A flesh-eating parasite that devastated the American cattle industry decades ago may once again be present in the United States.
The U.S. Department of Agriculture announced that the New World Screwworm may have been detected inside the country after slowly progressing northward from South America since 2024.
“A case of NWS may have been detected in South Texas. The sample is now at USDA’s National Veterinary Services Laboratories (NVSL) in Ames, Iowa for confirmatory testing,” USDA officials said in an X post on Wednesday afternoon. Officials did not specify where in South Texas.
“We will provide updates the moment results are available. We have already activated personnel on the ground and are working with local partners. What you can expect from us is transparency, candor, and most important — action,” the post further reads.
The New World Screwworm is a type of botfly maggot that can infest livestock, pets and people. Adult flies can lay eggs in open wounds as small as a tick bite but also in sensitive areas, like eyes. Untreated infestations can cause death.
Screwworm infestations were a common occurrence until the 1970s, when the United States, in concert with Mexico and several Central American countries, was successful in eradicating the deadly pest by pushing it back behind the Darien Gap. But that decades-long containment was ultimately breached in late 2024. Since then, reports of screwworm infestations have been inching ever northward. Federal lawmakers have said that a resurgence of the deadly parasite could cost American farmers and the economy billions of dollars.
The USDA’s announcement of a potential domestic screwworm infestation comes just one day after Agriculture Secretary Brooke Rollins pushed back on rumors that the parasite was within sight of the United States. And it comes just a few days after state Rep. Don McLaughlin, a Republican who represents the Uvalde and Laredo areas, issued a warning that New World Screwworm had been detected within a mile of the U.S.–Mexico border. McLaughlin serves on the statehouse’s Agriculture and Livestock Committee.
“This is not true — we have no confirmed case within one mile of the border,” Rollins told reporters during a press call on Tuesday, June 2, according to reporting by Beef Magazine.
Instead, Rollins said the nearest detection reported by Mexican authorities was at least 25 miles from the border in the Mexican state of Coahuila.
The USDA’s X post does not specify where in South Texas the sample of the potential pest was collected. But it does direct people to visit the department’s official New World Screwworm response website.
“NWS is not currently present in the United States,” the website reads.