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 periods, 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.

Trichinellosis

Trichinellosis develops when raw or inadequately cooked meat containing the encysted larvae of Trichinella species is eaten. The larvae are released from the cysts by digestive enzymes in the stomach of the host, migrate to the small intestine villi where they penetrate the intestinal mucosa, and undergo four successive molts in about 24 hours to develop into male and female adult worms. After ~1 week, infective newborn larvae are released and invade striated muscle via the circulation, where they encyst within individual muscle fibers.