Cysticercosis - Life Cycle

Life Cycle

The life cycle involves humans as a definite host and pigs as an intermediate host. Pigs ingest contaminated food or water that contains eggs or proglottids from human feces. The eggs (ova) develop into cysticerci in pig muscles. Humans become infected when they ingest raw or undercooked pork that contain viable cysticerci. Upon reaching the small intestine, the scolex attaches to the intestinal wall and a proglottid chain grows. T. solium releases three to six proglottids/day, bearing 30,000 to 70,000 eggs per proglottid into the intestine. Nearly 250,000 ova are passed daily into the human feces and to the environment, and the cycle continues. Infections with cysticercus occur after humans consume the ova from exogenous sources or through self-infection via the fecal-oral route. Humans, in this case, are intermediate hosts. Ova are digested in the stomach and release oncospheres which penetrate the intestinal wall and reach the bloodstream. These oncospheres develop into cysticerci in any organ but are common in brain, subcutaneous tissue, or eyes.