LA PRYOR, Texas — The U.S. Department of Agriculture (USDA) confirmed a second domestic case of the highly destructive, flesh-eating screwworm parasite in Texas on Friday, just days after the first U.S. detection in decades was reported nearby.
The newly confirmed infestation was identified on a ranch in Zavala County, located only 5.6 miles (9 km) from the initial positive case confirmed by federal authorities on Wednesday. According to the USDA’s Animal and Plant Health Inspection Service (APHIS), the second infection was detected in a one-month-old calf following targeted testing of several suspect animals in the immediate vicinity.
State and federal agricultural officials with APHIS and the Texas Animal Health Commission (TAHC) have expanded their containment grid, collecting and processing additional biological samples from surrounding areas, all of which have returned negative so far.
The dual detections near La Pryor—a rural town positioned roughly 30 miles (50 km) northeast of the U.S.-Mexico border—represent a major operational setback for American livestock producers. Ranchers across the region have been on high alert as the aggressive pest steadily migrated northward through Mexico over the past year.
Screwworms are parasitic flies that lay eggs within the open wounds, sores, or mucous membranes of warm-blooded animals. Once hatched, the larvae bore into living tissue to feed on the host, a process that causes extensive physical trauma and can be fatal to the animal if left untreated.
The livestock industry views a domestic resurgence with extreme concern. A major screwworm outbreak along the southern border during the 1960s decimated local wildlife populations and caused catastrophic financial losses for the agricultural sector. A modern, widespread outbreak could severely disrupt the economy of Texas, which stands as the largest cattle-producing state in the nation, by driving up animal mortality rates, labor monitoring requirements, and veterinary treatment costs.
To mitigate transmission risks, Washington has maintained a strict ban on live cattle imports across the U.S.-Mexico border for over a year. The federal government has deployed millions of dollars into intensive containment initiatives, including the mass production and release of sterile male flies to disrupt breeding cycles, expanding regional trapping networks, and enforcing rigorous livestock health inspections.
