agglutination tests, indicating that tularemia 
was prevalent in the band during the spring. 
Flock C 
The flock C sheep were on the Arco Desert 
during the spring season but they had been 
sprayed just before they were turned out on 
the range. Losses were light during the tick 
season; only 9 animals died, according to the 
owner’s estimate. On July 20, this flock was 
examined on summer range near the home 
ranch in Stanley Basin. Ten lambs and 4 
ewes showing broken fleeces or other evidence 
of previous illness were bled. Serum samples 
from 2 of the lambs gave positive agglutina- 
tion tests, both at a titer of 1:80. All of the 
ewes were negative. 
Both of the positive lambs had badly broken 
fleeces. In comparison with the other bands, 
this one was very little affected with tularemia. 
The difference may have been due to choice of 
range area or possibly due to the residual action 
of the insecticide in preventing tick infestation. 
Flock D 
According to Dr. McArthur, about 100 
sheep had died in another band of 2,500 
during the tick season. Some ticks from 
these sheep had been sent to the Boise 
Laboratory and inoculated into test animals, 
with fatal results. Tissues from these 
test animals were forwarded to the Rocky 
Mountain Laboratory but no infection was 
demonstrated in them. 
Flock E and Others 
Information was received from Tom Fica, 
deputy sheep inspector for the State of Idaho, 
Ketchum, Idaho, that a fifth band of sheep was 
seriously affected during tick season and that 
many animals had died. Of the E band, 3 
ewes and 1 sick lamb were bled on June 15. 
The lamb and 1 ewe were positive for tularemia 
at diagnostic titers. 
Dr. J. S. Allen, Sr., Idaho Falls, reported in a 
personal communication that he assisted in the 
treatment of still another flock during an out- 
break of disease on the Arco Desert during 
the 1952 tick season. No blood samples were 
obtained from this band for diagnostic studies. 
Owners of flocks involved in the 1952 out- 
breaks agreed that the weather was favorable 
during the outbreaks but that snow or pro- 
longed cold rains would have greatly increased 
their losses when the sheep were weakened and 
sick. 
In contrast to the agglutination tests on 
affected flocks showing a high percentage of 
positive reactions are the results on serums 
from 135 sheep taken for Q fever studies at 
Gooding, Idaho, March 28 and 29, 1951. 
Tularemia infection was not suspected in this 
flock, and none of the 135 samples gave any 
detectable agglutination at dilutions of 1:20 
or higher. 
Human Infections During Epizootics 
During the 1952 Arco Desert studies, no 
human cases of tularemia attributable in any 
way to the occurrence of the disease in sheep 
came to our attention. Individuals exposed 
to risk of infection included owners, herders, 
and tick control crews engaged in spraying 
and dipping sheep, and in some instances, even 
hand picking ticks from sick animals. 
Convalescent Pathology 
In 1952, the first sick sheep in several affected 
bands were observed about April 20 to 24. 
The epizootic was at its height about April 27 
to May 1 and had largely subsided by May 5. 
When the flocks were first examined by us on 
June 13 and 14 none of the sheep appeared 
acutely ill, although man} r showed broken 
fleeces, retarded growth, or emaciation as a 
result of recent illness. 
We had not previously tested convalescent 
sheep, infected in nature with tularemia, for 
the persistence of infection in their tissues. 3 
Two lambs from flock B were selected and 
brought to the laboratory alive for autopsy 
and testing. 
One lamb, whose serum sample gave complete 
agglutination of P. tularensis antigen at a 
dilution of 1:160, was autopsied on June 23, 
approximately 30 days after the epizootic had 
subsided. The lamb had a badly broken fleece 
and was thin and retarded in growth. Its 
weight was estimated at 40 pounds, compared 
with 80 to 100 pounds for healthy lambs in 
this flock. 
3 The pathology of acute tularemia infection has 
been described for three naturally infected and one 
experimentally infected sheep by Lillie, Francis, and 
Parker (13). 
8 
Tularemia in Sheep and in Sheep Industry Workers in Western United States 
