Epidemiology of amebiasis in a region of high incidence of amebic liver abscess in central Vietnam

The recent identification of Entamoeba dispar as a separate species, which is nonpathogenic for humans but morphologically indistinghuishable from Entamoeba histolytica, has prompted the World Health Organization to recommend reinforced efforts for reassessment of the epidemiology of amebiasis and, in particular, of E. histolytica. In this regard, the distribution of amebic liver abscess (ALA) cases were analyzed in the province of Thud Thien Hue (TT Hue) in central Vietnam, a region known for its high incidence of invasive amebiasis. In addition, in a particular area of Hue City, a parasitologic and seroepidemiologic survey was performed to identify possible risk factors for transmission of E. histolytica. Based on the analysis of hospital charts from April 4990 to April 1998, 2,031 cases of ALA were identified, indicating an ALA incidence of at least 21 per 100 000 inhabitants per year. Incidence varied substantially between the various districts of TT Hue and directly correlated with population density. The risk for ALA was significantly higher in summer and was age and sex dependent because 95% of the cases were adults, of which more than 80% were males. There was no clustering of cases within households and recurrent cases of ALA occurred more frequently than predicted in the study population. Despite the higher incidence of ALA in males, the parasitologic and seroepidemiologic survey revealed a significant higher infection rate for intestinal protozoon parasites, including E. histolytica in females. Besides level of education and access to a toilet or tapwater, use of river water was identified as an important risk factor for E. histolytica infection.