Key facts
- A screwworm infestation has been confirmed in a calf in La Pryor, Texas.
- The New World screwworm fly has not been present in the US for over 50 years.
- The larvae feed on live flesh and fluids, posing a threat to livestock, wildlife, pets, and humans.
- Texas has implemented a 12-mile quarantine zone in Zavala County.
- The USDA is dropping 4 million sterile flies weekly in south Texas.
- Ranchers are proactively administering preventative injections and treating wounds.
The New World screwworm fly, a parasite whose larvae feed on live flesh, has reappeared in south Texas, marking the first infestation in the U.S. in over 50 years. The discovery was made in a young calf in La Pryor, Texas, near the U.S.-Mexico border. This re-emergence poses a significant threat to the $113 billion U.S. cattle industry, with Texas being the leading state. The fly was last eradicated from the U.S. in the 1960s through the release of sterile male flies. Officials had been monitoring the fly's movement through Mexico since late 2024, after it was contained in Panama. The larvae can infest any warm-blooded animal, including wildlife, pets, and humans, with thousands of animals and hundreds of people affected in Central America and Mexico. Texas State Veterinarian Bud Dinges has imposed a 12-mile quarantine zone in Zavala County to prevent the movement of animals. The USDA is actively releasing 4 million sterile flies weekly in south Texas and has invested in a new breeding facility. Ranchers are taking proactive measures, including preventative injections and wound treatment, to protect their herds.