Federal officials confirmed the detection of the New World screwworm in a 3-week-old calf in Zavala County, Texas, marking the first confirmed case in the state since the early 1980s. The New World screwworm is a parasitic fly whose larvae burrow into living tissue, and its resurgence in the U.S. follows a spread through Central America and Mexico that began in 2023. While human infestations are rare, the presence of this parasite poses a potential threat to ranchers and the livestock industry, particularly as beef prices are already near record highs.
Texas officials are conducting surveillance and have implemented movement restrictions for warm-blooded animals in a 12-mile radius around the detection site. The Texas Animal Health Commission (TAHC) has been monitoring the area with fly traps since July 2025 and has deployed sterile flies to mitigate the infestation. The TAHC is investigating how the calf became infected, as there have been no recent movements of animals from the ranch.
The USDA is also working to increase sterile fly production capacity, including renovations in Mexico and new facilities in Texas. The sterile insect technique, which involves releasing sterilized flies to mate with wild flies, has been used successfully in the past to control screwworm populations. However, the current situation raises concerns about the adequacy of surveillance and response capabilities in light of recent budget cuts and staffing losses in animal health agencies.
