516 MANUAL OF FARM ANIMALS 



of the serum, whereas if the pig weighs 150 pounds, inject 

 30 c.c. of serum. This method gives immediate but tempo- 

 rary immunity lasting perhaps four or five weeks, possibly 

 longer. It is recommended for use in herds where cholera 

 already exists, but to be used on seemingly healthy pigs only. 

 Pigs already sick will probably not benefit by its use, 

 although if the animals should be infected with the disease 

 germ immediately after the serum is injected, the immunity 

 will last much longer than otherwise. There is no danger 

 attending this method. 



Serum-simultaneous method. — With the hypodermic syringe, 

 inject simultaneously into the arm and thigh pits 20 c.c. of 

 serum and 1 c.c. of virulent hog cholera blood for each 100 pounds 

 weight of pig. The virulent blood must be obtained from a hog 

 sick with cholera and the clot removed. Pigs treated by this 

 method are immune for six months to one year. This is the 

 method usually employed, but is attended with greater danger 

 than the serum-alone method; however, the resulting immunity 

 is much longer. 



Objections to the serum method. — There are two objections to 

 this method of vaccinating hogs to protect them against cholera: 

 it is expensive and somewhat dangerous. It is expensive because 

 a 12o-pound hog will furnish a comparatively small amount 

 of blood, perhaps 500 c.c. at each four bleedings and 1000 c.c. 

 more at death, making a total of only 3000 c.c, from which 

 the clot must be taken. Furthermore, this animal must be ren- 

 dered hyper-immune, which involves much labor and expense. 

 The process of immunization is dangerous because it requires 

 the use of the virulent hog cholera blood containing the living hog 

 cholera germ. When this is used without the protective serum, 

 an outbreak of hog cholera is immediately started. With proper 

 precautions, an attendant that takes an interest in the method 

 can prevent serious outbreaks of hog cholera and thus reduce the 

 risk in pork production. 



