The unprecedented rate of infectious disease emergence and need to sustainably feed 9 billion people in the next 50 years represent two of the most formidable ecological and public health problems of the 21st century. Agriculture has been rapidly expanded and intensified to feed the growing human population, yet we know little about how these changes affect disease spread. This is disconcerting given that most agricultural expansion is occurring in tropical, developing countries where the risk of disease emergence is greatest but where surveillance and research efforts, particularly for neglected tropical diseases (NTDs), are most limited. Schistosomiasis, a NTD caused by a snail-transmitted trematode (flatworm), affects >240 million people worldwide, is devastating to children, and its effects are poverty reinforcing. Our preliminary research supports the hypothesis that agricultural intensification facilitates the transmission of schistosomiasis throug novel ecological mechanisms. Specifically, agrochemicals used widely in schistosomiasis-endemic regions, including herbicides, insecticides, and fertilizers, can increase trematode abundance by stimulating snail resources and reducing snail predators, mechanisms commonly referred to in community ecology as bottom-up and top-down effects. Consequently, we postulate that community ecology theory can be coupled with epidemiological theory to predict the impact of expanded agrochemical use on the spread of disease. This project has three objectives: 1) we will parameterize mathematical transmission models of human schistosomiasis using laboratory, mesocosm and field experiments examining the effects of agrochemicals on vital rates of abundance of schistosomes, their hosts and host predators; 2) we will use these models to identify changes to agrochemical management that might enhance crop yields without increasing schistosomiasis, while identifying optimal timing of agrochemical applications and mass drug administration campaigns; 3) we then will test the public health interventions offered by our models by manipulating agrochemicals regimens and schistosome biocontrol agents (prawns) at replicate villages in Senegal, and quantifying the abundance of infected snail hosts, cercarial densities, and human re-infection.
The proposed work will simultaneously enhance our ability to predict and control infectious diseases while offering opportunities to promote public health, agricultural and ecosystem health, natural resource management, and economic development. The modeling in this project will be relevant to many systems such as other trematode diseases, vector-borne diseases sensitive to insecticides, and diseases of crops.
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