Invasive species are rarely considered allies in global health, and yet under certain ecological conditions, they can disrupt parasite life cycles and reduce disease transmission. 

The invasion of the marbled crayfish in Madagascar is widely viewed as a threat to biodiversity, but there is a silver lining: This crayfish might help researchers understand how natural enemies control schistosomiasis by preying on the snail species that transmit it. Schistosomiasis is a widespread and debilitating parasitic disease of poverty, endemic in the region. Preliminary data from nearly 200 freshwater sites reveal a consistent negative association between crayfish presence and snail abundance, supporting the hypothesis that crayfish may reduce transmission through ecological predation.

In partnership with the Universite d’Antananarivo and the Reseau International Schistosomiase Environnement Amenagement et Lutte and Bangor University in UK, researchers will integrate ecological field surveys, species distribution modeling, and public health mapping to assess disease risk in a rapidly changing landscape. The results will be shared in workshops with the Ministry of Health, NGOs, and academic partners to help develop effective disease control strategies based on local evidence. 

“With 11 million cases of schistosomiasis, Madagascar has one of the highest infection rates in the world,” said Dr. Giulio De Leo, a principal investigator and professor of oceans and earth system science and a senior fellow at the Woods Institute for the Environment. 

“Our established partnerships in the country position us to contribute significantly to understanding the environmental and ecological drivers of this disease, ultimately aiming to optimize control efforts for both schistosomiasis and the invasive crayfish.”

He added, “This approach considers the intricate interactions among humans, parasites, snails, and the broader ecosystems in which they exist. By addressing these interconnected factors, we hope to contribute to more effective and equitable health interventions that not only target schistosomiasis but also promote overall health and well-being in Madagascar.”

Principal Investigators:

Giulio De Leo, Professor of Oceans, of Earth System Science, Senior Fellow at the Woods Institute for the Environment and Professor, by courtesy of Biology

Nathan Lo, Assistant Professor of Medicine (Infectious Diseases) and, by courtesy, of Epidemiology and Population Health

Michele Barry, Drs. Ben & A. Jess Shenson Professor, Senior Associate Dean, Global Health, Director, Center for Innovation in Global Health,

Fiorenza Micheli, David and Lucile Packard Professor of Marine Science, Professor of Oceans, Senior Fellow at the Woods Institute for the Environment and Professor, by courtesy, of Biology

Funders:

Stanford Woods Institute for the Environment, Stanford School of Medicine Dean’s Office