With the detection of New World screwworm just 70 miles from the U.S.-Mexico border, alarm bells are ringing across the cattle industry on both sides of the Rio Grande. The parasitic fly, notorious for laying its larvae in wounds of warm-blooded animals—including cattle, wildlife, and even humans—has prompted emergency action in Mexico and a flurry of preventative measures in Texas and beyond, as reported by Border Report and the Associated Press.
On Monday, September 22, 2025, Mexican authorities confirmed the latest and closest case yet in Sabinas Hidalgo, Nuevo León, a small town near the Texas border. The infected cow, part of a shipment of 100 from Veracruz, had traveled over 1,000 miles from southern Mexico before being isolated and quarantined. Mexico’s Agriculture Secretary Julio Berdegué assured the public that, “We are managing an isolated case of New World Screwworm in Nuevo León and applying the measures agreed upon just over a month ago with the United States government,” as he posted on X (formerly Twitter).
But this is no ordinary pest. The New World screwworm, despite its misleading name, is actually a fly—Cochliomyia hominivorax—whose larvae can kill an animal in less than two weeks. The parasite’s life cycle is alarmingly fast: “It can be a matter of hours from the time that the female lays its eggs until the larvae have hatched and start boring into the animal,” said Colin Woodall, CEO of the National Cattlemen’s Beef Association (NCBA), in an interview with Brownfield. “So you may be out among your cattle on Tuesday, but that doesn’t mean on Wednesday you may not have a significant issue on your hands.”
Since November 2024, Mexico has reported more than 5,000 cases of New World screwworm, with over 500 active cases in the country’s southern states as of this month, according to Mexico’s National Health for Food Safety and Food Quality Service. The outbreak has already led to Washington suspending imports of live Mexican cattle, bison, and horses—a ban that, if it remains through the end of 2025, could cost Mexico’s ranching federation up to $400 million in losses.
In Texas, the stakes are even higher. U.S. Senator John Cornyn warned that if the screwworm crosses the border, it could inflict $1 billion in losses on the Texas cattle industry and $3.7 billion on the broader economy. Zapata County Judge Joe Rathmell, whose border county is closest to the outbreak, expressed deep concern: “Living along the border, and ranching on the border, we deal with fever ticks for many many years. That hasn’t gone away. But now the major concern is hopefully the screwworm won’t make it our way. It would place a big hurt on any ranchers trying to handle cattle down here and wildlife, too.”
Both U.S. and Mexican officials are scrambling to contain the threat. Texas Agriculture Secretary Sid Miller called for “the immediate use of pesticide bait to try to stop the spread of the New World screwworm.” He explained, “The screwworm is dangerously close. Using bait followed by sterile flies is the one-two punch we need to knock the New World screwworm out.” Historically, dichlorvos strips killed up to 90% of screwworm flies on contact, but Miller touted a new synthetic bait called Swormlure, which mimics the smell of rotting flesh and can lure adult flies into traps. “Deploy the bait, stop this pest, and protect our cattle industry. It’s that simple,” Miller said. “It nearly wiped out our cattle industry before; we need to act forcefully now.”
Meanwhile, the U.S. Department of Agriculture (USDA) has ramped up efforts at Moore Air Base in Hidalgo County, Texas, where many of the planes releasing sterile flies originate. Over $100 million worth of sterile flies are being released weekly across southern Mexico and the infected regions, a strategy that proved effective in eradicating the pest from the U.S. in 1966. But building a new sterile fly production facility at Moore Air Base could take up to two years, even as operations are being expedited. “This war for American agriculture demands TOTAL government firepower. Ensuring a resilient food supply is critical to safeguarding U.S. national security. Ranchers: Your fight is OUR fight. Stay vigilant!” posted U.S. Agriculture Secretary Brooke Rollins.
More than 8,000 traps have already been deployed across Texas, New Mexico, and Arizona, and the U.S. has spent over $100 million on eradication technology. The scale of the response reflects the lessons of the past: in the 1950s, screwworm outbreaks cost U.S. farmers $50-$100 million per year before being eradicated, and frequent outbreaks in Mexico continued to cost Texas’s economy hundreds of millions annually until joint eradication efforts pushed the parasite south.
Industry groups are urging even more action. “Time is no longer on our side,” warned NCBA CEO Colin Woodall, who called for faster construction of the domestic sterile fly facility and aggressive adoption of new technologies like electronic beams or modular systems to accelerate fly sterilization. The NCBA is also pressing the Environmental Protection Agency to authorize new pesticide products, and it applauded the Food and Drug Administration’s work to authorize emergency treatments for screwworm. “With the threat so close, we need more sterile fly dispersal to push this pest back from our border. Now is the time for USDA to expedite construction of the domestic sterile fly facility and eradicate this pest from our doorstep,” Woodall said in a statement.
On the ground, ranchers are dusting off old playbooks. Wayne Cockrell, a stocker operator in College Station and cattle health chair for the Texas & Southwestern Cattle Raisers Association, noted that producers are bringing back techniques from before screwworm’s eradication. “Once we brand, we can take some used hydraulic oil, motor oil, and rub that on the brand. That certainly helps.” He also emphasized the need to restrict cattle movement from infested areas of Mexico: “The same process that we had on our southern border with Mexico has got to be implemented there. Until we do that, it’s just going to continue to move northward.”
Mexican authorities, for their part, say that inspection protocols—including ivermectin treatment for all cattle in the infected shipment—are helping minimize the spread. The Ministry of Agriculture reports that the trapping system in northern Mexico has not detected any flies recently, and that the infected animal was intercepted early, with larvae in an early stage and no possibility of the fly emerging. Both Mexico’s Secretary of Agriculture Julio Berdegué and U.S. Agriculture Secretary Brooke Rollins have pledged to continue working together to contain the pest, even as Rollins insisted, “We will not rely on Mexico to defend our industry, our food supply or our way of life.”
As the border region braces for what could be a costly battle, one thing is clear: the fight to keep the New World screwworm at bay is far from over. With vigilance, coordination, and a bit of old-fashioned ranching ingenuity, officials and producers hope to prevent a repeat of the devastation that once haunted the American Southwest.