1. In people, adult flukes release eggs through the bile ducts into the intestine. Fluke eggs are passed in stool (feces).
2-3. In water, the eggs release larvae, which penetrate snails.
4. Inside the snail, the eggs go through several stages to develop into an immature form of the fluke that has a tail and can swim (cercariae).
5. Infected snails release the cercariae, which form cysts on watercress and other water plants.
6. People are infected when they eat plants (especially watercress) that contain the cysts.
7. In the intestine, the cysts release the larvae.
8. The larvae move through the wall of the intestine into the abdominal cavity and liver, then to the bile ducts. There, they develop into adult flukes, which produce eggs.
Image from the Centers for Disease Control and Prevention, Global Health, Division of Parasitic Diseases and Malaria.