With tighter checks for flesh-eating screwworm, a border crossing reopens

With the all-clear from U.S. agriculture inspectors, Mexican cattle began moving on Monday through a border crossing in New Mexico that had been closed for nearly two years as both nations work to stop the flesh-eating New World screwworm from spreading.

The screwworm — actually a fly larva that burrows into the flesh of livestock, pets and even humans — has threatened the $113 billion U.S. cattle industry. Containment efforts have cost jobs and trade in border communities, and it cut off a source of cattle as the U.S. struggles to rebuild drought-depleted herds. Reopening crossings could help ease that squeeze, although experts caution that shoppers shouldn't expect quick relief on beef prices.

The port at Columbus, New Mexico, is the third to resume Mexican cattle imports under new safeguards, which include tests, shots and inspections that happen before an animal even gets close to the border.

Officials and ranchers in the two countries say layers of treatment and inspection give them confidence that imported livestock won't carry screwworm through the ports. But flies can buzz across the border on their own, meaning ranchers, hunters and pet owners should remain vigilant.

The parasite was an annual livestock scourge before being largely eradicated in the U.S. in the 1960s. It reappeared in Mexico in 2024, and the first confirmed U.S. case was in Texas in June.

More than 60 cases have been confirmed in Texas and New Mexico, with infestations of cattle, sheep, goats, horses and dogs . Last week, the first case in U.S. wildlife was confirmed after a hunter found screwworm in an elk.

Before the current outbreak, the U.S. was importing about 1 million head of cattle per year. It will take time to get back to that number while keeping a sharp eye on the risks to animal health, said Dudley Hoskins, undersecretary for the Department of Agriculture.

“As long as we can manage and mitigate that risk at an acceptable level, we will continue to process the safe and legal movement of cattle through these ports,” he said, watching as cattle lined up in the chutes at Columbus.

About a third of all Mexican cattle imported to the U.S. each year pass through Columbus and the Santa Teresa port near El Paso, Texas. Gerardo Fierro, executive director of the New Mexico Border Authority, pegged the value of the cattle trade for the area at $1 billion.

Fierro said the community watched as jobs, cattle sales and even tax revenue from the diesel fuel used to transport the animals evaporated due to the closures. Ranchers were no longer crossing into New Mexico and spending money on supplies, lodging and food, and farmers had no customers for their alfalfa and grain.

“This means a lot,” he said of the reopening.

Another border crossing for cattle in Arizona is due to open in late November.

New Mexico state veterinarian Samantha Holeck said the rigorous process for getting cattle ready starts at their home ranches, where private veterinarians check for tuberculosis and other diseases and deliver medications that prevent screwworm.

At the next stop, veterinarians accredited by the Mexican government look for open wounds, signs of illness or other injuries. Then a head-to-tail inspection is done by the USDA while still in Mexico.

The last hurdle? Dipping — as it's commonly known — involves the cows being immersed in vats of insecticide to get rid of any missed parasites.

Holeck said the protocols developed over recent years helped to buy more time, and the USDA is using fly traps and drones to survey areas.

The government has a longstanding program to breed sterile male flies and drop swarms of them from planes to mate with wild females, causing the flies to die out. The government is building a $610 million factory in Texas that can produce 300 million sterile flies per week. That will augment production at facilities in Mexico and Panama.

“That’s our sharpest tool,” Hoskins said.

Mexican ranchers once again have a market for their feeder cattle, but experts say it will take time for U.S. ranchers to rebuild herds that have dwindled to record lows due to years of persistent drought. Constrained supplies have pushed prices higher.

Tom Paterson, president of the New Mexico Cattle Grower's Association, was among those who met with U.S. Agriculture Secretary Brooke Rollins last week in Columbus.

“I agree with the secretary,” he said, “when she says that food security is national security.”