those who
have occasion to go into the tick infested areas.