Morbidity from Schistosoma mansoni infections: an epidemiologic study based on quantitative analysis of egg excretion in Ethiopian children.

Abstract

Abstract Morbidity from infection with Schistosoma mansoni was investigated in a population of school children, aged 7 to 16 years, from the town of Chwahit, located north of Lake Tana in Highland Ethiopia. Malaria was under control in the area, and S. haematobium was not endemic. Quantitative fecal egg counts were determined for 336 children (94% of those in the school) by the Kato thick-smear method; other intestinal parasites were determined by the Ritchie formol-ether concentration method. Morbidity was measured by a standardized medical examination of 272 of these children and was analyzed in four categories of egg count intensity: 0 (12%), 1–100 (19%), 101–500 (40%), and 501 + (29%) eggs per gram (epg). Prevalence was 88%, and the geometric mean egg count was 259 epg. The highest prevalence and intensity were found in 12-year-olds (95% and 300 epg, respectively). No schistosomiasis-associated symptoms were significantly related to the intensity of S. mansoni infection, although the complaint of blood in the stool was more frequent in groups with higher egg counts. There was a trend for hepatomegaly (especially of the left lobe) to increase in frequency with increasing egg count, but this trend was not significant. These children had no splenic enlargement. Anthropometric weight-for-height measurements, average school grade, and days absent from school were not related to the intensity of S. mansoni infections. Physical performance in a standardized 12-minute walk-run was better in uninfected boys, but there was no correlation with the intensity of infection. The minimal morbidity found in this population is compatible with the moderately low intensity of S. mansoni infection and with the findings of a previous population-based study in a neighboring village.