Giardiasis

Giardia intestinalis

• a.k.a. G. lamblia or G. duodenalis
  • 「ランブル鞭毛虫」is named after G. lamblia

epidemiology

• worldwide
• human is main reservior
  • beaver in North America
• water-borne
  • food-borne thru uncooked vegetable or fruit washed with contaminated water
• feco-oral

life cycle

• ingestion of cyst
• hutch in intestinal wall into trophozoite
• trophozoite propagets in binary fission
• trophozoite does not invade human cells, just colonize
  • produces no bloody diarrhea
• trophozoite transforms into cyst under dry environment
• cyst is resistant to chlorinated water

morphology

• 2 nuclei in trophozoite
• 4 nuclei in cyst

clinical features

• incubation 3 days to months
• 10 cysts are enough to develop symptoms
• most asymptomatic
• repeated infections induce immunity
• abrupt onset of diarrhea
• abd cramps

diagnosis

• fecal microscopy
• duodenal fluid aspiration
  • "String test"
  • "Crosby capsule"
• antigen detection in feces
  • ELISA
  • EIA - rapid diagnostic test
• fluorescence microscopy of feces