Preventing Disease with Native Predators
20x20 | Averting spread of waterborne disease with natural solutions
In communities along the Senegal River, the temptation to wade rises with frequent triple-digit temperatures. But even a touch of the water can lead to a ubiquitous parasitic disease that later causes health woes ranging from diarrhea to bladder cancer. Schistosomiasis is considered the second most prevalent and destructive parasitic disease after malaria, and is a fact of life for more than 200 million people without access to clean water.
A Stanford-led team set out to control the disease with an unusual – and ecologically sound – approach: deploying African river prawns that prey on snails carrying the disease. The experiment has proved successful, leading to multi-institutional partnerships, awards and the development of a new interdisciplinary program advancing solutions to support healthy people and a healthy planet.
Those suffering from schistosomiasis can be treated with drugs, but usually contract the disease again once they come into contact with infected water. Stanford biologist Giulio de Leo and his co-researchers set out to address the problem at the source.
With initial funds from a Woods Institute Environmental Ventures Project grant, the team reintroduced native prawns at river access points along the West African river, upstream of the Diama Dam. Prawns prey on the snails that carry schistosomiasis, but the helpful aquatic predator had been blocked by the dam’s construction. Restoring the prawns led to fewer disease-carrying snails and reduced transmission of the disease, with the added benefit of creating a disease-free supply of marketable protein.
The project led to the creation of The Upstream Alliance, a multi-institutional partnership developed to explore this and other environmental interventions to address schistosomiasis, Success of the initial trials has spawned scaled up prawn farming enterprises, and has led to new research using big data to track spread of the disease that was recognized as the best health project in the Data for Development Challenge Senegal, in which international teams use anonymous mobile phone data to analyze issues ranging from agriculture to urban planning.
More broadly, the project has demonstrated that removing submerged aquatic vegetation can significantly reduce snail populations, the primary carriers of the Schistosoma parasite. This ecological intervention not only curbed the disease but also transformed the removed vegetation into a valuable resource. The team composted the vegetation and used it as fertilizer and animal feed, creating a circular economy that benefited both public health and local agriculture.
This approach, which reduces reliance on chemical fertilizers and pesticides, also improves water quality and boosts food production. Their proof of concept—using drone imagery to map snail habitats for targeted vegetation removal—showed how the intervention could be scaled up, offering a sustainable solution that integrates disease control with agricultural development. The research, published in Nature, earned recognition through the ESA Sustainability Science Award
The project also served as one of the foundational elements for launching the Program on Disease Ecology in a Changing World (DECO), within the Center for Human and Planetary Health at Woods. DECO aims to leverage the lessons learned from schistosomiasis to tackle other environmentally mediated infectious diseases worldwide.
In Costa Rica, the team aims to understand how land use change and agricultural intensification drive dengue fever in rural areas, and how ecosystem management that protects biodiversity could be at the root of the solution. In Kenya, the team has partnered with the non-profit HERI-Kenya to develop a sustainable solution to food waste by using it as feed for black soldier fly larvae, which convert the disease-carrying waste into valuable protein and frass for livestock feed and fertilizer. And expanding across Africa, the team aims to extend a menu of options to policymakers developing water infrastructure projects to reduce their burden of waterborne diseases, ranging from ecological control measures like vegetation removal and predator reintroduction to public health measures like surveillance and mass drug administration. Each project is a close partnership with academic, government, multilateral development, and nonprofit partners aimed at improving the health of people and the planet.
Related
- Just Add Prawns (Stanford Magazine)
- Prawn vs Snail: Natural Solution to Disease (video)
- Little Prawn, Big Data (Stanford Report)
- Africa-wide: Dams & Parasites (DECO)
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