The U.S. Department of Agriculture (USDA) announced an immediate suspension of live cattle, horse, and bison imports through southern border ports of entry due to the rapid northward spread of the New World Screwworm (NWS) in Mexico.

This decision, led by U.S. Secretary of Agriculture Brooke L. Rollins, aims to protect the U.S. livestock industry and food supply from the devastating parasitic fly, which has been detected as close as 700 miles from the U.S. border.

The New World Screwworm, scientifically known as Cochliomyia hominivorax, is a flesh-eating fly whose larvae burrow into the living tissue of warm-blooded animals, causing severe, often fatal damage.

NWS can infest livestock, pets, wildlife, birds, and, in rare cases, humans. The USDA reported the first case of NWS in Mexico in November 2024, prompting an initial border closure for live animal trade.

Although imports resumed in February 2025 under strict inspection protocols, the pest’s continued spread to regions like Oaxaca and Veracruz has necessitated renewed action.

The screwworm’s destructive impact is well-documented. A single female fly can lay up to 300 eggs, leading to rapid infestations that cause significant economic and animal welfare losses.

The U.S. eradicated NWS in the 1960s, and Mexico followed in the 1970s, but these efforts cost billions of dollars and took decades.

A previous outbreak in the U.S. required 30 years for the cattle industry to recover, underscoring the urgency of current containment efforts.