A horse in southern Texas has been infected with the New World screwworm, marking the first known case in a horse in the United States. Health officials are working to contain the outbreak of this flesh-eating parasite, which was discovered on the hind limb of a working ranch horse in Presidio County. The U.S. Equestrian Foundation issued a statement advising horse owners to check their animals daily for wounds, foul odors, or maggots. The screwworm is the larval stage of a fly that can burrow into open wounds and feed on the flesh of animals, causing serious harm if left untreated. The foundation recommended that horse owners keep wounds clean and covered, use veterinarian-approved fly control products, and use physical barriers like fly masks and clean stabling practices to reduce the risk of infestation. To prevent the spread of the parasite, the Texas Animal Health Commission has imposed restrictions on moving warm-blooded animals out of infected areas in parts of Presidio and Jeff Davis counties, among others. The screwworm had been eradicated from the U.S. decades ago but was detected in June on a calf in Zavala County, near the U.S.-Mexico border. Since then, the infestation has spread throughout Mexico. This year, 49 cases of screwworm have been reported in the U.S., all in Texas except for one in New Mexico, where the pest was found on a dog, according to the U.S. Department of Agriculture. The return of the parasite has raised concerns about the potential financial impact on Texas ranchers, prompting Texas Governor Greg Abbott to issue a disaster proclamation in June to mobilize state resources. In response to the outbreak, the Trump administration had previously announced the creation of a sterile fly dispersal facility in Edinburg, Texas. This facility releases sterile male screwworm flies, which mate with female flies, resulting in non-viable offspring. This method, known as the sterile insect technique, aims to reduce the population of the pest over time. The resurgence of the screwworm highlights the ongoing challenges of managing invasive species and maintaining animal health in border regions.