A parasitic fly known as the screwworm is moving north through Mexico toward South Texas, prompting ranchers to prepare defensive measures. The screwworm burrows into open wounds on any warm-blooded animal, with larvae that feed on living tissue and can kill hosts within days if untreated. The pest broke containment in Panama in 2023 and has since spread over 1,000 miles in two years, moving at an estimated 5-10 miles daily with favorable wind conditions.
