Detection and differentiation of two morphologically identical species of Entamoeba

Abstract

Background: Infection with Entamoeba histolytica is a worldwide public health problem. Diagnosis of this parasite by conventional microscopy is almost impossible, because it is morphologically indistinguishable from E. dispar, which is non pathogenic.Objective: To detect and differentiate E. histolytica from E. dispar by PCR technique and to determine the prevalence of trophozoites and cysts of E. histolytica /E. dispar by microscopy of fresh stool specimen among out patients of Jimma University Hospital to provide baseline data for further study. Method: A cross-sectional study was conducted from Feb. 24 – Mar. 23, 2003 in Jimma University Hospital among patients with clinical signs and symptoms of intestinal complaints. The stool samples were examined microscopically and by PCR and Solution Hybridization Enzyme Linked Immuno assay (SHELA). Results: Out of 228 stool specimens collected, 30(13.2%) E. histolytica/E. dispar were observed by microscopic examination of which 6(2.6%) were trophozoite and 24 (10.5%) were cysts. From the total 30(13.2%) microscopically observed E. histolytica /E. dispar, PCR-SHELA detected 28(12.3%) E.dispar while no E.histolytica DNA was found. Infections with one or more intestinal parasites were common, 151 (66.2 %). By far the most common intestinalparasitic infection was Ascaris lumbricoides, 87 (38.2%) followed by Trichuria trichiura, 53(23.3%). Conclusion: Infection with E. histolytica was not found in all the stool samples examined. Neither the trophozoites nor the quadrinucleated cysts reported by microscopy were those of E. histolytica. Our finding suggests that among the patients studied, the commonly reported trophozoites and cysts belong to the non-pathogenic E. dispar, which requires no treatment at all. Therefore, the commonly reported complaints of diarrhea require alternative explanation since the routine diagnostic microscopy of amebiasis is unsatisfactory.