Both cottontails and jackrabbits are often 
abundant on sheep ranges and around sheep 
corrals, and contact with these animals ac- 
counted for 6 cases. Deerfly bites are a com- 
mon source of infection in midsummer in cer- 
tain western States, and 4 cases from this 
source were recorded. 
The ulceroglandular type of infection pre- 
dominated, with 73 cases. There were also 25 
glandular cases; 4 oculoglandular; and 35 
typhoidal (table 7). With many of the in- 
fections contracted from tick bite or through 
wounds on the hands and arms, the ulcero- 
glandular type of infection is most likely. 
Although 35 cases were of the typhoidal type, 
suggesting infection from ingestion or oral 
contamination, in no instance was eating of 
mutton even suspected as a source of infection. 
Three persons on one ranch in Montana were 
thought to have acquired then’ infection from a 
contaminated water supply, but field investi- 
gations gave no convincing evidence as to the 
source of infection ( 16 ). However, in another 
instance, we were able to associate a number of 
rural cases with a contaminated domestic 
water supply ( 17 ). 
The information on seasonal incidence, shows 
a marked concentration of cases in the spring 
months (table 4). This is coincidental with 
the active period of adult wood ticks and with 
the shearing season. Of the 161 cases for which 
date of onset was recorded, 148 occurred in 
April, May, June, and July; 84, or approxi- 
mately 52 percent, occurred in May. Some of 
the summer and fall cases were attributed to 
deerfly bites and to handling old pelts. 
During the period 1934-52, from 1 to 42 
cases of tularemia have been reported each year, 
an average rate of over 9 cases per year (table 
5). There are records of 18 cases previous to 
that time, the first having been reported in 
1926. For the years 1941-45, there were re- 
ported 24, 42, 25, 16, and 8 cases, respectively, 
but this probably represents a period of greater 
case-finding activity and interest rather than 
any great increase in the actual number of cases. 
Serologic Evidence of Tularemia in Sheep Industry Workers 
Sheepshearing is an itinerant and largely 
seasonal occupation. Crews of 10 to 15 men, 
under the direction of a foreman and with 
complete equipment, start work in the south- 
western States in February or March. They 
move north as the season advances, stopping 
a few days or weeks at each of the ranches 
along then - scheduled route. Camp is often 
set up on the range in places distant from cities 
or medical care. The season ends in June or 
July in northern Montana and Washington. 
The foreman follows much the same route 
each year, but the membership of his crew is 
fluid; men may work with a different crew each 
season. Slieepshearers have a well-organized 
union, membership in 1949 was over 1,000. 
Wages are comparatively high and the work is 
hard. Work is not interrupted for minor 
illnesses. For a more serious illness the man 
stays around camp, moves along with the 
crew when it changes location, and resumes 
work at the earliest possible time. Only se- 
riously ill individuals consult a doctor or are 
hospitalized. Illness of several shearers at one 
time seriously disrupts the teamwork and 
schedule of the crew, and a long illness during 
the short working season is a major economic 
loss to the shearer. 
With a background of numerous case histories 
of tularemia in shearers, a survey of crews was 
made by the Rocky Mountain Laboratory in 
the State of Montana in 1950 near the end of 
the shearing season in cooperation with LaYor 
Taylor, president of the shearers' union. 
Shearing crews were contacted in the field 
at then- work. Blood samples and brief his- 
tories of illness, if any, were taken. Blood 
samples and histories were also taken from wool 
tiers, “wool trompers,” camp cooks, herders, 
wranglers, and owners who were present at 
the scene of operations. 
Blood samples suitable for testing were ob- 
tained from 140 shearers and from 41 persons 
otherwise employed in the sheep industry in 
14 
Tularemia in Sheep and in Sheep Industry Workers in Western United States 
