Subscribe to The Y’all — a weekly dispatch about the people, places and policies defining Texas, produced by Texas Tribune journalists living in communities across the state.
McALLEN — The U.S. Department of Agriculture announced a suspected case of New World screwworm — the parasitic fly poised to harm the state’s $15 billion cattle industry — in South Texas.
The USDA is testing a sample of the potential infestation at the USDA’s National Veterinary Services Laboratories in Ames, lowa, the agency announced on social media on Wednesday.
The USDA added it had already activated personnel on the ground and were working with local partners.
The announcement comes one day after Secretary Brooke Rollins debunked the claims of a state lawmaker that the screwworm was less than 1 mile from the U.S.-Mexico border.
State and federal officials have been bracing for the arrival of screwworm for months, fearing its potential impact to livestock and the agriculture industry at-large.
The parasitic fly targets the live flesh of warm mammals — especially cattle and other wildlife. Screwworms infect them by embedding their larvae in open wounds. The larvae feed off the flesh, causing severe wounds or death. Human and domestic animal infections are rare.
Screwworm had been eradicated in the U.S. since the 1960s when the pest was pushed back into Central America. However, cases began springing up in Panama, Costa Rica, Nicaragua, and Honduras. In 2024, Mexico reported its first case.
In an effort to prevent its spread, the USDA shut down the southern border to live animal imports in May 2025, preventing cattle from Mexico from entering the U.S. and limiting the supply of cattle in Texas.
U.S. officials are also working with officials in Mexico and Panama to try to eradicate the screwworm again using the sterile fly method. This practice consists of producing male sterile flies to have them reproduce unviable eggs with female flies who can only reproduce once in their lifetime.
At the time of their spread from Central America into Mexico, there was only one sterile fly production facility, located in Panama. Since then, U.S. officials have helped launch another in Metapa, Mexico and are building another in Edinburg, Texas.
They’ve also launched two fly dispersal facilities, which help distribute sterile flies in needed areas, in Tampico, Mexico and Edinburg.
On Monday, state Rep. Don McLaughlin, a Uvalde Republican, claimed the fly was just one mile away from Texas. Rollins dismissed those claims Tuesday at a news conference, calling McLaughlin “well intentioned” but wrong.
“Well… maybe we should listen to our state representatives,” McLaughlin tweeted after the USDA announced the suspected case Wednesday.
“If this case is confirmed I will stand lock step with every local, state and federal agency to work together and fight this horror,” he said on X. “As we gather more information and work with different agencies we will keep South Texas informed and protected.”
In February, Florida officials detected screwworm larvae in an imported horse from Argentina as the animal made its way through the required import process. Officials assured no case of screwworm had been detected outside of the quarantine area or in any Florida-based animal.
This is a developing story and will be updated.
Reporting in the Rio Grande Valley is supported in part by the Methodist Healthcare Ministries of South Texas, Inc.
