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2/ Parasitic cycle:
Filariform larvas in contaminated soil penetrate human skin and are transported to the
lungs where they penetrate the alveolar spaces. They are carried through the bronchial
tree to the pharynx where they are swallowed and then reach the small intestine. In the
small intestine they molt twice and become adult female worms. The females live in the
epithelium of the small intestine and by parthenogenesis produce eggs, which yield
rhabditiform larvas. The rhabditiform larvas can either be passed in the stool, or in
autoinfection, they transform to infective filariform larvas. These can penetrate either
the intestinal mucosa (internal autoinfection) or the skin of the perianal area (external
autoinfection). They can be carried successively to the lungs, the bronchial tree, the
pharynx, and the small intestine where they mature into adults; or they may disseminate
widely in the body. Life
cycle of Strongyloides |
