Tissue-dwelling helminths include a large number of nematodes, cestodes, and trematodes that cause a wide variety of clinical manifestations. Immunoglobulin E (IgE) elevations tend to accompany eosinophilia due to helminth infections, but a normal level does not eliminate parasitic disease. The diagnostic considerations can be narrowed through an understanding of the various parasites, specifically the geographic distribution, the likelihood of exposure in endemic areas, incubation period, and knowledge of the common manifestations of infection. Serologic tests are sometimes helpful, but panels of helminth serologic tests are most likely to be unrewarding if not confusing. Treatment strategies must be tailored to the individual parasitic disease.

TRICHINOSIS

Trichinosis develops when raw or inadequately cooked meat containing the encysted larvae of Trichinella species is eaten. The larvae are released from the cysts and attach to the mucosa of the small intestinal villi, where they develop into male and female adult worms. The infective newborn larvae invade striated muscle, where they encyst within individual muscle fibers.

Trichinosis has a worldwide distribution, occurring in temperate and tropical climates. In the United States, trichinosis has historically been associated with eating Trichinella-infected pork from domesticated sources. Improved observance of standards and regulations in the U.S. commercial pork industry has resulted in a steady reduction of Trichinella prevalence among swine. The number of reported cases related to eating nonpork products has remained constant, however, and now for the first time exceeds the number of reported cases related to eating pork.