This is a top national security priority,” wrote USDA Secretary Brooke Rollins in a Sept. 21 statement about the news on X, formerly Twitter. The affected animal, an 8-month-old cow, had recently been transported to a certified feedlot in Nuevo León from southern Mexico, where active screwworm cases are present. In a Sept. 21 press release, officials wrote that USDA has invested in new technology, expanding sterile fly production and strengthening cross-border cooperation. Working with Mexico, the USDA is monitoring thousands of traps across the American Southwest, and to date, no NWS flies have been found. USDA is urging those along the southern border to regularly check their pets and livestock for signs of screwworm.