Amebiasis
(am·e·bi·a·sis)
Click Image for Amebiasis Life Cycle
Amebiasis is caused by the protozoan parasite Entamoeba histolytica. Cysts shed in
human feces may contaminate food or drinking water or be transferred sexually, on
hands, or fomites. Incubation period is 1-4 weeks. Recreational waters such as lakes
and pools may also serve as transmission vehicles, since cysts are relatively
chlorine-resistant. While intestinal disease is often asymptomatic, symptoms may range
from acute abdominal pain, fever, chills, and bloody diarrhea to mild abdominal
discomfort with diarrhea alternating with constipation. Extraintestinal infection
occurs when organisms become bloodborne, leading to amebic abscesses in the liver,
lungs or brain. Complications include colonic perforation. There is no vaccine. The
most commonly ordered parasite test (microscopy of stool for ova and parasites) cannot
distinguish E. histolytica from E. dispar, a non-pathogenic amebic species. There is
an available EIA test, however, that can distinguish between the two.
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