PREVENTION 263 



breeding purposes, from herds in which this disease exists or 

 has existed within the preceding few months. These animals 

 are usually placed among the home raised swine without quar- 

 antine, thus affording every possible facility for starting up a 

 new outbreak. The reason for this is clear. 



2. The bacteria can be carried in the dirt on the animals 

 or, as is most usually the case, the pigs may have been but 

 recently infected and being transferred during the period of 

 incubation they develop the disease later. It not infrequently 

 happens that the purchased animals are actually suffering 

 from a chronic form of the disease, to which they eventually 

 succumb but meantime infect others. In purchasing swine, 

 therefore, it is of the greatest importance that the history ot 

 the herd should show that it had been free from infectious 

 disease for at least one year. In addition to this, newly 

 purchased swine should not be placed immediately after ship- 

 ment in the pens with the home stock, but they should be kept 

 in a separate enclosure until all danger of the disease has 

 passed. 



3. Swine are often shipped in crates, boxes or in open 

 cars in which hogs affected with hog cholera have previously 

 been confined. The history of hog cholera contains many 

 illustrations of this method of contracting the disease. 



4. The bacilli of hog cholera live for a considerable time 

 in water. On this account the bacteria from outbreaks which 

 start at or near the source of a creek or small river may be 

 carried in the current and infect animals which wallow in the 

 stream many miles below. By keeping swine in a small en- 

 closure away from infected streams and fields the disease is 

 often prevented. 



5. The bacilli of hog cholera can be carried in the dirt 

 which adheres to one's shoes or to farming utensils. It not ' 

 infrequently happens that the virus of this disease is carried 

 from farm to farm on the tools taken from an infected place. 



6. The virus may be carried by buzzards, crows and 

 other birds. There is no positive proof that the virus has been 



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