Six rounds of annual praziquantel treatment during a national helminth control program significantly reduced schistosome infection and morbidity levels in a cohort of schoolchildren in Zimbabwe.

Author summary Following a national helminth prevalence survey conducted in 2010/2011, Zimbabwe launched a national schistosomiasis and intestinal worm control program in 2012 targeting school children aged 6-15 years who carry the highest infection burden. The control strategy as advocated by the World Health Assembly in 2012 was adopted to suit the country context. We conducted a study in a cohort of children to assess the effect of praziquantel treatment on schistosome infection intensity and prevalence as well as on urogenital schistosomiasis morbidity prevalence after every annual MDA for 6 years. Maximum treatment coverage in a cohort of children reached 90% over the 6 rounds of annual treatment. Annual surveys in sentinel sites throughout the country showed that schistosome infection prevalence and intensity as well as the marker of urogenital schistosomiasis, haematuria decreased significantly after each round of treatment from the pre-treatment levels in the same year. Most notably, both urogenital schistosomiasis infection and morbidity prevalence reduced from 32% at baseline in 2012 to 1.56% before the 6(th)MDA in 2017, and infection intensity reduced and 28.75 eggs/10ml urine to a mean of 0.07eggs/10ml urine prior to the 6(th)MDA. Both infection prevalence and intensity fell to 0 after the 6(th)MDA. Intestinal schistosomiasis prevalence and intensity reduced from 4.6% and 0.28 eggs/25mg of stool to 0% and 0 eggs respectively. Thus, the control program significantly reduced schistosome infection and morbidity in this cohort of schoolchildren. Background The World Health Organization recommends that schistosomiasis be treated through Mass Drug Administration (MDA). In line with this recommendation, Zimbabwe commenced a national helminth control program in 2012 targeting schoolchildren throughout the country for 6 years. This study, part of a larger investigation of the impact of helminth treatment on overall health of the children, determined the effect of annual praziquantel treatment on schistosome infection and morbidity in a cohort of children during Zimbabwe's 6-year national helminth control program. Methodology/Principal findings A school-based longitudinal study was carried out in 35 sentinel sites across Zimbabwe from September 2012 to November 2017. The sentinel sites were selected following a countrywide survey conducted in 280 primary schools.Schistosoma haematobiumwas diagnosed using the urine filtration technique.Schistosoma mansoniwas diagnosed using both the Kato Katz and formol ether concentration techniques.S.haematobiummorbidity was determined through detection of macro and microhaematuria. A cohort of children aged 6-15 years old were surveyed annually before MDA and 6 weeks post treatment. Maximum treatment coverage reached 90% over the 6 rounds of MDA. At baselineS.haematobiuminfection prevalence and intensity were 31.7% (95% CI = 31.1-32.2) and 28.75 eggs/10ml urine (SEM = 0.81) respectively, whileS.mansoniprevalence and intensity were 4.6% (95% CI = 4.4-4.8) and 0.28 eggs/25mg (SEM = 0.02). Prior to the 6(th)round of MDA,S.haematobiuminfection prevalence had reduced to 1.56% (p<0.001) and infection intensity was to 0.07 (SEM 0.02). Six weeks later after the 6(th)MDA, both were 0. Similarly the prevalence ofS.haematobiummorbidity as indicted by haematuria also fell significantly from 32.3% (95% CI = 29.9-34.6) to 0% (p< 0.0001) prior to the final MDA. ForS.mansoni, both prevalence and intensity had decreased to 0 prior to the 6(th)MDA. After 6 rounds of annual MDA, prevalence and intensity of both schistosome species decreased significantly to 0% (p< 0.0001). Conclusion Zimbabwe's helminth control program significantly reduced schistosome infection intensity and prevalence and urogenital schistosomiasis morbidity prevalence in a cohort of school-aged children, moving the schistosome prevalence in the children from moderate to low by WHO classification. These findings will inform the design of the country next stage interventions for helminth control and eventual elimination.