1. Fluke eggs are passed in stool. 2. In the environment, the eggs are ingested by snails. Inside the snail, the eggs go through several stages to develop into an immature form of the fluke that can swim (cercariae). 3. The cercariae form cysts in various freshwater fish. 4. People are infected when they consume the cysts in raw or undercooked freshwater fish. 5. In the intestine, the larvae leave the cysts, 6. The larvae travel back up the intestine into the bile duct and then into the liver and/or gallbladder. There, they develop into adults and produce eggs.
Image from the Centers for Disease Control and Prevention Image Library.