Alert to Equine Practitioners: New World Screwworm Enters the United States

On June 3, 2026, the USDA reported the first case of New World Screwworm (NWS) in cattle in the United States in south Texas.

NWS is a serious threat because larvae infest living tissue and cause rapidly progressive, potentially fatal myiasis (maggot infestation) in warm-blooded animals, including horses and humans.

The AAEP New World Screwworm Working Group has prepared this resource for equine veterinarians about the disease. Topics discussed include: