The U.S. Department of Agriculture confirmed the presence of the New World screwworm fly in south Texas, marking the first sighting in decades. This parasite, notorious for its flesh-eating larvae, poses a significant threat to the cattle industry. Agriculture Secretary Brooke Rollins reported the discovery in a calf in LaPryor, Texas, near the Mexico border.

Texas State Veterinarian Bud Dinges has established a quarantine zone of 12 miles, restricting the movement of all warm-blooded animals, including pets, unless inspected. Rollins emphasized that, despite the larvae’s threat to livestock, they do not contaminate food. With appropriate treatment, the affected calf should recover.

“There is no reason to believe this incursion will result in establishment of the pest in our country.” — Brooke Rollins, Agriculture Secretary

Efforts to eradicate the screwworm fly include releasing millions of sterile flies to mate with the wild population. This method has proven effective in the past, giving officials confidence in their preparedness to prevent mass infestation.

The screwworm fly, once widespread in southern U.S., remained confined to Panama until late 2024. Females lay eggs in wounds or mucous membranes, and the larvae consume flesh, affecting livestock, wildlife, pets, and occasionally humans. If untreated, infestations can result in death. A previous outbreak occurred in the Florida Keys in 2016 but was contained quickly.

To bolster defenses, the USDA invested $21 million to convert a facility in southern Mexico for breeding sterile screwworm flies. A new dispersal center in Texas and a forthcoming $750 million factory will enhance eradication efforts. Additionally, 8,000 traps were set along the border, and over 58,000 fly samples have been tested.

The USDA closed the U.S.-Mexico border to livestock imports, a decision Rollins defended to maintain biosecurity. She noted that while flies travel with people and animals, they don’t cover long distances by themselves.

Dinges urged ranchers and pet owners to abide by the quarantine. “Please help us prevent any further movement of this pest by staying put,” he said.