Water, Sanitation and Hygiene (WASH) and environmental risk factors for soil-transmitted helminth intensity of infection in Timor-Leste, using real time PCR

Suzy J. Campbell, Susana V. Nery, Rebecca Wardell, Catherine A. D’Este, Darren J. Gray, James S. McCarthy, Rebecca J. Traub, Ross M. Andrews, Stacey Llewellyn, Andrew J. Vallely, Gail M. Williams, Archie C A Clements

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    Abstract

    Background: No investigations have been undertaken of risk factors for intensity of soil-transmitted helminth (STH) infection in Timor-Leste. This study provides the first analysis of risk factors for intensity of STH infection, as determined by quantitative PCR (qPCR), examining a broad range of water, sanitation and hygiene (WASH) and environmental factors, among communities in Manufahi District, Timor-Leste.

    Methods: A baseline cross-sectional survey of 18 communities was undertaken as part of a cluster randomised controlled trial, with additional identically-collected data from six other communities. qPCR was used to assess STH infection from stool samples, and questionnaires administered to collect WASH, demographic, and socioeconomic data. Environmental information was obtained from open-access sources and linked to infection outcomes. Mixed-effects multinomial logistic regression was undertaken to assess risk factors for intensity of Necator americanusand Ascaris infection.

    Results: 2152 participants provided stool and questionnaire information for this analysis. In adjusted models incorporating WASH, demographic and environmental variables, environmental variables were generally associated with infection intensity for both Namericanus and Ascarisspp. Precipitation (in centimetres) was associated with increased risk of moderate-intensity (adjusted relative risk [ARR] 6.1; 95% confidence interval [CI] 1.9–19.3) and heavy-intensity (ARR 6.6; 95% CI 3.1–14.1) Namericanus infection, as was sandy-loam soil around households (moderate-intensity ARR 2.1; 95% CI 1.0–4.3; heavy-intensity ARR 2.7; 95% CI 1.6–4.5; compared to no infection). For Ascaris, alkaline soil around the household was associated with reduced risk of moderate-intensity infection (ARR 0.21; 95% CI 0.09–0.51), and heavy-intensity infection (ARR 0.04; 95% CI 0.01–0.25). Few WASH risk factors were significant.

    Conclusion: In this high-prevalence setting, strong risk associations with environmental factors indicate that anthelmintic treatment alone will be insufficient to interrupt STH transmission, as conditions are favourable for ongoing environmental transmission. Integrated STH control strategies should be explored as a priority.

    Original languageEnglish
    Article numbere0005393
    Pages (from-to)1-20
    Number of pages20
    JournalPLoS Neglected Tropical Diseases
    Volume11
    Issue number3
    DOIs
    Publication statusPublished - 27 Mar 2017

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  • Cite this

    Campbell, S. J., Nery, S. V., Wardell, R., D’Este, C. A., Gray, D. J., McCarthy, J. S., Traub, R. J., Andrews, R. M., Llewellyn, S., Vallely, A. J., Williams, G. M., & Clements, A. C. A. (2017). Water, Sanitation and Hygiene (WASH) and environmental risk factors for soil-transmitted helminth intensity of infection in Timor-Leste, using real time PCR. PLoS Neglected Tropical Diseases, 11(3), 1-20. [e0005393]. https://doi.org/10.1371/journal.pntd.0005393