Eggs are passed in
the stool (1) , and under favorable conditions (moisture, warmth,
shade), larvae hatch in 1 to 2 days. The released rhabditiform larvae
grow in the feces and/or the soil (2) , and after 5 to 10 days
(and two molts) they become become filariform (third-stage) larvae that
are infective (3). These infective larvae can survive 3 to 4 weeks
in favorable environmental conditions. On contact with the human host,
the larvae penetrate the skin and are carried through the veins to the
heart and then to the lungs. They penetrate into the pulmonary alveoli,
ascend the bronchial tree to the pharynx, and are swallowed (4).
The larvae reach the small intestine, where they reside and mature into
adults. Adult worms live in the lumen of the small intestine, where they
attach to the intestinal wall with resultant blood loss by the host (5).
Most adult worms are eliminated in 1 to 2 years, but longevity records
can reach several years.