Life Cycle of the Pork Tapeworm

1. People may become infected when they eat raw or undercooked pork containing cysts of tapeworm larvae (called cysticerci).

2. In the intestine, the cysticerci mature into adult tapeworms and attach themselves to the wall of the intestine.

3. Adult tapeworms produce segments (called proglottids) that bear eggs. The proglottids may release the eggs or detach from the rest of the tapeworm and travel to the anus.

4. The eggs, proglottids, or both are passed in stool.

5. Pigs or, less often, people become infected by consuming the eggs or proglottids (for example, in food contaminated with human stool).

6. After the eggs are consumed, they hatch in the intestine and release spheres (called oncospheres) that penetrate the wall of the intestine.

7. The oncospheres then travel through the bloodstream to muscles and to the brain, liver, and other organs, where they develop into cysts.