The U.S. Department of Agriculture confirmed on Wednesday the first detection of New World screwworm in the United States in decades, identifying larvae in a 3-week-old calf in Zavala County, Texas.
Federal and state officials immediately activated containment protocols, including a quarantine zone and sterile insect releases.
This confirmation follows months of warnings about the pest’s northward advance through Mexico and Texas’ proactive preparations, including Gov. Greg Abbott’s disaster declaration in January 2026, as previously reported by The Dallas Express.
The Texas Animal Health Commission established an infested zone covering parts of Zavala and Uvalde counties. Warm-blooded animals may not leave the zone without prior authorization from the commission. A 20-kilometer buffer zone surrounds the detection site.
“Animal health officials are working quickly to protect U.S. livestock and wildlife,” USDA officials stated. The larvae were found in the calf’s umbilical area, and no additional detections have been reported to date.
New World screwworm larvae feed on the living flesh of warm-blooded animals, including livestock, wildlife, pets, and occasionally humans. The pest was eradicated from the U.S. in the 1960s using the sterile insect technique, but has advanced through Central America and Mexico in recent years.
The Dallas Express previously reported on the growing threat, including Agriculture Commissioner Sid Miller’s warnings after the pest was detected just 60 miles from the Texas border in April 2026, as well as earlier coverage of border preparedness efforts.
USDA APHIS and the Texas Animal Health Commission formed a unified Incident Command Team. Response actions include intensified surveillance, fly trapping, sterile male fly releases, and movement restrictions. Texas maintains a sterile fly production facility in South Texas to support rapid deployment.
Texas leads the nation in cattle production, with the industry valued at $15.5 billion (as of the 2022 market value). Officials have emphasized that prompt containment is critical to preventing widespread economic damage. No human cases have been linked to this detection.
Producers are advised to inspect animals for wounds and report any suspicious larvae immediately. The sterile insect technique releases sterilized males that mate with wild females, producing no viable offspring and gradually reducing the population.
State and federal partners continue monitoring across South Texas. The situation remains under active management with ongoing surveillance.
