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Simplified Schistosoma life cycle.

Simplified <i>Schistosoma</i> life cycle.
Simplified <i>Schistosoma</i> life cycle.

In the human host, eggs containing miracidia are eliminated with feces or urine into water. In water, the eggs hatch and release miracidia. The miracidia swim and penetrate a snail (intermediate host). Within the snail, the miracidia progress through 2 generations of sporocysts to become cercariae. The free-swimming cercariae are released from the snail and penetrate the skin of the human host. During penetration, the cercariae lose their forked tail, becoming schistosomula. The schistosomula are transported through the vasculature to the liver. There, they mature into adults. The paired (male and female) adult worms migrate (depending on their species) to the intestinal veins in the bowel or rectum or to the venous plexus of the GU tract, where they reside and begin to lay eggs.

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