Precision mapping of snail habitat provides a powerful indicator of human schistosomiasis transmission

PNAS
By: , and 

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Abstract

Recently, the World Health Organization recognized that efforts to interrupt schistosomiasis transmission through mass drug administration have been ineffective in some regions; one of their new recommended strategies for global schistosomiasis control emphasizes targeting the freshwater snails that transmit schistosome parasites. We sought to identify robust indicators that would enable precision targeting of these snails. At the site of the world’s largest recorded schistosomiasis epidemic—the Lower Senegal River Basin in Senegal—intensive sampling revealed positive relationships between intermediate host snails (abundance, density, and prevalence) and human urogenital schistosomiasis reinfection (prevalence and intensity in schoolchildren after drug administration). However, we also found that snail distributions were so patchy in space and time that obtaining useful data required effort that exceeds what is feasible in standard monitoring and control campaigns. Instead, we identified several environmental proxies that were more effective than snail variables for predicting human infection: the area covered by suitable snail habitat (i.e., floating, nonemergent vegetation), the percent cover by suitable snail habitat, and size of the water contact area. Unlike snail surveys, which require hundreds of person-hours per site to conduct, habitat coverage and site area can be quickly estimated with drone or satellite imagery. This, in turn, makes possible large-scale, high-resolution estimation of human urogenital schistosomiasis risk to support targeting of both mass drug administration and snail control efforts.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Precision mapping of snail habitat provides a powerful indicator of human schistosomiasis transmission
Series title PNAS
DOI 10.1073/pnas.1903698116
Volume 449
Issue 787
Year Published 2019
Language English
Publisher National Academy of Sciences
Contributing office(s) Western Ecological Research Center
Description 10 p.
First page 23182
Last page 23191
Country Senegal
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