Prevalence of infection caused by Entamoeba histolytica in public schools of Maceio city, Alagoas, Brazil

[摘要] Introduction: distribution of amebiasis has been reevaluated since it was demonstrated that two morphologically indistinguishable species of Entamoeba exist, but they differ in their capacity to cause disease: Entamoeba histolytica (pathogenic) and Entamoeba dispar (nonpathogenic). The use of techniques to identify specific antigenic characteristics makes it possible to establish differential diagnosis and to assess the actual prevalence of amebiasis cases (caused only by Entamoeba histolytica). Objective: to determine the prevalence of infection by Entamoeba histolytica/Entamoeba dispar complex and, in a second phase, the prevalence of infection by Entamoeba histolytica in stool samples of students from public schools in Maceió, Alagoas, Brazil. Methods: screening of Entamoeba histolytica/Entamoeba dispar complex infection cases was carried out by formol-ether concentration technique on stool samples of 1 798 students. The infection caused by this complex was confirmed with an enzyme linked immunosorbent assay (ENZYMEBA). Positive samples were then analyzed with a specific ELISA (Entamoeba histolytica II®) in order to detect an adesin only present in Entamoeba histolytica. Results: the microscopic observation of feces and the Enzymeba test allowed demonstrating the prevalence of Entamoeba histolytica/Entamoeba dispar infection amounting to 3.8 %. The Entamoeba histolytica II procedure showed the prevalence of infection by Entamoeba histolytica of 1.0%. Therefore, the microscopy presented a low predictive positivity value (26.4%) for detection of Entamoeba histolytica compared to Entamoeba histolytica II® method. Conclusions: although the prevalence figures are not high, the study shows for the first time the occurrence of Entamoeba histolytica in Maceió, Alagoas, Brazil. In spite of the fact that the optical microscopic test of feces is not the appropriate technique for amebiasis diagnosis, it can be used as a screening method in epidemiological studies. Cases of Entamoeba histolytica infection in positive samples by microscopy can be confirmed by using a specific test for detection of the parasite coproantigen like Entamoeba histolytica II®.

[学科分类] 传染病学

[关键词] Entamoeba histolytica;amebiasis;prevalence;microscopic test;immunoassays