Thursday, June 5, 2014

Taenia saginata

T. saginata adult/CDC

General Information

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

  • 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

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

  • 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

  • Praziquantel or niclosamide

  • Cattle infected while grazing on contaminated vegetation

  • Cook beef thoroughly
T. saginata proglottid

T. saginata scolex
Taenia spp. egg

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