Overview
- The U.S. Equestrian Federation and USDA confirmed a working ranch horse in Presidio County tested positive for New World screwworm larvae found in its hind leg on Sept. 9, the first confirmed equine case in the current U.S. outbreak.
- USDA data show two active infections in Texas, including the Presidio County horse and a dog in Crockett County, within a broader total of about 49 reported Texas cases and at least one case in New Mexico.
- Authorities are using zone designations, quarantines, increased field surveillance and sterile‑fly releases to contain the parasite and have declared two Texas zones cleared after local investigations.
- The USDA and the Texas Animal Health Commission are urging horse and livestock owners to inspect animals daily for wounds, swelling, drainage, foul odor or maggots, to seek prompt veterinary care, and to use wound care and fly control to reduce risk.
- New World screwworm is a parasitic fly whose larvae eat living tissue and can severely injure livestock, pets and wildlife, so the detection near the U.S.–Mexico border underscores ongoing cross‑border risk and the need for continued monitoring.