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Taenia saginata

Microbiology > Parasitology > Cestodes
Taenia saginata (Beef Tapeworm)

Structure:  Helminth, Cestode, Beef Tapeworm

• Cattle become infected upon ingesting contaminated vegetation and/or water. In the animal’s intestine, the eggs hatch, penetrate the intestinal wall and migrate to the striated muscles where they develop cysticerci (larval cysts).
• Humans become infected by ingesting cysticerci in undercooked beef muscle. The larvae develop in the human GI tract (small intestine) by adhering to the intestinal mucosa via suckers on its scolex (head). The tapeworm can grow to over 10 m long as it absorbs nutrients digested by the human host. As a hermaphroditic tapeworm matures, it releases proglottid segments containing fertilized eggs which migrate to the anus or are passed in feces.    
• Unlike the pork tapeworm, beef tapeworm eggs do Not cause cysticercosis in humans.

• Found worldwide, but more predominant in areas where undercooked beef is consumed such as eastern Europe and parts of Asia, Latin America and Africa.

Disease manifestations:
• Most carriers are asymptomatic, but occasionally there may be nausea, anorexia or epigastric  pain.  On occasion, proglottids may migrate to the appendix, common bile duct or pancreatic duct and cause obstruction.

Laboratory diagnosis:
• Microscopic stool exam for eggs and/or proglottids.  Several samples may be required as these are shed intermittently.
• Eggs are indistinguishable from Taenia solium (pork tapeworm).  The eggs are round, 30-40 microns in diameter surrounded by a double-walled radially striated membrane.  
• The proglottids are distinguishable;  T. saginata: 15-20 uterine branches, T. solium: <12 uterine branches.
• If a scolex (head) is found (rarely, unless treated),
T. saginata:  4 lateral suckers, no hooks   
T. solium: a crown of hooks and four suckers.
• Peripheral eosinophilia may occasionally be observed (15%)

Differential diagnosis:
• Other intestinal tapeworms

• Praziquantel (single dose) is the treatment of choice.

Prevention and control:
• Thoroughly cook beef products.
• Control disposal of human feces.
• Proper hand hygiene.
• Good food and water safety practices when in developing countries.

Key Words: Parasite, Helminth, Cestode, Taenia, Taenia saginata, Beef tapeworm, tapeworm

Taeniasis is the infection of humans with the adult tapeworm of Taenia saginata, T. solium, or T. asiatica. Humans are the only definitive hosts for these three species. Eggs or gravid proglottids are passed with feces (1); the eggs can survive for days to months in the environment. Cattle (T. saginata) and pigs (T. solium and T. asiatica) become infected by ingesting vegetation contaminated with eggs or gravid proglottids (2). In the animal's intestine, the oncospheres hatch (3), invade the intestinal wall, and migrate to the striated muscles, where they develop into cysticerci. A cysticercus can survive for several years in the animal. Humans become infected by ingesting raw or undercooked infected meat (4). In the human intestine, the cysticercus develops over two months into an adult tapeworm, which can survive for years. The adult tapeworms attach to the small intestine by their scolex (5) and reside in the small intestine (6). Length of adult worms is usually 5 m or less for T. saginata (however it may reach up to 25 m) and 2 to 7 m for T. solium. The adults produce proglottids that mature, become gravid, detach from the tapeworm, and migrate to the anus or are passed in the stool (approximately six per day). T. saginata adults usually have 1000 to 2000 proglottids, while T. solium adults have an average of 1000 proglottids. The eggs contained in the gravid proglottids are released after the proglottids are passed in the feces. T. saginata may produce up to 100,000 and T. solium may produce 50,000 eggs per proglottid, respectively.

Reproduced from: Centers for Disease Control and Prevention. DPDx: Taeniasis. Available at: http://www.cdc.gov/dpdx/taeniasis/index.html.

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