The U.S. Department of Agriculture confirmed Wednesday that the New World screwworm has arrived in South Texas.
Texas, USA— new world screwworm The U.S. Department of Agriculture confirmed Wednesday that a parasite with flesh-eating larvae has arrived in South Texas, marking the first time in decades that a parasite with flesh-eating larvae has threatened the U.S. cattle industry and the third time the virus has appeared in the United States during that time.
Agriculture Secretary Brooke Rollins said the case was in a 3-week-old calf in La Pryor, Texas, about 50 miles from the Mexican border. Texas veterinarian Bud Dinges said he has established a 12-mile quarantine zone that prohibits any warm-blooded animals, including pets, from leaving the area without inspection.
Rollins said no other such flies have been found in the United States, and officials were quick to say that while the fly’s larvae pose a threat to livestock production, they do not infest food. Rollins said even infected calves should recover if treated properly.
Rollins, U.S. and Texas agriculture officials and cattle industry leaders have been sounding the public alarm about the dangers of the fly. Sports across Mexico For more than a year, people were stoked by memories of it causing tens of millions of dollars in damage (possibly billions in today’s dollars) until it was eradicated in the 1970s.
Rollins said this is the first confirmed case in Texas since 1966.
For months, in an effort to stop the fly from entering the United States, we have released millions of sterile screwworm flies in the area to mate with wild females—the same method used successfully before eradicating the fly. Rollins said the USDA is confident in its preparedness and believes “there is no threat of widespread infection.”
“There is no reason to believe that this invasion will allow this pest to become established in our country,” Rollins said.
Just one day before Rollins announced the suspected cases, Rollins held an online press conference to emphasize the looming threat, with cases confirmed in Mexico 25 miles from the border, and to outline the USDA’s response.
The New World screwworm is a tropical species that infected cattle in warm weather in the southern United States decades ago, but it was not controlled in Panama until late 2024.
Female flies lay their eggs in open wounds or mucous membranes, which hatch into larvae that feed on flesh, making them different from most fly species and capable of infecting livestock, wild mammals, household pets and even humans. If left untreated, the infection can lead to death.
In August 2025, federal health officials confirmed a case Resident in Maryland A trip was made to El Salvador, but the victim recovered and officials found no spread of the parasite. Prior to this, the last outbreak was in the Florida Keys in September 2016, mainly among wild deer, and was controlled early the following year without further spread.
Female flies mate only once during their months-long lives, and if they mate with sterile flies, their eggs will not hatch – and over time, the population will become extinct. Past eradication efforts were so successful that the United States closed breeding facilities for sterile flies, leaving only one in Panama for decades.
This is changing. The USDA invests $21 million to transform a fruit fly breeding facility in southern Mexico into a screwworm breeding facility and put it into use A new center for repelling sterile flies Breed elsewhere in South Texas, where construction of a $750 million screwworm factory has begun. Rollins said the breeding facility in Mexico will be operational next month.
Officials have also deployed 8,000 fly traps along the U.S.-Mexico border, and Rollins said the USDA has tested more than 58,000 fly samples and 19,000 wild animals.
Rollins also closed the U.S.-Mexico border last year to banning livestock imports from Mexico, a decision she defended at a news conference on Tuesday. Officials noted that the fly can also travel with people and their pets, as well as wildlife, but Rollins stressed Wednesday night that it cannot fly very far distances on its own.
Dinges said ranchers and pet owners need to understand it’s important to respect quarantine areas.
“Please help us stay put and prevent this pest from moving further,” he said.
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