Taenia saginata

T. saginata adult/CDC

General Information

• Beef tapeworm
• Definitive host is humans, herbivores are intermediate hosts

Geography

• Worldwide, particularly where beef is eaten raw or undercooked

Morphology (adults)

• Strobila is 15-20 ft
• 1000-3000 proglottids
• Gravid proglottids are longer than wide
• Mature proglottid has 12-30 lateral uterine branches, can be differentiated from Taenia solium (7-13)
• Quadrate (four suckers), unarmed scolex

Morphology (eggs)

• 30-35 um in diameter, radial striated
• Internal oncosphere contains three pairs of hooklets
• Indistinguishable from Taenia solium eggs

Life Cycle

• Adult in small intestine
• Gravid proglottids with infective eggs passed in feces
• Eggs can survive for months in the environment
• Eggs ingested by cattle
• Eggs hatch> onchospheres released> invade intestinal wall> becomes lodged in striated muscle
• Develop into cysticerci (survive for years)
• Humans are infected by eating raw or undercooked beef
• Cysticerci attach to small intestine and mature to adults

Pathology

• Most patients asymptomatic
• Mild abdominal symptoms
• Migrating proglottids- appendicitis or cholangitis possible

Diagnosis

• Identification to the species level not possible based solely on microscopic exam of eggs
• Egg stage a potential health hazard (T. solium)
• Identification of proglottids and/or scolex

Treatment

• Praziquantel or niclosamide

Epidemiology

• Cattle infected while grazing on contaminated vegetation

Prevention

• Cook beef thoroughly

T. saginata proglottid

T. saginata scolex

Taenia spp. egg