18 HOG CHOLERA 



all other factors combined, and in the country 

 as a whole this practice plays an exceedingly im- 

 portant part in the spread of the virus from local- 

 ity to locality. Many hogs are killed while they 

 are in the incubation period of cholera, and pork 

 that comes from their carcasses, even though it is 

 fit for human food, will produce hog cholera when 

 fed in small portions to hogs. Bits of this in- 

 fected pork find their way into garbage which is 

 fed to susceptible swine, and the cycle is com- 

 plete. 



The use of hog cholera virus in the field in 

 serum-virus immunization has now become a rou- 

 tine measure, and despite the advantages that re- 

 sult from this practice, it must in truth be said 

 that it is responsible for many new outbreaks of 

 hog cholera. The practice of giving feeding 

 shoats serum-virus treatment and shipping them 

 immediately to distant points operates to infect 

 much new territory, and is often the cause of 

 heavy losses among the hogs thus handled. 

 "Vaccination cholera," as these " breaks " follow- 

 ing serum-virus treatment are called, although it 

 usually runs a less rapid course which invites sec- 

 ondary infection, is not fundamentally different 

 from hog cholera contracted as a result of natural 

 infection, but there is a marked tendency in some 

 quarters to avoid the issue and attribute the 

 deaths to causes other than hog cholera virus. 



