New World Screwworm Spreads Beyond Texas

The New World screwworm has spread beyond Texas, with a new confirmed case in New Mexico, the Department of Agriculture announced Monday, just five days after the parasite was identified in the United States for the first time in six decades.

A dog in Lea County, New Mexico, located on the Texas state line, tested positive for the parasite, and the USDA believes it to be an isolated case.

Agriculture Secretary Brooke Rollins insisted the confirmed cases — which now include two calves and a goat that tested positive in Texas — haven’t caught the department off guard, but acknowledged that the agency’s current tools to fight the parasite need to be ramped up. The screwworm is a fly larva that eats living flesh, mainly in livestock but that can also spread to wildlife, pets and, in rare instances, humans.

Currently, the U.S. produces 100 million sterile flies a week, which helped eradicate the pest in the country in 1996. Rollins says these flies will be used to eradicate screwworm again, but the country needs between 400 million and 500 million flies a week.

“Our goal is to have enough sterile flies deployed and out into Texas and wherever else this happens to be before the summer season pops up,” Rollins said in a press conference.

Rollins said a new facility in Mexico that can produce sterile flies will be operational by the end of the month.

Rollins also continues to blame the Biden administration, without evidence, for the arrival of the screwworm, claiming open border policies and the illicit movement of cattle contributed to the spread inside the United States. The Biden administration implemented port closures for livestock in 2024 to prevent the spread of the parasite. After the beginning of Trump’s second term, the ports were reopened and closed multiple times.

Rollins said models projected the flies would reach the U.S. by last summer. “We bought ourselves an additional year to prepare for this moment,” Rollins said Monday.

The parasite has been moving north through Central America and Mexico for several years with recent cases detected near the U.S.-Mexico border. The USDA confirmed a case in Coahuila, Mexico, about 25 miles south of the Texas border, on Tuesday.

Texas Agriculture Commissioner Sid Miller, a Republican, has criticized the Trump administration and the USDA, arguing the response has not been strong enough. The Trump administration shut down animal disease-tracking programs under the U.S. Agency for International Development, including screwworm tracking, in March 2025.

Miller has raised concerns about farmers not self-reporting because they’re concerned their animals will be quarantined, which Rollins, when asked, called “an unserious comment” from an “unserious commissioner.”