• cure rate
  
• egg reduction rate
  
• re-infection prevalence and intensity of infection *resolution of urinary tract pathology
  
• re-appearance of pathology after re-infection.
  

• reduction in worm burden (CAA);
  

General objective To provide knowledge about the influence of transmission season (high and low) on the outcome of treatment assessed by cure rate, re-infection rate, regression and reappearance of urinary tract morbidity rate after treatment in order to optimise praziquantel treatment strategies for morbidity control in urinary schistosomiasis.

Specific objectives To determine the prevalence and intensity of Schistosoma haematobium infection before chemotherapy and compare cure rates and levels of re-infection after chemotherapy administered during high and low transmission seasons.

To assess urinary tract morbidity due to Schistosoma haematobium by ultrasonography and compare the regression and reappearance of urinary tract pathology chemotherapy administered during high and low transmission seasons.

To correlate morbidity determined by ultrasound with infection and morbidity parameters such as intensity of infection, micro- and macrohematuria, circulating cathodic antigen (CCA) in urine, proteinuria and leucocyturia and determine sensitivity, specificity and positive predictive values in relation to urinary tract morbidity.

Study design The main research question concerning the influence of transmission season on treatment outcome will be addressed in a consecutive cohort study with two separate but comparable cohorts. The first cohort will be examined and treated with praziquantel during the season with high transmission, February/Mach (group A) and the second cohort will be examined and treated during the low transmission season, in July approximately 5 months later (group B). Each cohort will be examined before treatment and 2, 6 and 18 months after treatment.

The study will be carried out in 4 primary schools; two from Machava J area and two from Costa do Sol area. The schools will be selected based on the following criteria: similar prevalence (> 50%) and intensity of S. haematobium infection; absence or very low levels of S. mansoni infection; a minimum of 2 classes (>35 pupils per class) at each level (3rd and 4th level) and similar distribution of boys and girls.Examinations will include urine for parasitology and haematuria and ultrasonography of upper and lower urinary tract