Humans may develop intestinal infection with adult worms after ingestion of contaminated pork or may develop cysticercosis after ingestion of eggs (making humans intermediate hosts).

1. Humans ingest raw or undercooked pork containing cysticerci (larvae).

2. After ingestion, cysts evaginate, attach to the small intestine by their scolex, and mature into adult worms in about 2 months.

3. Adult tapeworms produce proglottids, which become gravid; they detach from the tapeworm and migrate to the anus.

4. Detached proglottids, eggs, or both are passed from the definitive host (human) in feces.

5. Pigs or humans become infected by ingesting embryonated eggs or gravid proglottids (eg, in fecally contaminated food). Autoinfection may occur in humans if proglottids pass from the intestine to the stomach via reverse peristalsis.

6. After eggs are ingested, they hatch in the intestine and release oncospheres, which penetrate the intestinal wall.

7. Oncospheres travel through the bloodstream to striated muscles and to the brain, liver, and other organs, where they develop into cysticerci. Cysticercosis can result.