Tularemia in Sheep 
The earliest publication on tularemia in 
sheep was entitled “Tularemia in Sheep in 
Nature,” and was prepared by Dr. R. R. 
Parker of the Rocky Mountain Laboratory 
and Dr. J. S. Dade of the Idaho State Sheep 
Commission (4). It stated: 
In the spring of 1923 there were reported to the 
field station of the Public Health Service at Hamilton, 
Mont., several instances of heavy losses among sheep 
that were believed to be due to the wood tick, Der- 
macentor andersoni Stiles. These reports were from 
eastern Montana and southern Idaho and were the 
first complaints of probable tick-caused trouble in 
sheep that had been received. Each report was in- 
vestigated by Parker either by personal visit to the 
locality concerned or by correspondence, and in one 
instance ticks from affected eastern Montana sheep 
were tested at the Hamilton laboratory. 
All of the guinea pigs injected with ticks 
from sick sheep in eastern Montana died, but 
the nature of the infection was not determined. 
Later experience suggests a diagnosis of tula- 
remia in these affected animals, but at that time 
it was not known that the wood tick was a 
carrier of P. tularensis, and the workers con- 
cerned were not yet familiar with tularemia in 
laboratory animals. 
Within the year, Parker, Spencer, and Francis 
(5) demonstrated that the wood tick could 
acquire and transmit tularemia and that the 
infection was present in adult ticks collected 
in nature. In 1925, P. tularensis was re- 
covered from ticks collected from sick sheep, 
and agglutinins were demonstrated in serums 
from two recovered sheep by Parker and 
Butler (6). 
During the next few years, several serious 
outbreaks of disease associated with heavy tick 
infestations were experienced in Idaho. How- 
ever, for various reasons no diagnosis was 
established. 
Blackwell Band 
When an episode of sickness in sheep as- 
sociated with heavy tick infestations oc- 
curred in 1928, tularemia was immediately 
suspected and conclusively proved by Parker 
and Dade (4). Although their first publication 
inadvertently omits mention of the locality, 
a later report (7) gives considerably more 
detail. This outbreak occurred in the Black- 
well band of sheep between Mountain Home 
and Boise, Idaho. 
The significant history of this band was 
related as follows: 
. . . This band consisted of 900 old ewes, 300 year- 
lings and 700 lambs. They had wintered at Grandview, 
south of Mountain Home and, in the early spring, 
were purchased by H. Blackwell. Delivery was made 
at Mountain Home about the middle of March. Thence 
they were trailed by way of Orchard and Round Butte 
to Black Creek, 15 miles south of Boise, where spring 
range had been leased. While en route they traversed 
a section near Round Butte and Orchard in which the 
losses has been experienced by the Thompson Brothers 
bands ... in 1927, and where bands of the same 
owners were again affected in 1928. 
The loss of lambs was noted for several days prior 
to reaching Black Creek and immediately on arrival 
they called on Dade for assistance and the band was 
visited on April 1, by Dade and Dr. Huffman. Dade 
recommended the removal of the band from the sage 
brush to a tick-free area, but local range of this char- 
acter all being occupied, the owner was forced to 
hold his sheep on Black Creek. It was therefore 
necessary to treat each affected animal individually, 
either the ticks being hand-picked or Kreso dip applied 
to points of attachment. Affected animals with 
temperatures of from 106.0° to 107.8° F. were nu- 
merous. Many were scouring. The band was again 
visited by Dade and Parker, April 12, and though much 
improved, losses were still being experienced, and the 
band showed marked loss of condition. Three ewes 
were “down,” several recently dead lambs were seen, 
and there were about twenty sheep which showed by 
high carriage of the head, by stiff-legged walk or the 
presence of scours that, they were affected. Up to this 
date, 50 percent of the lambs, 25 percent of the yearlings, 
and a smaller percentage of the ewes had been affected. 
Sixty lambs and 15 ewes had died. 
Dead jackrabbits were reported as numerous along 
the trail followed to Black Creek and on the Black 
Creek range. 
On April 1, when Dr. Dade and Dr. Huffman 
visited the band, they autopsied a dead lamb 
that had been acutely ill and another that had 
been dead for 12 to 24 hours. Both tissues 
and ticks from each lamb produced tularemia in 
guinea pigs when tested by Dr. Parker at the 
Rocky Mountain Laboratory. Infected guinea 
pig tissues were sent to Dr. Edward Francis 
of the Hygienic Laboratory at Washington, 
D. C. Dr. Francis recovered cultures of P. 
tularensis and confirmed the diagnosis of 
natural infection with tularemia in sheep. 
2 
Tularemia in Sheep and in Sheep Industry Workers in Western United States 
