U.S. halts livestock imports from Mexico amid rapid spread of screwworm

In an urgent move to protect American agriculture and food security, U.S. Secretary of Agriculture Brooke L. Rollins announced today an immediate suspension of all live cattle, horse, and bison imports from Mexico through ports of entry along the southern U.S. border. The decision comes as the New World Screwworm (NWS) — a parasitic fly known for causing severe and often deadly wounds in animals — continues its alarming spread northward through Mexico.

NWS infestations have now been confirmed as far north as Oaxaca and Veracruz, roughly 700 miles from the U.S. border, in areas previously thought low-risk due to limited cattle movement. This marks a significant escalation in the pest’s reach and raises red flags for U.S. livestock safety.

“The protection of our animals and the safety of our nation’s food supply is a national security issue of the utmost importance,” said Secretary Rollins. “This action is not political. It is about preventing the re-establishment of a pest that we spent decades and billions of dollars to eliminate.”

The suspension, enacted jointly by USDA’s Animal and Plant Health Inspection Service (APHIS) and U.S. Customs and Border Protection (CBP), will be reviewed monthly. Livestock already in holding for entry into the U.S. will be allowed to proceed under strict inspection and treatment protocols to ensure they are free from NWS.

While the United States continues to work in close partnership with Mexican authorities, Rollins emphasized that the recent acceleration in NWS spread requires stronger containment. “We will reopen the border for livestock trade when we see clear progress and containment,” she said.

The current strategy to stop the pest includes three key pillars:

Active field surveillance and education,

Controlled animal movement, and

Sterile fly dispersal — a method that helped the U.S. and Mexico previously eradicate NWS decades ago.

However, officials warn that NWS can still spread via wildlife that move freely across the border, posing a challenge beyond regulated animal trade.

USDA’s “Tick Riders” — trained livestock inspectors on horseback — will monitor remote areas for signs of infestation along the border between official ports of entry.

First detected in Mexico in late 2024, the NWS larvae burrow into the flesh of living animals, leading to painful, often fatal wounds. While the pest primarily affects livestock, it can also infect wildlife, pets, and in rare cases, humans.

This marks the second major suspension of cross-border livestock trade since the initial detection. The border was reopened in February 2025 after the implementation of a bilateral inspection and treatment protocol, but the recent detections have made clear that more stringent measures are needed.

The USDA encourages farmers and ranchers in border states to remain vigilant and report any suspicious wounds or animal health issues. Ongoing updates and a list of affected regions are available on the USDA APHIS website.