Texas horse infected with New World screwworm

The United States Department of Agriculture (USDA) has confirmed the first equine case of New World screwworm (Cochliomyia hominivorax) in the United States this century. The parasite, which consists of blow fly larvae that feed on the living tissue of warm-blooded animals, was detected on a working ranch horse in Presidio County, Texas.

In response, the Texas Animal Health Commission has issued an ordinance prohibiting the movement of warm-blooded animals out of designated infested zones in Presidio and Jeff Davis counties. While the parasite was eradicated in the U.S. during the 1960s, recent cases have emerged, starting with a calf in Zavala County in June. Since then, approximately 49 cases have been reported nationally, primarily affecting cattle, goats, sheep, and dogs.

The infestation poses a significant threat as the larvae can burrow into joints and tendons, causing extensive tissue damage and death. Officials note that the parasite continues to circulate in Mexico, making the border region a critical area for containment efforts.