A flesh-eating parasite has been confirmed in the Mexican state of Coahuila — just 119 miles from the Texas border — triggering emergency alerts from state agriculture officials and prompting at least one state to impose new restrictions on livestock imports from high-risk counties.
The Texas Department of Agriculture issued a formal alert on May 1, 2026, following the first confirmed detection of New World screwworm (NWS) in Coahuila, a border state roughly at the same latitude as Zapata, Texas. The detection marks a significant northward advance of the parasite and has intensified calls for immediate, multi-layered containment efforts across the Southwest and beyond.
A Parasite That Kills Livestock Within Days
New World screwworm (Cochliomyia hominivorax) is a parasitic fly whose larvae burrow into the living tissue of warm-blooded animals. Adult flies deposit eggs in open wounds, mucous membranes, or body orifices. Once hatched, the maggots use razor-sharp mouth hooks to screw deeper into flesh, rapidly enlarging wounds and causing severe myiasis — a potentially fatal condition if untreated. Livestock including cattle, sheep, horses, and goats are the primary targets, but the parasite can also infect wildlife, pets, and humans. Animals can die within days of infestation without treatment.
The United States eradicated NWS domestically decades ago through the sterile insect technique (SIT), which involves releasing sterile male flies to disrupt reproduction. The last U.S. outbreak occurred in September 2016, when the screwworm was found in Key deer in Monroe County, Florida. That outbreak was eradicated by early 2017 in coordination with USDA and state partners. Since then, NWS has been spreading northward through Central America and Mexico.
Texas Ramps Up Surveillance, Florida Moves to Restrict Imports
The Texas Department of Agriculture (TDA) has launched what Commissioner Miller describes as an “aggressive biosecurity response,” including expanded trapping using TDA’s proprietary Swormlure attractant in high-risk border zones, export pens, and port areas. The agency is conducting weekly surveillance and maintaining rapid response capabilities in coordination with federal and Mexican counterparts.
Florida has also taken action. On April 28, 2026, Florida Agriculture Commissioner Wilton Simpson issued an emergency rule placing temporary restrictions on the importation of warm-blooded animals into Florida from six high-risk Texas counties. Under the rule, all animals from those counties must be accompanied by an Official Certificate of Veterinary Inspection confirming they are free of NWS and other contagious diseases. Animals with wounds must receive approved oral, injected, or topical treatments within specified timeframes before entry.
Commissioner Miller acknowledged Florida’s action as “understandable,” noting that the economic ripple effects are already being felt. “The extended halt on cattle movement from Mexico alone is straining supply chains, cutting into Texas meatpacking capacity, and pushing prices higher for families nationwide,” Miller said.
Federal Response Underway, But Officials Warn It May Not Be Enough
At the federal level, USDA’s Animal and Plant Health Inspection Service (APHIS) is currently releasing approximately 100 million sterile screwworm flies per week along the Texas border region. In late April, the U.S. Army Corps of Engineers broke ground on a new sterile fly production facility in Edinburg, Texas, which is expected to scale output to 500 million sterile flies per week once operational in about a year from now.
USDA has maintained that NWS is not currently present in the United States. However, Commissioner Miller and other state officials have expressed concern that federal containment efforts have not halted the parasite’s northward advance.
An NWS incursion into the United States would pose a severe threat to the livestock industry, which supports hundreds of thousands of jobs and billions of dollars in economic activity, particularly across the South and Southwest. Beyond agriculture, the parasite’s ability to infect wildlife, companion animals, and humans elevates the public health stakes. Veterinarians and animal health professionals are being urged to remain vigilant and report any suspected infestations immediately.
Sources and further reading:
Commissioner Miller Alerts Texans as New World Screwworm Detected in Coahuila – Texas Department of Agriculture
Florida issues New World screwworm emergency animal import rule – National Hog Farmer