Gender distribution in asymptomatic and invasive amebiasis

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.