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THE MONTANA

STATE BOARD

ENTOMOLOGY

SIXTH BIENNIAL
REPORT

1925 ' 1926

THE MONTANA

STATE BOARD

ENTOMOLOGY

SIXTH BIENNIAL
REPORT

1925 - 1926

(No report was issued for the biennium 1923-1924)

MONTANA STATE BOARD OF ENTOMOLOGY

W. F. COGSWELL, M. D^ Secretary State Boaid 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, Mont., December 15, 1926

To His Excellency, J. E. Erickson
Governor of Montana
Helena, Mont.

Sir:

In behalf of the Montana State Board of Entomology
it gives me pleasure to transmit to you the Sixth Report
which covers the years from 1923 to 1926, inclusive, no re-
port having been issued in 1925.

The work of this Board began in the year 1913 and has
been continuous since that year. The primary object in
passing the law which crea.ted this Board was to provide
for the investigation and control of Rocky Mountain Spotted
Fever, though the study of any insect borne diseases of
man and domestic animals was authorized. From the first.
Spotted Fever has been almost the only subject studied.

The problem has turned out to be a long and difficult
one. There was very little known in medical science or in
entomology to guide and aid us, and we have been obliged to
make advances into the unknown in any progress we have
made.

It has been the policy of the Board to enlist the cooper-
ation of any agencies that might aid and we have had the
assistance of various agencies, including the U. S. Public
Health Service, the U. S. Bureau of Entomology, the U. S.
Biological Survey, the U. S. Forestry Service, the Rocke-
feller Foundation for Medical Research, and Harvard Uni-
versity, all of which have rendered valuable assistance.

In the nature of the case, there has been much that
the State of Montana has had to do and in the future the
State will be obliged to take an active part if the problem
is to be successfully completed.

We are pleased to report progress which may best be
appreciated by a reading of the report.

Very respectfully,

R. A. COOLEY, Secretary.

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SIXTH BIENNIAL REPORT OF THE STATE BOARD OF

ENTOMOLOGY

by
R. A. Cooley, Secretary

The State Board of Entomology is made up of the
following state officers, who are ex-officio members; the
Secretary of the State Board of Health, the State Veterinary
Surgeon, and the State Entomologist. There has been no
change in the personnel of the Board since it was first
established in 1913. This fact has done much to make for
continuity and effectiveness in the labors of the member-
ship. The Board was organized primarily for the investi-
gation of Rocky Mountain Spotted Fever and for puttmg
into effect such control measures as the investigations might
uncover. Time has shown that the form of organization
was an effective one, for the expert services of specialists
and the organized official forces of the State have been
brought to bear on the problem. At the outset it was seen
that the solution of the problem must involve medical
science, the health and control of domestic animals, and
service in the field of the entomologist. All of these are
covered in the organization and without the expense to the
State of personal compensation, excepting for employees of
the Board.

Formerly the Board employed Doctor R. R. Parker as
Assistant Entomologist and valuable work was done by him.
However, when in 1921 a sharp increase in the number of
cases occurred in Western Montana, and when at the same
time it became evident that the disease was getting closer
to certain large centers of population in western Montana,
the United States Public Health Service was called upon for
assistance, and at this time Dr. Parker was transferred to
the United States government pay roll. He is now an em-
ployee of the Public Health Service but, being stationed in
Montana under the present plan of cooperation, we still have
the benefit of his wide knowledge of the work.

In 1924 Mr. F, J. O'Donnell was employed to conduct
the tick control work of the Board which involves rodent
destruction and the dipping of livestock. Mr. O'DonneH has
become a very valuable aid in the work. He has supervision
of all of the control districts and all of the employees of the
State, conducts the cooperative work with the County of-
ficers and is generally in charge for the State.

Cooperation

Since 1921 the work at the Hamilton laboratory has
been conducted under an informal plan of cooperation be-
tween the State and the United States Public Health Service

6 SIXTH ANNUAL REPORT

which will be continued indefinitely, so for as we are now
informed. Doctor R. R. Spencer, Surgeon, is in charge for
the United States, and Doctor Parker is closely associated
with him. A number of important publications eminating
from this work have been published from Washington by
the Public Health Service under the joint authorship of
Doctors Spencer and Parker.

Owing to the form of organization, it is impossible to
state just how much money the U. S. government is allot-
ting to this work, but the sum is nearly twice the amount
of. the State appropriation.

The Montana State Board of Entomology has much
pleasure in acknowledging the assistance of the United
States Public Health Service and particularly desires to
commend the high type of personal service rendered by
Doctor Spencer and Doctor Parker. Both of these men are
daily exposed to infection by spotted fever and their families
are in constant danger. Both of them during the period
since the last report, have gone through distressing and
protracted illness from tularaemia, contracted while on duty
in the laboratories.

Acknowledgement is also made of the cooperation and
assistance of both the U. S. Biological Service and the U.
S. Forestry Service in connection with giving information
and aiding in the destruction of rodents in public domains
bordering the tick control districts operated by the State.

Control Measures

It is the general policy of the Board to conduct invest-
igations into the causes of Rocky Mountain Spotted Fever,
experiment with methods of control or eradication, and,
as rapidly as useful information is obtained, put it into
practical use.

The control work now being conducted is covered in a
paper by the Field Agent, Mr. O'Donnell, which appears on
later pages and may be summarized as follows. For the
purpose of conducting the control work portions of Ravalli
and Missoula Counties have been set off and bounded as
control districts. In these districts the destruction of rodents
and the dipping of livestock is being carried on as previously.
In the growth and development of the tick from the egg to
the adult condition, the early stages, larvae or "seeds" and
nymphs, feed on rodents and the full grown ticks or adults
feed on domestic animals, principally horses and cows. The
killing of ground squirrels on which the young ticks feed
principally and the dipping of horses and cattle for the
killing of adult ticks are the best known methods of control

BOARD OF ENTOMOLOGY 7

which we have. This work which has been going on for
some years has resulted in a very marked reduction in tick
abundance and a lessening of the danger of residents being
bitten.

It is highly desirable that this control work be con-
tinued, even though we now know that it is not a sufficient
method for eradicating spotted fever or the tick. It is
certain that the killing of rodents and dipping of livestock
has greatly reduced the ticks and that a continuance of the
same work will futher reduce the deplorable condition that
formerly existed.

The recent investigations by the Public Health Service
into the conditions concerned in the maintenance and per-
petuation of the spotted fever virus in nature have pointed
to new avenues of control. Their use however is being held
in abeyance pending the securing of additional information
on certain points and the results of the tests to determine
the value of the parasite, Ixodiphagus caucurtei and its place
in the plan of control.

The control work is being done wholly on State funds.

It should further be pointed out that in conducting the
control work a large amount of valuable notes, maps and
experience have accumulated which are certain to be of
great value in future work, whatever it may be. For ex-
ample, the notes which show present conditions will be of
value in judging the measure of progress being made when
the work with tick parasites is taken into the field, which
we hope to do in the spring of 1927.

WORK OF THE PUBLIC HEALTH SERVICE

Throughout the whole history of the spotted fever
investigations in Montana, the Public Health Service has
at times allotted funds to the project and has had repres-
entatives engaged in various phases of the study. The
arrangement now in force began in 1921, when Dr. R. R.
Spencer took up his study and Dr. R. R. Parker, formerly
employed by the Board of Entomology as Assistant Entom-
ologist, was transferred to the government pay roll.

The investigations of the Public Health Service have
been concerned mainly with the following:

1. A vaccine that will provide protection,

2. The organism of spotted fever and other micro-
organisms found in ticks.

3. Characteristics of the virus of spotted fever, par-
ticularly with reference to differences as it occurs in ticks
and in animals.

8 SIXTH ANNUAL REPORT

4. The conditions physical and biological that are con-
cerned in the maintenance and perpetuation of the virus in
nature.

5. The relation of the rabbit tick (Haemaphysalis lep-
oris-palustris Packard), in the spotted fever complex,

6. Tularaemia.

7. Tick paralysis.

We are pleased to report real progress, particularly in
the search of a vaccine. A brief article on this subject by
Drs. Spencer and Parker appears in another part of this
report. Another article on tularaemia, a disease which turn-
ed up in ticks brought in from nature for use in the work
on spotted fever, is included and shows important findings
which are in the nature of a bi-product of the laboratory. A
third article by Drs. Parker and Spencer on the distribution
and spread of spotted fever in Montana, places on record a
vast amount of information which does much to emphasize
the problem as one of more than local significance.

The Public Health Service workers have also found the
common rabbit tick, a species entirely different from the
spotted fever tick, has the spotted fever virus in nature and
may transmit it from one rabbit to another. This finding
is of much importance, not because this tick ever bites
men, but rather because it may be a important factor in the
complex conditions that harbor the infection in nature. A
fuller understanding of some of the natural conditions back
in the mountains that border the Bitter Root Valley has
been reached. It has been found that the Rocky Mountain
Goat, which occurs rather abundantly in the mountains, is
a very important factor in keeping up the tick poDulation
and that the ticks on goats and in the goat ranges are par-
ticularly high in the percentage of infective individuals.

IMPORTANCE OF THE TICK PROBLEM IN MONTANA

Prior to the year 1906, when Dr. H. T. Rickitts by his
admirable experiments conducted in Montana under the
auspicies of the State Board of Health, definitely established
the fact that the common "wood tick" is the agency of man's
infection with Rocky Mountain Spotted Fever, not much
interest was taken in this parasite. It was known to infest
livestock and to bite man, but it was not considered to be of
much importance and certainly not a factor in the develop-
ment of a great commonwealth. In twenty years' time,
however, we have come to realize this arachnid to be of
great importance. We are concerned with it for the follow-
ing reasons:

BOARD OF ENTOMOLOGY 9

1. It is the means, and the only means, of man's in-
fection with Rocky Mountain Spotted Fever.

2. It causes the definite but obscure disease known as
tick paralysis in human beings, of which there are several
cases in Montana each year. This disease generally occurs
in children. It is induced by the bite of the tick generally
in the region of the base of the head and is always fatal
unless the tick is discovered and removed before the para-
lysis reaches vital organs.

3. It is one of the agencies of man's infection with
tularaemia and is an important factor in keeping this disease
alive in nature by transmitting it from one rodent to an-
other.

4. By its bite it frequently induces resistant ulcers
on man.

5. It is a generally objectionable parasite of man,
causing apprenhension and discomfort to many persons who
love the open air and delight in tramping.

6. It causes a definite disease known as tick paralysis
in sheep and at times causes heavy loss by killing sheep
and making necessary the hand picking of the ticks.

7. It is a severe parasite of both domestic and wild
animals such as horses, cows, sheep, elk, deer and mountain
goats. "Down with ticks" is an expression among stock
men and refers to animals so heavily infested that they are
devitalized and unable to get up. Whether there ?s a
paralysis connected with this condition is not now clear.

The fact that the tick causes spotted fever is beyond
doubt the principal score against it but all of the foregoing
reasons, collectively, have created a real problem for Mon-
tana and for the other northwestern states. A correct idea
of the prevalence and spread of spotted fever in Montana
may best be gained by a study of the accompanying table
and a map shown in another part of this report. The map
and table show that the number of cases has increased and
that the disease is spreading. The table of cases by years,
if compared with the same table presented in the last re-
port will show that during a period of four years, spotted
fever has appeared in four new counties. Two of these were
new in 1926. The total in the state for this four year per-
iod is 152 against 122 for the four years preceding, an in-
crease of 30. It appears to be evident that changes in con-
ditions brought about by the increase in population and the
advancing of agriculture in new territory has brought about
the increase and spread of cases.

10 SIXTH ANNUAL REPORT

There can be no doubt that the increase in automobiles
in the United States, improved roads, extensive tourist
travel together with more intermingling of people residing
in different parts of the country have brought about a much
greater familiarity of the people of the United States gener-
ally, with the fact that there is such a condition here. This
is in evidence whenever one travels in the east and whenever
residents of the east visit here, as well as by the letters
received by the Board of Health in Helena and the State
Entomologist. The following is an example. The Secretary
of the Board of Health recently received a letter from an
individual in Iowa, who stated that he represented thirteen
families who were thinking of moving to the Bitter Root
Valley but having heard of ticks and spotted fever, he
wanted to know about the conditions that existed.

The presence of ticks and spotted fever in Montana
cannot fail to be a serious obstacle in the way of normal
development until an adequate solution to the problem is
found.

The Spencer-Parker vaccine, now in an experimental
stage, looks encouraging, but it should be understood that
this vaccine can never completely solve the problem. At
the present time it is costing approximately twenty dollars
to make the vaccine for one person. With quantity pro-
duction and more experience the cost can be reduced some-
what but we believe that it will always be so high as to
make it difficult to induce the general public to use it. We
can hardly expect the Federal Government to continue the
production of vaccine, and administer it free much beyond
the experimental stage, at least not without a special act
of congress.

If this vaccine is finally demonstrated to be entirely
successful, and if it may be produced at a cost to put it
within the reach of all who want it, it will still be true that
the presence of spotted fever is a menace to the state. If
persons knew where and how they became infected with the
diseases for which vaccination is ordinarily practiced, such
as small pox, typhoid fever, etc, they would generally avoid
the possibility of becoming infected in preference to taking
the protective treatment.

With an effective vaccine for this disease available
people will still continue to avoid places where ticks are
found and, excepting in cases in which their habits take
them into places where they are in danger, will not generally
be vaccinated.

A successful vaccine will be of great value in aiding to
solve the problem but we will still need to eliminate spotted
fever as we would small pox and typhoid fever.

BOARD OF ENTOMOLOGY 11

Spotted Fever Chart.

A graphic chart prepared by Doctor Frank H. Parker,
under the supervision of Doctor R. R. Parker, showing the
Hfe cycle of the spotted fever tick and the supposed cycle
of the virus, is presented herewith. This chart should do
much to make clearer the intricate relationships between the
virus, the tick and the hosts of the tick in the various stages
of development.

SIXTH ANNUAL REPORT

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SIXTH ANNUAL REPORT

GEORGE HENRY COWAN
Born January 10, 1886.

Died October 29th, 1924, of Rocky Mountain Spotted Fever contracted
while on duty, after twelve years of service in the investigations.

BOARD OF ENTOMOLOGY 15

GEORGE HENRY COWAN

Yet again it becomes our painful duty to record the
death from Rocky Mountain Spotted Fever of one of those
engaged in the investigations. George Henrv Cowan, an
employee of the United States Public Health Service, con-
tracted the disease, in some unknown manner ,while on duty
and died on October 29th, 1924.

Mr. Cowan was first employed by the Public Health
Service during the period of Doctor Thomas B. McClintick',1
service in the Bitter Root Valley about 1912, then by the
United States Bureau of Entomology and later by the State
in the work of dipping livestock and killing rodents and
finally again by the Public Health Service. His services
were therefore almost continuous to the time of his death.
Of tremendous physique, with a keen intellect, and with
a willing heart, which made him invaluable alike in the
field and in the laboratory, he had done very much to ad-
vance the work on spotted fever.

Something more than the thought of the usual monetary
compensation to be received must have actuated him to take
up the work on spotted fever and to continue it with devo-
tion for a period of twelve years. Every school boy in
Montana should be told the story so they may know that
true heroism still lives and that men of high motives place
duty first.

A Parasite of Ticks

In years past we have had correspondence with Doctor
M. E. Brumpt, of the Faculte de Medecine de Paris, an
eminent parasitologist, regarding a specific parasite of
ticks in which he was much interested. This parasite,
scientifically known as Ixodiphagus caucurtei Buysson, was
first described in 1912 (Un Hymenoptere Parasite des Ixodes.
In Archives de Parasitology, Tome XV, p. 246.) It is a
minute, dark-colored, very active insect about one milli-
meter in length which feeds in and destroys the tick in the
nymphal stage. At Dr. Brumpt's request some of our ticks
were sent to him, alive, for his experiments.

Doctor Brumpt's preliminary experiments were so en-
couraging that the subject was written up in an article en-
titled, "Utilisation des Insectes Auxiliares Entomophages
dans la Lutte contre les Insectes Pathogenes," which ap-
peared in La Presse Medicale, (No. 36, du 3 Mai, 1913).

This parasite was introduced into America during 1926.
Near Woods Hole, Massachusetts, just off the shore, is a
small island, Naushon, which is privately owned and used for
purposes of residence and recreation. Several families, all

16 SIXTH ANNUAL REPORT

branches of one family, reside on the island. The island
is so overrun by the American Dog Tick, Dermacentor vari-
abilis Say, as to be much less desirable for residence pur-
poses. Through Doctor S. B. Wolbach, professor of Path-
ology, Harvard Medical School, arrangements were made
for Dr. Brumpt to send over an assistant with a brood of
parasites for the purpose of attempting to colonize and es-
tablish them on the island. Accordingly, in the early part
of the summer of 1926, Dr. F. Larrousse arrived in Boston
and, after a conference with Dr. Wolbach, set up his experi-
ments on Naushon. It is too early to judge reliably of the
results of the experiments but since Dr. Larroussee was
able later in the season to recover parasitized ticks in nature
there is hope that the attempt will be successful.

Soon after Dr. Larrousse arrived in America, Dr. Cogs-
well, Chairman of the Board of Entomology, received a
telegram from Dr. Wolbach, inviting the State to send a
representative to Massachusetts for the purpose of becom-
ing acquainted with the method of handling and rearing the
parasites, with a view to attempting to introduce them into
Montana. The Secretary left for Boston on July 8th and
after a stay of a few days on Naushon Island in conference
with the French scientist and in observation of his work,
returned with a small but sufficient supply of parasitized
nymphs. Every possible courtesy and assistance was ex-
tended both by Doctor Wolbach and Doctor Larrousse and
our success in rearing the parasites since July is due to the
careful and thorough manner in which the experience gained
in France was explained.

It was learned that in France, where the insect is
native, ticks are practically exterminated in those parts
where the parasite is found, and it had previously been
learned from Dr. Brumpt that ,in experimenting in the
laboratory with different species of ticks brought in alive
from different parts of the world, our spotted fever tick
was the only one in which he had obtained a one hundred
percent parasitism.

These facts, together with the success we have had during
the few months since we obtained our stock of parasites,
lead us to hope for success in their use, not only in Ravalli
and Missoula Counties, but elsewhere in Montana. It must
be borne in mind, however, that there may be many factors
which will be against success in the enterprise. Climatic
conditions, both in summer and in winter, may make it
impossible for the parasite to live here. The parasites work
only in the nymphal stage of the tick and it is not yet clear
that the life histories of the tick and of the parasite are so
timed as to enable the parasite to pass through the full
year's cycle.

BOARD OF ENTOMOLOGY 17

Such points can be determined only by experiments and
steps have already been taken to conduct such investigations
as are necessary. The parasites multiply very rapidly and
by the spring of 1927 we shall have a supply which will
enable us to begin our experiments in liberating them. This
work will begin in the Bitter Root Valley and in the moun-
tains nearby, where the ticks are very numerous.

It should be known also that the proposed investigations
of the parasite will involve a tremendous amount of labor.
It will be necessary to maintain at all times a reserve stock
of the parasites in the laboratory. To do this it is necessary,
first, to rear ticks on animals in laboratory cages. Since
only the nymphs can be used, we shall have to begin with
adult engorged ticks, either picked from domestic animals or
fed to repletion on laboratory animals, allow them to lay
eggs, wait for the eggs to hatch, feed the larvae on labor-
atory animals, and finally wait for the nymphs to emerge
from the engorged larvae. Throughout this stage of the
process it is necessary to prove that the ticks being used
are non-infective, as it would be unwise to liberate infected
ticks in nature.

Having the stock of unfed nymphal ticks, it is neces-
sary to allow them to feed on laboratory animals and, while
being fed, to liberate the parasites in the cloth bags in
suitable temperatures. The parasitized ticks must later be
separated from those not parasitized and held under suitable
conditions of temperature and humidity until ready to em-
erge as adult parasites.

Several experimental methods will be tried in liberating
the parasites in nature. One will be to obtain wild rodents
by trapping, infest them with nymphal ticks and ,after
parasitizing them as with laboratory animals, liberate the
rodents where they may go back to their old haunts and
drop the parasitized ticks where we want them to be and
under natural conditions.

In order to avoid proceeding blindly with methods the
effectiveness of which is unknown, it will be necessary to
conduct experiments to check up results. Other wild rodents
will be shot or trapped and the ticks will be carried through
to determine the percentage of parasitism for comparison
with other methods.

In order to carry out this work, several assistants will
be needed and much more laboratory space than we now
have.

18 SIXTH ANNUAL REPORT

PLANS AND NEEDS

The plans of the Board of Entomology contempla'ie
continued cooperation with the Public Health Service, that
the destruction of rodents and dipping of live stock shall
be carried on as formerly; and that the new tick parasite
shall be experimented with and made use of as far as
possible.

Through the proper channels budget estimates have
been submitted. The figures presented are carefully ad-
justed to the actual needs and are conservative. Larger
and more suitable quarters are very badly needed and the
present legislature should make available a sufficient fund
to permit the erection of suitable building.

A LABORATORY NEEDED

During recent years the laboratory work in connection
with this problem has been conducted in a vacated school
building across the river to the west of Hamilton. It is an
old structure wholly unadapted to our work, far too small,
and badly in need of repair. It was formerly rented from
the local school board but has recently been turned back to
the original owners, by a court action, because no longer
used for school purposes. The laboratory work has so in-
creased that a larger and better equipped building is the
Board's most urgent need.

It is impossible to place too much emphasis on the fact
that this building is not suitable for the purpose of this
investigation. Such work calls for order and cleanliness
which cannot now be had. A very large amount of ex-
perimental work on laboratory animals is necessary, re-
quiring the use of hundreds of caged animals. At present
these are stacked up in the same rooms with equipment,
records, work tables, and office desks. As would be expected
unnecessary human cases of laboratory infection have oc-
curred. Since the fall of 1921 eleven out of sixteen persons
who have been engaged in the United States Public Health
Service investigations have been infected either with spotted
fever or tularaemia. Five of these men have contracted
spotted fever and six tularaemia. Two of the former re-
sulted fatally while the last three, who had received the
vaccine, recovered. These three recovered cases all occurred
during season of 1926 and resulted from attempting to pro-
duce increased quantities of vaccine without suitable facilit-
ies. Without the vaccine it is partically certain that we
would have been obliged to report five deaths instead of two
from accidental infections originating in this improvised
laboratory. All prior laboratory cases, five in number had
proved fatal.

BOARD OF ENTOMOLOGY 19

A representative of the Public Health Service has re-
cently stated that their v^ork would be increased in Montana
if adequate quarters are provided. The laboratory is full
to the limit and there is no space in which to take up the
proposed new work on tick parasites. In this work alone
a large amount of space will be necessary for the cages in
which laboratory animals are held and for other uses in
the same connection.

It should not be understood that all danger of infection
may be avoided if suitable housing is provided. The work is
dangerous at best, but the state can do no less than provide
every protection possible, and with every thing possible
done to protect the workers there is still danger that ticks
or other infectious materials will be taken to the homes
of the workers. The older members of the family may be
vaccinated but the younger children cannot be, at present.

DISTRIBUTION AND SPREAD OF ROCKY MOUNTAIN
SPOTTED FEVER IN MONTANA. '

R. R. Parker, Special Expert, and R. R. Spencer, Surgeon,
U. S. Public Health Service.

(Cooperating with Montana State Board of Entomology)

During the past ten years there has been a spread-
of Rocky Mountain spotted fever in Montana that is with-
out precedent in any section of the northwest. The ac-
companying map shows the three relatively small areas in
which the disease was definitely known to be endemic prior
to 1914. Beginning in that year, infection has spread until
now it is present in 34 counties extending from the east-
ern to the western and the northern and southern state
boundaries.

On the map, the endemic areas known prior to 1914
are indicated by solid black. The subsequent spread is in-
dicated by black circular dots, each of which indicates an
individual case and its approximate point of origin.

1. Data subsequent to 1913 are from records of the Montana State
Board of Entomology and the United States Public Health Service.
Prior data are partly from records of these org-anizations, partly
from literature.

2. The terms "spread" and "extension" as here used mean the occur-
rence of human cases in new localities It is possible, however,
that infection has long been endemic in the new areas, without the
occurrence of earlier cases in man.

20 SIXTH ANNUAL REPORT

ENDEMIC AREAS PRIOR TO 1914— WESTERN
MONTANA.

In western Montana, there are two areas in which
Rocky Mountain spotted fever of the most virulent type has
been endemic for many years, probably long before white
settlement. The mortality rate has approximated 75 per
cent, and in persons of adult age has been nearer 90. "•

One of these areas is on the west side of the Bitter
Root River, partly in Missoula and partly in Ravalli county.
It is about 90 miles long and with an average width of less
than 15 miles. Although there is strong evidence of the
infection among the Indians before the Valley was settled,
the earliest authentic record was in 1873, Several hundred
deaths have occurred. Land values were depreciated, and,
due to the actual or potential high priced agricultural value
of the land, a serious economic situation has been created. *

The second area lies along the lower portion of Rock
Creek, east of Missoula, mostly in Granite County but in-
cludes the southern corner of Missoula County. It is not
to exceed 15 miles in length. The earliest recorded case was
in 1891, but an unverified report indicates its occurrence
at least 10 .years earlier. It is a narrow mountain valley
chiefly used for grazing.

In Missoula County, outside these two well defined
endemic areas isolated cases have been reported as follows:
1 each in Grant and Butler Creeks and in Pattee Canyon in
1904; 2 on Rattlesnake Creek and 1 in Dry Gulch in 1909;
and near the mouth of the Blackfoot River, 1 each in 1899,
1904 and 1906.

The third endemic area of long standing is southern
Carbon County, east of the mountains. Prior to 1914, cases
had been reported from the Clark Fork of the Yellowstone
River, Dry Creek, Boulder Creek, and Sage Creek. The
mortality rate was approximately 15 per cent.

The only cases reported outside these counties prior
to 1914 were 1 each in Beaverhead, Gallatin, Park and
Fergus counties, all in 1904. In view of their isolated oc-
currence and the distances from known endemic areas one
can but wonder as to the correctness of the diagnoses.

3. These percentages are based on the case records for the last ten
years. Recoveries among young children are far more frequent
than in adults.

4. Most sections of the northwest in which Rocky Mountain spotted
fever occurs are sage brush areas, of relatively low agricultural
vahie.

RDCKY MDUNTAIN SPDTTED FEVER

LIFE CYCLE OF THE SPDTTED FEVER TICK AND SUPPD5ED CYCLE Dr THE VIRUS

THt VIRUS 16 THANSnnriD BY TWO TICKS, THE WOOD TICK AND THE RABBIT TICK .
IT IS MAINTAINED (1) BY PASSAGE EROn STAGE TO 6TAGE OF THESE TICKS AND
(2) BY NEW LINTS OE INFECTION STARTED IN PREVIOUSLY UN INFECTED TICKS ST
TEEDING ON INFECTED HOSTS. THE WOOD TICK IS THE ONLY KNOWN
AGENT OF HUMAN INFECTION.

TICK-DERMACENTOR VENU5TUS

1 EGGjS 4 NYMPHS

2 LARVAE 5 ENGORGED NYMPHS

3 ENGORGED LARVAE 6 MALE and FEMIALL
7 ENGORGED FEFIALE

THE WOOD TICK COMPLETES ITS LIFE CVCLEl IN
TWO YEARS, FEEDING THREE TIMES, FIRST AS LARVAE
THEN AS NYHPHS AND LAST AS ADULTS.
EACH STAGE FEEDS ON A SEPERATE HOST

sTLV on LAftGe

CONTROI METHOnfi
AREDIRECTrO AGAINST THE LARVAE
AND NYMPHS OM RODENTS AND THE ADULT
TICKS ON DOMESTIC ANIMALS.
THE METHODS USED ARE RODENT
DESTRycr/ON , DIPPING OF DOnESTIC
ANIMALS, RESTRICTION OF GRAZING,
HAND PICKING AND THE APPLICATION
OF REPELLANTS.

+ ROCKY MOUNTAIN SPOTTEID FEVER f MAN AND RODEwrs

+ TICK PARALYSIS (nosTLY in childreln )

+ TICK PARALYSIS (SHEtPi

+ TULARAEMIA (Man and rooCnTSI

O SEPTIC INFECTION Chan)

BOARD OF ENTOMOLOGY 21

SPREAD OF ROCKY MOUNTAIN FEVER
BEGINNING IN 1914.

The first authoritative reports of the occurrence of
Rocky Mountain spotted fever outside the above three old
endemic areas was in 1914. The subsequent spread can best
be outhned by considering separately the eastern and west-
ern parts of the state, the former to include the plains sec-
tion east of the mountains where the fever mostly occurs
in sage brush areas, the latter, the western, more moun-
tainous portion where the fever commonly occurs under
mountainous conditions.

Eastern Montana. The most extensive spread has
taken place in this section. Before 1914, infection was
known only in Carbon County. It now occurs in 23 counties
and a line^ drawn to connect the peripheral cases would en-
close an area of many thousand square miles. This must
be considered as one vast endemic area and each year there
is new evidence of either extensive or intensive spread or
both.

The accompanying tabulation shows the occurrence of
cases in this area from 1914 to 1926, giving totals by years
and counties.

The first evidence of spread was in 1914, when two
cases were reported from widely separated points; one from
Richland and one from Musselshell county. In 1915 cases
were again reported from Musselshell county, and the fol-
lowing new counties: Big Horn, Carter, Custer, Garfield,
Prairie, Powder River, Rosebud, and Treasure. Fergus,
Valley and Yellowstone counties were added in 1916; Still-
water in 1917; Daniels in 1919; McCone and Golden Valley
in 1921 ; Blaine, Dawson and Fallon in 1922 ; and Phillips and
Wheatland in 1926.

The number of cases by counties has been : Blaine, 1 ;
Big Horn, 11; Carbon, 25; Carter, 9; Custer, 13; Daniels, 1;
Dawson, 1; Fallon, 7; Fergus, 25; Garfield, 37; Golden
Valley, 5; McCone- 2: Musselshell, 36; Prairie, 4; Phillips,
2 ; Powder River, 6 ; Richland, 1 : Rosebud, 35 ; Stillwater, 6 ;
Treasure, 7; Yellowstone. 21; Valley, 5; Wheatland, 1.

The total number of cases has been 261 of which 246
have been outside Carbon County. Of the 25 which have
occurred in Carbon County at least half represent new areas
of infection or extension of old areas.

Reference to the year by year totals on the tabulation of
eastern Montana cases shows two peaks of abundance seven
years apart; one in 1915 (32 cases) and one in 1922 (48
cases). From the peak in 1915 cases decreased to 5 in 1918,
then rose to the second peak in 1922, following which cases

22 SIXTH ANNUAL REPORT

again declined to 21 each year in 1925 and 1926. This
variation in prevalence has been repeatedly noted by the
writers in other sections of the northwest and is especially
characteristic of the occurrence of Rocky Mountain spotted
fever in sage brush plains areas. It occurs not only in large
endemic areas but also in local foci. The intervals between
peaks of prevalence is not constant, but is more regular
over large areas than locally. In eastern Montana we are
probably at a low point in one of these cycles just now, and
increase in case prevalence beginning in 1927 is very prob-
able.

BOARD OF ENTOMOLOGY

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24 SIXTH ANNUAL REPORT

The mortality rate in eastern Montana has averaged
about 15 per cent, but in 1926, it was SS^i per cent.

Western Montana. While the spread of infection in
western Montana has not been as great as in the eastern
section, it has, nevertheless, been considerable. Cases have
been reported from nine new counties; Gallatin, Madison,
Lewis and Clark, Broadwater, Jefferson, Powell, Meagher,
Beaverhead, and Mineral, and a new endemic area has ap-
peared just north of Missoula River, partly in Missoula and
partly in Granite county.

Gallatin. Two cases were reported in 1915 from the
Sixteen Mile Creek country in the northern part of the
county. One case in the same district occurred in 1922.

Madison. Two cases were reported from between Wall
and Horse Creek on the west side of the Madison River in
1^17. A third case of unknown point of infection occurred
in 1922.

Lewis and Clark. The first report was of three cases
in 1920. Others have since occurred, as follows: 1 in
1921 ; 2 in 1923 ; 1 in 1924 ; and 1 in 1925. These have been
much scattered, one being close to the northern boundary
near Teton County.

Broadwater. The first case was in 1920. Cases have
been reported as follows: 1 in 1920; 1 in 1921; 2 in 1923;
1 in 1924; 1 in 1926. The localities of infection indicate a
wide distribution of the virus in nature.

Jefferson. Four cases have been reported, one each in
1922, 1923, 1925, and 1926. These have all been in the
northeastern section of the county.

Powell. Only one case has been reported. This was in
1922. There is a strong probability that the tick causing
this case, which resulted fatally, was brought in on lumber
shipped from Bonner in Missoula county.

Meagher. A single case has occurred in Meagher
county. This was in 1923, and was just over the line from
Gallatin County. It doubtless represents an extension of in-
fection from the Sixteen Mile Creek country.

Beaverhead. Two cases, both from Brown's Lake have
been reported, one in 1924, the other in 1925.

Mineral. A single case occurred near Quartz in 1926.

The new focus of infection that lies partly in Missoula
and Granite counties, is on the north side of the canyon of
the Missoula River. It is of interest that all four cases that
have occurred in this area have recovered, whereas in the
old Rock Creek area lying just south on the other side of
the Missoula River cases have been almost uniformly fatal.

BOARD OF ENTOMOLOGY

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26 SIXTH ANNUAL REPORT

It is possible, though unhkely that the single case in
Mineral County in 1926, which resulted fatally, represents
a northward extension of the Bitter Root area. There has
been a very slow northward spread that has covered many
years from the higher portions of the Bitter Root Mountains
in Ravalli County. The northern limit of known infection at
the present time is Deep Creek, in Missoula County.

DISCUSSION

The appearance of human cases of Rocky Mountain
spotted fever within a short period in many new localities
scattered over the vast extent of new territory reported
above has naturally led to speculation as to where the in-
fection came from, especially since this apparent spread has
been without precedent.

The obvious explanation is spread from old endemic
areas, the virus being carried in wood ticks borne by their
animal hosts, wild and domestic. But if this means could
accomplish its spread to new areas as easily and as rapidly
as necessary to account for the conditions under discussion,
then it is difficult to understand why it did not take place
many years ago. Our observations have shown that the
virus may spread from an endemic area by a pushing out
of the old boundary to include new adjacent and favorable
territory, but we have never had an atom of evidence that
the mere introduction of a few infected ticks would result
in establishing infection in a locality at any appreciable
distance from the parent focus. In fact it is our opinion
that it is only under the most unusual circumstances that
new foci of wood tick infection can be thus established.
There is no better example of this than the fact that infec-
tion has never crossed from the west side to the east side
of the Bitter Root Valley, yet no one can doubt that in-
fected ticks have repeatedly been carried across on wild and
domestic animals during the many years that west side
infection has existed.

If we are correct, and the occurrence of human infec-
tion in the new sections cannot be satisfactorily accounted
for by the introduction of wood tick infection, there is but
one alternative, namely, that the virus has actually been
present in the areas concerned for some years but that con-
ditions have only recently become favorable for human in-
fection. In favor of this hypothesis is the fact that all our
field and experimental evidence indicates that the rabbit tick,
Haemaphysalis leporis-palustris, is able to maintain the virus
of Rocky Mountain spotted fever in nature independently of,
and even in the absence of, the spotted fever tick. It does
not bite man and hence in an area where this tick is the sole

BOARD OP ENTOMOLOGY 27

transmitting agent, the virus of Rocky Mountain spotted
fever could be present for years without evidence of its
existence. The danger of human infection would only occur
if the spotted fever tick, which is solely responsible for
human infection, were introduced. It does not follow, how-
ever, that this danger would be immediate. As compared to
the wood tick, the rabbit tick carries a very mild strain of
spotted fever virus, and infected ticks collected in nature
never cause severe infections in laboratory animals. Usually
an immunity test of virus from a virulent strain is neces-
sary before specific diagnosis can be made. It is, indeed,
doubtful if the rabbit tick spotted fever virus is sufficiently
aggressive to infect man. Therefore, following wood tick
invasion of an infected rabbit tick area a considerable lapse
of time might be necessary before human infection would
occur. Rabbit ticks only infest rabbits, so that in an area
infested solely by this tick the virus would be passing only
through this one species of rodent. The wood tick, on the
other hand, infests numerous species of susceptible rodents
and the weak rabbit tick virus after being picked up by
wood ticks would thereafter continually be passed through
multiple susceptible species instead of only one, and it seems
reasonable to believe that virulence or aggressiveness would
gradually be built up in this way, until it finally reached the
point of human infectiousness.

This idea, as just outlined, is admittedly hypothetical,
but there is, nevertheless, considerable supporting evidence
which cannot be detailed in this paper. Suffice it to state
here that differences in the virulence of spotted fever virus
in nature are amply proven by the differences in the virul-
ence of human infection in the different portions of the
northwest in w*hich the disease is known to be endemic. It
therefore requires no feat of the imagination to visualize
still more mild strains in nature, so weak that they cannot
cause human infection. That there may be a gradual stepp-
ing up of virulence in nature is indicated by reports from
certain localities of gradually increasing virulence of human
infection over a period of years. In a rough way, the relat-
ive virulence of the virus in different localities, as evidenced
by the relative severity of human infection, seems to be in
direct relation to the number of susceptible local species of
host rodents, virulence increasing with increase of the num-
ber of susceptible rodents.

The conditions of this hypothesis agree especially well
with known facts in the new large area of infection in east-
ern Montana. On a large portion of this area wood ticks are
a relatively recent introduction; in fact, some sections are
still uninfested. Conditions in the new western Montana

SIXTH ANNUAL REPORT

foci are far more complex than in eastern Montana, and
less well understood, but there is no evidence which is op-
posed to the hypothesis of long resident infection prior to
the first occurrence of cases in man.

BOARD OF ENTOMOLOGY 29

PROPHYLACTIC VACCINATION AGAINST
ROCKY MOUNTAIN SPOTTED FEVER

R. R. Spencer, Surgeon, and R. R. Parker, Special Expert,
United States Public Health Service.

(Cooperating with Montana State Board of Entomology)

During the past four years the United States Public
Health Service, in cooperation with the Montana State Board
of Entomology has been engaged in the preparation and
testing of a prophylactic vaccine for use against Rocky
Mountain spotted fever.

The vaccine is a phenolized virus prepared from the
tissues of infected wood ticks (Dermacentor andersoni
Stiles). Following the demonstration of its value for the
prevention of infection in guinea pigs, rabbits, and monkeys,
its harmlessness for the vaccination of man was determined
by its use, in 1925, in a small group of 34 persons. ^ -

During the season of 1926, the vaccine has been used
experimentally, on as large a scale as supply permitted, for
the prevention of human infection both against the virulent
Bitter Root Valley type and the mild southern Idaho type.
The dosage has been purely arbitrary. For adult administra-
tion two injections of 2 c. c. each were given, which is equiv-
alent to the phenolized virus content of four adult ticks fed
three days, the average live virus content per tick being
5,000 to 10,000 minimal infectious doses for a guinea pig.
The results have been distinctly encouraging and suggest
full protection against the mild southern Idaho type and
partial protection, with sufficient modification to insure
recovery, against the Bitter Root Valley type.

Spencer, R. R. , and Parker, R. R. , Rocky Mountain Spotted Fever:
Experimental Studies on Tick Virus; Public Health Reports, Vol.
39, No. 48, Nov. 28, 1924, pp. 3027-3040; Reprint No. 976.

Spencer, R. R. . and Parker, R. R. , Rocky Mountain Spotted Fever:
Vaccination of Monkeys and Man; Public Health Reports, Vol. 40,
No. 41, Oct., 1925, pp. 2159-2167.

30 SIXTH ANNUAL REPORT

TULARAEMIA AND ITS OCCURRENCE IN MONTANA

R. R. Parker, Special Expert and R. R. Spencer, Surgeon
United States Public Health Service.

(Cooperating with the Montana State Board of Entomology)

Tularaemia is a specific infectious disease. Although
it has undoubtedly been present in Montana for many years,
its presence was first established in 1923 by its recovery
from wood ticks (Dermacentor andersoni) collected in the
Bitter Root Valley. Diagnosis of the first reported human
case was made in the spring of 1925 by Dr. Pfunder of Miles
City. During 1925 and 1926, fifty-five cases have been re-
ported.

This paper gives a summarized account of the general
information concerning this disease, followed by slightly
more detailed record of what is known of its occurrence in
Montana.

The disease was first described as a specific infection
by Surgeon G. W. McCoy of the Public Health Service who
discovered it as a plague-like disease in the California
ground squirrel (Citellus beecheyi) in 1910, in the course ol
routine examination of these rodents for lesions of plague.
In 1912, McCoy and Chafin described the infectious agent
as Bacterium tularense.

There are records of human infection from Arizona in
1907, Utah in 1911, and two laboratory cases at San Fran-
cisco in 1911. The specific identity of these cases, however,
was not then suspected. The first specific diagnosis was in
an Ohio case which occurred in 1914. Our real knowledge of
the disease as a human infection, however, dates from 1919,
when Dr. Edward Francis, of the Public Health Service,
began an investigation of a deer fly borne disease in man in
Millard county, Utah, which he was able to identify with the
plague-like infection found by McCoy in the California
ground squirrel in 1910. Since that time he has devoted his
entire time to the study of tularaemia, and to him we are
indebted for most of our present information of this disease
and the bringing together of a rapidly growing literature
into concise form.

BOARD OF ENTOMOLOGY

SIXTH ANNUAL REPORT

DISTRIBUTION

Tularaemia is thus far only known from the United
States and Japan. In the United States human cases have
been reported from the following twenty-nine states: Ari-
zona, New Mexico, Oregon, Idaho, Utah, Wyoming, Nevada,
Colorado, Iowa, Kansas, Arkansas, Montana, Missouri, Min-
nesota, Kentucky, Pennsylvania, Texas, Tennessee, Missis-
sippi, Ohio, Indiana, Illinois, Georgia, North Carolina, South
Carolina, Maryland, Virginia, West Virginia and Florida.
They have also occurred in the District of Columbia. In
California, infection has been found in ground squirrels and
rats, but no naturally infected cases in man have yet been
reported.

TULARAEMIA IN NATURE

The studies on tularaemia have shown that it is a dis-
ease of nature, its maintenance and perpetuation being en-
tirely independent of human infection, which is of accidental
nature. Primarily it is a disease of wild rodents. Its con-
tinuity is maintained by transmission from rodent to rodent
by blood sucking parasites and by carriage over the winter
in certain of these parasites, perhaps by other means as well.

It is likely that all species of rodents are susceptible to
greater or less degree. The course of infection may be
acute, subacute, or chronic. Jack, cottontail and snowshoe
rabbits, ground squirrels and rats have been found infected
in nature, anl all other wild rodents whose susceptibility has
thus far been tested in the laboratory have become infected.
In most of them it is highly fatal.

There is far more evidence of the prevalence of infec-
tion in Wild rabbits than in other rodents, probably because
man comes in contact with rabbits far more frequently, due
to their use as food for man and other animals and other
purposes. Certain it is that rabbits have thus far proved
the most common source of human infection.

Little is known of the natural occurrence of infection
in other rodents. In California since 1910, it has repeat-
edly been recovered from California ground squirrels from
over a wide area, and in 1925, from three wild rats trapped
in the city of Los Angeles.

Still less is known of its occurrence in animals other
than rodents. In experiments performed at Hamilton with
coyotes following a human case due to a coyote bite, it was
shown that coyotes are susceptible and will acquire infec-
tion by eating infected rabbits, which in young animals, at
least, may result fatally. Francis has shown opossums to
be susceptible. Cats and possibly dogs may acquire mild in-

BOARD OF ENTOMOLOGY 33

fections from eating tissues of infected animals. It is there-
fore evident that some carnivorous animals are susceptible
and may acquire infection of greater or less severity by eat-
ing infected rodents. Of the large domestic animals, sheep
and goats are mildly susceptible.

The parasites actually known to be concerned in trans-
mission of infection among rodents are the wood tick (Rocky
Mountain spotted fever tick), Dermacentor andersoni, and
the rabbit tick Haemaphysalis leporis-palustris. They were
first incriminated through studies made at Hamilton. Both
these ticks are true biological hosts of the infectious agent,
Bacterium tularense. The former is largely confined to the
Rocky Mountain region. The larvae and nymphs are found
on numerous species of rodents, the adults mostly occur on
large animals, wild and domestic, but are also numerous on
jack rabbits in sage brush areas. It is a frequent parasite
of man. The latter, except that it is not infrequently found
on birds (game birds are quite commonly infested) occurs
only on rabbits, especially cottontails and snowshoes. Snow-
shoe rabbits particularly are heavily infested, hundreds of
them often being present on a single animal. On jack rab-
bits they are less numerous, doubtless due solely to the dif-
ferent habitat conditions of this host. It is quite generally
distributed throughout the United States. It rarely bites
man. Both are three host ticks, that is, the larvae, the
nymph and the adult all feed on separate individual hosts.
Infection acquired as larvae or nymphs is passed on to the
adult and can be transmitted to a rodent host by any stage
that follows the one in which infection was acquired. In the
case of the wood tick certainly, and probably the rabbit tick
as well, infected female ticks may transmit infection through
their eggs to the following generation.

Besides these parasites, others are doubtless concerned.
Francis has found, in laboratory experiments, that the
biting rabbit louse, Haemodipsus ventricosus, will transmit
infection from rabbit to rabbit and the mouse louse, Poly-
plax serratus, will carry it between mice. He has further
found that the deer fly, Chrysops discalis, carries infection
from jack rabbits to man but it is not certain that it con-
veys it from rabbit to rabbit. McCoy experimentally trans-
mitted infection between California ground squirrels by tho
squirrel flea. Ceratophyllus acutus. There are many species
of biting lice and flees that infest rodents and it is very
probable that some at least are natural carriers of infection
and play a part along with ticks in maintaining the continu-
ity of the organism in nature.

34 SIXTH ANNUAL REPORT

TRANSMISSION TO MAN

Records of 281 cases have shown that there are sev-
eral means by v^hich man has acquired infection.

1. By the contamination of the hands (less commonly
of other exposed parts of the body) or the conjunctival sac
with the tissues or body fluids of infected rabbits or ticks,
or with tick excreta.

2. By the bite of an adult wood tick (Dermacentor
andersoni) which, in some preceding stage, has acquired
infection from an infected host.

3. By the bite of a deer fly, (Chrysops discalis), which
transmits infection mechanically, its mouth parts havinj)
become contaminated by previously biting an infected jack
rabbit.

4. By the bite of an animal which is either itself in-
fected or which transmits infection mechanically by teeth
or mouth contaminated by eating an infected rodent.

Contamination. — This is the most frequently reported
means of human infection. The most common source is the
tissues of infected jack or cottontail rabbits. In the east
where infection of man by parasites is not known, cotton-
tail rabbits, purchased in the market or shot while hunting
and prepared for the table, have caused numerous cases.
The disease has been known for some years as "rabbit fever"
among market-men who dress rabbits for sale. November,
December and January, the months during which rabbits
are on sale in the markets, are the months in which infec-
tion is most frequent east of the Mississippi. In the west-
ern mountain states, jack rabbits are more commonly the
source of contamination. Cases so contracted occur most
frequently during the spring and summer.

In most cases infected by contamination, the causative
agent is introduced through an abrasion on the hands. In
a minority of such cases, however, no abrasion is present
and it is probable that infection has passed through the un-
abraded skin. Contamination of the conjunctival sac is by
no means infrequent, the hand or fingers carrying infection
to the eye. In the northwest several instances of infec-
tion in this way have followed the handpicking of wood
ticks from domestic stock, the fingers carrying to the eye
tick excrement or the tissues of a crushed tick, both of
which are highly infectious.

Wood Tick Transmission. — Although the possibility of
human infection by Dermacentor andersoni was first sug-
gested only in 1924, cases so called have already been re-
ported in Montana, Wyoming, Idaho, and Utah It is only

BOARD OF ENTOMOLOGY 35

of importance in the western states within the Hmits of
its natural range. Infection is acquired by the larval or
nymphal tick and passed on to the adult stage which alone
will bite man, or it may even be passed on from one genera-
tion to the next. The infective bite may occur on any por-
tion of the body but in most instances thus far reported it
has been on the lower extremities. It is not known whether
it is the bite of the tick which infects, or if it is the getting
into the bite Wound of the highly infectious excrement.
Perhaps both are concerned. Tick caused cases occur during
the season of greatest adult wood tick activity, i. e., from
March to June, inclusive. Sometimes ticks remain active
into July and August but always in relatively small num-
bers. Judging from the evidence to date, the most acute
danger of wood tick infection is in the sage brush plains
sections where jack rabbits, a potent source of tick infec-
tion, abound.

Deer Fly Transmission. — The possibility of infection
by the deer fly, Chrysops discalis, is, like that of infection
by the wood tick, limited to the natural range of this par-
asite. It is much more spotted in its distribution than the
wood tick because of its breeding habits; swampy ground
is essential. It occurs in parts of California, Oregon, Utah,
Idaho, Montana, Wyoming, Colorado, and North Dakota.
Deer fly borne infection has been reported from Oregon,
Utah, Idaho, Wyoming, Colorado and Montana. Whereas the
wood tick may bite any part of the body, the deer fly usually
only bites exposed portions, most often the head and neck.
Deer fly infection has been reported during the months of
June, July, August and September.

Bites of Animals. — This is not a common source of in-
fection. Only three cases thus infected have been reported.
One was bitten by a coyote, one by a ground squirrel, and
the third by a hog. In the last case, the hog not itself
susceptible, is supposed to have previously eaten a rabbit,
many of which were dying in the locality concerned, with a
resulting mechanical transfer of infection. Coyotes and
ground squirrels are both susceptible. The salivary glands
of infected coyotes contain the bacterium and resulting in-
fection in the mouth could doubtless cause infection in a
person bitten, but mechanical transfer from an infected
rabbit recently devoured, as in the case of the hog, is also
hkely.

36 SIXTH ANNUAL REPORT

THE DISEASE IN MAN

Tularaemia in man follows a subacute course that some-
times approaches chronicity. Clincial manifestations have
resulted in the distinguishing of two principal types, the
glandular and the typhoidal. The course of infection is much
the same in both. In the glandular type, into which most
cases fall, there is an enlargement of certain of the regional
lymph gland which may or may not proceed to suppuration.
A primary lesion indicating the site of infection is usually
present, but is absent in a minority of cases. Infection
occurs by contamination of the conjunctival sac, the primary
lesion is a conjunctivities which is accompanied by enlarge-
emnt of the regional lymph glands of the same side of
the head. If elsewhere, the primary lesion is a papule
which later becomes an ulcer of the skin and is accompanied
by an enlargement of the lymph glands which drain the site
of infection.

In the typhoidal type, there is no enlargement of the
regional lymph glands or any evidence of a primary site of
infection. Most cases of this type have occurred among
laboratory workers.

The average incubation period is about, three days, but
may be as short as one day or as long as nine.

The onset is usually sudden and is characterized by
headache, chills or chilly sensations, muscular pains, vom-
iting, sweating, fever and prostration.

The usual febrile period is two or three weeks, but may
be much longer. There ^'s an initial fever which lasts one
to three days. This is followed by a remission of one or
more days duration which is accompanied by general ameli-
oration of symptoms. A secondary rise of temperature fol-
lows, then a gradual decline to normal. Prostration is marked
and there is a continually increasing weakiness. A skin
eruption is present only in small percentage of cases. _ If
present, it is most frequently confined to the upper portion
of the body. Its character is not constant, and it may
be popular. Only eight deaths have been reported, or less
than 3 per cent of recorded cases.

Convalescence is slow and if the course of infection is
at all severe it is usually several months before the patient
is able to perform full time work. Return to normal health
may require a year or even longer in extreme cases. Re-
lapses, eight months after the original infection, have oc-
curred in cases of the typhoid type.

BOARD OP ENTOMOLOGY 37

Tularaemia has been confused with glanders, typhoid
fever, influenza, septic infection, sporotrichosis, undulant
fever, glanders, and tuberculosis.

Diagnosis may be confirmed by an agglutination test
Blood for this test should not be taken before the middle
of the second week of illness, agglutinins being absent dur-
ing the first week. Agglutinins are persistent and have
been demonstrated in the blood as long as eighteen years
after recovery.

NATURAL OCCURRENCE OF TULARAEMIA IN
MONTANA

Since tularaemia is maintained and perpetuated in na-
ture independently of man, it is of interest to record what
is known of the natural conditions under which it occurs in
Montana. Since it is primarily a rodent infection we are
fundamentally interested in the kinds of rodents that are
susceptible. As a matter of fact, it is probable that all
Montana rodents are susceptible in greater or less degree.
The following list, however, includes only those species that
have either been found infected in nature or have been
proven susceptible by laboratory tests.

White tailed jack rabbit, Lepus campestris

Cottontail rabbit, Sylvilagus nuttalli

Snowshoe rabbit, Lepus bairdi

Woodchuck, Marmota flaviventer

Mountain rat, Neotoma cinerea

Yellow-bellied chipmunk, Eutamias b. luteiventris

Pine squirrel, Sciurus h. richardsoni

Porcupine, Erethizon epixanthus

Deer Mouse, Peromyscus m. artemisiae

House mouse, Mus musculus

To all these rodents the disease is highly fatal, death oc-
curring a few days after infection.

In Montana, the jack rabbit is by far the most import-
ant rodent concerned. It is one of the most common sources
of human infection because of the frequency with which it
is used for human food and for other purposes. Cottontails
and snowshoes are not less dangerous but are less commonly
used, snowshoes quite rarely. Tularaemia is frequently, at
least, the cause of the epidemics which periodically decimate
rabbits populations. They are sometimes local and some-
times they involve large areas. It is during these epidemics
that the danger is greatest and that infection in man is'
most prevalent. Besides human infection, the deaths of
cats, dogs, and chickens following the eating of rabbits

38 SIXTH ANNUAL REPORT

killed during these eqidemics have been reported in the
state, but it is not clear that tularaemia was the inciting
cause, since in the dogs and cats at least, laboratory evidence
thus far has only indicated mild susceptibility.

One must next turn to the parasites that spread infec-
tion among these rodents for it is the combination of the
two which results in the perpetuation of the disease. Both
species of ticks known to carry infection are numerous in
Montana. One, the common Montana wood tick, Derma-
centor andersoni, which has already acquired an evil reputa-
tion as the carrier of Rocky Mountain spotted fever and the
cause of tick paralysis, not only infests all the known sus-
ceptible rodents but also many other species whose sus-
ceptibility is probable. It is an important parasite of rabbits
and in sage brush areas where jack rabbits and ticks abound,
is a frequent cause of human infection.

The rabbit tick, Haemaphysalis leporis-palustris, is an-
other important carrier. Its importance, however, as previ-
ously brought out, is purely in relation to the part which it
plays in the natural ma^'ntenance of the disease since it
rarely bites man. It infests only rabbits and game birds,
^ - but is often present in enormous numbers.

As previously noted it is less numerous on jackrabbits
than on cottontails and snowshoes. An uninfested rabbit
during the spring and summer months is uncommon.

It seems certain that natural infection is widely dis-
tributed in the State. Thus far there is evidence of its
prevalence in the following localities; the Bitter Root Valley
and adjoining mountains, Gallatin and Madison counties,
and over a large portion of eastern Montana.

The first evidence of infection in the State came from
the Bitter Root Valley and adjoining mountains when the
infection was recovered from wood ticks which had been
injected into guinea pigs in the course of routine tests for
the presence of the virus of Rocky Mountain spotted fever.
In this area it has been repeatedly recovered from wood

1. What may have been a case of tularaemia following the bite of a
rabbit tick occurred in the practice of Dr. Weldon of Lewistown, in
1923. Tliis is the only record of this tick biting- man in Montana.
The patient. Mrs. G.. had dressed a grouse sliot in the Judith

Mountains on September 29 and became ill on October 1, with
chills and rather marked aching over entire body.

2. Game birds are probably susceptible to tularaemia. A joint investi-
gation by the U. S. Public Health Service and the Bureau of the
Biological Survey to determine the relationship of tularaemia to

epidemics of unknown cause occurring among grouse is being carried

on at Hamilton laboratory. Recent tests indicate their susceptibility,

and therefore point to the dressing of grouse as another possible
source of human infection.

BOARD OF ENTOMOLOGY 39

ticks, rabbit ticks and snowshoe rabbits. Although no cases
in man have thus far been reported, the evidence of local
physicians is suggestive that they have occurred.

Wood ticks collected from Owl Canyon, near Bozeman
in Gallatin county, in April 1925, proved heavily infected.
Guinea pigs and Belgian hares on which these ticks were
fed died to tularaemia. Infection in these lots of ticks was
entirely unexpected and was the direct cause of three labor-
atory cases. During the summer of 1926, infection in the
vicinity of Logan was proven by the occurrence of a case
in a section laborer treated by Dr. A. R. Foss, of Missoula.
This man had been bitten by a deer fly.

In November 1926, Dr. H. F. Carmen of Butte, reported
a case which originated near Reichel in Madison County.
The sourse of infection was not determined.

In eastern Montana, there has been the most evidence
of a w^idespread distribution of infection in nature. During
both 1925 and 1926, a high mortality among jack rabbits
which began following the appearance of ticks in the spring
was reported. That tularaemia was rampant among them
was shown by the fact that a considerable portion of the
cases occurring in the same area resulted from the handling
or cutting up of these rabbits. High jack rabbit mortality
associated with the known prevalence of tularaemia among
them has in other instances (notably in Utah and New
Mexico) been coincident with epidemics of human cases.
Reports further told of greater numbers of ticks noted on
dead rabbits, and it is certain that they played an import-
ant part in the occurrence of the disease among them. Ticks
also caused a considerable number of human cases. Tick
caused human cases and the mortality among tick infested
rabbits, however, was not the only evidence of infection in
ticks. As the result of an investigation of reported "tick
paralysis" in sheep in this area, made in conjunction with
the Montana Livestock Sanitary Board, tularaemia infection
was recovered from ticks collected from sheep of several
widely separated bands. In each instance the sheep concern-
ed were "down with ticks" and supposed to be affected with
tick paralysis. Of one Jot of ticks collected from two sick
ewes, from Calabar, a minimum of 50 per cent were found
infected. Infection in coyotes in this same area was in-
dicated by a human case treated by Dr. Garberson of Miles
City, in which all evidence pointed to a coyote bite as the
source of infection. Infection in Richardson ground sauir-
rels was indicated by another case, treated by Dr. Pigot of
Roundup, in which the bite of a ground squirrel of this
species was the cause of infection.

40 SIXTH ANNUAL REPORT

TULARAEMIA IN MAN IN MONTANA

During the season of 1925 and 1926, fifty-five cases of
tularaemia have been reported in Montana, all but 2 being
in the eastern part of the State, These are exclusive of 6
cases of laboratory infections which have accurred at Hamil-
ton. Twenty-three of these cases have been in Garfield
County, 4 in Powder River, 7 in Custer, 4 in Rosebud, 2 in
Musselshell, 7 in Fallon, 2 in Dawson, 3 in Yellowstone, and
one each in Gallatin and Madison. For one case the locality
of infection is unknown except that it was in eastern Mon-
tana.

Of the total cases, 18 have been reported by Dr. B. C.
Farrand of Jordan, 14 by the Miles City Clinic, (Drs. Garb-
erson, Pf under and Winter), 3 by Dr. W. H. Blackmore of
Baker, 9 by Dr. G. H. Crary of Ismay, 2 each by Drs. W.
R. Morrison of Billings and E. S. Murphy of Glendive and
one each by Drs. A. R. Foss of Missoula, S. E. Light and
W. H. Young of Glendive, V. L. Oler of Billings, C. T. Pigot
of Roundup, G. T. Hayward, Forsyth, and H. F. Garman of
Butte.

For 47 of these 55 cases the diagnoses have been con-
firmed by agglutination tests.

Thirteen cases were definitely due to ticks and in 10
others tick bite or contamination by tick tissues or excreta
was the probable source. Of the latter group 4 were en-
gaged in handling sheep. One of these four definitely re-
called pricking the fingers on burs which were being re-
moved from a ewe's wool and all had primarly lesions of
the hands and all denied having handled or cut up rabbits.
The handling of the wool on sheep might easily result in
introducing infection into an abrasion, since the highly in-
fectious tick excrement is held by the wool. Sheep some-
times crush ticks by rubbing to allay irritation and such
crushed tissue could also cause infection. Three of the
definite tick cases were primary infections of the eye.
They occurred in persons who had been handling ticks from
horses or cattle, and who, by rubbing the eye with the
hand, had contaminated the conjunctiva either with tick
tissue or excreta. These tick caused cases occurred in the
months of March, April, May, June, and July, the largest
number having been infected in May.

Fourteen cases were definitely due to the handling or
cutting up of infected rabbits, and 2 other cases were pro-
bably thus infected. In two instances 3 cases resulted from
handling a single rabbit, in one 3 brothers cut up a jack rab-
bit, and in the other 3 persons used the flesh of the same

BOARD OF ENTOMOLOGY 41

rabbit for fish bait. Two rabbit caused cases were primary
eye infections. June, July, August and October were the
months in which these cases were reported.

Two cases were caused by the bites of animals and
have been previously referred to. One was infected by a
coyote, the other by a Richardson ground squirrel.

Deer fly bites are apparently a less frequent cause of
infection in Montana than in certain other northwestern
states. Only one case definitely so caused has been re-
ported. This man was bitten near Trident in Gallatin
county. The species of deer fly concerned is not known.
One case reported from Billings was supposed to have been
due to the introduction of crushed fly tissue into the eye.
There was no information to suggest what kind of fly was
concerned, but Chrysops discalis, the species concerned in
Utah and other sections is known to occur locally.

For 6 cases the primary lesion occurred at the site of
abrasions on the hand caused as follows: One by briar
pricks, one by sage brush, one by splinters (both hands
infected), one (railroad employee) by the corner of an old
trunk, and two by barbed wire. None of these gave his':ory
of contact with rabbits or of tick bites, and there was no
evidence of the means by which infection was introduced
introduced into the abrasions. Another case had a primary
lesion on the dorsum of the left foot, but cause of abrasion
and source of infection were not determined. For seven
other cases there is even less information.

CONTROL WORK: ROCKY MOUNTAIN SPOTTED

FEVER

CONTROL DISTRICTS, BITTER ROOT VALLEY,

FOR THE PERIOD JANUARY 1, 1923, TO DECEMBER

31, 1926,

F. J. O^Donnell, Field Agent
Montana State Board of Entomology

As there was no published report of the State Board
of Entomology for the biennium ending December 31, 1924,
this report of the control work, therefore covers the period
January 1, 1923, to December 31, 1926. During the first
thirteen months of this period, that is, January 1, 1923, to
February 29, 1924, the control work was in charge of Mr.
W. E. Pollinger. The writer took charge March 1, 1924,
with R. R. Parker, Special Expert, U. S, Public Health
Service, serving in an advisory capacity.

42 SIXTH ANNUAL REPORT

The control program for the past four seasons does not
differ essentially from the program as outlined in the
Fifth Biennial Report of the Board of Entomology (1921-
1922), with the exception that the quarantine regulations
have not been enforced, and is briefly as follows:

Rodent control is given first consideration, both because
it is the control measure which can be most effectively^
applied under present working conditions and at the same
time affords a considerable degree of protection to the resi-
dents of the agricultural section of the infected area. Dip-
ping is second in importance. Other measures such as graz-
ing control, hand picking of stock and quarantine, etc., have
been dropped temporarily for the reason that sufficient
funds have not been available to properly enforce them.

RODENT CONTROL

Rodent control work is confined largely to the ex-
termination of the Columbian ground squirrel as this rodent
is by far the most numerous of the immature tick hosts,
and is also most difficult to exterminate. Ground hogs or
woodchucks, while being considerably less of a factor as tick
hosts, because they are relatively few in number in the
control area as a whole are, nevertheless, a potential menace
in these areas where they are more or less abundant, and for
this reason a special effort is made to exterminate them.
Rabbits, chipmunks, and other rodents are also baited where
it is convenient to do so. Two poisonings are required each
season; one in the early spring when the rodents first be-
come active, and a second in' June following the appearance
of the young rodents.

The boundaries of the control districts up to and in-
cluding 1921, extended from the Missoula-Ravalli county
line on the north to Lost Horse Creek south of Hamilton.
In 1922, a control district was created in Missoula County.
In 1923, the southern boundary of the control district was
extended from Lost Horse Creek to Burnt Ridge south of
Darby, and in 1925 a narrow strip of land on the west bank
of the Bitter Root River, extending from the Missoula-
Ravalli county line to a point west of Hamilton, which had
been released by the Board in 1917, was again included
within the control area, thus making a continuous control
area extending from Burnt Ridge on the south to the Big
Flat north of Missoula, a distance of about 69 miles, vary-
ing in width from three to seven miles and embracing an
area of 212,180 acres on which active control work is per-
formed.

BOARD OF ENTOMOLOGY • 43

In order to systematically carry on the rodent control
work the area has been divided into districts as follows:
Darby North, Darby South, Gold Creek, Hamilton, Victor,
Stevensville, Florence, and Missoula County. These districts
are then grouped with one district supervisor in charge of
each of the following groups: Darby North, Darby South,
and Gold Creek; Hamilton and Victor; Stevensville and
Florence; and Missoula County. The area in charge of each
supervisor varies from 3 to 7 miles in width and from 13 to
18 miles in length.

It is the duty of the supervisor to employ a sufficient
number of suitable field men to properly poison the infested
lands in his district. It is also his duty to supervise and
direct the field men, to establish and move camp when nec-
essary, to transport field men to and from their work when
transportation is necessary, to see that field notes are prop-
erly made by the poisoners relative to the amount of poison
and labor expended on each parcel of land treated, to es-
tablish contact with the resident land owners or renters in
his district, to inspect land both before and after treatment,
to supervise stock dipping operations, to file a weekly re-
port with the Hamilton office, and to attend to such other
matters as may arise in his district pertaining to control
work. The supervisors are employed by, and are directly
responsible to the Field Agent in charge at the Hamilton
field Station. They receive a definite monthly salary, and
must be equipped with a suitable car for transporting
men, moving camp, etc., for which they receive a fixed
monthly allowance. The men employed to do the actual
field work, or poisoning, are active, trustworthy young men,
and are generally familiar with the area in which they are
working. The field crews are usually quartered in camps
established by the supervisor, conveniently located adjacent
to or within the area to be treated. The camp equipment,
tents, stoves, dishes, etc., are furnished by the Board. The
active work of poisoning is accomplished by the field men
by placing the poisoned grain at or near the rodent burrow,
or, when calcium cyanide is used, this material is placed
into the burrow.

The rate of pay for the field men is fixed by law at
$3.50 for an eight hour day, or $0.4375 per hour, and the
field men average between nine and ten hours per day in
the field. There is an average of about twenty field men
employed each season.

The method of financing the rodent control work in
Ravalli County during the past season (1926) differed some-
what from the method used during the season just preced-
ing. For the year 1919 to 1922, inclusive, the "full cost of

44 SIXTH ANNUAL REPORT

poison and labor was charged against the land ; from 1923
to 1925, inclusive, one-third of the expense was borne by
the land owners, and two-thirds jointly by the County and
State. This plan was not satisfactory for the reason 'hat
many of the land owners availed themselves of a provision
in the law — Chapter 27 Sessions Laws, 1919 — which gives
them the privilege of poisoning their owm land and there-
by avoiding payment of the additional tax. Land thus
poisoned frequently had to be re-poisoned by the State, as
the land owner seldom does thorough work, and the work
was not done at the time when it would be most effective.
This plan was also unsatisfactory in that it required a large
amount of detailed records on the part fo the field men,
(the poisoners), and a great deal of office work and expense
were involved in preparing maps showing each individual
land holding in the control area, in maintaining up-to-date
files of land ownership and areas, and in preparing cost
summary data for the county assessment roll. With these
facts in mind, it was therefore decided to take the matter
up with the Commissioners of Ravalli County with the re-
quest that the county appropriation for rodent work be in-
creased so that it would not be necessary to assess any part
of the expense directly against the land treated. The Com-
missioners acted favorably in the matter, and made an ap-
propriation from the County general fund, thereby relieving
the land owner of a direct rodent tax. This change in the
method of financing the rodent control work created a much
better feeling among the land owners toward the control
program as a whole, resulted in better cooperation, and
therefore much more effective control work.

In Missoula County rodent control has been on the same
basis as during the preceding biennium ; that is, a part of
the funds for labor and material has been appropriated from
the general fund of the county, supplemented by funds from
the State. There is, therefore, no direct charge made
against the land. The general plan of rodent control is the
same as in Ravalli County and is in direct charge of the
Field Agent of the Board of Entomology.

The following table summarizes the rodent control work
for the years 1923 to 1926, inclusive. The years 1919 to
1922, inclusive, are for comparative purposes.

BOARD OF ENTOMOLOGY

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46 SIXTH ANNUAL REPORT

DIPPING

Although stock dipping is recognized as an important
and effective accessory control measure, it has not been
compulsory since 1921. This has been due largely to in-
sufficient funds, and inadequate dipping facilities.

An inspection of the vats in the spring of 1924, showed
that all of them needed more or less repairing. The O'Brien
Creek vat which is constructed of heavy galvanized iron,
has been crushed by a ground movement and rendered use-
less in its present location. No attempt has yet been made
to repair it. The Florence vat which is also of galvanized
iron construction was found to be open at the seams, due
to ground pressure but was repaired at a relatively small
cost and again placed in service. Repeated efforts made to
repair leaks in the Stevensville and Blodgett Creek vats,
which are of concrete construction, proved useless, and the
Stevensville vat was therefore not used during the season
of 1924. A galvanized iron lining was installed in the Blod-
gett Creek vat and it was made serviceable for the 1924
season. In February 1925, a similar lining was installed
in the Stevensville vat. The Victor vat was in a leaky con-
dition, but with some temporary work was in service for a
part of the 1924 season. A galvanized iron lining was also
installed in this vat early in 1925. The Gold Creek vat, of
concrete construction, has developed some slow leaks which
permit ground seepage into the vat, thereby diluting the
dip solution and rendering it useless. It is hoped that funds
will be available to install a lining in this vat before the
next season. Dipping pens, chutes, corrals and fencing at
all of the vats were in a poor state of repair, and several
were unfit for use. These conditions have gradually been
improved until they are all now serviceable. It is, however,
necessary to do considerable repairing each spring before
the dipping season begins.

Experience has shown that to be most effective dipping
must be done at not greater than ten day intervals and that
usually the stock should be dipped at least three times each
season. The actual number of dippings, however, depends ;
(a) on the season, whether early or late; (b) the length of
time during which ticks are active; (c) whether cattle or
horses are concerned; and (d) the condition under which
they are being grazed.

To enforce a practical as w^ell as an effective dipping
program, it is necessary that a sufficient number of con-
veniently located vats be available. As there are only five
vats in the control districts in a serviceable condition, at
the present time, it is, therefore, obvious that to require
dipping of all stock at ten day intervals would work an hard-

BOARD OF ENTOMOLOGY 47

ship on stock owners living at considerable distances from
the vats. Though dipping has not been compulsory for
several years, the value of this method of control has, never-
theless, been emphasized to the stock owners, and such
vats as could be used have each season been filled with dip
solution, and with the assistance of the District Supervis-
ors, a considerable number of stock has been voluntarily
dipped by the owners. During the season just passed (1926)
2,191 head of stock (horses, mules and cattle) were passed
through the vats. This is a somewhat larger number than
was dipped during the preceding seasons, due in part to the
fact that more vats are available and also due to the result
of personal interviews by the District Supervisors with the
stockmen. As there is a better spirit of cooperation gradu-
ally developing among the stockmen, it is hoped that the
number of stock dipped in the future will greatly exceed
the record of the past.

Compulsory dipping should be made a part of the con-
trol program, but in order to properly carry out this phase
of the program, it will first be necessary to increase the
number of vats so that there would be not to exceed five
miles between the vat sites. State controlled pastures,
acquired by purchase or long lease, should provide for range
stock and all stock now grazing on unfenced areas in the
control districts. These pastures should be equipped with
vats so that dipping could be done at the proper intervals.
State controlled pastures properly operated would make
grazing control possible, and would also, to a great extent,
solve the problem of dipping range stock which, under
present conditions, graze in timbered areas and brushy
pastures where it is at times impossible to round them up
and deliver them at the vats at regular intervals and at a
reasonable expense.

RODENT POISONS

During the past four seasons, as in preceding years,
an effort was made to develop new poison formulas for
rodent extermination. However, no grain mixture has thus
far been found which equals the preparation now in use
and which is as follows:

Crushed whole oats S quarts

Strychnine alkaloid 1 ounce

Saccharine 1 teaspoonful

Gloss starch % pound

Water 1 pint

Molasses (stock) 1 pint

The substitution of various materials such as dried
apples, prunes, corn meal, rolled oats, wheat , barley, etc.,
for the crushed oats now used, failed to improve our present
mixture, and usually were more expensive and less effective.

48 SIXTH ANNUAL REPORT

In 1924, experiments were made with calcium cyanide flakes.
This material is placed into the burrow, where, coming in
contact with the soil moisture, it readily decomposes and
releases hydrocyanic acid gas. The gas thus released is
very deadly to rodents, and only a small amount is required,
in the case of the Columbian ground squirrel, for a lethal
dosage. Six hundred pounds of calcium cyanide were used
in 1924, and the results obtained as to its effectiveness were
highly satisfactory. The initial cost of this material, how-
ever, together with the additional expense in labor required
in treating the land would make its general use, as a sub-
stitute for grain poison, prohibitive. A quart of grain poison
costs about twenty cents, and will average about 80 baits,
while a like amount of calcium cyanide will cost about thirty-
two cents and contains not more than 35 baits. Also, calcium
cyanide requires from one-fourth to one-third more time
in distribution than is required when grain poison is used.
Even with this disadvantage, however, it is felt that calcium
cyanide is a valuable aid in control of the Columbian ground
squirrel, particularly in hog and sheep pastures, as these
animals will eat the poisoned grain readily, and also near
farm dwellings where there may be ducks and geese, and in
areas where the poisoned grain has not been effective.

In order to determine the relative stability of calcium
cyanide, a number of experiments were carried on during
the season of 1925. The material was exposed in the bur-
rows in the same manner as when poisoning rodents and
then recovered at stated intervals varying from 30 minutes
to 15 days. The recovered material was then sent to Dr.
Starz, Chemist, Livestock Sanitary Board, Helena, and the
following report from Dr. Starz gave the result of the lab-
oratory tests:

June 8, 1925.

Mr. F. J. O'Connell, Field Agent,
State Board of Entomology,
Hamilton, Montana.

Dear Sir:

With reference to the matter of investigation of the
more or less exposed calcium cyanide samples, I beg leave
to report as follows:

Technical calcium cyanide, as is used in the eradica-
tion of rodents, is not of a definite chemical composition,
frequently containing calcium carbide and other chemical
compounds. The sample you forwarded and which was
taken from the lot used by your field force in poisoning

BOARD OF ENTOMOLOGY 49

rodents, was made up of brownish, black flakes, which up-
on exposure to the air gave off the odor of hydrocyanic acid
and when put in water rapidly developed hydrocyanic acid
gas and some acetylen gas, the latter from the calcium car-
bide present.

At your request I have made a series of experiments
and tests to determine the relative amount of hydrocyanic
acid left in the more or less exposed samples. The hydro-
cyanic acid was determined volumetrically with the aid of a
1/10 normal silver nitrate solution. There might have been
other methods than the above but for the purpose of making
quick comparative tests with the samples submitted, the
volumetric silver nitrate method was found to be all right.

Preliminary tests showed that all samples gave off
gaseous hydrocyanic acid upon exposure to air. That was
proven by inserting strips of solium Picrate paper and
Gaujac copper paper, the former turning brownish red
rapidly, and the latter sapphire blue.

Tests showed the unexposed crude calcium cyanide
flakes to yield 50.1% hydrocyanic acid. The inclosed chart
shows the relative loss of hydrocyanic acid during a definite
time of exposure in dry and damp ground. It seems that
the loss of hydrocyanic acid from the calcium cyanide by
exposing it in dry ground is not so very rapid, while the
calcium cyanide exposed in damp ground shows considerable
loss in proportion to the time of exposure and presence of
humidity, of course. Naturally, the presence of moisture
is essential in liberating quickly the poisonous gas in the
gopher holes.

In conclusion I may state that the tests showed that
sufficient hydrocyanic acid gas was set free from the cal-
cium cyanide to kill the rodents in their burrows.

Respectfully submitted,

EMIL STARZ, Chemist.

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BOARD OF ENTOMOLOGY 51

July 9, 1925.

Mr. F. J. O'Donnell, Field Agent,
State Board of Entomology,
Hamilton, Montana.

Dear Sir:

Inclosed find tabulated result of tests made with the
exposed samples of calcium cyanide flakes to determine the
residual hydrocyanic acid.

Naturally, the residual amount of hydrocyanic acid was
found greater in the samples exposed in dry than in those
exposed in damp ground. That was very noticeable in the
samples which had been exposed fifteen days in dry and
damp ground. From the tests it can be noticed that there
is a more or less progressive loss of hydrocyanic acid cor-
responding to time exposure and humidity of the soil. After
fifteen days of exposure of the cyanide of calcium in the
ground, only small amounts of hydrocyanic acid were found
to be left and the danger from accidental poisoning of live-
stock may be considered practically nil.

Some of the samples were so intimately mixed with
particles of soil, sand, and other extraneous material that
it was impossible to completely remove these impurities and
for this reason you will notice some discrepancy in the
amounts of residual hydrocyanic acid found. Some of the
samples were wet and these also, naturally, showed consider-
able differences from those in dry condition.

The investigation is insofar interesting and of value
for your purpose, as it has shown clearly that after the
fifteenth day of exposure of the calcium cyanid under proper
conditions there could no longer be any danger of poisoning
live stock if they should accidentally get hold of the ex-
posed material.

It also shows the initial rapid liberation of the gaseous
hydrocyanic acid, which ceased after a short time if suffici-
ent moisture were present to decompose the material.

These facts are of value in cases of lawsuits, and dis-
putes where losses of livestock are claimed to have been
due to cyanide poisoning with exposed calcium cyanide. The
investigation also proved the great efficiency of the cyanide
of calcium in the destruction of rodents and its comparat-
ively greater safety with regard to live stock than that of
other poisons used heretofore.

Trusting the above will furnish you some data which
will be of value in your work, I remain
Very truly yours,

EMIL STARZ, Chemist.

52 SIXTH ANNUAL REPORT

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BOARD OF ENTOMOLOGY ' 53

REPELLANTS

During the spring of 1924, a series of experiments was
carried on for the purpose of developing, if possible, a suit-
able tick repellant for farm and range stock. Various oils
such as raw cotton seed oil, raw linseed oil, lard, some pe-
troleum oils, and others, have for some time been known to
certain tick repelling properties, but are of value only where
the animals are being handled frequently and the repellants
!an be applied as indicated. The purpose of our experiment
was to develop a repellant that could be applied early in the
spring before the ticks became active and that would remain
on the animals and serve as a repellant over the greater
portion of the active tick season. For the purpose of our
xperiments 65 animals were used; three dairy herds of 12
animals each, one herd of 8 animals, 15 range cattle and six
horses. The horses were grazed in the Stevensville district
and the cattle were grazed; one each in the O'Brien Creek,
Florence, Stevensville and Darby districts, and two herds in
the Hamilton district.

Before applying the repellant each animal was care-
fully inspected and a record made of the number of ticks
found attached, of the number found crawling, the condition
of the animal and other data.

The repellants used in our experiments weye as follows.

Raw linseed oil, raw cottonseed oil, linseed plus para
cresol, cottonseed oil plus pinene, lanolin plus cottonseed oil,
lanolin plus vaseline, cottonseed oil plus pine tar, cottonseed
plus derrisine, vaseline plus para cresol, linseed plus derris-
ine, lanolin plus sulphur, plus cottonseed oil, plus pine tar,
plus pinene, heavy crankcase oil and paraffine oil. These
oils and other substances were used in various proportions,
and on cattle, were applied to the base of the horns, along
the neck and withers, and on horses, under the jaws, on the
breast, between the fore legs and between the hind legs. Six
ounces of the preparation were used on each animal at each
treatment. After the repellants were applied, the animals
were pastured in tick infested areas and inspected in about
seven days, when note was again made of the number of
ticks attached, the number found crawling on the animal, the
general condition of the animal and the condition of the
repellant; that is, whether the repellant was still on the
animal in sufficient quantities to prevent ticks attaching.
In a few instances there was apparently sufficient amount
of the material still in evidence to act as a repellant; on
other animals there was only a slight trace of the material,
and in most cases the repellant had entirely disappeared in
from seven to ten days.

54 SIXTH ANNUAL REPORT

Our experiment was a failure so far as developing a
suitable repellant was concerned, but it did demonstrate that
it would be extremely difficult to develop a repellant with
an oil base that would be effective for any considerable
length of time. Lack of funds and personnel has thus far
prevented further experiments along these lines, but it is
hoped that these experiments will be again taken up in the
near future.

The Bureau of the Biological Survey, has, as in previous
years, cooperated with this office in the control work on
federal lands lying within the control districts and on the
National Forest lands which border the districts on the
west. The amount of money made available by the Bureau
for control work has not been large, but it has helped con-
siderably in reducing the migration of rodents from the
mountains to the adjoining valley areas.

Our relations with the County Commissioners of both
Ravalli and Missoula counties have been most cordial. They
have given us their hearty cooperation at all times, and
have expressed themselves as pleased at the manner in
which the work has been conducted.

This station is indebted to the Livestock Sanitary
Board, and particularly to Dr. Emil Starz, Chemist, for the
splendid service rendered us in making laboratory tests of
our dip solutions, in making analyses of the stomach con-
tents of animals killed, allegedly, as the result of eating
rodent poison, and other laboratory work.

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