Effectiveness of a timed praziquantel treatment of school children in relation to seasonal transmission of urogenital schistosomiasis in Northwestern Tanzania.

Abstract

Background: Regular mass drug administration of praziquantel has a positive impact on reducing the burden of human schistosomiasis, however transmission still persists in many areas. To reach disease elimination; tailored interventions are needed to not only further reduce infections but also to tackle areas of persistent high prevalences of infection. One proposed approach is timed treatment based on the natural disease transmission cycle in relation to seasons. This study assessed the effectiveness of timed praziquantel treatment in a seasonal transmission foci of S. haematobium in northwestern Tanzania.

Methods: A longitudinal study was conducted among school aged children (SAC) between November 2022 and May 2023 in the Simiyu region, Tanzania. A single urine sample was collected from each of the participant and examined for S. haematobium eggs by the urine filtration method. Infected children were divided into two cohorts and treated with one dose of praziquantel, 40mg/kg of body weight in two different seasons. The first cohort was treated during the low transmission season, following the conclusion of the dry season in November 2022. In contrast, cohort two was treated during the high-transmission season, after the rainy season ended in May 2023. Cure rates and egg reduction rates were recorded at three-weeks post-praziquantel treatment for both cohorts.

Results: Out of 5265 screened participants, 517 and 274 S. haematobium infected SAC from the first and second cohorts respectively, participated in the study. The mean age for both cohorts was 11.2 ± 1.8 years. The prevalence of S. haematobium infection decreased by 12.0%, from 17.7% (95%CI:16.4-19.1) to 5.7% (95%CI: 4.9-6.5) in cohort one, and by 11.4%, from 15.5% (95%CI:13.9-17.1) to 4.1% (95%CI:3.2-5.0) in cohort two. The mean intensity of infection also decreased by 37.4 eggs/10 ml, from 41.2 to 3.8 eggs/10 ml of urine in cohort one (p<0.001), and by 4.1 eggs/10 ml, from 10.3 to 6.2 eggs/10 ml of urine in cohort two (p<0.001). The egg reduction rate was higher in cohort one (91%) than in cohort two (40%). Finally, there was a non-significant difference in cure rates between cohort one (64.2%) and cohort two (69.7%), (χ²(1) = 2.4107, p= 0.121).

Conclusion: Timed treatment with Praziquantel was effective in both cohorts, in terms of reduction in prevalence, heavy intensities, cure rate and egg reduction rates. However, it was less effective in the second cohort, which was treated during the high transmission season. In areas with seasonal transmission of Schistosoma haematobium, praziquantel should be administered during the low-transmission season to enhance its efficacy and increase the effectiveness of preventive chemotherapy programmes.