Taenia solium life cycle

Cysticercosis is an infection of both humans and pigs with the larval stages of the cestode T. solium. This infection is caused by ingestion of eggs shed in the feces of a human tapeworm carrier (1). Pigs and humans become infected by ingesting eggs or gravid proglottids (2,7). Humans are infected by ingestion of eggs spread directly from another tapeworm carrier, from the environment, or by autoinfection. In the latter case, humans infected with adult T. solium can ingest eggs produced by that tapeworm, most likely by adherence of eggs to the hands and subsequent spread from hand to mouth. Once eggs are ingested, oncospheres hatch in the intestine (3,8), invade the intestinal wall, and migrate to striated muscles as well as the brain and other tissues, where they develop into cysticerci (9). In humans, cysts may cause serious sequellae if they localize in the brain, resulting in neurocysticercosis. The parasite life cycle is completed, resulting in human tapeworm infection, when humans ingest undercooked pork containing cysticerci (4). Cysts evaginate and attach to the small intestine by their scolex (5). Adult tapeworms develop, (up to 2 to 7 m in length and produce less than 1000 proglottids, each with approximately 50,000 eggs) and reside in the small intestine for years (6).