EVOLUTION OF SCHISTOSOMA-HAEMATOBIUM-RELATED PATHOLOGY OVER 24 MONTHSAFTER TREATMENT WITH PRAZIQUANTEL AMONG SCHOOL-CHILDREN IN SOUTHEASTERN TANZANIA

Little is known about the dynamics of pathology due to schistosomiasis following treatment. Public health authorities in endemic areas requi re such information to decide on the timing of treatment and re-treatm ent schedules. A study to assess the rate of clearance and reappearanc e of pathologic lesions due to Schistosoma haematobium using ultrasoun d has now been carried out in two schools in southeastern Tanzania, an area of moderate-to-high transmission. Baseline data collection found urinary tract pathology in 67% of 533 children. Lesions of the bladde r were significantly associated with egg positivity and microhematuria . The attributable fraction estimate of major bladder lesions due to S . haematobium was 75%. In a cohort study, 224 infected children were e xamined by ultrasound and then treated with a standard dose of 40 mg o f praziquantel/kg of body weight. They were re-examined at two, four, six, 12, 18, and 24 months after treatment. Before treatment, 76% had pathologic lesions of the urinary tract. The proportion showing lesion s decreased sharply during the first months after treatment to 11% at six months. At 24 months, lesions were detected in 57%, and 11% had de veloped new severe pathology. In Is cases, pathology was present throu ghout, and 34 did not show any pathology throughout the study. This st udy provides the first detailed report on the evolution of urinary tra ct pathology due to S. haematobium infections at the community level. The results will help in making decisions on treatment and re-treatmen t schedules and more generally will provide a basis for designing cont rol strategies in areas of moderate-to-high transmission.