The New World screwworm fly has reached south Texas, the U.S. Division of Agriculture confirmed June 3, the primary time in a long time that the parasite with flesh-eating larvae has threatened the nation’s cattle business and solely the third time it is appeared within the U.S. in that point.
Agriculture Secretary Brooke Rollins mentioned the case was in a 3-week-old calf in La Pryor, Texas, about 50 miles from the Mexico border. Texas State Veterinarian Bud Dinges mentioned he has established a 12-mile quarantine zone, prohibiting the motion of any warm-blooded animal — together with pets — outdoors that zone with out an inspection.
Rollins mentioned there have been no different detections of the fly within the U.S., and officers had been fast to say that whereas the fly’s larvae are a menace to livestock manufacturing, they don’t infest meals. Correctly handled, even the infested calf ought to recuperate, Rollins mentioned.
Rollins, U.S. and Texas agriculture officers, and cattle business leaders have been sounding public alarms in regards to the fly’s motion throughout Mexico for greater than a yr, spurred on by reminiscences of it inflicting tens of hundreds of thousands of {dollars} of losses — probably billions in right now’s {dollars} — earlier than its eradication within the Seventies.
It’s the first case confirmed in Texas since 1966, Rollins mentioned.
The months of effort to maintain the fly out of the U.S. have included dropping hundreds of thousands of sterile screwworm flies within the space to mate with wild females — the identical technique used efficiently earlier than the fly was eradicated. Rollins mentioned the USDA is assured sufficient in its preparations that it believes “there isn’t any menace of mass infestation.”
“There isn’t a cause to imagine this incursion will lead to institution of the pest in our nation,” Rollins mentioned.
The announcement of the suspected case comes solely a day after Rollins had an internet information convention to spotlight the nearness of the menace, with instances being confirmed in Mexico as shut as 25 miles from the border — and to stipulate the USDA’s efforts to fight it.
The New World Screwworm fly is a tropical species that a long time in the past infested cattle in heat climate throughout the southern United States, nevertheless it was contained in Panama till late in 2024.
The feminine fly lays its eggs in open wounds or mucous membranes they usually hatch into larvae that eat flesh — making them in contrast to most fly species — and may infest livestock, wild mammals, family pets and even people. Infestations can result in dying if left untreated.
In August 2025, federal well being officers confirmed a case in a Maryland resident who had traveled to El Salvador, however the sufferer recovered and officers discovered no transmission of the parasite. Earlier than that, the final outbreak was within the Florida Keys in September 2016, principally amongst wild deer, and it was contained early the following yr with out spreading additional.
The feminine flies mate as soon as of their monthslong lives, and in the event that they accomplish that with a sterile fly, their eggs wouldn’t hatch — and the inhabitants would die out over time. Previous eradication efforts had been so profitable that the U.S. shut down amenities for breeding sterile flies, leaving just one in Panama for many years.
That’s altering. The USDA devoted $21 million to transform a fruit-fly breeding facility in southern Mexico into one for breeding screwworm flies, opened a brand new heart for dispersing sterile flies bred elsewhere in southern Texas and has began development on a $750 million screwworm fly manufacturing facility there. The breeding facility in Mexico needs to be working subsequent month, Rollins mentioned.
Officers additionally deployed 8,000 fly traps alongside the U.S.-Mexico border, and Rollins mentioned the USDA has examined greater than 58,000 fly samples, together with 19,000 wild animals.
Rollins additionally closed the U.S.-Mexico border final yr to livestock imports from Mexico, a choice she defended throughout her information convention Tuesday. The fly can also journey with individuals and their pets and with wild animals, officers famous, however Rollins confused Wednesday night that it would not fly nice distances by itself.
Dinges mentioned ranchers and pet homeowners want to grasp that it is essential to respect the quarantine zone.
“Please assist us forestall any additional motion of this pest by staying put,” he mentioned.
