Table 5. Incidence of tularemia in the sheep 
industry, according to year, by State, 1934—52 
Year 
Colorado 
Idaho 
Montana 
Nevada 
Oregon 
Utah 
Wyoming 
Total 
1934 and previous _ 
1 
4 
6 
1 
1 
1 
4 
18 
1935 
4 
4 
1936. . 
1 
1 
1937 _ 
2 
3 
1 
6 
1938 
1 
1 
2 
1939. _ 
1 
1 
1 
3 
1940 
2 
2 
4 
8 
1941 . 
1 
7 
1 
15 
24 
1942 
4 
4 
24 
1 
1 
8 
42 
1943 . 
3 
1 
15 
6 
25 
1944 ______ 
4 
1 
4 
2 
5 
16 
1945 
1 
i 
4 
2 
8 
1946. 
1 
1 
4 
3 
9 
1947 
1 
1 
2 
1948-. 
2 
2 
4 
1949 
2 
1 
1 
2 
6 
1950 
1 
2 
3 
1951 __ 
1 
1 
2 
1952. 
1 
1 
Unknown _ 
1 
2 
2 
5 
Total _ 
20 
19 
60 
3 
3 
20 
64 
189 
Table 6. Sources of tularemia infection in the sheep 
industry, by State, 1934-52 
Source of infection 
Colorado 
Idaho 
Montana 
Nevada 
Oregon 
Utah 
Wyoming 
Total 
Sheep. _ 
Tick bite 
Rabbit 
5 
4 
1 
7 
4 
40 
13 
T 
l 
1 
1 
r 
7 
7 
1 
5 
27 
16 
3 
2 
16 
87 
46 
6 
4 
46 
Deerfly. 
1 
7 
Other or unknown. _ 
T otal 
10 
7 
i 
20 
19 
60 
3 
3 
20 
64 
189 
Table 7. Clinical types of tularemia infection in the 
sheep industry, by State, 1934-52 
Type of infection 
O 
T5 
c3 
o 
o 
O 
o 
rG 
c3 
l—( 
G 
G 
g 
4^ 
G 
O 
§ 
G 
TJ 
G 
> 
£ 
G 
o 
hD 
<D 
o 
rG 
G 
4-3 
£> 
&0 
G 
a 
o 
>> 
£ 
"3 
4-3 
O 
H 
Ulceroglandular .... 
Typhoidal 
6 
1 
1 
12 
8 
1 
7 
1 
2 
28 
12 
8 
1 
11 
2 
2 
5 
2 
1 
28 
14 
8 
1 
13 
73 
35 
25 
4 
52 
Glandular 
Oculoglandular 
Other or unknown.. __ 
Total. __ 
1 
1 
12 
20 
19 
60 
3 
3 
20 
64 
189 
Although the data from the above sources 
are admittedly incomplete, we have on file 
information on 189 human cases of tularemia 
associated with the sheep industry. When 
these data are analyzed and tabulated, some 
idea is obtained of the geographic distribution 
(map, p. 13), occupational incidence (table 3), 
seasonal and yearly incidence (tables 4 and 5), 
sources of infection (table 6), and clinical types 
(table 7) of infection experienced. 
Shown on the map is the geographic distri- 
bution of the recorded cases for which the 
county where infection was supposedly ac- 
quired is known. In addition, there were many 
cases in which the county was unknown but 
the State was given. The numbers of cases for 
the several States, with a figure in parentheses 
showing the number of cases for which county 
data is lacking, are as follows : Colorado 20 (0) ; 
Idaho 9 (10); Montana 47 (13); Nevada 2 (1); 
Oregon 3 (0); Utah 13 (7); Wyoming- 43 (21); 
or a total of 137 (52). 
The occupational incidence of tularemia 
within the sheep industry based on these case 
data is rather evenly shared among shearers, 
64 cases; owners, 54 cases; and herders, 42 cases 
(table 3). As a general rule, the shearers have 
contact with the animals only during a 4- or 
5-month season, March to July, but this period 
includes the entire active season of the adult 
ticks. Four housewives on sheep ranches had 
tularemia. Women frequently help in the 
care of sheep and lambs and are exposed to 
ticks or contaminated materials brought into 
the house on work clothes., 
In 46 cases, the source of infection (table 6) 
was not stated, but it was attributed to sheep 
in 87 cases, to tick bite in 46, to rabbits in 6, 
and to deerflies in 4 cases. Some of the sheep- 
contact cases were attributed to skinning dead 
sheep, and many of the others occurred in 
shearers who became grossly contaminated 
with crushed ticks and tick feces in the wool of 
sheep. Shearers’ hands are often cut and 
abraded, thus allowing ample exposure to in- 
fection. Twelve of the sheep-contact cases 
were more specifically attributed to lambing. 
In tlieir daily routine, herders are highly 
exposed to ticks. Loose ticks readily transfer 
from sheep to man, so the high incidence of 
infection from tick bite is to be expected. 
12 
Tularemia in Sheep and in Sheep Industry Workers in Western United States 
