Giardiasis

Basics

Description

  • Noninvasive diarrheal illness
  • Found worldwide:
    • 2–15% prevalence in developed nations
    • 20–40% prevalence in developing nations
  • Most common intestinal parasite in the US:
    • Highest incidence in early summer months through fall
    • Highest incidence in children aged 1–9 yr and adults aged 30–39 yr
  • Waterborne, foodborne, and fecal–oral transmission:
    • Humans are major reservoir
    • Zoonotic reservoir in both domestic and wild mammals
    • Reservoir in contaminated surface water
  • Populations at risk:
    • Travelers and hikers to endemic areas (developing countries, wilderness areas of the US)
    • Living in poor sanitation or poor water treatment areas
    • Infants/children in day care centers and their close contacts
    • International adoptees
    • Immunocompromised or individuals with cystic fibrosis

Etiology

  • Giardia lamblia:
    • A protozoan flagellate
  • Also called Giardia intestinalis or Giardia duodenalis
  • Ingested Giardia cysts attach to intestinal villi
  • Alters the intestinal mucosal barrier function
  • Pathogenesis poorly understood
  • No toxin produced

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