1. Animals (such as pigs) that are fed other animals or animals (such as bears, foxes, or boars) that eat other animals get trichinellosis if they eat meat that contains cysts of Trichinella roundworms. People may be infected when they eat raw, undercooked, or underprocessed meat from infected animals. 2. In the stomach, enzymes break down the cysts, and the larvae are released from the cysts in the small intestine. They invade the tissues of the intestine. 3. In the intestine, they develop into adult worms. 4. After 1 week, the females produce larvae that travel to muscles where the larvae form cysts. The cycle continues only if larvae in cysts are eaten by another animal.
Image from the Centers for Disease Control and Prevention Image Library.