Swine 417 



true sense of the word. It is true that a number of preparations on 

 the market composed of drugs and chemicals are advertised to pro- 

 tect hogs against cholera or to cure hogs affected with cholera. Many 

 of these so-called cures have been tested by Federal or state institutions, 

 and one and all have been found to be worthless. Farmers therefore 

 are warned against investing their money and placing their faith in 

 hog-cholera medicines. Only one agent known can be regarded as a 

 reliable preventive. That agent is " anti-hog-cholera serum," prepared 

 according to the methods originally worked out by the Bureau of 

 Animal Industry. This serum is prepared as follows : 



Hogs that are immune against cholera, either naturally, as a result 

 of exposure to disease, or as a result of inoculation, are injected with 

 large quantities of blood from hogs sick of cholera. The blood, which 

 contains the virus from the sick hogs, even in minute quantities, 

 would kill susceptible pigs but does not injure immunes ; on the con- 

 trary, it causes immunes to become more highly immune. After the 

 immunes are injected with virus as stated, they are called "hyper- 

 immunes." About ten days or two weeks after an immune has been 

 hyper-immunized, its blood contains a large amount of protective sub- 

 stances or antibodies, and it is from such blood that anti-hog-cholera 

 serum is prepared. 



Two systems are used in protecting hogs from cholera by inocula- 

 tion the "serum-alone inoculation" and the "simultaneous inocula- 

 tion." The serum-alone inoculation consists merely in injecting, 

 underneath the skin with a syringe, the serum which is obtained from 

 hyper-immunized hogs. The serum may be used either to immunize 

 healthy hogs or to treat those that are sick of cholera. Good serum, 

 properly administered, is incapable of causing any harm to the treated 

 animals. It does not contain the germs of hog cholera and therefore 

 can not start an outbreak of cholera, even when the methods of applica- 

 tion are faulty or the serum is of low potency. It is in the safety of 

 this method of treatment that its chief advantage lies. 



This method is always to be recommended in preference to any 

 other for treating sick hogs. Unfortunately, in healthy hogs not 

 infected with cholera it does not produce a permanent protection. 

 If it did it would certainly be the only method to be recommended. 

 The length of protection which follows the injection of serum alone 

 seems to depend to a certain extent on the peculiarities of individual 

 hogs, which can not be determined beforehand, and also to some 

 extent on the dose of serum. Certain experiments have indicated that 

 the immunity lasts somewhat longer in hogs which receive exceptionally 

 large doses. Ordinarily a farmer may count on the immunity lasting 



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