428 HOG CHOLERA 
various organs early in the course of the disease so that when infected 
hogs are slaughtered for food before they exhibit symptoms, or the 
lesions are recognizable, their tissues if fed to healthy pigs may pro- 
duce the disease. It is of the highest importance, therefore, that 
scraps of fresh pork that come from an unknown source should not be 
given to healthy swine unless they are thoroughly cooked. It is impor- 
tant that healthy hogs should not be shipped in infected crates or cars or 
placed in infected pens. Great care should be exercised in exhibiting 
hogs at fairs or stock shows. It is important that people who have 
the care of infected hogs should not be allowed to come in contact with 
healthy ones. 
When hog cholera breaks out in a herd of swine it is of first import- 
ance that the diagnosis be made at once, that the apparently healthy 
hogs should be separated from the diseased ones and treated at once 
with anti-hog-cholera serum. If the diagnosis is promptly made and 
the prophylactic treatment administered at once, most of the individ- 
uals can be saved. 
Anti-hog-cholera serum. Anti-hog-cholera serum is the defibrin- 
ated blood obtained from hogs that have been hyperimmunized 
against cholera. In some laboratories the defibrinated blood is 
centrifuged and the clear serum is used. It is employed to immunize 
hogs that have been or that are liable to be exposed to the disease. 
Experience has shown that serum will when properly administered 
protect healthy hogs against infection. It is not a therapeutic agent 
but frequently infected pigs carrying a high temperature have 
recovered after its administration. 
In the use of serum care must be exercised to prevent common 
infections that are liable to result in abscesses. The serum is usually 
injected into the ham, the jowl or subcutaneously in the flank. There 
is some difference of opinion as to the application of serum to young 
pigs. While it is generally not considered with favor a few have used 
it with success. 
Use of hog cholera serum. Three methods are employed in the use of hog cholera 
serum in the field: serum alone, serum and virus at the same time (simultaneous 
method), and serum alone followed in a week or more by simultaneous treatment 
(double method). Serum alone produces a transcient immunity in sound herds and a 
permanent immunity in infected herds. Its chief indications:are for well animals in 
infected herds, in all cases where immunity lasting a month will meet the requirements, 
and in cases where the simultaneous method cannot safely be used. The simultaneous 
method produces a lasting immunity and is indicated in sound herds where all possible 
sanitary precautions seem unlikely to prevent infection. Contra-indications are: 
