Horse smuggling threatens U.S. efforts to contain New World screwworm

Illegal horse trafficking across the U.S.-Mexico border is creating biosecurity risks regarding the return of the New World screwworm. This flesh-eating parasite, which was eradicated in the United States decades ago, has recently reappeared in the region, with over 2,000 equine cases reported in Mexico since early 2024.

Investigations indicate that smuggled animals bypass the mandatory veterinary inspections, health certificates, and quarantine procedures required for legal livestock imports. This lack of oversight complicates disease traceability, as officials cannot accurately track the origin or movement of animals entering through unauthorized routes. In one documented instance near Redford, Texas, deputies intercepted six horses smuggled across the Rio Grande; while these specific animals were not infected, the incident highlighted gaps in border enforcement.

The U.S. Department of Agriculture (USDA) confirmed the presence of the parasite in a Texas calf in June, marking the first domestic detection in decades. To combat the spread, federal and state agencies are utilizing surveillance traps, veterinary monitoring, and the release of sterile flies. While the USDA maintains that the current risk to people and animals in the U.S. remains very low, the ability of smuggled livestock to move undetected poses a significant challenge to containment efforts.