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Adult worms
live in the lumen of the small intestine. A female may produce
approximately 200,000 eggs per day, which are passed with the feces
.
Unfertilized eggs may be ingested but are not infective. Fertile eggs
embryonate and become infective after 18 days to several weeks
,
depending on the environmental conditions (optimum: moist, warm, shaded
soil). After infective eggs are swallowed
, the
larvae hatch
,
invade the intestinal mucosa, and are carried via the portal, then systemic
circulation to the lungs
. The
larvae mature further in the lungs (10 to 14 days), penetrate the alveolar
walls, ascend the bronchial tree to the throat, and are swallowed
. Upon
reaching the small intestine, they develop into adult worms
.
Between 2 and 3 months are required from ingestion of the infective eggs to
oviposition by the adult female. Adult worms can live 1 to 2 years. |
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