Blastocystis sp. is an enteric protozoan that frequently colonizes humans and many animals. Despite impacting on human health, data on the prevalence and subtype (ST) distribution of Blastocystis sp. remain sparse in Africa. Accordingly, we performed the first multicenter and largest epidemiological survey ever conducted on Blastocystis sp. for this continent. A total of 731 stool samples collected from healthy school children living in 10 villages of the northwestern region of Senegal were tested for the presence of Blastocystis sp. by real-time polymerase chain reaction followed by subtyping of positive samples. Considerable variation in prevalence between villages (51.7 to 100%) was evident with the overall prevalence being 80.4%. Mixed infections were identified in 23% of positive individuals. Among 453 school children with a single infection, ST2 was predominant, followed by ST1, ST3, ST7, ST10, and ST14; this is the first report of ST10 and ST14 in humans. Genetic polymorphisms were evident at the intra-ST level with the identification of numerous ST1 to ST3 genotypes. ST1 showed the greatest intra-ST diversity followed by ST2 and ST3. The prevalence and distribution of STs and genotypes varied among target villages, pointing to several potential infection sources, including human-to-human, zoonotic, and waterborne transmission.

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Global health and development communities lack sustainable, cost-effective, mutually beneficial solutions for infectious disease, food, water, and poverty challenges despite their regular interdependence worldwide1-7. Here, we show that agricultural development and fertilizer use in west Africa increase the devastating tropical disease schistosomiasis by fueling the growth of submerged aquatic vegetation that chokes out water access points and serves as habitat for snails that transmit Schistosoma parasites to >200 million people globally8-10. In a randomized control trial where we removed invasive submerged vegetation from water points, control sites had 124% higher fecal Schistosoma reinfection rates in schoolchildren and lower open water access than removal sites without any detectable long-term adverse effects of the removal on local water quality or freshwater biodiversity. The removed vegetation was as effective as traditional livestock feed but 41-179 times cheaper and converting the vegetation to compost yielded private crop production and total (public health plus private benefits) benefit-to-cost ratios as high as 4.0 and 8.8, respectively. Thus, we provide an economic incentive - with important public health co-benefits - to maintain cleared waterways and return nutrients captured in aquatic plants back to agriculture with great promise of breaking poverty-disease traps. To facilitate targeting and scaling of this intervention, we lay the foundation for using remote sensing technology to detect snail habitat. By offering a rare, profitable, win-win innovation for food and water access, poverty, infectious disease emergence, and environmental sustainability, we hope to inspire the interdisciplinary search for other planetary health solutions11 to the numerous and formidable, co-dependent global grand challenges of the 21st century.