New World Screwworm (NWS) Resources

New World Screwworm (NWS) (Cochliomyia hominivorax) is a parasitic fly that affects livestock, pets, wildlife, birds, and, less commonly, people. Adult screwworm flies are about the size of a common housefly or slightly larger. They are attracted to wounds and natural body openings, including the nose, eyes, ears, mouth, genital area, and newborn animals’ navels, where they lay eggs. The eggs hatch into larvae (maggots) that feed on living tissue, causing painful, worsening wounds that may have a foul odor.

NWS is endemic in Cuba, the Dominican Republic, and parts of South America. The fly has moved northward through Central America and Mexico since 2023, increasing concerns about spread into new areas. In June 2026, the USDA’s Animal and Plant Health Inspection Service (APHIS) confirmed the first U.S. cases of the current outbreak in Texas and New Mexico.

The USDA and state animal health officials are responding with surveillance, quarantines, sterile fly releases, wildlife monitoring, and outreach efforts. The current risk to animals and people in the United States remains very low. Veterinarians, livestock owners, and pet owners in affected areas are encouraged to monitor animals for draining or enlarging wounds, signs of discomfort, and the presence of larvae or eggs