Can these tiny insects stop the next wildlife pandemic?

In a panoramic Appalachian meadow in Great Smoky Mountains National Park, a pair of scientists hover over a nebula of little black flies. Unlike visitors in town for the early fall elk rut, Charity Owings, a University of Tennessee assistant professor and National Geographic Explorer, and her graduate student Makhali Voss aren’t particularly interested in catching a glimpse of the park’s charismatic megafauna. Instead, they’ve set up a small plastic canister stuffed with putrid chicken livers, fumes wafting off of them like vapors from a cartoon pie. The flies love it. Voss slaps a net over the entomological melee, surprising the insects into flight, and before they can escape, she whips her haul in a figure eight pattern to force them into the net’s bottom. It’s an impressive move, balletic even.

“Who taught you to do that?” Owings quips.

“You did!”

Owings and Voss study blowflies, a family of insects that gorge, and lay their eggs, on decaying animal flesh and feces. True crime fans will be familiar with the power of these flies as tools of science. Forensic entomologists log cycles of blowfly egg laying and maggot maturation in a corpse to reveal how much time has passed since a person died. But Owings and her team are using the insects to solve other types of mysteries—such as, in the case of today’s experiment, whether a tapeworm parasite called Echinococcus granulosus is spreading through the Great Smokies’ elk population.

Blowflies carry in their stomach clues about the world around them, including DNA from the animals they touch or chemicals those animals have encountered. Owings and her team are using a revolutionary method she co-developed in graduate school to test the flies’ stomach contents for DNA from bacteria, viruses, and parasites.

“Our whole goal is to try to make surveillance of pathogens really quick and easy,” Owings says. Instead of spending time and money trying to locate sick animals and test them, the team can gather nearby flies and analyze them in the field. “That’s a game changer,” she says.

Some biologists think Echinococcus might have arrived in elk brought down from Canada during a species reintroduction effort, which has since created a local reservoir for the tapeworm. The worry is that the parasite, which can form large cysts in the heart, lungs, and liver, could spread to carriers like coyotes and domestic dogs and eventually humans.

A few hours later, at a motel in North Carolina’s rural Maggie Valley, Voss carries the desk from her room over to Owings’s to construct a makeshift laboratory next to the TV. The scientists cut off the flies’ abdomens with scissors and a pair of pointed tweezers, smash them with a few drops of DNA extraction liquid, and place them into a white-and-orange laptop-size console called a Bento Lab before heading out to grab some pizza.

The Bento Lab is a portable DNA analysis machine created by a pair of students at University College London to bring the kind of hard science normally performed in labs out into the field. When Owings read about the device in a paper by a team of scientists who were using it to analyze seawater on a boat, she knew it would be perfect for analyzing fly guts. While Owings and Voss are gone, the Bento Lab runs the abdomens through cycles of PCR (polymerase chain reactions), amplifying the DNA pattern associated with Echinococcus until it can be seen as an obvious line on a gel electrophoresis screening tool. It’s simple work, if you’re a researcher.

The long-term goal is to make the on-location analysis even easier, by creating something akin to a COVID or pregnancy test that an ecologist—or a park ranger without any scientific training—could use. The road to such a test could be a long one: Simpler testing tools would require the help of chemists and product designers, not to mention funding.

In the morning, preliminary results have come back positive for Echinococcus. After running more tests for confirmation, Owings and her team will alert the Tennessee Wildlife Resources Agency and work jointly on a plan to mitigate the parasite’s spread. They can inform public health officials, local veterinarians, and the public of the risk, but it’s not feasible to treat infected elk.

The next day, Owings and Voss head over to collect more flies near the park’s Oconaluftee visitors center and meet up with their colleague Richard Gerhold, a veterinary parasitologist who has helped Owings come up with new applications for her research. “We are only limited by funding and our imagination,” he says of flies’ potential as an ecological tool. Already, Owings and her colleagues have used data from blowflies to track chemicals commonly used in chemical weapons materials—an undertaking supported by the Defense Advanced Research Projects Agency that could eventually be used in conflict zones.

Owings can rattle off a list of other possible uses that range from locating missing hikers through their DNA to identifying new animal species. “There’s always a new question,” she says. Inevitably, the response is “Well, let’s test it.”