A Cross-Sectional Study of Entamoeba histolytica/dispar/moshkovskii Complex in Salvador, Bahia, Brazil

Epidemiological studies on species-specific Entamoeba infections are scarce due to the morphological similarity of pathogenic Entamoeba histolytica and nonpathogenic E. dispar and E. moshkovskii. The diagnosis of E. histolytica is frequently based on coproantigen (E. histolytica-Gal/GalNAc lectin specific) detection by immunoassays. However, specific E. histolytica-lectin is not expressed in cysts, which are eliminated by asymptomatic individuals leading to false-negative results and an underestimation of amebiasis prevalence. Molecular techniques based on the amplification of parasite DNA have been shown to be a highly sensitive and specific method that allows the detection of different Entamoeba species. This study aimed to assess the frequency of the species from E. histolytica/dispar/moshkovskii complex by molecular and immunological techniques in individuals attended at a public health system in Salvador-Bahia, Brazil. A cross-sectional study involving 55,218 individuals was carried out. The diagnosis was based on microscopy revealing E. histolytica/dispar/moshkovskii complex. The species differentiation was performed by E. histolytica-specific antigen, serological evaluation and by molecular technique. The overall prevalence of E. histolytica/dispar/moshkovskii complex determined by microscopy was approximately 0.49% (273/55,218). E. histolytica-specific antigen detection and molecular characterization returned 100% negativity for E. histolytica. However, serological evaluation returned an 8.9% positivity (8/90). In the stool samples analysed by PCR, it was not possible to identify E. histolytica and E. moshkovskii, although circulating IgG anti-E. histolytica has been detected.