A New World screwworm fly was confirmed in a three-week-old calf [1] in La Pryor, Texas, on June 3, 2026 [2].
The detection of the flesh-eating parasite represents a significant biosecurity risk. If the parasite spreads beyond this isolated case, it could devastate U.S. cattle herds and disrupt the national food supply chain.
Officials identified the parasite, known scientifically as Cochliomyia hominivorax [1], in the calf near the U.S.-Mexico border [2]. The parasite likely crossed the border from Mexico [3]. This event marks the re-emergence of the pest in the United States after approximately 60 years [1] of eradication.
Unlike many other flies, the New World screwworm is particularly destructive because its larvae feed on the living tissue of warm-blooded animals [1]. The infestation typically begins when the fly lays eggs in an existing wound, such as a naval cord or a scratch, and the resulting larvae eat deep into the animal's flesh [1].
Agricultural authorities are monitoring the situation in La Pryor to prevent further spread. The case has prompted renewed vigilance among ranchers and livestock producers in the border region. Because the parasite is highly invasive and can cause rapid deterioration in animal health, early detection is critical to containing the outbreak [1].
The U.S. Department of Agriculture has been involved in the confirmation and response process. The agency's efforts focus on preventing the parasite from establishing a permanent population within the U.S. livestock population [3].
“The parasite likely crossed the border from Mexico.”
The reappearance of the New World screwworm after six decades suggests a vulnerability in the biological barriers that previously kept the parasite out of the U.S. Because the parasite targets living tissue rather than decaying matter, it poses an immediate threat to livestock productivity and animal welfare. A wider outbreak would necessitate aggressive eradication efforts and could lead to stricter movement restrictions on cattle across the southern border.
