Urinary schistosomiasis in schoolchildren in Dar-es-Salaam, Tanzania, and the factors influencing its transmission.

The prevalence of urinary schistosomiasis among the schoolchildren living in Kigogo administrative ward of the Kinondoni district of Dar-es-Salaam city, Tanzania, and the factors influencing the transmission of the causative agent, Schistosoma haematobium, were investigated in a cross-sectional study. The estimate of overall prevalence, based on microscopical examination of a single urine sample/subject, was 47.6%. Compared with the girls, the boys were more likely to be excreting schistosome eggs (54.6% v. 40.8%; P = 0.004) and had, in general, higher intensities of infection (54 v. 38 eggs/10 ml urine; P = 0.001). The children aged 10-14 years had higher prevalences and intensities of infection than those in the younger or older age-group studied. The sensitivity of micro-haematuria as an indicator of infection (compared with the microscopical examination of single urine samples) was 84.3% overall, reaching 92% among the children excreting > or = 50 eggs/10 ml urine. The corresponding positive and negative predictive values were 77% and 84%, respectively. The sensitivity, specificity and positive and negative predictive values of the history of haematuria as an indirect screening technique for S. haematobium were 60.4%, 72.7%, 67% and 67%, respectively. Recreational activities such as bathing, swimming and playing in the water were the most frequent activities attracting children to water bodies and carried the highest risks of infection with S. haematobium. Knowledge about the disease, especially on the symptoms and mode of transmission, was generally good but the methods of prevention were inadequately known. Chemotherapy to control urinary schistosomiasis in schoolchildren is recommended; infected children may be identified on the basis of haematuria, detected using questionnaires or reagent strips. Additional health education, to heighten awareness of the disease and its prevention, would also be beneficial.