On their April 12 visit, Dade and Parker 
obtained specimens for testing from 6 dead, 
sick, or convalescent sheep. Tularemia was 
produced in test guinea pigs by tissues of 1 
dead sheep and by ticks of 2 sick sheep. Blood 
samples from 5 of the sick and convalescent 
animals agglutinated P. tularensis at maximum 
dilutions of 1 160, 1/640, 1/640, 1/1,280, and 
1 1,280, respectively. The 8 animals in which 
tularemia was demonstrated included 4 lambs, 
1 yearling, and 3 old ewes. 
'Thus, a disease entity in range sheep asso- 
ciated with heavy tick infestations and which 
bad been repeatedly observed causing serious 
k >ss of condition and numerous fatalities was 
identified as tularemia. 
Mingling Epizootic 
A more complete stud}' of an outbreak of 
tularemia in sheep near Ringling, Mont., in 
1934 was made by this laboratory and the 
Montana Livestock Sanitary Board as reported 
by Philip, Jellison, and Wilkins (5). The 
significant facts, not quoted verbatim, regard- 
ing this epizootic were related as follows: 
A band of yearlings numbering 1,320 had been 
lambed in the spring of 1933. In November of that 
year it was moved to winter range near Melville, about 
35 miles southeast of Ringling. The band left Melville 
April 1 and was driven overland, arriving near Ringling 
on April 8. 
Presence of wood ticks was first noticed by the herder 
on April 7 when the flock was about 10 miles from 
Ringling. 
On April 13, a few “gaunt looking” sheep were 
noticed. On April 16. 2 were definitely sick and about 
30 more were sick the next day. On April 18, so mam- 
looked ill that the owners became alarmed, thinking 
some poisonous plant might be responsible, and moved 
the band, with the exception of 38 which were too se- 
verely affected to travel. Two, possibly 4, sheep died 
that day and by April 21, 17 had succumbed. On 
April 25. 60 head of moribund sheep and some 400 
others, obviously ill, were scattered singly or in varying- 
sized groups over an area a mile square. Though 
■■deticking” operations were begun by the owners, addi- 
tional prostrated sheep continued to appear until 
about April 30. 
The last moribund y-earling was necropsied May 8. 
Except for this animal and a few that were still conva- 
lescent, the epizootic had ended. A count of dead 
carcasses in the epizootic area totaled 200 or about 15 
percent of the flock. 
The band of ewes (mothers of the affected yearlings) 
that had not been taken to winter range but had been 
pastured continuously near Ringling did not become 
ill, although they too were infested with quite a few 
ticks. 
The affected band was visited April 23 and 
24 by Dr. H. F. Wilkins of the Montana Live- 
stock Sanitary Board and Dr. Fred Stimpert of 
the State Hygienic Laboratory. Three or four 
blood samples obtained from sick animals on 
April 24 agglutinated P. tularensis at low 
dilutions. In view of the heavy tick infesta- 
tions, a tentative diagnosis of tick-borne 
tularemia was made by Dr. Wilkins, who also 
recommended dipping all the animals. On 
April 25 a field laboratory was set up near the 
affected band for the collection and processmg 
of specimens. 
Numerous autopsies were performed on 
sheep that were found moribund or dead. 
Tissues were preserved in glycerine or in buf- 
fered glycerine solution for testing at the Rocky 
Mountain Laboratory. Blood samples for ag- 
glutination tests were taken from apparently 
normal, sick, moribund, convalescent, and 
recovered sheep. Ticks were collected from 
sheep and from sagebrush areas for testing. 
Tissues from 6 moribund sheep were tested 
for tularemia by injection of guinea pigs. 
Tissues from 5 of the 6 sheep produced typical 
tularemia infections, and cultures of P. tula- 
rensis were established. Tissues yielding mfec- 
tion were: external lymphatic glands, 4 of 6 
tests; spleen, 1 of 4 tests; and liver, 1 of 4 tests. 
P. tularensis was recovered from 6 of 9 
groups of ticks taken from sick sheep. Ticks 
from 5 animals selected as normal and ticks 
from sagebrush produced no infection. 
Serum samples from 36 of the yearlings were 
tested for agglutinins. Twenty-seven of these 
were positive, giving complete agglutination at 
maximum dilutions varying from 1:80 to 
1:2,560, as shown in table 1. 
Table 1. Results of agglutination tests on ranyc 
yearling sheep, Ringling, Mont., 1931 
Positive (4 — 
Condition of animals 
Apparently- normal 
111 
Very ill 
Moribund 
Recovering 
“Recovered” 
at 1:80 or Negative 
higher) 
1 3 
7 1 
4 U 
4 1 
4 3 
Public Health Monograph No. 28, 1955 
