Cestodes cause intestinal (eg, taeniasis, hymenolepiasis) and/or tissue parasitoses (eg, cysticercosis, echinococcosis). Most of intestinal tapeworm infections are meat-borne zoonoses, whereas tissue infections with larval cestodes are fecal-borne, acquired mainly through ingestion of the tapeworm eggs from human, dog, or fox faeces.

TAENIA SAGINATA AND TAENIA ASIATICA TAENIASIS

Taenia saginata, the beef tapeworm, sometimes >5 m long, may live up to 30 years in the small intestine of humans, who are its only natural host. Humans are infected by ingestion of the cysticercus, a bladder worm <1 cm in diameter, present in raw or undercooked beef.

Taenia saginata infections can spread easily because of a high fecundity of the tapeworm (>500 000 eggs produced daily for years), wide and long-term contamination of the environment with eggs, bovine cysticercosis that may escape routine meat inspection when of a low intensity, and, finally, common consumption of raw beef. More than 10% of nomads are infected in East Africa; in Europe the annual incidence in urban populations is <0.1%; in the United States and Canada, T. saginata taeniasis is uncommon and observed mainly among migrants from Latin America.

Taenia saginata infection occurs mainly in well-nourished middle-aged individuals who are raw beef eaters. Complaints include vague abdominal pains, nausea, weight loss or gain, and some perianal discomfort caused by gravid proglottids (about 6 per day) crawling actively out of the anus.