PREVENTION 1 83 



epizootics. A few of the common means of its dissemination 

 are worthy of note. 



1 . The virus of hog cholera is frequently introduced into 

 a non-infected locality by the purchase of animals, usually for 

 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 

 quarantine thus affording every possible facility for starting 

 up a new outbreak. The reason for this is clear. 



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 ot 

 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 infecting others. In purchasing swine, 

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

 the herd should show that it had been free from infectious 

 diseases 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. 



2. 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. 



3. 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 enclosure 

 away from infected streams and fields the disease is often 

 prevented. 



4. 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. 



