8 BULLETIN 674, U. S. DEPARTMENT OF AGRICULTURE. 
It is very difficult to distinguish swine plague from hog cholera. 
The two diseases may occur in the same animal. Should the out- 
break seem to be but slightly contagious and not inclined to spread 
from the premises upon which it first appeared, it is probably not 
hog cholera, but, on the other hand, if it spreads rapidly throughout 
the neighborhood, it is undoubtedly due to hog-cholera infection. 
The presence of bipolar oval bacilli does not alone establish a diag- 
nosis of swine plague, since those organisms are frequently found as 
secondary invaders in true cases of hog cholera, and again they are 
often present in the noses and throats of healthy swine. 
PREVENTION. 
Animals and fowls may be protected experimentally from contract- 
ing hemorrhagic septicemia through the use of bacterins. Cattle, 
sheep. swine, rabbits, and fowls, if treated with heated cultures of 
hemorrhagic septicemia germs obtained from animals or birds of the 
same species as that to which they themselves belong, will almost in- 
variably become protected against injections of living cultures of 
the same germ, even though apphed in comparatively large quanti- 
ties. Tests made by this bureau have shown that the use of cultures 
from animals of another species often affords similar complete im- 
munity. Sheep have been made immune from virulent cultures 
obtained from other sheep by the use of prepared cultures from cat- 
tle. Rabbits have been made resistant to hemorrhagic septicemia 
cultures, derived from a variety of different species of animals, by 
treatment with prepared cultures coming from animals of other 
species. They have been protected perfectly from inoculations with 
virulent cultures of the true Bacillus bovisepticus in doses four times 
as large as that required to produce fatal results in a rabbit receiv- 
ing no previous treatment. Fowls have been protected from injec- 
tions of deadly quantities of virulent fowl-cholera organisms by the 
use of prepared bouillon growths of the same germ, or by the use of 
strains of the fowl-cholera bacillus possessing but little virulence. 
However, when the colon or paratyphoid B group of organisms is 
found to be responsible for the deaths, the bacterins should include 
these germs. 3 ; 
As a result of these investigations, and of others reported in medi- 
cal literature, it is customary, at the present time, in manufacturing 
bacterins for the protection of stock from attacks of hemorrhagic 
septicemia to use several cultures coming from a number of out- 
breaks of the disease for treating the same species of animals as that 
from which the cultures were obtained. For example, the bacterin 
for bovine hemorrhagic septicemia is being prepared from strains of 
the B. bovisepticus and not the B. suisepticus, or vice versa. 

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