Emily Selland collects snail samples from fish trench in a Senegal rice field – Credit: Paula Senff / CIRAD
The chronic disease schistosomiasis wreaks havoc on more than 220 million people around the world, with the vast majority of cases being in sub-Saharan Africa.
New research published in Nature Sustainability by scientists from Notre Dame has explored how raising freshwater fish in the rice paddy could help reduce disease incidence and poverty along the northern Senegal River basin, a hot spot for schistosomiasis.
Despite decades of mass drug administration campaigns, schistosomiasis remains one of the world’s most widespread neglected tropical diseases. Rice farmers and their families are particularly at risk, as the parasitic worms that cause the disease are spread by freshwater snails found in the standing water of rice fields.
“By restoring native fish to rice fields, we may be able to reduce disease transmission while helping farmers produce more food and generate additional income. Those kinds of win-win-win solutions are rare, but they are exactly what sustainable development requires,” said Jason Rohr a professor of biological sciences at the University of Notre Dame and corresponding author of the study.
“One of the most exciting aspects of this research is that it suggests we don’t always have to choose between improving human health, increasing food production and protecting the environment.”
Researchers used data from more than 400 households in rural Senegal and found that the children of rice farmers had higher prevalence of the disease than children of non-farmers, indicating farmers and their families stand at increased risk of contracting the disease. And while there is a drug that can treat the disease, it cannot prevent reinfections, which will continuously occur and contribute to a cycle of poverty and disease.
To reduce disease transmission, the research team led by Rohr introduced African Bonytongue and Nile tilapia into rice fields, two native fish species that naturally suppress snail populations by eating snails or competing with them for resources. Through two trials, the team found that although the fish were not actively fed, both species thrived.
The researchers found that fields containing both fish species had fewer of the snails that host the parasite that causes the dominant form of schistosomiasis in the region. Fewer snails could reduce the risk of infection faced by rice farmers and their families.
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But benefits of the intervention reached beyond disease transmission. The research team also found the intervention increased rice yields by more than 25% and improved the soil nutrients of the rice fields, all while offering a potential secondary source of income through the sale of harvested fish.
“What is most meaningful to me about this work is that we’re taking an agricultural technique used in other regions and expanding it to infectious disease transmission,” said Emily Selland, lead author of the study and graduate student in the Rohr Lab at Notre Dame. “We can tackle schistosomiasis and also support the development of these communities by designing a sustainable and multidisciplinary solution.”
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Researchers believe the initial findings are encouraging, and additional work is already underway.
“The next step is determining how this approach can be scaled across schistosomiasis-endemic rice-growing regions. If these results hold, rice-fish coculturing could become a model for addressing health, food security and poverty simultaneously,” said Rohr, an affiliate of Notre Dame’s Eck Institute for Global Health and Environmental Change Initiative.
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