A 38-year-old Chinese man suffering from abdominal pains and excreted a 20-foot tapeworm has made headlines in recent days. The man, who had a history of eating raw beef, excreted the large flatworm after doctors prescribed a laxative.

The tapeworm was identified as Taenia saginata, or the beef tapeworm. What is T. saginata?

In a concise, “bullet-point format” from my blog, Parasitology 101:

General Information

  • Beef tapeworm
  • Definitive host is humans, herbivores are intermediate hosts
Geography
  • Worldwide, particularly where beef is eaten raw or undercooked
T. saginata adult/CDC
T. saginata adult/CDC

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