Amebiasis (Entamoeba histolytica)
1990 Case Definition
The 1990 case definition appearing on this page was re-published in the 1997 MMWR
Recommendations and Reports titled Case Definitions for Infectious Conditions Under Public
Health Surveillance [MMWR 1997;46(RR10)] (available at http://www.cdc.gov/mmwr/preview/mmwrhtml/00047449.htm).
Thus, the 1990 and 1997 versions of the case definition are identical.
Clinical description
Infection of the large intestine by Entamoeba histolytica may
result in an illness of variable severity ranging from mild, chronic
diarrhea to fulminant dysentery. Infection also may be asymptomatic.
Extraintestinal infection also can occur (e.g., hepatic abscess).
Laboratory criteria for diagnosis
Intestinal amebiasis
- Demonstration of cysts or trophozoites of E.
histolytica in stool or
- Demonstration of trophozoites in tissue biopsy or
ulcer scrapings by culture or histopathology
Extraintestinal amebiasis
Case classification
Confirmed, intestinal amebiasis:
a clinically compatible illness that is laboratory confirmed
Confirmed, extraintestinal amebiasis: a parasitologically
confirmed infection of extraintestinal tissue, or among symptomatic
persons (with clinical or radiographic findings consistent with extraintestinal
infection), demonstration of specific antibody against E. histolytica as
measured by indirect hemagglutination or other reliable immunodiagnostic
test (e.g., enzyme-linked immunosorbent assay)
Comment
Asymptomatic intestinal carriage of E. histolytica should
not be reported. Among asymptomatic persons, a positive serologic test
does not necessarily indicate extraintestinal amebiasis.
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