HOG CHOLERA 427 
associated with cases presenting extensive ulcerations, which certainly 
are much older than the extravasations. . 
Diagnosis. Hog cholera is diagnosed by finding in the various 
organs of the dead animal the lesions that are at present considered 
characteristic of the disease; and by inoculating susceptible pigs with 
the blood from a suspected case and producing hog cholera. If a 
mixed infection is suspected the blood should first be filtered through a 
Berkefeld filter before injecting it. The inoculation is sometimes 
necessary because frequently pigs die of cholera before they show the 
lesions peculiar to the infection. 
The diagnosis must be made in the field by the practitioner except- 
ing in those cases where pig inoculations are to be made in which case 
blood from the suspected animal should be carefully taken. As 
experimental animals, such as rabbits and guinea pigs, are not sus- 
ceptible the only assistance the laboratory can render in making the 
diagnosis is to inoculate one or more pigs. By this method the diag- 
nosis cannot be made for several days which renders it of little value 
from the practitioner’s point of view. 
Hog cholera is to be differentiated ‘from septicemiz, from death 
caused by dietary conditions and poisons such as alkali or brine poison- 
ing brought to pigs in their food. The particular diseases from which 
it is to be differentiated are Salmonellosis, hemorrhagic septicemia, 
infectious pneumonia, shoat typhoid and swine erysipelas, necrotic 
laryngitis, anthrax, heat stroke, lightning or sudden deaths from other 
causes. In the differentiation it is necessary to take into account the 
history and the general conditions under which the affected animals 
exist. It is of the greatest importance that practitioners understand 
that with hog cholera the prompt diagnosis is dependent upon the 
findings on the post mortem and that the sending of pieces of tissue 
to a laboratory for assistance is, in most instances, of little or no 
assistance. 
Prevention. As hog cholera is caused by a specific virus, the pre- 
vention consists in keeping away from healthy swine any and all 
agencies that may bring the virus to them. It is known that litter 
from infected pens that has been brought into enclosures where 
healthy hogs were kept has caused infection. The virus is found in 
nearly, if not all, tissues of the body of the diseased hog and this 
virus remains alive and virulent in the tissues of infected animals 
for a considerable length of time after death. It is present in the 
