Giardia lamblia

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Key Points

  • Giardia lamblia
    • Characteristics
      • Parasite
    • Transmission
      • Fecal-oral transmission
        • Consumption of trophozoites or cysts released in stool of infected people
        • Usually in contaminated water (e.g. outdoors, camping, hiking, traveler)
          • Small inoculum needed (<10 organisms)
    • Presentation: Giardiasis
      • Abdominal pain, bloating, flatulence
      • Non-bloody steatorrhea
        • Foul-smelling fatty yellow diarrhea
        • Due to malabsorption due to colonization of jejunum and ileum
        • Non-bloody as parasite does not invade intestinal wall
      • Increased risk with IgA deficiency
        • Secretory IgA normally prevents adherence of microbes to GI mucosa
        • May be caused by selective IgA deficiency or X-linked agammaglobulinemia
    • Diagnosis
      • Stool O&P (ova and parasite exam)
        • Specific use of stool microscopy; trophozoites and cysts seen in stool
      • ELISA for antigen detection is also used
    • Treatment
      • Metronidazole