Urinary tract morbidity due to Schistosoma haematobium infection in Mali

A total of 824 Malian villagers in a region endemic for Schistosoma (S.) haematobium were examined clinically, parasitologically and by abdominal ultrasound. Systematic schistosomicidal treatment had never been applied to this population. Prevalence of S. haematobium infection ranged from 77% in adolescents to 51% in adults older than 40 years. Intensity of infection was generally mild, 91% of all patients excreting less than 100 ova/10 ml urine. Bladder wall enlargement and irregularities, bladder masses, pseudopolyps and dilation of the upper urinary tract were found ultrasonographically in about one third of infected individuals. Bladder lesions were more frequent in children than in adults and correlated with the intensity of infection in younger age groups only. Hydronephrosis was rare (7 of 824) and never seen in uninfected individuals. Prevalence of urinary tract pathology dropped significantly with age (P < 0.001) and was lowest in patients older than 40 years. Logistical regression identified age and infection as independent parameters affecting the prevalence of urinary tract pathology (P < 0.001). We conclude that Schistosoma haematobium infection causes substantial morbidity in children and younger adults. The reduction of urinary tract morbidity with age despite a considerable prevalence of infection in older age groups suggests spontaneous resolution during adulthood in most cases.