142 SWINE DISEASES 



Trichinosis 



Trichinosis assumes two forms, intestinal and mus- 

 cular. Both types occur in the same animal, the intestinal 

 preceding the muscular form. 



This disease is quite prevalent, particularly in North 

 America. From two to eight per cent of American 

 hams imported into Germany have been found infested. 

 The disease is less prevalent in Europe, or at least the 

 statistics so indicate. 



The cause of trichinosis is the Trichinella spiralis. 

 This is a small, round worm, the adult rarely exceeding 

 one-twelfth of an inch in length. The life cycle of the 

 parasite is as follows: 



The larva? gain entrance to the digestive tract in 

 meat, where the surrounding capsule is dissolved by the 

 digestive juices, and thus are liberated within twenty- 

 four hours. They pass into the small intestine, where 

 they become sexually mature in about three days. About 

 five days after copulation, or within ten or twelve days 

 after ingestion, the pregnant female and the male are 

 found in the crypts of Lieberkiihn and the female begins 

 to deposit her young in the form of living embryos. 

 This process is continued by the female for from six to 

 eight weeks, during which time she produces from eight 

 to fifteen thousand young. A few of the embryos pass 

 out with the feces, but most of them pass through the 

 tissue of the intestine, some of them gaining entrance to 

 capillary lymph and blood vessels, while others wander 

 through the tissue. Those passing into the lymphatics 

 ultimately reach the blood stream, as do those passing 

 directly into the blood capillaries, and finally they are 

 distributed by the blood or by direct migration to all 

 parts of the body. The embryos thus distributed pass 

 into various tissues, but as a rule only those entering 

 the muscular tissue survive and develop. The embryo 

 matures into a larva in the muscle in a period of about 

 two months; by this time the irritation produced has 

 resulted in the formation of a capsule. These encapsu- 

 lated larvae will retain their vitality in swine for a period 



