HOG CHOLERA 213 



Hog cholera vaccination. — The Dorset-Niles serum is now 

 freely available and is reliable when properly used. The method 

 of producing this serum is, in general, as follows : 



A hog that is immune by reason of having passed through 

 the disease or having been vaccinated is given a large quantity 

 of virulent hog-cholera serum. His own blood then develops a 

 property which protects other hogs when it is injected under 

 the skin or into muscular tissue. The serum of this hog's blood 

 produces a prompt but temporary immunity. If the hog which 

 has received such serum be given pen exposure with sick hogs, 

 or an injection with a small quantity of virulent blood (simul- 

 taneous vaccination), it then becomes rather permanently im- 

 mune, for it has had the disease in a mild form and recovered. 

 There are, therefore, two ways of vaccinating by the Dorset- 

 Niles method : serum only, which gives prompt but temporary 

 immunity; and simultaneous vaccination, which gives perma- 

 nent immunity. The dose of serum varies according to the 

 weight of the hog treated. Serum should be kept unopened 

 and cool until used, and all precautions should be taken to insure 

 clean work in vaccinating. 



There are other useful fields for this vaccine: Owners may 

 wish to vaccinate valuable hogs in advance of any possible out- 

 break, or exposure to disease at stock shows. Another and per- 

 haps the most important field relates to outbreaks of the disease 

 where vaccine can be used early in an outbreak to prevent or 

 lessen losses and thus protect surrounding herds and check the 

 outbreaks. 



Common mistakes. — It is a mistake to bury hogs that have 

 died of cholera when the carcasses can be burned, for burning 

 is by far the most efficient means of destroying the germs of 

 such diseases. If it is not convenient to burn the carcasses, they 

 should be buried under at least four feet of earth and covered 

 freely with fresh lime. 



It is a mistake, and frequently a serious one, for a farmer to 

 ship in strange hogs from stockyards, and put these with stock 

 hogs already on hand without vaccination or quarantine. The 

 mere fact that the hogs came from an uninfected district is no 

 argument to the contrary, for the car in which they were shipped 

 may have recently carried hog-cholera victims. New breeding 

 stock should usually be isolated for three weeks before putting 

 them with hogs already on the place unless the latter be immune. 



