Ascariasis (Ascaris lumbricoides)

Published on 25/03/2015 by admin

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Last modified 25/03/2015

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Chapter 283 Ascariasis (Ascaris lumbricoides)

Etiology

Ascariasis is caused by the nematode, or roundworm, Ascaris lumbricoides. Adult worms of A. lumbricoides inhabit the lumen of the small intestine and have a life span of 10-24 mo. The reproductive potential of Ascaris is prodigious; a gravid female worm produces 200,000 eggs/day. The fertile ova are oval in shape with a thick mammillated covering measuring 45-70 µm in length and 35-50 µm in breadth (Fig. 283-1). After passage in the feces, the eggs embryonate and become infective in 5-10 days under favorable environmental conditions. Adult worms can live for 12-18 mo (Fig. 283-2).

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Figure 283-1 Soil-transmitted helminth eggs.

(From Bethony J, Brooker S, Albonico M, et al: Soil-transmitted helminth infections: ascariasis, trichuriasis, and hookworm, Lancet 367:1521–1532, 2006.)

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Figure 283-2 Adult male and female soil-transmitted helminths.

(From Bethony J, Brooker S, Albonico M, et al: Soil-transmitted helminth infections: ascariasis, trichuriasis, and hookworm, Lancet 367:1521–1532, 2006.)

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