192 SWINE DISEASES 



cholera serum the enforcement of sanitary regulations 

 has been neglected. In order to obtain and enforce 

 efficient sanitary measures the pork producers must first 

 be educated to the necessity of such measures. 



The application of some of the simple sanitary rules 

 have proved of great monetary value to swine raisers. 

 As an illustration, the separation of the infected from the 

 healthy swine by means of a clinical thermometer, and 

 the proper after-care, have been the means of saving over 

 fifty percent of many infected herds. 



If more consideration were given to proper hygienic 

 care and sanitary control, and less to the production, dis- 

 tribution, and application of serum, it is possible that 

 hog cholera would soon become a much less serious dis- 

 ease economically. 



Preventive Treatment. The first use of serum for 

 the prevention of hog cholera was made in 1897 by 

 Preisz, who obtained it from a swine that had recovered 

 from cholera. In 1904 De Schweinitz and Dorset de- 

 monstrated that hog cholera was caused by a filterable 

 virus, and soon thereafter Dorset, McBryde, and Niles 

 devised a plan of hyperimmunizing swine for the purpose 

 of producing anti-hog-cholera serum. This serum came 

 into general use about 1908, and is now being used ex- 

 tensively in the United States. It is prepared on the 

 following general plan, different manufacturers having 

 slightly different methods. 



The production of serum is of considerable importance 

 and a brief description of the general process follows : 



Swine having a large carcass and weighing 225 to 275 

 pounds are selected, and if they are not known to be im- 

 mune they are immunized by using twenty-five to thirty- 

 five cubic centimeters of serum to the hundred pound hog 

 weight, and from one to two cubic centimeter of virus. 

 The swine used for hyperimmunes are tuberculin tested 

 and reactors are discarded. After the swine has recovered 

 from the immunizing process, which requires from ten 

 to twenty days, it is then hyperimmunized. A pre- 

 requisite of the hyperimmunizing process consists in 



