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Proc Natl Acad Sci U S A. 2018 Jan 23;115(4):E584-E591. doi: 10.1073/pnas.1708729114. Epub 2018 Jan 4.

Impact and cost-effectiveness of snail control to achieve disease control targets for schistosomiasis.

Lo NC1,2, Gurarie D3,4, Yoon N3, Coulibaly JT5,6,7,8, Bendavid E9,10, Andrews JR11, King CH4,12,13.

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Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine, Stanford, CA 94305;
Division of Epidemiology, Stanford University School of Medicine, Stanford, CA 94305.
Department of Mathematics, Applied Mathematics and Statistics, Case Western Reserve University, Cleveland, OH 44106.
Center for Global Health and Diseases, School of Medicine, Case Western Reserve University, Cleveland, OH 44106.
Unité de Formation et de Recherche Biosciences, Université Félix Houphouët-Boigny, Abidjan 01, Côte d'Ivoire.
Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, Abidjan 01, Côte d'Ivoire.
Swiss Tropical and Public Health Institute, 4051 Basel, Switzerland.
Epidemiology and Public Health, Swiss Tropical and Public Health Institute, University of Basel, 4001 Basel, Switzerland.
Primary Care and Population Health, Stanford University, Stanford, CA 94305.
Center for Health Policy and the Center for Primary Care and Outcomes Research, Stanford University, Stanford, CA 94305.
Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine, Stanford, CA 94305.
Schistosomiasis Consortium for Operational Research and Evaluation, University of Georgia, Athens, GA 30602.
WHO Collaborating Centre for Research and Training for Schistosomiasis Elimination, Cleveland, OH 44106.


Schistosomiasis is a parasitic disease that affects over 240 million people globally. To improve population-level disease control, there is growing interest in adding chemical-based snail control interventions to interrupt the lifecycle of Schistosoma in its snail host to reduce parasite transmission. However, this approach is not widely implemented, and given environmental concerns, the optimal conditions for when snail control is appropriate are unclear. We assessed the potential impact and cost-effectiveness of various snail control strategies. We extended previously published dynamic, age-structured transmission and cost-effectiveness models to simulate mass drug administration (MDA) and focal snail control interventions against Schistosoma haematobium across a range of low-prevalence (5-20%) and high-prevalence (25-50%) rural Kenyan communities. We simulated strategies over a 10-year period of MDA targeting school children or entire communities, snail control, and combined strategies. We measured incremental cost-effectiveness in 2016 US dollars per disability-adjusted life year and defined a strategy as optimally cost-effective when maximizing health gains (averted disability-adjusted life years) with an incremental cost-effectiveness below a Kenya-specific economic threshold. In both low- and high-prevalence settings, community-wide MDA with additional snail control reduced total disability by an additional 40% compared with school-based MDA alone. The optimally cost-effective scenario included the addition of snail control to MDA in over 95% of simulations. These results support inclusion of snail control in global guidelines and national schistosomiasis control strategies for optimal disease control, especially in settings with high prevalence, "hot spots" of transmission, and noncompliance to MDA.


cost-effectiveness; environmental control; epidemiology; mathematical modeling; parasitology

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