2-'A SWlNE PRACTICE 



This disease is quite prevalent, particularly in North America. 

 From two to eight per Lent of American hams imported into Ger- 

 many 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 bj' 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 fcr 

 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, 

 som.e 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 sti'eam, as do those passing 

 directly into the blood capillaries, and finally they are distributed 

 by the blcod 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; 

 bj- this time the irritation produced has resulted in the formation cf 

 a capsule. These encapsulated larvae will retain their vitality in 

 swine for a period of about eleven years, but the capsule and some 

 of the interior of the cj^st undergo calcification, the process begin- 

 ning about one or one and a half years after encapsulation. 



Swine become infested by eating trichinous flesh of pigs, rats, or 

 other animals, or from eating the excretions of infested animals. A'l 

 breeds of swine, regardless of age, are equally susceptible. Triflii- 

 ncsis is most prevalent in swine kept in smaU pens, especially when 

 sanitation is not observed. 



Lesions. — The adults produce an intestinal catarrh wliich is most 

 evident in the proximal portion of the intestine. Soon after the 

 embryos begin to migrate the mesenteric lymphatic glands become 

 enlarged, and there may be pulmonary congestion and parenchym- 



