CAÑONES — Rancher Carlos Salazar said he’s “staying tuned” to see if a sometimes-deadly pest will return to the U.S. for the first time in decades and threaten the cattle industry.
Hundreds of cattle winter on the Salazar family’s 3,000 or so acres in the shadow of Cerro Pedernal. In a few weeks, the herd will move to grazing allotments bordering the Valles Caldera National Preserve for the summer.
Common in the Caribbean and Central America, New World screwworm flies’ larvae burrow into the flesh of warm-blooded creatures — including livestock, pets, wildlife and, in some rare cases, people — and feast upon healthy tissue, causing painful, putrid wounds.
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The pest, effectively eliminated from the U.S. in the 1960s, hasn’t yet crossed the U.S.-Mexico border. But they’ve gotten uncomfortably close: The U.S. Department of Agriculture has reported hundreds of infestations in the Mexican border states of Tamaulipas and Nuevo León. The closest detection of the flies is a little over 60 miles from the border with Texas.
It’s less a question of if New World screwworm will return to the U.S. and more a question of when.
“It continues to creep closer, and I think it’s going to be very difficult at this point to keep it out of the United States,” said Dr. Samantha Holeck, state veterinarian with the New Mexico Livestock Board.
For ranchers, whose herds are susceptible to New World screwworm infestations, the flies pose just one more challenge in a year full of challenges, said New Mexico Cattle Growers’ Association President Tom Paterson. He said New World screwworm, combined with other problems ranchers are facing, has the potential to drive up the cost of production, posing a risk to New Mexico’s many small family ranches.
“When you raise those costs, they can’t stay in business,” Paterson said. “Families got to eat; they got to pay the bills. So do they leave the industry and leave production?”
Nathan Burton / The New Mexican
Curbing the spread
New World screwworm has been on health and agricultural officials’ radar for over a year — even though no infestations have yet occurred in the U.S.
The Department of Agriculture has been working with Mexican agricultural sanitation agency to track the northward movement of the flies. As of April 20, there were nearly 1,400 active animal infestations and more than 21,000 total cases in Mexico. More than 100 active cases were identified in the Mexican states of Nuevo León and Tamaulipas — both of which border eastern Texas.
No cases have yet been identified in Chihuahua or Sonora, Mexican states that border New Mexico and Arizona.
The U.S. Department of Agriculture in July 2025 closed all southern ports of entry to livestock trade. That means the hundreds of thousands of cattle that would typically enter the U.S. from Mexico at Santa Teresa each year are no longer coming into the country.
The federal agency has also ramped up efforts to breed and disperse sterile New World screwworm flies, which can’t produce the larvae that would otherwise pose a threat to warm-blooded critters. The Department of Agriculture in recent months has announced the completion of a sterile fly dispersal facility and the groundbreaking of a sterile fly production facility, both near the southern tip of Texas.
Meanwhile, the U.S. Food and Drug Administration has issued emergency use authorizations for medications to prevent and treat New World screwworm infestations in cattle, sheep, goats, horses, birds, dogs and cats.
There has been “great effort” by federal officials in Mexico and the U.S. to curb the spread of New World screwworm and produce sterile flies, Holeck said.
“I think that has bought us a lot of additional time,” she said.
Several state agencies — including the departments of agriculture, health and wildlife and the state livestock board — are also working with the U.S. Department of Agriculture and U.S. Fish and Wildlife Service to monitor the presence of New World screwworm.
Those agencies are also working on a statewide response plan, which Holeck said will ensure everyone has a “starting point” from which to manage any infestations.
“We know that there’s going to be extra work involved,” Holeck said. “If we do get a detection, it’s going to be extra work on everybody’s part — the producer, the livestock inspector, the veterinarians.”
She added, “The most important thing is trying to maintain continuity of business for livestock as best as we can.”
Nathan Burton/The New Mexican
‘Management nightmare’
When it comes to New World screwworm, the response has to be “all hands on deck,” said Manny Encinias, a fifth-generation rancher who raises cattle at Buffalo Creek Ranch in Moriarty and sells beef under the Trilogy Beef Community name.
“You always have to keep your head above the horizon with these kinds of things, and it’s a lot easier to plan and prepare to minimize the impact,” he said.
Encinias anticipated the threat will be twofold — actual and perceived.
If the pest returns to the U.S., infestations will have a real effect on ranchers’ herds and their operations. But the threat of New World screwworm is also likely to bring volatility to the market at a time when beef prices are already at record highs. Encinias said instability could lead small producers to shut down operation.
“There’s so many ranchers in the general area, the regional area, that are still just barely making it — barely breaking even if that — because of the higher cost of production,” he said. “This is just another challenge that we put in front of them.”
He encouraged state and federal officials to make plans now to ensure New Mexico farmers — some of whom don’t have internet access — are kept up-to-date on the latest screwworm news. Old media, like mail, radio and TV, are probably the best ways to reach ranchers, Encinias said.
As president of the New Mexico Cattle Growers’ Association, Paterson is bracing for bad news.
“When it does get here, we know that it’s going to be sort of a management nightmare for livestock producers,” he said.
Screwworm detections are expected to trigger a kind of quarantine process, during which ranchers won’t be able to move their herds and each animal will need to be inspected from tip to tail, Paterson said. That’s going to be a “real disruption,” he said, as ranchers expend effort, time and money to feed and water unmovable animals.
Paterson argued the threat of screwworm — combined with the drought-ridden climate, the advancing age of farmers, high fuel costs and, in some parts of the state, wolves — will make it hard for ranchers to stay in business. Paterson, whose family ranch straddles the New Mexico-Arizona border, said he’s already scaled back production to a “skeleton herd.”
“The cost to us of raising beef — the beef that New Mexicans, the American people and, frankly, consumers around the world want — it’s going to drive people out of business. It’s got to be profitable,” he said.
For Salazar, optimism — even in the face of mounting challenges — is part of the job. He said there’s no such thing as a perfect year for farmers and ranchers.
“You have to have a lot of faith and hope. If you don’t, we wouldn’t survive,” Salazar said.