Tapeworm heads ("scolices") with attached segments ("proglottids"). a: pork tapeworm, Taenia solium (note hooks allowing gut wall attachment); b: beef tapeworm, Taenia saginata, which lacks hooks ("unarmed scolex"). Full-size Image
Taenia (/TEEN-ee-yuh/ or /TEEN-yuh/) is a genus that includes two important human parasites, the pork tapeworm, Taenia solium, and the beef tapeworm, Taenia saginata.
A tape worm is composed of:
a head, or scolex, by which it attaches itself to the wall of the small intestine of its host; and
- a long chain of segments, or proglottids — typically a thousand or more – each of which may contain up to 100,000 eggs.
Eggs and gravid proglottids are passed in the feces of the host. When ingested, they hatch in the gut of the new host, invade the blood stream, and then encyst, primarily in muscle tissue. When a carnivore eats infected tissue, the encysted larvae complete the life cycle, by developing into mature tapeworms in the small intestine.
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