Echinococcus

Paul G. Auwaerter, M.D.
Echinococcus is a topic covered in the Johns Hopkins ABX Guide.

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MICROBIOLOGY

  • E. granulosus sensu lato complex
    • Composed of a complex of 10 specific genotypes, G1–10 that has been divided into species: E. granulosus sensu stricto (G1–G3), E. equinus (G4), E. ortleppi (G5), E. intermedius (G6–G7), and E. canadensis (G8–G10)
  • Additional Echinococcus spp. include E. shiquicus, E. vogeli, E. felidis, E. oligarthra, and E. multilocularis.
  • Zoonotic cestode parasite: two major forms for clinical human disease.
    • Echinococcus granulosus: most common, cause of cystic echinococcosis (CE).
      • Intermediate hosts: sheep, cattle, pigs, camels, goats
      • Definitive hosts: dogs and other canids that eat internal organs of the intermediate host [Fig 1].
        • Humans infected by the ingestion of eggs indirectly from canid feces via environmental contamination of food/water.
    • E. multilocularis: less common, cause of alveolar (tumor-like) echinococcosis (AE).
      • Intermediate hosts: rodents, domestic pigs, wild boars, dog, monkeys
      • Definitive hosts: foxes, dogs, cats
      • Most cases described in Europe, Asia. Three cases described in North America.
    • Other:
      • Echinococcus vogeli (very rare): rodents intermediate host, while bush dogs definitive host in central, south America.
      • E. oligarthus (rare)
  • Larval forms (metacestodes) infectious to humans.
    • Organism growth in the host is extremely slow, hence often asymptomatic x many years.

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MICROBIOLOGY

  • E. granulosus sensu lato complex
    • Composed of a complex of 10 specific genotypes, G1–10 that has been divided into species: E. granulosus sensu stricto (G1–G3), E. equinus (G4), E. ortleppi (G5), E. intermedius (G6–G7), and E. canadensis (G8–G10)
  • Additional Echinococcus spp. include E. shiquicus, E. vogeli, E. felidis, E. oligarthra, and E. multilocularis.
  • Zoonotic cestode parasite: two major forms for clinical human disease.
    • Echinococcus granulosus: most common, cause of cystic echinococcosis (CE).
      • Intermediate hosts: sheep, cattle, pigs, camels, goats
      • Definitive hosts: dogs and other canids that eat internal organs of the intermediate host [Fig 1].
        • Humans infected by the ingestion of eggs indirectly from canid feces via environmental contamination of food/water.
    • E. multilocularis: less common, cause of alveolar (tumor-like) echinococcosis (AE).
      • Intermediate hosts: rodents, domestic pigs, wild boars, dog, monkeys
      • Definitive hosts: foxes, dogs, cats
      • Most cases described in Europe, Asia. Three cases described in North America.
    • Other:
      • Echinococcus vogeli (very rare): rodents intermediate host, while bush dogs definitive host in central, south America.
      • E. oligarthus (rare)
  • Larval forms (metacestodes) infectious to humans.
    • Organism growth in the host is extremely slow, hence often asymptomatic x many years.

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Last updated: December 9, 2019