Pilot Assessment of Soil-Transmitted Helminthiasis in the Context of Transmission Assessment Surveys for Lymphatic Filariasis in Benin and Tonga

Background: Mass drug administration (MDA) for lymphatic filariasis (LF) programs has delivered more than 2 billion treatments of albendazole, in combination with either ivermectin or diethylcarbamazine, to communities co-endemic for soil-transmitted helminthiasis (STH), reducing the prevalence of both diseases. A transmission assessment survey (TAS) is recommended to determine if MDA for LF can be stopped within an evaluation unit (EU) after at least five rounds of annual treatment. The TAS also provides an opportunity to simultaneously assess the impact of these MDAs on STH and to determine the frequency of school-based MDA for STH after community-wide MDA is no longer needed for LF. Methodology/Principal Findings: Pilot studies conducted in Benin and Tonga assessed the feasibility of a coordinated approach. Of the schools (clusters) selected for a TAS in each EU, a subset of 5 schools per STH ecological zone was randomly selected, according to World Health Organization (WHO) guidelines, for the coordinated survey. In Benin, 519 children were sampled in 5 schools and 22 (4.2%) had STH infection (A. lumbricoides, T. trichiura, or hookworm) detected using the Kato-Katz method. All infections were classified as light intensity under WHO criteria. In Tonga, 10 schools were chosen for the coordinated TAS and STH survey covering two ecological zones; 32 of 232 (13.8%) children were infected in Tongatapu and 82 of 320 (25.6%) in Vava'u and Ha'apai. All infections were light-intensity with the exception of one with moderate-intensity T. trichiura. Conclusions: Synchronous assessment of STH with TAS is feasible and provides a well-timed evaluation of infection prevalence to guide ongoing treatment decisions at a time when MDA for LF may be stopped. The coordinated field experiences in both countries also suggest potential time and cost savings. Refinement of a coordinated TAS and STH sampling methodology should be pursued, along with further validation of alternative quantitative diagnostic tests for STH that can be used with preserved stool specimens. Author Summary: Since 2000, some 2 billion preventive chemotherapy treatments have been delivered for lymphatic filariasis (LF), many in areas co-endemic for soil-transmitted helminthiasis (STH). A transmission assessment survey (TAS) is recommended to determine if such ‘mass drug administration (MDA)’ for LF can be stopped in a specified evaluation unit. The TAS also provides an opportune platform to simultaneously conduct STH assessments and make informed programmatic decisions about STH control. Through piloting this coordinated TAS and STH survey approach in Benin and Tonga, we found that after 5–6 rounds of annual MDA, STH prevalence was 4.2% in Benin and 13.8–25.6% in Tonga. All infections were light intensity except one moderate A. lumbricoides case in Tonga. Our study highlights that a coordinated strategy is operationally feasible, programmatically relevant, and potentially cost-effective. A more robust sampling methodology for coordinated TAS and STH surveys should be further explored, as well as alternative diagnostic tests for STH.