174 SWINE DISEASES 



by eating of the flesh, and the soil and surroundings will 

 be contaminated with the virus. Some men have shown 

 their faith in the protection of swine against cholera with 

 serum by putting the carcass of a swine dead of cholera in 

 their pens and thus infecting their premises. 



From the lack of care in the use of virus in producing 

 a permanent immunity there is little doubt but that hun- 

 dreds of farms have become infected. Food hauled in 

 wagons or other vehicles that have been previously used 

 in transporting cholera-infected swine may become 

 contaminated and infect healthy, susceptible swine and 

 thus produce hog cholera. Water, too, is frequently the 

 source of infection. This is especially noticeable in the 

 spread of hog cholera in sections of country in which there 

 are many small streams. Such en zoo tics usually follow 

 the streams. The contamination of surface water is due 

 to the discharges, and even to the carcasses of cholera- 

 infected hogs being washed by rain water into the small 

 streams. Many hog raisers have fenced and made 

 pastures of the low lands and the small streams of water, 

 thus favoring the introduction of infection into their 

 herds. 



Almost every state in the Union, and many foreign 

 countries, permit the shipment of cholera-infected swine to 

 market centers. By this means stock yards, stock cars, 

 and the railroad right of way become contaminated with 

 the discharges of cholera-infected swine, and the chances 

 are that some of the discharges contain the virus of hog 

 cholera in a sufficiently virulent form to produce cholera 

 in healthy, susceptible swine. By this means cholera is, 

 no doubt, frequently transported hundreds of miles, and 

 new centers produced. As yet few if any states actually 

 require the cleaning and disinfecting of cars that are 

 known to have been used to transport cholera-infected 

 hogs to market, and therefore the cars continue as a 

 source of infection for some time after the cholera- 

 infected hogs have been unloaded. By the practice of 

 shipping cholera hogs to market, practically all public 

 stock yards become infected and are therefore a source of 



