Species-specific field testing of Entamoeba spp. in an area of high endemicity.
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 t0). The prevalence of the E. histolytica/E. dispar species complex at t0 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 (t1 and t2) from (i) all the children who were positive by microscopy at t0 (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 (t1 and t2) revealed an additional 43 infections with the species complex E. histolytica/E. dispar, so that the cumulative microscopical prevalence for t1 and t2 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.
Heckendorn
F
F
Swiss Tropical Institute, Department of Public Health and Epidemiology, P.O. Box, CH-4002 Basel, Switzerland.
N'Goran
E K
EK
Felger
I
I
Vounatsou
P
P
Yapi
A
A
Oettli
A
A
Marti
H P
HP
Dobler
M
M
Traoré
M
M
Lohourignon
K L
KL
Lengeler
C
C
D000293:Adolescent; D000818:Animals; D000871:Anthelmintics / Q000627:therapeutic use; D002648:Child; D007560:Cote d'Ivoire / Q000453:epidemiology; D003430:Cross-Sectional Studies; D004747:Entamoeba; D004748:Entamoeba histolytica; D004749:Entamoebiasis / Q000188:drug therapy / Q000453:epidemiology / Q000469:parasitology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005873:Giardiasis / Q000188:drug therapy; D006801:Humans; D008297:Male; D008795:Metronidazole / Q000627:therapeutic use; D016133:Polymerase Chain Reaction; D011223:Praziquantel / Q000627:therapeutic use; D015995:Prevalence; D012555:Schistosomiasis mansoni / Q000188:drug therapy; D013045:Species Specificity
D000871:Anthelmintics; D008795:Metronidazole; D011223:Praziquantel