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Enterobius life cycle.

1. Eggs are deposited on perianal folds. 2. Eggs may be ingested when people touch their mouth after they scratch their perianal area (autoinfection) or after handling contaminated clothes or other objects (eg, bed linens, curtains, carpeting); handling contaminated objects may also cause a few eggs to become airborne and thus ingested. 3. After eggs are ingested, they travel to the small intestine, where they hatch, releasing larvae. 4. The adult worms establish themselves in the cecal lumen. 5. At night, gravid females migrate outside the anus and lay eggs as they crawl on the skin of the perianal area.

Image from the Centers for Disease Control and Prevention Image Library.