ramie hail never been under cultivation and in these 
areas sagebrush predominated. 
The first sick animals were noticed on April 28, 13 
days after the sheep were turned out on the range. A 
ewe anil a lamb were found dead the following day. 
At this time, the sheep were grazing in high sagebrush 
ju-t -until of the prominent butte some 12 miles north 
of Paul More dead sheep were observed on May 1, 
and 12 sick lambs, some of which eventually recovered, 
were brought back to the ranch during the next few 
days. 
Heavy infestations of wood ticks, Dermacentor ander- 
snni Stiles, were observed on the sheep, and ticks were 
abundant, in the grazing area. At the recommendation 
of veterinarians of the Idaho Department of Agricul- 
ture, the flock was sprayed on May 5 by a commercial 
concern using an insecticide containing benzene-hexa- 
chloride and DDT, in addition to other ingredients. 
The flock was then moved from sagebrush range to 
grass areas on the dry-land farms where the ticks were 
less abundant. The outbreak quickly subsided. 
Preceding and during the epizootic, the flock watered 
at two temporary ponds on the range and also received 
some water hauled from the home ranch wells. 
A total of 7 or 8 ewes and 35 lambs died during the 
outbreak, a mortality of 8 to 10 percent. No unusual 
illness was observed in a small band consisting of 2 
bucks, 10 ewes, and 16 lambs kept on the home ranch 
throughout the spring and summer. 
On May 5, a sick lamb was shipped to the State 
Veterinary Laboratory at Boise, Idaho, where it was 
slaughtered and autopsied. Tissues from this animal 
were injected into guinea pigs. The guinea pigs died, 
and spleen and liver tissues of one were sent to the 
Rocky Mountain Laboratory with the request that 
they be tested for the presence of Pasteurella tularensis. 
These tissues produced infection and death 
in all test guinea pigs. All had lesions charac- 
teristic of tularemia, and one culture of P. 
tularensis was isolated. 
During the epizootic, blood specimens from 
six of the affected sheep were sent to the Idaho 
Department of Public Health at Boise for 
agglutination tests. The individual titers as 
given by McArthur and Brown (11) were: 
1:640, 1:1,280, 1:1,280, 1:2,560, 1:5,120, and 
1:5,120, respectively. 
By the time a diagnosis had been established, 
the epizootic had largely subsided and the sheep 
were back on the open range, where further 
studies were not feasible. However, when the 
lambs were brought in for shipment in Septem- 
ber, 5 months after the outbreak, blood samples 
were taken, and in November, when the ewes 
were brought in, they also were bled and all 
serums were tested for agglutination of P. 
tularensis antigen. The results of these tests 
are shown in table 2. 
The highest dilution of serums at which 
complete agglutination occurred was 1:80 for 
4 of the lambs. However, serums from 2 of the 
mature sheep gave complete agglutination at 
dilutions of 1:160. 
Table 2. Results of agglutination tests on range 
sheep, Rupert, Idaho, 1949 
Agglutination reaction 
148 lambs 
283 mature 
sheep 
Num- 
ber 
Per- 
cent 
Num- 
ber 
Per- 
cent 
3+ or 4+ at 1:20 or 
higher 
23 
15. 5 
56 
19. 8 
Lower titer or negative. _ 
125 
84. 5 
227 
80. 2 
Although these titers are not especially high, 
the}’ are diagnostic in well-controlled tests and 
show that a diagnosis of spring outbreaks can 
be established in the fall when flocks are 
brought in from the range and are accessible in 
shipping pens or feed lots. Agglutinins for 
P. tularensis are extremely persistent in man 
and remain at diagnostic levels for 8 to 10 years 
after infection. They seem to be less persistent 
in sheep. 
Apparently wool damage as a result of 
tularemia infection in sheep had been over- 
looked because few or no followup studies had 
been made. The owner of this band identified 
certain of the animals that had been sick by 
their poor or broken fleeces. A few lambs had 
completely shed their fleeces during the con- 
valescent period and others had great patches 
of wool missing. It is possible that some of the 
damage may have resulted from application of 
the insecticide used to control ticks, but later 
(1952) we observed similar damage to wool in 
lambs that had not been sprayed or dipped but 
which were recovering from tularemia. 
Wool samples were saved from 8 of these 
lambs with broken fleeces, that is, some por- 
tion of the fleece had been completely shed. 
These samples were submitted to the Mont ana 
Wool Laboratory, at Bozeman, for examina- 
tion. In taking the samples, a piece was 
clipped at the border of both the shed and un- 
Public Health Monograph No. 28, 1955 
