**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