Comparison of immunodiagnosis (ELISA) and stool examination (Kato technique) in the diagnosis of Schistosoma mansoni in Ethiopia.

Schistosoma mansoni tegument antigen, extracted with 3M KCl, was employed to detect total antibodies due to the parasite in sera from 559 people living in endemic and nonendemic areas in Ethiopia. Cut-off point for positive and negative ELISA values was defined based on sera from the nonendemic area and results were compared with results of stool examination (Kato's thick smear technique). S. mansoni prevalence was 53.0% and 51.2% by ELISA and Kato, respectively. The ELISA system detected Schistosoma antibodies in 99.0% of the parasitologically positive individuals and in 4.8% and 12.5% of the negative ones from endemic and nonendemic areas, respectively. The sensitivity and specificity of ELISA test was 99.0% and 87.5%, respectively. The false positive reactions appear to be related to the presence of other parasites. The peak intensity of infection, as measured by both ELISA and Kato, was at 14 years of age and infection appears to be more prevalent in males than females. No relationship was established between intensity of infection and ELISA results. The use of the ELISA system in the diagnosis of S. mansoni in Ethiopia is discussed.