The U.S. Department of Agriculture verified Wednesday that the New World screwworm fly has appeared in southern Texas. This marks the first occurrence in decades for the parasite whose larvae consume living tissue and threatens domestic cattle operations, representing only the third such detection in the country over that span.

Agriculture Secretary Brooke Rollins identified the incident in a three-week-old calf located in LaPryor, Texas, roughly 50 miles from the Mexico border. Texas State Veterinarian Bud Dinges established a 12-mile quarantine area that bars transport of any warm-blooded creatures, including companion animals, beyond the boundary absent prior examination.

Rollins noted no additional finds elsewhere in the nation and emphasized that although the larvae endanger livestock output, they do not affect food supplies. With proper care the affected calf is expected to recover fully, she added.

Rollins along with federal and state agriculture leaders and cattle sector representatives have raised warnings for more than a year regarding the fly's northward progress through Mexico, recalling earlier losses that reached tens of millions of dollars and could equate to billions today before eradication in the 1970s.

This instance represents the first confirmed detection in Texas since 1966, according to Rollins.

Preparations to block entry have featured release of millions of sterile screwworm flies to mate with wild females, replicating the prior successful strategy. Rollins expressed confidence that current measures ensure no risk of widespread establishment.

"There is no reason to believe this incursion will result in establishment of the pest in our country," Rollins said.

The suspected case announcement followed by one day an online briefing by Rollins detailing the fly's proximity, with confirmed Mexican cases as near as 25 miles from the border, and describing USDA countermeasures.

The New World screwworm fly is a tropical insect that once infested southern U.S. cattle during warm seasons but remained contained in Panama until late 2024.

Female flies deposit eggs in open wounds or mucous membranes; hatched larvae consume flesh unlike typical fly species and may affect livestock, wildlife, pets, and humans. Untreated cases can prove fatal.

Federal health authorities confirmed a Maryland case in August 2025 involving a traveler returning from El Salvador, yet the individual recovered and no local spread occurred. The previous U.S. outbreak took place in the Florida Keys in September 2016, primarily among wild deer, and was contained by early the following year.

Females mate only once during their lives spanning several months; mating with a sterile male prevents egg hatching and gradually reduces the population. Successful past campaigns led the U.S. to close domestic sterile-fly production sites, leaving a single facility in Panama for many years.

That situation is shifting. The USDA allocated 21 million dollars to repurpose a fruit-fly facility in southern Mexico for screwworm production, launched a new dispersal center in southern Texas, and began building a 750-million-dollar factory in the same region. The Mexican breeding site is slated to begin operations next month, Rollins stated.

Authorities placed 8,000 traps along the border and tested over 58,000 fly samples plus 19,000 wild animals, Rollins reported.

Rollins also halted livestock imports from Mexico last year, a step she defended in Tuesday's briefing. While the fly can move via humans, pets, and wildlife, she stressed Wednesday that it does not travel long distances independently.

Dinges urged ranchers and pet owners to observe the quarantine strictly.

"Please help us prevent any further movement of this pest by staying put," he said.