USDA confirms – The USDA confirmed a new New World screwworm case in Texas—a dog in West Texas—more than 300 miles from the original outbreak zone. The discovery has expanded detections to three Texas counties and triggered quarantines, surveillance, and continued sterile fly
The moment the sample reached the people tracking a deadly livestock threat, it changed the map.
On Monday, June 8, the U.S. Department of Agriculture confirmed two new New World screwworm cases in Texas: a calf in La Salle County and a dog in Andrews County. By then. the alarm already had teeth—earlier confirmations had begun with cases in South Texas. and now the USDA says one of the detections landed in West Texas. more than 300 miles from the original outbreak zone.
The USDA said the risk to the U.S. food supply, animals, and people remains very low. Any affected animal, the agency said, would be identified during USDA Food Safety and Inspection Service inspection, and no contaminated product would enter commerce.
Still, the geography is what unsettles ranchers and veterinarians: New World screwworm has now been detected in three Texas counties, including a dog in West Texas, and epidemiological investigations are ongoing for both June 8 cases.
For the Andrews County dog, early reports had suggested it recently had been in Mexico. The USDA said a veterinarian submitted samples, and investigation work continues.
The most recent Texas detections arrived after additional cases confirmed earlier in June—two cases were confirmed on Wednesday, June 3, and another was confirmed on Friday, June 5, in Zavala County in South Texas.
The response is being run on two tracks at once: tight control where the detections occurred, and broader monitoring to catch movement early.
USDA and the Texas Animal Health Commission are leading the effort. with a reported 75 people actively responding on the ground and hundreds more around the country providing laboratory diagnostics. logistics. treatment distribution. air operations. outreach. operational planning and resource support.
Both agencies have taken steps to limit spread of New World screwworm. including establishing and maintaining a 20km infested zone with quarantines. movement controls. and heightened surveillance around confirmed detections. They are also increasing trapping along the border and outside the dispersal zone.
Surveillance and management strategies are being conducted in wildlife as well, and the response includes targeted outreach to local producers, veterinarians and communities.
At the same time, sterile New World screwworm fly releases are continuing over the infested areas and along the U.S.-Mexico border. Beginning on Tuesday, June 9, aerial dispersal flights originating from the sterile fly dispersal facility at Moore Air Base in Edinburg, Texas, will begin.
Because of how sterile releases work, the USDA said it is possible that sterile NWS flies could be caught and reported. The agency said it has taken steps to ensure officials can differentiate between sterile and wild NWS flies.
The screwworm itself is a parasitic fly whose larvae feed on the living tissue of warm-blooded animals. According to the USDA, infestations begin when a female fly lays eggs on a wound or body opening. The eggs hatch into larvae that burrow into the wound and feed on living tissue. After about 7 days of feeding, larvae drop to the ground, burrow into the soil, and pupate.
The adult screwworm fly then emerges from the soil after 7 to 54 days.
The USDA emphasizes that the threat is not spread through contagion—New World screwworm is not contagious. Instead, it moves through egg-laying and infestation of wounds.
Adult screwworm flies have orange eyes, a metallic blue or green body, and three dark stripes across the back, according to the USDA. The telltale signs of infection are growing wounds or lesions and the presence of feeding maggots on still-alive animals.
Dr. Jennifer Bloodgood. assistant professor of practice and wildlife veterinarian at Cornell University. said some other species of maggot can be found on live animals—but the difference is what they’re eating. She explained that NWS feeds on healthy, living flesh, while most other maggot species feed on dead tissue.
That distinction is hard to make in the real world, especially when dealing with wild animals that can’t be observed closely. Because of that, public health officials encourage the public to report suspected cases.
Even with the low risk to people and the food supply. the expanded detections—moving from Zavala County into additional Texas counties. including a dog in West Texas—have put the focus on speed: quarantines. trapping. wildlife monitoring. and sterile fly releases are all geared toward stopping the next step before it takes hold.
USDA Texas New World screwworm USDA Food Safety and Inspection Service Texas Animal Health Commission Moore Air Base sterile fly releases quarantine surveillance La Salle County Andrews County Zavala County