Trichinosis, also known as trichinellosis, trichiniasis, or trichinelliasis, is a disease of humans and of other mammals infected with the nematode worm Trichinella spiralis. The pathological changes and the symptomatology of Trichinella infection are manifestations of three successive stages in the life history of the worm: (1) penetration of adult female worms into the intestinal mucosa, (2) migration of juvenile worms, and (3) penetration of juvenile worms and subsequent encystment in muscle cells.

Distribution and Incidence

Although trichinosis occurs worldwide, in humans it is found principally in the United States, Canada, and eastern Europe. It is also well known in Mexico, parts of South America, Africa, southern Asia, and the Middle East. People acquire trichinae by ingesting uncooked or poorly cooked meat, especially pork. Home-made sausages have caused many recent outbreaks in the United States. Hence, the prevalence of trichinosis is less in the tropics and subtropics, where less meat is consumed. Trichinosis does not occur among Hindus, Jews, and Moslems, for whom there are religious bans on eating pork.

Although the prevalence of trichinosis in human populations is low (probably 2.2 percent or less in the United States, based on autopsy surveys), epidemic outbreaks are not infrequent. Incidence of infection is likely to be higher than suspected because of the vagueness of symptoms, which usually suggest other conditions.