OBJECTIVE: The majority of individuals infected by the protozoan parasite E
ntamoeba histolytica experience subclinical infections. However, a small pr
oportion of parasitized individuals develop severe invasive disease such as
amebic dysentery or amebic liver abscess. Invasive amebiasis affects predo
minantly men the usual explanation for this has been that men have a higher
rate of asymptomatic infections and therefore experience a higher rate of
invasive disease. To date, there is no convincing evidence of an increased
rate of asymptomatic infection of men as compared with women. The purpose o
f this study was to evaluate the evidence supporting the hypothesis that me
n have higher rates of asymptomatic infection and thus an increased frequen
cy of invasive amebiasis.
METHODS: We reviewed published reports of invasive amebiasis and population
-based parasitological studies from 1929-1997 to compare the gender ratio o
f asymptomatic and symptomatic E. histolytica infection. Infections with E.
histolytica were differentiated from the nonpathogenic E. dispar whenever
possible.
RESULTS: The reports of invasive amebiasis (dysentery, liver abscess, colon
ic perforation, peritonitis, appendicitis, and ameboma) showed a higher pro
portion of men than women (ratio, male:female = 3.2.1, p < 0.05). This cont
rasts with the epidemiological surveys, where the rate of asymptomatic infe
ction with E. histolytica was the same (1:1) for both genders (p > 0.05).
CONCLUSIONS: Asymptomatic E. histolytica infection is equally distributed b
etween the genders. The high proportion of men with invasive amebiasis may
be due to a male-related susceptibility to invasive disease. (C) 2000 by Am
. Cell. of Gastroenterology.