Trichinella spiralis is a nematode (roundworm) parasite and is the causal organism of trichinosis, a disease of worldwide distribution affecting both man and other animals. Infection is acquired by consumption of inadequately cooked meat, usually pork, containing encysted larvae. Following ingestion, the organisms excyst in the stomach by acid/pepsin digestion. The larvae pass into the small intestine, where they attach to the mucosa at the bases of the villi and mature into adult worms. Fertilized females release several hundred larvae over a two week period prior to excretion in the faeces. Newborn larvae make their way via the intestinal lymphatics and the thoracic duct to the general circulation, by which means they are distributed throughout the body. Encystment occurs within skeletal muscle, most commonly of the diaphragm, chest wall, biceps and gastrocnemius, and the organisms may remain viable and infectious for several years. The cyst wall may become calcified with the passage of time. The majority of infections are sub-clinical but there may be diarrhoea and abdominal pain associated with a heavy worm burden, fever, muscle pain, and periorbital oedema due to larvae in the muscles. In very severe infection a fatal myocarditis or encephalitis may occur. The systemic symptoms are usually maximal after 2–3 weeks and then subside, although in some cases more persistent myalgia and cardiac abnormalities may occur.
KeywordsAdult Worm Cyst Wall Thoracic Duct Periorbital Oedema Muscle Creatine
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