Could the return of New World screwworm impact beef prices in NC? Expert opinion
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- Six cases confirmed: five in Texas and one in New Mexico.
- All Southern ports are closed to livestock trade while controls proceed.
- Eradication used quarantines plus mass release of sterile male flies.
The New World screwworm, a parasitic fly that feeds on the living flesh of mammals and people, has been spotted in Texas and New Mexico after being eliminated from the United States in 1966.
As of June 10, six cases are confirmed. Five are in Texas, and the sixth is a dog in New Mexico. The screwworm lays eggs in open wounds, and then larvae burrow and eat the host.
While the screwworm is generally found in the Caribbean and South America, it has been identified moving Northward in Mexico since 2023, according to the USDA.
What kind of impact could the screwworm have here in North Carolina?
Zach Raff, an assistant professor of agricultural and resource economics at NC State who previously worked for the USDA as a research economist, said the screwworm poses low risk to North Carolinians, both in terms of infestation and supply chain problems.
“I kind of predicted this would happen, but I didn’t know when it would happen. We’ve actually stopped, the USDA stopped Mexican beef imports about a year ago, so this has definitely been on people’s radar as being a possibility,” Raff said.
How does the screwworm spread?
Raff said that the odds are low the screwworm will end up in North Carolina, but monitoring and quarantining infected animals is essential to stop a spread. His work focuses on livestock production costs and the environment.
The screwworm fly can only travel 10 to 15 miles, but if the maggots are transported in animals, such as cattle and dogs, the parasite can make it a lot farther.
“If it’s transported, then the screw worm can make it pretty far, but if it’s just left to its own devices, or if there is a proper quarantine, it’s going to take a really long time for it to move,” Raff said. All Southern ports are closed to livestock trade, according to the USDA. Surveillance, movement control and other measures are being taken to contain and eradicate the screwworm.
Could the screwworm impact U.S. beef supply?
Raff said if the screwworm makes it to states like Nebraska, with large beef cattle populations, the cost of beef could shoot up as ranches are required to take on more veterinary staff and expenses. But it isn’t likely, as long as the screwworm cases are handled appropriately.
If it went unchecked, the screwworm could also mess up the supply chain by preventing the transportation of cows and calves from states like North Carolina to other places. It is more expensive to raise cattle in North Carolina than in some other parts of the country.
“We don’t have a whole lot of corn to fatten up the calves with in North Carolina, so it’s better and cheaper to ship them to Nebraska,” Raff said. “If we expand, if the quarantine areas are larger, the whole supply chain is messed up, and we have to raise the calves all the way up to slaughter in North Carolina, which is going to be more expensive.” Raff stressed that these scenarios are unlikely.
Preventing the spread of screwworm
Raff said the screwworms were eradicated in the mid 1900s not just with quarantine, but by the production of male flies that could not reproduce.
“In addition to the quarantines, they produce hundreds, hundreds of thousands, if not millions of sterile male flies, so they then put that (sterile population) over the area, and the female fly then mates with the sterile male fly. They can only mate once in their life, so then they can’t produce any offspring,” Raff said.
At the time the screwworms were eradicated, the United States was producing up to 150 million sterile flies per week, according to the USDA.
“As long as people are diligent, as long as the state departments of agriculture continue with the quarantine and USDA continues with this information awareness campaign and quarantining, and then producing the sterile flies, I would speculate, I’m not expecting it to be a full-blown endemic,” Raff said.
How to protect your pets from screwworm
Raff said that while risk is low, people should be careful of taking pets out of the U.S. to Mexico, especially those with open wounds. The dog in New Mexico is the first case documented in a pet.
“Definitely be careful if you know you’re taking your dog to Texas or Mexico, or if you know they start acting funny, really be sure to report immediately, so then we can get the quarantine in,” Raff said.
Watch for these signs in livestock, pets
NC State Veterinary Medicine says to watch for:
- Maggots or white egg masses in wounds or body openings, including the nose, ears, genitalia or the navel of newborn animals.
- A foul odor or the smell of decay.
- Signs of pain, such as irritability, not eating, depression or pulling away from the rest of the herd.
If you see a suspicious wound or maggots, Contact your veterinarian right away. New World screwworm is a reportable disease in the United States, which means suspected cases must be reported to animal health officials. In North Carolina, you can report a suspected case to the North Carolina Department of Agriculture and Consumer Services Veterinary Division at 919-707-3250.
This story was originally published June 12, 2026 at 10:15 AM with the headline "Could the return of New World screwworm impact beef prices in NC? Expert opinion."
