Species-specific field testing of Entamoeba spp. in an area of high endemicity

• Published in: Transactions of the Royal Society of Tropical Medicine and Hygiene 2002-09, Vol.96 (5), p.521-528
• Main Authors: Heckendorn, F., N'Goran, E.K., Felger, I., Vounatsou, P., Yapi, A., Oettli, A., Marti, H.P., Dobler, M., Traoré, M., Lohourignon, K.L., Lengeler, C.
• Format: Article
• Language: English
• Subjects: Adolescent; Amibiasis; amoebiasis; Animals; Anthelmintics - therapeutic use; Biological and medical sciences; Child; Cote d'Ivoire - epidemiology; Cross-Sectional Studies; Côte d'Ivoire; diagnosis; Entamoeba; Entamoeba dispar; Entamoeba histolytica; Entamoebiasis - drug therapy; Entamoebiasis - epidemiology; Entamoebiasis - parasitology; Enzyme-Linked Immunosorbent Assay; epidemiology; Female; Giardiasis - drug therapy; Human protozoal diseases; Humans; Infectious diseases; Male; Medical sciences; Metronidazole - therapeutic use; Parasitic diseases; Polymerase Chain Reaction; Praziquantel - therapeutic use; Prevalence; Protozoal diseases; Schistosomiasis mansoni - drug therapy; Species Specificity; Tropical medicine
• ISSN: 0035-9203; 1878-3503
• DOI: 10.1016/S0035-9203(02)90426-8

Entamoeba histolytica has been separated in recent years into 2 morphologically identical species: the apathogenic E. dispar and the pathogenic E. histolytica, only the latter being pathogenic. Although various laboratory techniques allow discrimination between the 2 species there is a lack of field data about the suitability of available diagnostic tests for use in epidemiological studies and few epidemiological studies using species-specific diagnosis have been performed at community level in endemic areas, especially in sub-Saharan Africa. We conducted a repeated cross-sectional study of 967 schoolchildren in central Côte d'Ivoire to compare and evaluate light microscopy, 2 different antigen detection assays, and one polymerase chain reaction (PCR) assay. Microscopy and a non-specific antigen capture Entamoeba enzyme-linked immunosorbent assay (ELISA) were used for the primary screening of all children (time t 0). The prevalence of the E. histolytica/E. dispar species complex at t 0 was 18 · 8% by single microscopical examination and 31 · 4% using the non-specific ELISA. Approximately 2 months after the initial screening, fresh stool specimens were collected on 2 consecutive days ( t 1, and t 2) from (i) all the children who were positive by microscopy at t 0 ( n = 182) and (ii) 155 randomly selected children who were negative at the primary screening. These samples were tested with a second antigen detection ELISA specific for E. histolytica ( n = 238) and with a species-specific PCR assay ( n = 193). The second and third examinations ( t 1, and t 2) revealed an additional 43 infections with the species complex E. histolytica/E. dispar, so that the cumulative microscopical prevalence for t 1 and t 2 was 27 · 7%. The overall prevalence of E. histolytica by species-specific ELISA antigen detection was low (0 · 83%), while the prevalence of E. dispar was 15%. When analysing only microscopically positive samples by PCR ( n = 129), the ratio E. histolytica: E. dispar was very low (1:46), suggesting that the vast majority of Entamoeba infections in this area were apathogenic. Both species-specific tests performed well but the ELISA was easier to use for large-scale field screening.