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. Synopsis Limited 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. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was funded by the Bill and Melinda Gates Foundation grant numbers OPP1200651 and OPP1129535. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: IRB approval was obtained from Christian Medical College, Vellore (IRB Min no. 10392 dated 08.01.2018), the Ministry of Health in Benin (No. 15/MS/Dc/SGM/DRFMT/CNERS/SA), KEMRI Scientific and Ethics Review Unit (Protocol No. 3823), and Tufts Health Sciences Institutional Review Board (#13205). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present work are contained in the manuscript.