The distribution of the Rocky Mountain spotted fever tick [Dermacentor venustus Banks]

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Material Information

Title:
The distribution of the Rocky Mountain spotted fever tick Dermacentor venustus Banks
Series Title:
United States. Dept. of Agriculture. Bureau of Entomology. Circular ;
Physical Description:
ii, 4 p. : map ; 23 cm.
Language:
English
Creator:
Bishopp, F. C ( Fred Corry ), 1884-1970
United States -- Dept. of Agriculture
United States -- Bureau of Entomology
Publisher:
Government Printing Office
Place of Publication:
Washington
Publication Date:

Subjects

Subjects / Keywords:
Rocky Mountain spotted fever tick   ( lcsh )
Genre:
federal government publication   ( marcgt )
non-fiction   ( marcgt )

Notes

Statement of Responsibility:
by F.C. Bishopp.
General Note:
Title from caption.
General Note:
"Issued March 31, 1911."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 029685381
oclc - 27980619
lccn - agr11000420
Classification:
lcc - SB818 .C6 no.136 1911
System ID:
AA00022890:00001

Full Text









LUBR ARY
STATE PLANT BOARD
Issued March 31, 1911.


U. S. DEPARTMENT OF AGRICULTURE,
BUREAU OF ENTOMOLOGY-CIRCULAR No. 136.
L 0. HOWARD. Entomologist and Chief of Bureau.



THE DISTRIBUTION OF THE ROCKY MOUNTAIN

SPOTTED-FEVER TICK.


BY
F. C. BISHOP,
Agent and Expert.


81261-11


WASHINGTON : GOVERNMENT PRINTING OFFICE : 1911


II~3
~33


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BUREAU OF ENTOMOLOGY.


L. 0. HOWARD, Entomologist and Chief of Bureau.
C. L. MARLATT, Entomologist and Acting Chief in Absence of Chief.
R. S. CLIFTON, Executire Assistant.
W. F. TASTET, Chief Clerk.

F. H. CHITTENDEN, inll charge of truck crop and stored product insect investigations.
A. D. HOPKINS. in charge of forest insect investigation.
W. [). HUNTER, in charge of southern field crop insect investigations.
F. M. WEBSTER, in charge of cereal and forage insect investigations.
A. L. QUAINTANCE, in charge of deciduous fruit insect investigations.
E. F. PHILLIPS, in charge of bee culture.
D. M. ROGERS, in charge of preventing spread of moths, field work.
RIOLLA P. CURRIE, in charge of editorial work.
MABEL COLCORD, librarian.

SOUTHERN FIELD CROP INSECT INVESTIGATIONS.

W. D. HUNTER, in charge.

F. C. BISiOPP, H. P. WOOD, W. V. KING, G. N. WVOLCOTT, engaged in tick investi-
gations.,
WV. D. PIERCE. J. D. MITCHELL, E. S. TUCKER, T. E. HOLLOWAY, G. D. SMITH,
E. A. MCGREGOR, HARRY PINKUS, AV. A. THOMAS, THOMAS LUCAS, engaged in
rot ton boll weceil inrestigations..
A. C. MORGAN, G. A. RUNNER, S. E. CRUMB, engaged in tobacco insect investiga-
ltions.
'T. C. BARBER, C. E. HOOD, cngagf'd in stigar tcanc and rice insect investigations.
F. (C. PRATT, engaged in cactus insect inrcstfigations.
It. A. COOLEY, D. L. VAN D)INE, WILMON NEWELL, A. F. CONRADI, C. C. KRUMB-
JIAAR, collaborators.












CIRCULAR NO. 136. Issued March 31, 1911.

United States Department of Agriculture,
BUREAU OF ENTOMOLOGY.
L. 0. HOWARD, Entomologist and Chief of Bureau.


THE DISTRIBUTION OF THE ROCKY MOUNTAIN
SPOTTED-FEVER TICK.
(Dermacentor venu.ftus Banks.)
By F. C. BISHOP,
Agent and E.ipert.
The demonstration of the fact that Rocky Mountain spotted fever,
an important disease of man, is conveyed by the common wood tick
of the Rocky Mountains, has naturally attracted considerable atten-
tion. In the year 1902 Drs. Wilson and Chowning advanced the
theory that the "wood tick" acts as a carrier of the disease. In
1906 the late Dr. H. T. Ricketts began a series of admirably planned
and executed experiments which showed that the tick Dermnacento'
venustus Banks is principally, if not entirely, responsible for the
transmission of this disease to man.
While the disease appears in its most virulent form in the Bitter
Root Valley in western Montana, it is known definitely to occur in a
less severe form in parts of Idaho, Wyoming, Utah, and Nevada.
Although no authentic records to that effect are to be found, there is
-little doubt that it occurs occasionally in certain sections of Colorado
and Oregon. In the Bitter Root Valley from TO70 to 80 per cent of
the cases terminate fatally, while in southern Idaho there is a mor-
tality of about 5 per cent. The cases of the disease which have ap-
peared in the other States mentioned seem to be of this less virulent
type.
Since it has been determined that a tick is the transmitter of this
disease, the importance of ascertaining the distribution of the species
concerned is at once apparent. In 1909 Prof. R. A. Cooley, as Ento-
mologist of the Montana Agricultural Experiment Station, under-
took the determination of the distribution of this tick in the State of
Montana. He accumulated 172 lots of ticks, including 142 lots of
Dermacentor ven-ustus, from 49 localities. During the same season





2 DISTRIBUTION OF THE SPOTTED-FEVER TICK.

Mr. W. V. King was employed as an agent of this bureau for the
purpose of collecting specimens especially outside of Montana. In
this investigation he worked under the general direction of Mr.
W. D. Hunter, but under the immediate supervision of Prof. R. A.
Cooley. At the same time Mr. J. D. Mitchell, Mr. F. C. Pratt, and
the writer, as agents of the Bureau of Entomology, made collections
in the southern and central portions of the Rocky Mountain region.
In 1910 Mr. W. D. Hunter formulated plans for obtaining further
information regarding the distribution of the species. By the use of
circular and personal letters, the aid of several hundred individuals
throughout the Western States was obtained. Through the coopera-
tion of these correspondents a large number of ticks was procured.
All of the material was sent to the laboratory at Dallas, Tex., where
the immature ticks were reared to adults and all specimens were
carefully determined. Mr. Nathan Banks, a specialist in this group
of animals, identified much of the material received during 1909.

WHERE THE TICK OCCURS.

As a result of this investigation the distribution of the spotted-fever
tick, as shown by the accompanying map (fig. 1), was determined.
The map includes a number of localities in Montana where, in 1909,
Prof. R. A. Cooley determined the species to occur. Our knowledge
of the distribution is based upon 1.300 lots of ticks, 815 of which were
Dermacentor renustus. The specimens of this species were obtained
from 225 different localities. The numbers of localities in the dif-
ferent States in which this tick was collected are as follows: Cali-
fornia 3, Colorado 15, Idaho 42, Montana 72, Nevada 11, New Mexico
2, Oregon 15; Utah 12, Washington 27, Wyoming 26. The shaded
portion of the map 'includes all of the localities where the tick has
been found. The darker shading indicates the regions where the
species occurs in greatest abundance. There is no doubt that there
are areas of considerable extent, within the territory indicated as
being infested by the Rocky Mountain spotted-fever tick, where the'
tick is entirely absent or where it is found only occasionally.
The northern part of the Roclky Mountain region in the United
States is the territory principally infested, but the-river valleys and
sagebrush plains to the west are more or less heavily infested. Al-
though the spotted-fever tick occurs in the eastern edge of the Cas-
cade Mountains, it does not appear to exist in the main Cascade range
and lhas never been found to the west of the divide formed by those
mountains. It has )een found in the western portion of the. Black
Hills of South DI)akota, and probably occurs throughout those hills.
There is no doubt that the species is common in southern British
Columbia and possibly eastern Alberta. Two females were collected
by Dr. 11. G. Dyar at Kaslo, British Columbia. This locality is about






DISTRIBUTION OF THE SPOTTED-FEVER TICK. 3

65 miles from the United States boundary, directly north of the line
between Idaho and Washington.
This tick does not seem to be limited particularly as regards life
zones. It appears to be most abundant in the Transition Zone, but
occurs commonly in the Canadian and Upper Sonoran Zones. It is
probably also to be found in the Hudsonian Zone. Specimens have
been collected at various elevations from slightly over 500 feet to


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FiG. 1.-Map showing region In the United States in which tim Rocky Mountain spotted-
fever tick occurs. The degree of shading indicates the relative abundance of the tick
in different sections. (Original.)

nearly 9,000 feet. above sea level. The species seems to reach its
highest development and occur in greatest numbers between 3,000
and 5,000 feet.
FACTORS INFLUENCING ABUNDANCE.

The abundance of the Rocky Mountain spotted-fever tick is greatly
influenced by the presence of numerous host animals, as well as such





DISTRIBUTION OF THE SPOTTED-FEVER TICK.


protection as is afforded by timber. Ticks have been found to be
especially abundant in localities where there is much fallen timber
and brush. The immature ticks have been found to feed almost ex-
clusively on the small mammals, and adults on the large domestic
animal. Hence. the absence or scarcity of either of these classes of
hosts greatly influences the number of ticks occurring in i. given
region.
Mr. Vernon Bailey, of the Bureau of Biological Survey, has
pointed out that the distribution of a subgenus of the ground squir-
rels-namely. Colobotis-corresponds very closely to the area in
which the spotted-fever tick occurs. The relation between the tick
and its host. as well as control measures, will be discussed at length
in a publication to be issued utinder the auspices of the Bureau of
Entomology, the Biological Survey, and the Montana Agricultural
College.
THE IMPORTANCE OF THE DISTRIBUTION OF THE TICK.

It is not desired to cause undue alarm regarding the danger from
Rocky Mountain spotted fever. Since, however, the malady is known
to occur in a number of the States where this species of tick is found,
and there is reason to believe that the disease is spreading, a knowl-
edge of the range of the species is important. In fact there is good
reason to suppose that Rocky Mountain spotted fever may occur and
be transmitted to man in any region where this species of tick is
presenCt if tlhe disease is once introduced into a locality by a tick
from a d(isease-infected region, or by man or some other animal sus-
ceptil)le to the disease. It may also be stated that the tick is of
somle imI)ortanice a.- a parasite of live stock. These considerations
make it inoperative that tihe tick be kept under control in all regions
where it occtirs aind that steps be taken to lessen the danger of the
introduction of disease-infected ticks into uninfected regions.
Approved:
JAMES WILSON.
A,;ccir',arq AgIcrilture.
\VASiIJNGTON. I). (.. February 15, 1911.
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