Life cycle

Adult E. vermicularis inhabit the lumen of the caecum and appendix. The female is about 10mm long and 0.5mm broad. The male is smaller, only 2-5mm long. Males have a curved tail and a single large copulation spicule. Besides E. vermicularis, a variant, E. gregorii, has been described from France and from the United Kingdom (Hugot and Tourte-Schaefer 1985; Chittenden and Ashford 1987; Ahn et al. 1992; Hasegawa et al. 1998). The life-cycle of this variant is identical, but the E. gregorii male has a shorter copulation spicule.

After ingestion of eggs, these are hatched in the stomach and the small intestine. The larvae then migrate downwards the intestine and after moulting twice the larvae become adults. The number of worms may vary considerably from a few up to several hundreds of adults, but their life span is short and adult worms do not live for more than 1-3 months.

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Oviposition starts after approximately 5 weeks of age and a gravid female may contain 10 000 eggs. The gravid worm migrates via the colon to the anus where egg deposition occurs. The worm will then disintegrate and die, often disrupting during itching. The larvae in the eggs laid around the anus become infective already within 6h and auto-infection via fingernails/finger sucking is common (Herrstrom et al. 1997). Hatching larvae near the anus may also migrate back to the intestine. Eggs are also found in high numbers in beds and on the floor.

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