Johns Hopkins ABX GuidePathogensParasites

Trichinella species

Trevor A. Crowell, M.D.
Trichinella species is a topic covered in the Johns Hopkins ABX Guide.

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MICROBIOLOGY

  • Trichinosis occurs with ingestion of undercooked meat contaminated with infective larvae of Trichinella spp.
    • 7 species of roundworms from the genus Trichinella cause human disease: T. spiralis (most common), T. nativa, T. nelsoni, T. britovi, T. pseudospiralis, T. murelli, T. papuae.
    • Species differ in infectivity for humans, host reservoirs, pathogenicity and resistance to freezing.
  • Epidemiology: worldwide.
    • From 1986-2009, there were 65,818 reported cases across 41 countries.
  • Life cycle:
    • Undercooked meat containing encysted larvae is eaten.
    • Larvae are released from the cysts with exposure to gastric acid and pepsin.
    • Larvae invade the small bowel mucosa, where they mature into adults.
    • Adult females release larvae that migrate to striated muscle where they encyst and may remain infective for years.
  • Adult worms are 1.5 x 0.05mm (male) and 3.5 x 0.06mm (females).
  • Carnivorous animals keep the life cycle going by feeding on infected rodents or meat from other animals.
  • Common hosts: pigs (most common source for human infection worldwide, but most U.S. swine fed grains and therefore uninfected), bears (most common source in U.S.), foxes, birds, horses, hyenas, lions, and panthers.

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Last updated: November 30, 2015