Live animal imports suspended along southern border

U.S. Secretary of Agriculture Brooke Rollins on May 11 announced the suspension of live cattle, horse and bison imports through United States ports of entry along the southern border due to the continued and rapid northward spread of New World screwworm in Mexico, effective immediately.

NWS has been recently detected in remote farms with minimal cattle movement as far north as Oaxaca and Veracruz, about 700 miles away from the U.S. border, according to USDA in a news release.

The U.S. and Mexico continue efforts to interdict and eradicate NWS in Mexico and work in good faith. However, despite these efforts and the economic impact on both countries due to this action, there has been unacceptable northward advancement of NWS and additional action must be taken to slow the northern progression of this deadly parasitic fly, Rollins said.

As such, effective immediately, the USDA Animal Plant Health Inspection Service in conjunction with U.S. Customs and Border Protection will restrict the importation of live animal commodities originating from, or transiting Mexico. This import suspension will persist on a month-by-month basis, until a significant window of containment is achieved.

Continued collaboration

USDA will continue constant collaboration with Mexico, including a review of latest data and metrics in two weeks. Teams have been in daily communication discussing how to build what has been accomplished to improve a strategy toward eradication, the USDA said. Any livestock currently in holding for entry into the U.S. will be processed normally, this includes an APHIS port veterinary medical officer inspection exam and treatment to ensure they are not carrying NWS.

“The United States has ordered the suspension of livestock imports through ports of entry along our southern border after the continued spread of the New World screwworm in Mexico. Secretary Berdegué and I have worked closely on the NWS response; however, it is my duty to take all steps within my control to protect the livestock industry in the United States from this devastating pest,” Rollins said. “The protection of our animals and safety of our nation’s food supply is a national security issue of the utmost importance. Once we see increased surveillance and eradication efforts, and the positive results of those actions, we remain committed to opening the border for livestock trade. This is not about politics or punishment of Mexico, rather it is about food and animal safety.”

Effective eradication, remains the shared goal of the U.S. and Mexico, the USDA said, and requires a three-pronged approach: Robust active field surveillance with education and outreach to ensure prevention, treatment, and early detection; controlled animal movement to limit spread; and sustained sterile insect dispersal.

Suspending livestock transport through southern ports of entry will assist in the effort to limit northbound transport of NWS through livestock commerce and will allow the U.S. to reassess whether current mitigation standards remain sufficient. It is important to note the northward spread of NWS is possible through natural wildlife movements, including wildlife that transit the border region without impediment.

Action supported by industry

The action was supported by a cattle organization based in Fort Worth, Texas.

“Texas and Southwestern Cattle Raisers Association takes the threat of New World screwworm seriously,” said President Carl Ray Polk Jr. “We commend Secretary Rollins and USDA for making a difficult but necessary decision to close the southern border. While this action presents short-term challenges for cattle raisers, it is a critical step to secure the long-term health of the U.S. cattle herd. 

“Cooperation from the Mexican government is essential, and this move sends a clear signal about the urgency of the situation. Our association has consistently supported a border closure if warranted, and while we continue to work toward a domestic sterile fly production facility, we are left to rely more heavily on ground-based containment efforts.”

The National Cattlemen’s Beef Association also supported the move.

“For months, NCBA and affiliated state cattle industry associations have been working with USDA officials urging their counterparts in Central America to take stronger action to stop the spread of New World screwworm,” said NCBA CEO Colin Woodall in a news release. “In the 1960s, America’s cattle and livestock producers spent years and millions of dollars to eradicate New World screwworm from the United States.”

The U.S. has long maintained its commitment to fighting New World screwworm by funding the production of sterile flies needed to keep this pest out of Central and North America. Despite the U.S.’s work to control the pest, weak governmental participation in Central America allowed the insect to spread north out of Panama, the NCBA noted.

The U.S. previously and successfully led the eradication of NWS in the U.S. and Mexico; however, this cost billions of dollars and took decades. Unfortunately, these recent detections in Mexico show that this dangerous pest is back.

• The first case of NWS in Mexico was reported to the U.S. in November 2024. When NWS fly larvae (maggots) burrow into the flesh of a living animal, they cause serious, often deadly damage to the animal. NWS can infest livestock, pets, wildlife, occasionally birds, and in rare cases, people.
• In November 2024, after a positive detection of NWS in southern Mexico, USDA shut down the border for live animal trade.
• In February 2025, USDA resumed imports after APHIS and Mexico agreed to and implemented a comprehensive pre-clearance inspection and treatment protocol to ensure safe movement and steps to mitigate the threat of NWS.
• APHIS is releasing sterile flies through aerial and ground release at strategic locations, focusing on southern Mexico and other areas throughout Central America. A complete list of regions APHIS recognizes as affected by NWS as well as more detailed information on trade restrictions can be found on the USDA APHIS Animal Health Status of Regions website.