1. In infected people, the adult flukes produce eggs, which pass out of the body in stool (feces).
2–3. In water, the eggs hatch and release immature larvae (called miracidia). The miracidia enter a snail.
4. In the snail, the miracidia go through two stages, then develop into a form that has a tail and can swim in water (called cercariae).
5. The cercariae are released from the snail into the water.
6. They form cysts on aquatic plants. People (or other mammals such as pigs) become infected if they eat plants that contain the cysts.
7. In the small intestine, fluke larvae leave the cysts and attach to the wall of the small intestine.
8. There, the larvae develop into adult flukes in about 3 months.
Image from the Centers for Disease Control and Prevention Image Library.