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  • in humans is a diarrheal infection of the small intestine caused by a single-celled protozoan parasite Giardia lamblia.
  • giardiasis is caused by the ingestion of infective cysts
  • multiple modes of transmission, including person-to-person, water-borne (eg. hikers drinking contaminated stream water from cattle faeces), and venereal
  • occurs worldwide
  • annual incidence is estimated at 2 million people
  • has a wide range of mammalian hosts besides humans, thus making it very difficult to eradicate.
  • can be fatal in the immunocompromised such as those with HIV / AIDS
  • incubation period 1 to 2 weeks (average 7 days)
  • symptoms may last 2 to 6 weeks in healthy individuals although may last longer.

clinical features

  • the majority of infected persons develop gradual symptoms that become recurrent.
  • a small number of infected individuals experience an abrupt onset of abdominal cramps, watery diarrhea, vomiting, foul flatus, and fever which may last for 3–4 days before proceeding into a more sub-acute phase.
  • stools become greasy and malodorous but do not contain blood or pus because giardiasis does not involve dysenteric symptoms.
  • watery diarrhea may cycle with soft stools and constipation
  • upper GI symptoms including nausea, early satiety, bloating, substernal burning, egg-smelling halitosis, and acid indigestion may be exacerbated by eating and are generally present in the absence of soft stools.
  • anorexia, malaise, fatigue are common
  • weight loss affects more than 50% of patients.
  • other possible features:
    • lactose intolerance
    • biliary tract disease
    • allergic manifestations such as erythema multiforme, bronchospasm, and urticaria.


  • serology
  • stool for ova and parasites
  • can be found on duodenal biopsies


  • metronidazole 5mg/kg up to 250 mg orally three times a day for 5 days, or,
  • tinidazole 50mg/kg up to 2g stat dose orally
giardiasis.txt · Last modified: 2015/12/03 22:14 by

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