Thomas Gillespie is going to the ends of the earth to find answers to a big question: How does global environmental change impact the way disease moves between animals and people?
“I’m looking at things like forest fragmentation,” says Gillespie, a professor of environmental sciences and environmental health in Emory College of Arts and Sciences. “When a large forest is subdivided, it alters the behavior of the animals living there. In selectively logged forests, for example, it reduces forest cover by 50%, which alters how animals access food resources.”
When animals change their behavior, it can affect their interactions with people, creating health implications for both. Gillespie and his colleagues are currently working in Madagascar to study how antibiotic resistance — a huge global health problem — moves between the human population and the country’s endemic population of wild lemurs.
“It’s very different from most places in the world because it’s so biogeographically and evolutionarily distinct,” he says. “If you go to Madagascar and find a trend that’s generalizable, it gives you a very strong certification of that pattern. Every time we go out looking, we find new things.”
When antibiotic resistance transfers between species, it can encourage the spread of disease. However, little is known about how antibiotic resistance genes are distributed within and between humans and animals or how they move between species.
With seed funding from Emory’s University Research Committee (URC), Gillespie’s team recently studied the gut microbiomes of communities of humans and brown mouse lemurs — small primates found only in rural Madagascar — where a variety of environments are shared.
Thomas Gillespie, a professor of environmental sciences and environmental health, has worked in Madagascar studying how antibiotic resistance may transfer between species.
“You've got all of this natural diversity,” Gillespie says. “And part of that is resistance to antibiotics. Our work showed that this resistance can pass from people to wildlife at the interface where they interact.”
The researchers started by surveying households in eight rural communities, already known for high prevalence of intestinal infections and resistance genes, to learn about demographics, antibiotic usage, health and exposure to wildlife.
“We looked at livelihoods and education, quality of housing,” Gillespie says. “We also looked at things like the distance from a major road, which would make it easier to access commercial antibiotics.”
The team then performed metagenomic sequencing on DNA samples from the humans and lemurs; the technique captures the genetics of every microorganism present in each species. While there wasn’t much overlap between humans and lemurs, all classes of antibiotic resistance genes seen in humans showed up in at least one lemur microbiome.
The important thing, Gillespie says, is how this research contributed a piece to the larger puzzle of interspecies disease transmission.
“We didn’t expect to see a lot of overlap,” he says. “More importantly, we saw a lot of capacity for resistance developing in the natural system, the kind that conventional approaches have been ignoring for a long time.”
Gillespie points out that tropical rainforests are the most diverse system on earth, and 90% of the megaspecies have not been characterized.
“All of that life has microbial life associated with it, a subset of which is pathogenic with the capacity to jump between species. We need to better understand what patterns could lead to resistance. What patterns could lead to a pandemic?”
Besides leading to future studies, Gillespie says the URC funding also allowed him to forge new collaborations. He helped create Pivot, a new nonprofit in Madagascar that has worked with the Ministry of Health to build a model health system in one of the poorest parts of the country.
“The URC lets you actually go where you believe you could find something that could really change the game,” he says. “That, to me, is the value of it.”