Scientists at a U.S.-funded facility in Panama are preparing to launch the first outdoor tests of genetically modified screwworm flies, a critical step in efforts to protect livestock and ranchers from a flesh-eating parasite that has already returned to Texas farms after 60 years and threatens to inflict more than $1 billion in losses across the state's agriculture sector. Researchers will keep the flies confined in mesh cages, exposing them to Panama's heat and humidity to measure their survival rates before moving to larger field trials that could determine whether this biotechnology can stem an outbreak that conventional methods haven't been able to stop.
Screwworms are parasitic flies whose females lay eggs in open wounds and mucous membranes on any warm-blooded animal. Once hatched, hundreds of larvae burrow through living flesh with sharp mouths, eventually killing their host if left untreated. The parasite infested Texas livestock in June for the first time in decades, spreading over such a large area that existing control methods can't keep pace.
A Technology Gap That's Costing Ranchers
For decades, the most effective tool against screwworms has been widespread dispersal of sterile flies, mostly produced at the Panama facility jointly managed and financed by the U.S. Department of Agriculture and Panama's Ministry of Agricultural Development. Opened in 2006 on the narrow isthmus, the plant was intended to maintain a barrier stopping wild screwworm flies from moving north into Central America and North America. It produces about 100 million sterile flies per week.
That's nowhere near enough. Experts said they need 500 million a week to push screwworm flies back to the geographic boundary of the Darien Gap, the stretch of rainforest between Panama and Colombia. Wild screwworm flies have now spread throughout Mexico, and with cases covering such vast territory, the production shortfall leaves ranchers and their animals vulnerable.
NovoFly is genetically engineered to produce only males. Once sterilized through radiation, they could be released to mate with wild female screwworm flies, which then lay unfertilized eggs. Wild females normally mate only once, so sterile males can make the population progressively decline until it's eradicated. The USDA started using the technique in 1957 to fight the pest, which was eradicated from the United States in 1966.
Doubling Protection for Livestock
The NovoFly project is designed to boost the production of sterile flies and address a fundamental inefficiency. The Panama facility currently produces males and females, and the females are useless in controlling the wild population, but there's no easy way to separate them, according to the USDA and entomologists. By engineering flies to produce only males, the technology could nearly double the number of effective insects fighting the outbreak.
Scott Hutchins, USDA's chief scientist and an undersecretary, said at a news conference in June, "It's going to allow us to almost instantaneously double the number of sterile flies that we put in the fight," and, "It's going to give us a tremendous edge."
Officials at the Knipling-Bushland U.S. Livestock Insects Research Laboratory in Kerrville, Texas—a facility named after American entomologists who developed the process to sterilize screwworm flies—said scientists were expecting approval soon from Panama's biosecurity agency to begin NovoFly tests outdoors at the Panama lab. The Panama-United States Commission for the Eradication and Prevention of Screwworm, which operates the Panama plant, deferred requests for information to the USDA, and the Panamanian Food Agency declined to comment.
Field Trials and Timeline
After the initial tests in Panama, larger field trials on NovoFly are expected to begin at a ranch nearby in nine to 12 weeks, when researchers will release 50,000 of the insects every few days, said Alex Arp, a USDA research geneticist working in Panama. The flies will be marked with fluorescent dyes visible under black light, and traps around the ranch will allow researchers to track how long each release survives.
Maxwell Scott, an entomologist at North Carolina State University who helped develop NovoFly, said field tests typically run for about six to eight weeks and warned, "We may get out in the field, and it may not fly very well."
If NovoFly performs well in trials, it would take time to scale up production. Experts said it may be less risky to produce it at a new sterile-fly production facility expected to open in Texas late next year rather than initially in Panama. Adding NovoFly to the Panama facility could risk disrupting the largest source of sterile flies and cause a collapse of production if scientists fail to establish the correct diets, temperatures and conditions for the new strain.
Rear Admiral Michael Schmoyer, who is leading USDA's efforts against screwworm, said at a legislative hearing in Texas, "The last thing we'd want to do is rush a process to be able to have what's called a total brood collapse," and, "You start with zero, and then you have to build up again."
The U.S. Environmental Protection Agency published a proposed decision to register NovoFly in June. If fully approved, NovoFly would become the first genetically modified insect to get full EPA clearance, Scott said.
Edwin Burgess, an assistant professor of veterinary entomology at the University of Florida who isn't involved in the project, said even a modest increase in the number of sterilized males could lead to a quicker eradication of wild screwworm flies. He said researchers need to make sure NovoFly is competitive against wild male screwworm flies for mating and can be reared successfully on a large scale. Burgess said, "There are still a lot of things that need to be done to get that technology to where it needs to be. But it's certainly very, very promising."
Mexico supports using the male-only flies and could be producing them by the end of the year at a newly reopened production plant, said Gabriel Ayala, head of animal health for Mexico's National Service for Agri-Food Health, Safety and Quality. Eventually, they could be produced in Panama, Mexico and at the planned U.S. plant in Texas, he said.
Kim Lohmeyer, Kerrville lab director, said she hopes the U.S. can eradicate screwworms much faster than the decades it took before the pests were controlled in the 1960s. But even if the NovoFly trials succeed and it's brought into production, it will likely take more than a year to control the pest, she said. "It will take some time and effort," she said. "We need more flies."
Why This Matters:
The screwworm outbreak represents a direct threat to the livelihoods of ranchers and agricultural workers across Texas and potentially other states, with estimated losses exceeding $1 billion if the parasite isn't controlled. The production gap—needing 500 million sterile flies weekly but producing only 100 million—leaves livestock vulnerable and highlights how underfunded public health infrastructure struggles to respond to agricultural emergencies. NovoFly's potential to double effective fly production demonstrates the value of sustained public investment in agricultural research and international cooperation through facilities like the Panama plant. If approved, this would mark the first genetically modified insect to receive full EPA clearance, setting a regulatory precedent for biotechnology tools that could protect workers, animals, and rural economies from parasitic threats. The timeline—at least a year even with successful trials—underscores the need for adequate funding and production capacity before crises hit, rather than scrambling to scale up during an active infestation that's already causing economic harm to farming communities.