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ND professor researches impact of climate change in tropical disease interventions

| Thursday, March 18, 2021

Department of Biological Sciences chair and professor Jason Rohr has been published in Proceedings of the National Academy of Sciences (PNAS) for his research on schistosomiasis — a tropical disease caused by a worm — and the impact of climate change on intervention strategies.

One particular intervention method, by which the worm’s proliferation can be slowed, is impacted by temperatures. Rohr’s research addresses how warming temperatures could change the way this intervention is approached.

Rohr began this research at the University of Southern Florida with the Patel School of Global Sustainability and the Department of Biological Sciences. Interested in studying the effect of climate change on schistosomiasis, Rohr and his team identified a need for new research.

“We discovered that a variety of the parameters needed to properly model the effects of climate on schistosomes were not documented in the literature, and so my grad student conducted some studies to fill in those gaps,” Rohr said.

According to the World Health Organization (WHO), in 2018 an estimated 290.8 million people were in need of preventative treatments for schistosomiasis, which is largely found across sub-Saharan Africa. The parasitic worms that cause the infection are released by their hosts, freshwater snails, thus contaminating water and infecting those who come in contact with said water.

There are different methods used to curtail infections at different stages: methods that target the snails, methods that target the parasites and mass drug administration to treat infected humans. 

“It turns out that the snail stage and the parasite stage are quite sensitive to temperature,” Rohr said. “So, when temperatures get too warm, the snails tend to die, and when they get too cold, the parasites tend not to replicate.”

At first, it might seems like higher temperatures may be beneficial to stop the spread of this disease. However, Rohr noted, the climate is headed toward an optimal temperature for these snails and parasites — a middle ground between temperatures that are too hot for snails and too cold for parasites.

The intervention strategy aimed to reduce the number of snails and free-living parasites reduces the natural mortality of the organisms at extreme temperatures, thus raising the temperature that is optimal for transmission. Rising global temperatures, coupled with rising optimal temperatures for transmission, mean that climate change is working against this particular intervention strategy.

But this is just one method of fending off schistosomiasis. Other methods include mass anthelmintic drug administration to fight off worms, which is helpful for humans, but is not preventative.

Rohr and his colleagues are currently looking into more intervention strategies that can withstand the trends of climate change. His team is working on clinical trials in Senegal to study reinfection rates when school-age children are given the anthelmintic drugs, as well as the effects of removing aquatic vegetation, which serves as food for the snails.

While finding new ways to combat schistosomiasis, Rohr’s team is putting in effort to support the villages in Senegal.

“We’re training them to turn that aquatic vegetation into compost to increase food production and livestock feed, in order to increase meat and milk production,” Rohr said. 

With climate change at the forefront of scientific and political discussions, Rohr’s research adds to growing concerns surrounding the negative impacts of rising temperatures. However, researching adjustments to existing disease intervention strategies and new methods on the horizon, he aims to continue the fight against this often-forgotten disease.

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About Siobhan Loughney

Siobhan is a sophomore majoring in Economics. She comes from Elkins Park, Pennsylvania, but lives in Welsh Family Hall at Notre Dame.

Contact Siobhan