New World screwworm (NWS) larvae cause severe, often fatal damage by burrowing into the flesh of livestock, pets, wildlife, birds, and even humans. Photo courtesy USDA APHIS The Texas Parks and Wildlife Department (TPWD) urges hunters and outdoor enthusiasts in South Texas to watch for signs of New World Screwworm (NWS) after its detection in a cow in Chiapas, Mexico. In a statement released last Dec. 30, Texas animal health officials urged those along the southern Texas border to monitor wildlife, livestock, and pets for clinical signs of NWS and encourage immediate reporting of potential cases. NWS flies lay eggs in wounds or body openings, leading to severe tissue damage and potential death. The parasite primarily affects livestock but can also infect humans, pets, and wildlife. Although eradicated in the U.S. in 1966, NWS reportedly remains widespread in parts of the Caribbean and South America. According to the USDA Animal and Plant Health Inspection Service (APHIS), the parasite gets its name from the maggots’ feeding behavior, burrowing into wounds like screws, causing severe tissue damage with sharp mouth hooks. Infestations can grow as more maggots hatch, often leading to fatal outcomes. Adult screwworm flies, slightly larger than houseflies, have orange eyes, metallic blue or green bodies, and three dark stripes on their backs. Report mammals and birds with the following signs: Irritated behavior Head shaking The smell of decay Evidence of fly strike Presence of fly larvae (maggots) in wounds Suspected cases in wildlife should be reported to a local wildlife biologist, while livestock concerns should be directed to the Texas Animal Health Commission (TAHC) or U.S. Department of Agriculture (USDA). “Those enjoying Texas’ natural resources have an opportunity to serve as the first line of defense in protecting wildlife, livestock, and human health,” says TPWD wildlife veterinarian J Hunter Reed, DVM, MPH, in a statement. “Their eyes and ears will be critical to quickly responding and managing this threat.”
