A 5-Year intervention study on elimination of urogenital schistosomiasis in Zanzibar: Parasitological results of annual cross-sectional surveys

Abstract

Background The Zanzibar Elimination of Schistosomiasis Transmission (ZEST) project aimed to eliminate urogenital schistosomiasis as a public health problem from Pemba and to interrupt Schistosoma haematobium transmission from Unguja in 5 years. Methodology A repeated cross-sectional cluster-randomized trial was implemented from 2011/12 till 2017. On each island, 45 shehias were randomly assigned to receive one of three interventions: biannual mass drug administration (MDA) with praziquantel alone, or in combination with snail control or behavior change measures. In cross-sectional surveys, a single urine sample was collected from ~9,000 students aged 9- to 12-years and from ~4,500 adults aged 20- to 55-years annually, and from ~9,000 1 st year students at baseline and the final survey. Each sample was examined for S . haematobium eggs by a single urine filtration. Prevalence and infection intensity were determined. Odds of infection were compared between the intervention arms. Principal findings Prevalence was reduced from 6.1% (95% confidence interval (CI): 4.5%-7.6%) to 1.7% (95% CI: 1.2%-2.2%) in 9- to 12-year old students, from 3.9% (95% CI: 2.8%-5.0%) to 1.5% (95% CI: 1.0%-2.0%) in adults, and from 8.8% (95% CI: 6.5%-11.2%) to 2.6% (95% CI: 1.7%-3.5%) in 1 st year students from 2011/12 to 2017. In 2017, heavy infection intensities occurred in 0.4% of 9- to 12-year old students, 0.1% of adults, and 0.8% of 1 st year students. Considering 1 st year students in 2017, 13/45 schools in Pemba and 4/45 schools in Unguja had heavy infection intensities >1%. There was no significant difference in prevalence between the intervention arms in any study group and year. Conclusions/Significance Urogenital schistosomiasis was eliminated as public health problem from most sites in Pemba and Unguja. Prevalence was significantly reduced, but transmission was not interrupted. Continued interventions that are adaptive and tailored to the micro-epidemiology of S . haematobium in Zanzibar are needed to sustain and advance the gains made by ZEST.

Analytical and Clinical Assessment of a Portable, Isothermal Recombinase Polymerase Amplification (RPA) Assay for the Molecular Diagnosis of Urogenital Schistosomiasis

“…Urine samples were originally provided by school children aged 9–12 years from Pemba island, Zanzibar, as part of the Zanzibar Elimination of Schistosomiasis Transmission (ZEST) project (2011–2017), in 2016 and 2017 [ 49 , 50 , 51 ]. All urine samples were produced between 10:00 am and 14:00 pm to coincide with optimum egg output [ 18 ].…”

Core components, concepts and strategies for parasitic and vector-borne disease elimination with a focus on schistosomiasis: A landscape analysis

“…Successful WASH programs include sectors such as engineering, water authorities, non-governmental organizations (NGOs) and environmental health agencies for the installation of sanitary and hygiene infrastructure, making safe water accessible, and providing health education. Hardware-based solutions have shown limited impact on the local epidemiology of schistosomiasis unless they are accompanied by sustained changes in water contact behaviors [ 12 , 68 ]. Monitoring of integrated WASH/NTD implementation and generating evidence on the impact of strategies need to be enforced in view of long term investment and sustainability [ 66 ].…”

“…Multipronged strategies tailored to the local microepidemiology are needed to interrupt transmission. This was again highlighted by recent studies from the Zanzibar islands of the United Republic of Tanzania where ten rounds of biannual MDA implemented over 5 years were not sufficient to interrupt Schistosoma haematobium transmission [ 12 , 13 ]. This is in contrast to estimates from mathematical models suggesting MDA alone could result in transmission interruption if maintained over sufficient time at moderate to high coverage of school-aged children and other key community groups [ 14 , 15 ].…”

Financial Costs of the Zanzibar Elimination of Schistosomiasis Transmission Project

“…9 At the end of the study in 2017, urogenital schistosomiasis was eliminated as public health problem from most of the 90 study sites. 9,10 Moreover, the overall S. haematobium prevalence was significantly reduced from 6.1% to 1.7% in children aged 9-12 years and from 3.9% to 1.5% in adults aged 20-55 years from 2012 to 2017. 10 However, 10 rounds of MDA with praziquantel over 5 years failed to interrupt S. haematobium transmission, even when supplemented by the implementation of additional elimination measures.…”

“…9,10 Moreover, the overall S. haematobium prevalence was significantly reduced from 6.1% to 1.7% in children aged 9-12 years and from 3.9% to 1.5% in adults aged 20-55 years from 2012 to 2017. 10 However, 10 rounds of MDA with praziquantel over 5 years failed to interrupt S. haematobium transmission, even when supplemented by the implementation of additional elimination measures. 9,10 In this study, we used the programmatic and financial information made available by the ZEST project partners to conduct a cost analysis aimed at estimating the financial costs of the interventions against urogenital schistosomiasis on the two main islands of Zanzibar.…”