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Brief Summary

The parasitic nematode worms known as human pinworms (Enterobius vermicularis, formerly known as Oxyuris vermicularis) infect humans worldwide, although pinworm infection (enterobiasis) seems to be more common in temperate than in tropical countries. Another putative species, Enterobius gregorii, has been reported from Europe, Africa, and Asia, but it appears that this is not actually a distinct species in which case this name would be just a junior synonym of E. vermicularis (Hasegawa et al. 1998; Nakano et al. 2006). Children and individuals living in crowded conditions are more commonly infected. In the United States, this is the most common helminth ("worm") infection of humans, with an estimated 40 million infected people. (Centers for Disease Control Parasites and Health Website)

Human pinworm eggs are deposited on the human host's perianal folds. Self-infection occurs by transferring infective eggs to the mouth with hands that have scratched the perianal area. Person-to-person transmission can also occur through handling of contaminated clothes or bed linens. Enterobiasis (pinworm infection) may also be acquired from surfaces in the environment that are contaminated with pinworm eggs (e.g., curtains, carpeting). A small number of eggs may become airborne and inhaled. These would be swallowed and follow the same development as ingested eggs. Following ingestion of infective eggs, the larvae hatch in the small intestine and the adults establish themselves in the colon (large intestine). The time interval from ingestion of infective eggs to oviposition by the adult females is about one month. The life span of the adults is about two months. Gravid females migrate nocturnally outside the anus and oviposit while crawling on the skin of the perianal area. The larvae contained inside the eggs develop and the eggs become infective in 4 to 6 hours under optimal conditions. Retroinfection, or the migration of newly hatched larvae from the anal skin back into the rectum, may occur but the frequency with which this happens is unknown. (Centers for Disease Control Parasites and Health Website)


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© Shapiro, Leo

Source: EOL Rapid Response Team


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