18 The Bulletin 



Mortality. 



The mortality will vary in different localities and on different farms. 

 When cholera first makes its appearance in a locality" the per cent of 

 deaths, as a rule, is higher than it is at the end of the outbreak. The 

 same is also true in communities where cholera has appeared for a 

 number of years in succession. The per cent of losses Avill range around 

 fifty per cent in some localities ; in other as high as ninety-five per cent. 

 This depends on the virulency of infection and the susceptibility of the 

 hogs. 



As a rule hogs recovering from cholera are greatly depreciated in 

 value. Unless the hogs are exceptionally valuable ones, it would be 

 more economical to destroy and burn them when they have developed a 

 well defined case of cholera. 



Anti-Hog Cholera Serum. 



In order to make potent anti-hog cholera serum, it is necessary to 

 select a hog that is "immune" to cholera. This hog is one that has 

 been treated with serum and virus at least twenty-one days, or one that 

 has recovered from an attack of cholera. One attack of cholera confers 

 life immunity. Into this "immune" hog ten cubic centimeters of virus 

 are injected direct or indirect into the circulation for every pound of 

 live weight. This hog is then known as a hyper-immune. 



In the course of eight to ten days the hyper-immune is bled by the tail, 

 taking as much blood as the hog will stand. As soon as the hog recovers 

 from the effect of having a large quantity of blood removed from it, 

 which is about a week, the hog is then bled again and this is continued 

 until four bleedings have been made. Then the hog is re-hyperimmun- 

 ized and bled four more times. This is continued until the tail becomes 

 short, when the final bleeding is made by cutting the throat, and all of 

 the blood is removed. 



The blood from the tail and throat of the hyper-immunized hog is 

 defibernated (the clot is removed) leaving the liquid j^ortion of the blood, 

 which is the serum. To this serum is added enough carbolic acid to 

 make one-half of a one per cent solution. The acid is added as a pre- 

 servative. This serum is a preventive to hog cholera and cannot produce 

 hog cholera because it contains the anti-bodies which are antagonistic 

 to the germs of hog cholera. 



Virus. 



The virus used to hyper-immunize the immune hog is secured by in- 

 jecting a small amount of virus (the liquid portion of the blood) from 

 an acute case of hog cholera into a susceptible hog, or by exposing a 

 susceptible hog to hog cholera infection. When the hog has developed an 

 acute case of cholera, the hog is bled by the throat and the blood is then 

 defibernated. The virus or liquid portion of the blood is injected direct 

 or indirect into the circulation of the immune hog. 



