giardiasis

see also:

• parasites
• gastroenteritis
• the febrile returned traveller

• 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.

• 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