Texas A&M team to sequence thousands of screwworms in search of drug resistance markers

Researchers at Texas A&M University are planning what one of the project’s investigators calls the largest genetic study of New World screwworm (NWS) ever conducted to learn whether the parasite could become resistant to the drugs used to control it.¹

A team led by scientists at the Texas A&M College of Veterinary Medicine & Biomedical Sciences (VMBS) received approximately $4 million through the USDA’s New World Screwworm Grand Challenge for the 2-year project in collaboration with Texas A&M AgriLife and animal health experts in Honduras.¹ Investigators will use screwworm samples collected during the ongoing outbreak in Honduras to examine how populations spread, change, and respond to treatments.¹

“It doesn’t discriminate,” Guilherme Verocai, DVM, PhD, DACVM (Parasitology), an associate professor in the VMBS Department of Veterinary Pathobiology and director of the Parasitology Diagnostic Laboratory, said in a news release.¹ “It will infest pretty much any living warm-blooded animal.”

Related: dvm360’s ongoing New World screwworm coverage

NWS is a parasitic fly whose larvae infest wounds and feed on the living tissue of warm-blooded animals. Infestations can cause devastating wounds and can be fatal without prompt treatment.¹ Cattle are among the species most affected, but the parasite can also infest horses, sheep, goats, pigs, pets, wildlife, and humans.¹

The parasite was eradicated from the US through an effort that began in the 1950s and eventually pushed screwworm populations south through Mexico and Central America to a biological barrier in Panama. Cases began increasing again in Panama in 2021 and 2022. Within a few years, the outbreak had moved north through Central America and Mexico, reaching the US in June 2026.¹

Sequencing whole genomes, not single genes

According to Brian Davis, PhD, an assistant professor in the Department of Veterinary Pathobiology and a geneticist on the project, previous genetic studies of NWS largely focused on specific genes researchers suspected could play roles in traits such as drug resistance.¹ The Texas A&M project will take a much broader approach.

“We can sequence 99.99% of the screwworm genome in every single individual across time and across space,” Davis said. “That gives us a really powerful computational approach.”

Using Texas A&M’s High Performance Research Computing resources, the team plans to compare whole genomes from thousands of individual screwworms. According to the release, the scale will allow researchers to search for genetic similarities and differences that smaller studies could miss.¹

Researchers will have access to samples collected throughout the Honduran outbreak. The samples come with information such as when and where they were collected, which species they infested, and, when available, how the animals were treated.¹ Representatives from Honduras’ National Service of Agricultural Health and Food Safety, the country’s counterpart to the USDA, visited Texas A&M in late 2025 for a meeting hosted by Texas A&M AgriLife. Conversations from that meeting opened the door to the collaboration when the USDA later announced the Grand Challenge.¹

Co-principal investigators on the project are Davis; Rafael Ramos, a postdoctoral research associate in the Department of Veterinary Pathobiology; and Sarah Hamer, DVM, PhD, DACVPM (Epidemiology), a professor in the VMBS Department of Veterinary Integrative Biosciences.¹

Looking for signs of drug resistance

Researchers do not yet know whether screwworms in the current outbreak carry genetic markers associated with resistance to the drugs used to prevent and treat infestations. Drug-resistant populations have previously been reported in endemic areas of South America, however.¹ By pairing genomic data with where samples were collected and, when available, how the animals were previously treated, the team hopes to identify patterns that could indicate reduced susceptibility to certain drugs.¹

“We hope to develop a validated molecular test that will screen screwworm for drug resistance markers,” Verocai said. “That test could remain available and potentially be implemented in the US or across endemic countries.”

Verocai said information from veterinarians responding to cases in Honduras could provide another piece of the puzzle. If those veterinarians report that a particular treatment appeared less effective, researchers could compare the observations with the genetics of screwworms collected from the same cases.¹

Building a database for future outbreaks

The researchers expect the genomic database to have uses beyond the current outbreak. Comparing screwworm genetics across locations may eventually help scientists determine how populations are related and trace where new outbreaks originated.¹

“If there was a potential outbreak in Florida, we could understand how related it might be to what’s going on in Texas,” Verocai said.

The data could also reveal whether portions of the screwworm genome remain consistent across populations, potentially identifying targets for future drugs or genetic control technologies.¹ Once the analyses are complete, the genomic data will be made available to other researchers, allowing scientists in the United States, Central America, and elsewhere to build on the work.¹

“We’re here to help solve a pretty big problem,” Davis said. “Hopefully, we can provide information to advance control mechanisms.”

References

1. Haines C. Texas A&M researchers to study New World screwworm genetics to strengthen U.S. response. News release. Texas A&M College of Veterinary Medicine & Biomedical Sciences. October 28, 2026. Accessed October 29, 2026. https://vetmed.tamu.edu/news/press-releases/new-world-screwworm-genetics-drug-resistance/