CONTROL AND ERADICATION OF HOG CHOLERA 233 



infections. The three most important methods by 

 which hog cholera travels from locality to locality 

 are: 



1. Marketing from infected herds. The hogs 

 thus shipped are a menace to others as they are 

 taken to market, they keep stock cars and stock- 

 yards constantly infected, they are sometimes sold 

 from the yards as feeders, and their carcasses are 

 regularly placed on the market in large numbers 

 where they serve to infect many new localities 

 through the medium of garbage feeding. 



2. The transportation from public stock- 

 yards of susceptible feeder hogs, and those 

 which receive simultaneous treatment imme- 

 diately prior to shipping. When susceptible 

 feeders are placed in public stockyards they often 

 become infected, and though they leave the yards 

 apparently in good health they soon develop 

 cholera and the farms which receive them become 

 new centers of infection. Feeder hogs that receive 

 simultaneous treatment and which are at once 

 shipped to distant points, frequently ' ' break " as 

 a result, and thus introduce hog cholera into new 

 territory. 



3. Wide and indiscriminate use of hog cholera 

 virus in immunizing, especially by untrained 

 men. " Vaccination cholera" is still too common 

 in farm herds, despite the fact that experienced 

 men know how to avoid most of it. 



