Texas cattle producers and agriculture officials are closely monitoring the threat of the New World screwworm, a parasitic fly that feeds on living tissue in livestock wounds and could pose a major risk to the state’s multibillion-dollar cattle industry if it spreads northward.
The New World screwworm is a species of fly whose larvae infest open wounds on warm-blooded animals, including cattle, wildlife and, in rare cases, pets and humans. Unlike typical flies that feed on dead tissue, screwworm larvae consume living flesh, often worsening injuries and leading to severe infection or death if untreated.
The United States eradicated the pest decades ago through a large-scale federal effort that used the sterile insect technique. Under the program, millions of male screwworm flies were bred in controlled facilities, sterilized with radiation and released into the wild. When sterile males mated with wild females, no offspring were produced, eventually collapsing the population.
Despite that success, the parasite remains present in parts of Central and South America, raising concerns about reinfestation through animal movement, wildlife migration or gaps in surveillance along the southern border.
Agriculture officials say Texas is particularly vulnerable because of its large cattle population and extensive ranching operations. An outbreak could lead to quarantines, livestock movement restrictions, increased veterinary costs and potential disruptions to domestic and international trade.
The Texas cattle industry is a major part of the state’s economy, valued at tens of billions of dollars annually. Ranchers and regulators say even a small outbreak could spread quickly because screwworm larvae can infest minor wounds, making early detection and rapid response critical.
Federal and state agriculture agencies continue to monitor livestock health and maintain surveillance programs designed to detect any signs of reintroduction. Officials also support maintaining readiness for emergency response measures, including potential renewed sterile fly production if needed.
Agriculture experts say continued vigilance is key as global trade and shifting climate conditions increase the risk of invasive species expanding their range.