This article was originally published on the Duke Global Health Institute website on November 20, 2023 by Lindsay Key.
When Duke professor Charlie Nunn, Ph.D., first visited Madagascar in 2007 as a research scientist with the Max Planck Institute, he was there for the wildlife: from long-fingered lemurs to neon-green geckos to tiny pink snakes, the forests are teeming with animals that can only be found in that part of the world.
The island country drifted from India approximately 88 million years ago, leaving species to evolve in isolation and Seussian-level strangeness. For a young scientist focused on large-scale evolution, it was a dream classroom.
“I quickly fell in love with Madagascar,” says Nunn. “If you're an evolutionary biologist, there are a few places at the top of your bucket list, and Madagascar is one of those.”
Now, more than fifteen years later, Nunn is still in awe of the country’s wildlife. But the professor of evolutionary anthropology, who also serves as the Gosnell Family Professor of Global Health at the Duke Global Health Institute (DGHI), has followed a calling to help another population living there: its people. “Over time, as I kept going back there, I got more and more interested in doing something that would be more relevant for the people of Madagascar in terms of human health,” he says.
And as his interests have shifted, Nunn has become a prime example of the multidisciplinary approach DGHI researchers are taking to understand the complex relationships between the environment and animal and human health. He now leads an international team of researchers from the US, Madagascar, France, Israel, and Singapore that is discovering new connections between land use and ecological change on the island and the spread of infectious diseases and other health threats.
Where Animal and Human Health Intersect
Nunn came to Duke in the early 1990s as a graduate student of evolutionary biologist Carel van Schaik, who was best known for his studies of primates and the insights they offered on human evolution. At the time, phylogenetic trees were all the rage. The availability of genomic data, along with improvements in computational methods, allowed scientists to chart and predict the evolution of species over huge chunks of time. Nunn collaborated with the Duke Lemur Center on several projects, but “by the time my Ph.D. was ending, I wanted to really push the frontiers even further, you know, I wanted to go into some areas where nobody had done this kind of work before,” he says.
He used the same approach to take a closer look at parasites and pathogens, which launched him into the up and coming field of evolutionary medicine. Scientists in the field use evolutionary and ecological principles to better understand how infectious diseases are transmitted between humans and animals. For Nunn, it was a way to add a public health component to the work that intrigued him.
When he returned to Duke in 2013 as a professor, Nunn knew exactly where he wanted to focus his research: Madagascar. For starters, he could plug into the work that Duke was already doing in the region through the Duke Lemur Center. But he also knew that the country faced interesting challenges due to geographic isolation and increasing proximity of animal and human populations as forests became farmland. He was eager to learn how environmental factors were impacting the spread of disease.
Nunn found a fast research partner in Randy Kramer, Ph.D., DGHI research professor and professor emeritus of environmental economics in the Nicholas School of the Environment. Kramer, an expert in survey research methods, has continued to work post-retirement on passion projects. He and Nunn co-hosted trips through Bass Connections, a university-wide program that exposes Duke students to societal problems through faculty research projects.
Together, they received funding from DGHI and a five-year grant from the National Institutes of Health to develop baseline health information about residents of Mandena, a farming and ecotourism village next to Marojejy National Park in Madagascar’s Sava region. Nunn and Kramer assembled a team of Malagasy scientists and their students through their NGO partner Vahatra[RK1] , which is based in Madagascar’s capital, Antananarivo. Nunn and Kramer also brought on Michelle Pender, a DGHI research associate, to help manage the complexity of the field research and the many partners.
“When the team is on the ground actively collecting data, I'm in daily contact with the team members, making sure everything's going smoothly for them, that they have everything they need, and the surveys are going well,” says Pender.
Pender helped establish community focus groups around the region to introduce Duke as a research partner and to keep an ear to the ground for the types of issues that are important to residents. More than 70 percent of Sava residents farm, with rice and vanilla being the most popular crops. However, three out of four farmers in the region report not having enough to eat. Food insecurity as well as proximity to domesticated animals and wildlife in the national park are key health challenges.
Tracing Disease Pathways
With this in mind, the research team recruited approximately 500 participants to submit blood and fecal samples, wear GPS tracking devices, and answer detailed survey questions about their daily activities and social lives. They also collected blood and fecal samples and tracked the movement of participants’ domesticated animals–dogs, cats, pigs, and cows– to start piecing together the movement of parasites and pathogens. Additionally, they trapped and collected samples from small wild mammals living in the area to get an idea for the movement of wildlife.
“The project is really focused on how land use decisions by farmers in the area affect infectious disease,” Kramer says. “As people clear land or allow land to go back into some kind of forest or scrub cover, those land use changes affect the populations of small mammals, and particularly the mammals that transmit zoonotic disease to humans.”
“We aren't really focused on any one given disease,” Nunn explains. “We screen for a wide range of diseases and we do this with fecal samples and with metagenomics approaches, where we’re looking for the genetic signatures in different pathogens.”
So far, data collection has revealed that more than half of the human population in the study area had hookworm, an intestinal parasite that can cause abdominal pain, diarrhea, loss of appetite, weight loss, fatigue and anemia.
Hookworm is transmitted through contact with fecal material, and GPS tracking showed a pattern of infections connected to latrines near the edges of rice fields. “If you're commonly in those areas, you're more likely to have this infection,” says Nunn. “So we get a sense in essence here of how people are moving, using their environment, and becoming exposed to disease.”
All research findings are reported to Madagascar’s Ministry of Health, he adds. “The frontier for us is really two fold: how do we communicate these findings appropriately to the people that matter, and how do we help shape the policies that are needed.”
Facing the Climate Crisis
Establishing this baseline data helps identify current threats but also assists with pandemic preparedness. With news of the spread of Sars-Cov-2 in 2020, the research team was able to quickly screen their samples for coronavirus. Thankfully, no patterns emerged.
However, through focus groups in the community, the researchers heard that people were worried about another threat: climate change. Based on this feedback, Nunn and Kramer applied for and received a supplement to the NIH grant to focus on how climate change is impacting human health in the region. Working with Pender and the team of scientists and students in Madagascar and Durham, they developed a survey to gather information about farmers’ perceptions of the looming threat.
The results were astounding, with more than 90 percent of the 485 Malagasy farmers surveyed reporting a warmer climate and decreased rainfall in the past five years. Additionally, more than 90 percent of those surveyed reported concerns about food insecurity, but only 20 percent had made any sort of changes in their farming practices to account for climate change.
Some examples of these changes, Kramer explains, might include mulching to accommodate less rainfall or planting a more diverse range of crops. Kramer and Nunn have applied for additional funding to investigate the disconnect between climate change awareness and adaptation.
“We really want to move forward and understand how Malagasy farmers are getting the information they need to change their practices,” says Kramer. “Madagascar doesn't have a very robust agricultural extension service, but there are NGOs that are out there trying to help farmers figure out more climate resilient practices.”
Another factor in the equation is the changing economic market in Madagascar, as there is an increasing trend to move from farming subsistence crops like rice to cash crops like vanilla. This is the focus of Duke Ph.D. candidate Tyler Barrett’s research.
“I'm really interested in social networks, but I'm also interested in changes in people's livelihoods related to ongoing market integration in the region,” says Barrett. “As people transition from growing more subsistence crops like rice, and start growing more cash crops like vanilla, how does that impact their everyday life?”
Barrett joined Nunn’s research group in 2021. “I was really drawn to how he doesn't shy away from the complexity of the systems he's studying,” says Barrett. “A lot of people will focus on one aspect of conservation or health but he's bringing together a huge interdisciplinary team with ecologists, sociologists, anthropologists, and biologists all focusing together on understanding how land use change and climate change impact disease burden in the country.”
In addition to his research and teaching at Duke, Nunn also wears many other professional hats. He is the director of the Triangle Center for Evolutionary Medicine (TriCEM), a nonprofit institute exploring the intersection of evolutionary science and medicine jointly operated by Duke University, North Carolina A&T State University, North Carolina Central University, North Carolina State University and the University of North Carolina at Chapel Hill.
During the 2023-24 academic year, with support from the Burroughs Wellcome Fund, Nunn is taking a sabbatical to write a textbook about evolutionary medicine. On top of that, he is the principal investigator on a National Science Foundation Predictive Intelligence for Pandemic Prevention (PIPP) seed grant to build a community of scientists in the Triangle committed to studying infectious diseases and pandemics.
But one thing hasn’t changed through his scientific evolution: his abiding interest in Madagascar. That regard may have begun with the island’s unique plant and animal life, but it’s only grown deeper as he’s spent more time with the people who are trying to carve out a living in its rare environment.
“The Sava region is one of the richest environments in Madagascar and still the majority of people there are saying that climate change is causing food insecurity and it's going to get worse,” he says. “We realized, wow, we've really stumbled on something pretty significant, and we're really disturbed by it, by what this means for the people there and how they're going to navigate this in the future.”