Soil surveillance for monitoring soil-transmitted helminth infections: method development and field testing in three countries

One-fifth of the global population is infected with soil-transmitted helminths (STH). Mass drug administration (MDA) with deworming medication is widely implemented to control morbidity associated with STH infections. However, surveillance of human infection prevalence by collecting individual stool samples is time-consuming, costly, often stigmatized, and logistically challenging. Current methods of STH detection are poorly sensitive, particularly in low-intensity and low-prevalence populations. Here, we developed a sensitive and specific molecular method for detecting STH DNA in large volumes of soil by conducting laboratory and proof of concept studies across field sites in Kenya, Benin, and India. We collected human stool (n=669) and soil (n= 478) from 322 households across the three study sites. The overall prevalence of STH in soil was 31% for Ascaris lumbricoides, 3% for T. trichuris, and 24% for any hookworm species. Detection of an STH species in household soil was strongly associated with increased odds of a household member being infected with that species. Soil surveillance for STH has several benefits over stool-based surveillance, including lower cost and higher success rates for sample collection. Considering that delivery of MDA occurs at the community level, environmental surveillance using molecular methods could be a cost-effective alternate strategy for monitoring STH in these populations. SynopsisLimited data exists on the prevalence and reliability of environmental soil-transmitted helminth (STH) DNA as a marker of human infections in endemic populations. We developed a new molecular detection method for STH DNA in large-volume soil samples and field-tested it across three countries.