The Department of Agriculture confirmed on Wednesday that the New World screwworm fly has been detected in Texas, marking the first time the parasite has threatened America’s cattle industry since 1966.
Agriculture Secretary Brooke Rollins said the USDA Animal and Plant Health Inspection Service confirmed the flesh-eating larvae was detected in a calf in Zavala County, Texas, roughly 50 miles from the Mexican border, adding that her department is “taking immediate action” to mitigate the spread.
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A 12-mile quarantine zone has been established, barring any warm-blooded animal, including pets, from entering from outside the perimeter. Rollins said there have been no other detections and that the larvae do not pose a threat to the food supply, emphasizing the detection has been contained.
“Our food supply is 100% safe. This potential New World Screworm detection is being fully contained and is not a harm to the American food supply or consumer safety,” Rollins said in a statement posted to X.
Rollins added that additional resources have been sent to the farm in La Pryor, Texas, to provide support in containing the fly, telling producers to be “vigilant and watchful.”
Screwworms pose a serious threat to the cattle industry, as well as other animals, because the fly’s 10- to 30-day lifespan gives way for an infestation to spread quickly throughout a herd. Screwworms lay eggs in warm-blooded animals’ open wounds and orifices, which then hatch into parasitic maggots that feed on the animals’ tissue.
Reports of a screwworm infection were first reported Tuesday in a 5-year-old goat in Mexico’s Coahuila state, which put Rollins and the cattle industry on alert. She said then that “there’s no doubt that this is a very, very serious threat to our livestock.”
A potential outbreak could cost Texas livestock producers hundreds of millions of dollars, and hit the state’s economy with over $1.8 billion in losses, according to estimates by the Agriculture Department.
The New-World screwworm first entered the United States in 2025, but USDA Under Secretary for Marketing and Regulatory Programs Dudley Hoskins said in a press release that officials were able to “buy time” and prepare for the threat of a larger outbreak.
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Rollins said the recent detection is a result of open border policies under the Biden administration that allowed illegal cattle trading across borders.
“Unfortunately, the open-border policies of the last administration and the resulting illicit cattle movement throughout Mexico have caused NWS to potentially reach our side of the border,” Rollins said. “BUT, there is no one better than Texas and our live stock producers to have in this fight.”
Guidelines for what to do if a screwworm is on your animals can be found on the USDA’s webpage dedicated to the larvae.