Federal and state officials are urging pet owners and livestock producers across the southern United States to remain vigilant this summer as the New World screwworm, a parasitic fly whose larvae feed on the living tissue of warm-blooded animals, continues to spread following its first confirmed U.S. detection in nearly 60 years.

The parasite, commonly abbreviated NWS, resurfaced domestically on June 3, when the U.S. Department of Agriculture's Animal and Plant Health Inspection Service confirmed a case in a three-week-old calf in Zavala County, Texas, located roughly 50 miles from the Mexico border. Since then, the outbreak has expanded significantly. According to the Centers for Disease Control and Prevention, USDA has confirmed 16 domestically acquired animal cases, spread across multiple Texas counties and Lea County, New Mexico, involving cattle, goats and at least one dog, the first confirmed case in a companion animal since the parasite's reappearance.

New World screwworm infestations begin when a female fly lays eggs on an open wound or body opening, where the eggs hatch into larvae that burrow into the wound and feed on living tissue, according to USDA. The pest affects livestock, pets, wildlife and, less commonly, birds and people, though officials have emphasized that NWS is not contagious and does not spread directly between animals or from animals to humans. Instead, infestations occur individually, when a fly lays eggs on a susceptible wound, meaning even a small, untreated cut can put a pet or farm animal at risk.

According to the USDA, common warning signs of a potential infestation include wounds that appear to be enlarging or draining unusual discharge, visible signs of discomfort in an affected animal, and, in........

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