WASHINGTON — U.S. agricultural authorities have activated heightened nationwide biosecurity measures following the confirmation of New World screwworm in a calf in Texas, the first detection in the United States in decades, officials said.
The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (USDA-APHIS) confirmed the case on June 3 in a three-week-old calf in Zavala County, Texas, near the Mexico border. No additional cases have been reported, and there have been no locally acquired human infestations.
Federal and state officials launched an immediate response including quarantines, enhanced surveillance, movement restrictions for livestock, and expanded releases of sterile flies to prevent spread. The parasite, whose larvae feed on living tissue of warm-blooded animals, poses a significant threat to livestock, pets, wildlife and, less commonly, people.
“Animal health officials are working quickly to protect U.S. livestock and wildlife,” USDA-APHIS stated. The agency has deployed personnel to the area and established a 20-kilometer infested zone around the detection site.
The detection follows an ongoing outbreak of New World screwworm that has spread northward through Central America and Mexico since 2023, with more than 171,700 cumulative cases reported in animals and more than 2,070 cases in people in those regions as of early June.
USDA and partner agencies have intensified sterile insect technique operations, releasing millions of sterilized male flies to mate with wild females and reduce populations. Enhanced inspections at borders and livestock facilities are underway across the country, particularly in southern states.
State agriculture departments, including in Texas, have issued alerts urging producers to inspect animals for wounds or signs of infestation and report any suspicions promptly. The Texas Animal Health Commission and other state agencies are coordinating with federal efforts.
The New World screwworm was eradicated from the United States in 1966 through a large-scale sterile fly program but reemerged as a concern after advancing through Mexico. Officials have stressed that the food supply remains safe, as the parasite affects living animals rather than processed meat.
As of Saturday, no further detections had been confirmed beyond the initial Texas case. Surveillance and containment operations continue nationwide, with authorities monitoring for any additional signs of the pest. Details on the full extent of the response measures remain subject to ongoing assessments.
