Describe how Taenia solium infection can lead to cysticercosis in humans and what ingestion route is responsible.

• A. Ingesting eggs from a tapeworm carrier leads to cysticercosis; taeniasis proper results from eating cysticerci in undercooked pork
• B. Ingesting cysticerci in undercooked pork leads to cysticercosis
• C. Ingesting eggs from contaminated water leads to cysticercosis
• D. Ingesting adult tapeworms in undercooked beef leads to cysticercosis

Answer: (A)

Cysticercosis happens when humans ingest the eggs of Taenia solium, not the cysticerci. The adult tapeworm lives in an infected person’s intestine and releases eggs in the feces. If someone ingests those eggs—typically through fecal-oral exposure from a tapeworm carrier in the community—the eggs hatch in the intestine, release oncospheres that penetrate the intestinal wall, and migrate through the bloodstream to tissues. There they develop into cysticerci, which can lodge in muscle, eyes, or brain; when the brain is involved, neurocysticercosis can cause seizures and other neurologic symptoms. Taeniasis, the intestinal infection with the adult tapeworm, results from eating cysticerci in undercooked pork, not from ingesting eggs. Beef is associated with Taenia saginata, not Taenia solium.