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

PLoS Negl Trop Dis. 2019 May 6;13(5):e0007268. doi: 10.1371/journal.pntd.0007268. eCollection 2019 May.

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 1st 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 1st 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 1st year students. Considering 1st 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.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Animals
  • Anthelmintics / administration & dosage*
  • Child
  • Cross-Sectional Studies
  • Disease Eradication
  • Female
  • Humans
  • Indian Ocean Islands / epidemiology
  • Islands / epidemiology
  • Male
  • Middle Aged
  • Praziquantel / administration & dosage*
  • Prevalence
  • Schistosoma haematobium / drug effects
  • Schistosoma haematobium / physiology*
  • Schistosomiasis haematobia / epidemiology
  • Schistosomiasis haematobia / parasitology
  • Schistosomiasis haematobia / prevention & control*
  • Snails / parasitology
  • Urine / parasitology
  • Young Adult

Substances

  • Anthelmintics
  • Praziquantel

Grants and funding

This study received financial support from the University of Georgia Research Foundation Inc., which is funded by the Bill & Melinda Gates Foundation (https://www.gatesfoundation.org/) for these Schistosomiasis Consortium for Operational Research and Evaluation (SCORE; https://score.uga.edu/) projects (prime award no. 50816). Sub-award no. RR374-053/4893206 was awarded to DR. SK was financially supported by sub-award no. RR374-053/4893196. SK received additional funding by a direct grant from the Bill & Melinda Gates Foundation (Investment ID: OPP1191423). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.