NWS Closer: Border Closed for Animals

REDFIELD, Iowa (DTN) -- U.S. Secretary of Agriculture Brooke Rollins closed the United States border to Mexican cattle, bison and horses as the threat of New World screwworm (NWS) moved within 700 miles of the border.

Effective immediately, as of May 11, imports of live cattle, bison and horses are halted as NWS was found in cattle as far north as Oaxaca and Veracruz, Mexico.

"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," she said.

Rollins added that Mexico Secretary of Agriculture and Rural Development Julio Berdegue Sacristan and her 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 stated in a news release.

On May 1, Rollins announced the border would stay open after an agreement with Mexico to continue to combat the pest, but with the movement northward, the border is closed to protect the U.S. cattle herd.

The National Cattlemen's Beef Association continues to support USDA's decision. "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. In the 1960s, America's cattle and livestock producers spent years and millions of dollars to eradicate New World screwworm from the United States," said NCBA CEO Colin Woodall in a news release.

PEST FIRST DETECTED

The U.S. temporarily banned Mexican cattle imports on Nov. 22, 2024, after the first case of NWS was found in southern Mexico and reopened the border to those cattle on Feb. 1, 2025. Imports of Mexican cattle to the U.S. have been considerably lower in 2025 compared to 2024.

NWS are fly larvae that infest mammals and birds, feeding as they go like a screw being driven into wood. Symptoms in these animals include irritated behavior, head shaking, smell of decay, evidence of fly strike, and presence of fly larvae in the wounds, according to the Animal and Plant Health Inspection Service (APHIS). NWS can cause serious damage and even kill an animal.

APHIS said the effective eradication of the pest requires a three-pronged approach with a robust active field surveillance to ensure prevention, treatment and early detection with education and outreach; controlled animal movement to limit the spread of NWS; and sustained sterile insect dispersal to prevent further hatching of the larvae.

The import suspension will continue until a significant window of containment is achieved. The hope is that by limiting northbound transport of livestock, the spread of NWS will slow the threat. However, the spread could continue through wildlife movement, which is often not stoppable.

"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," continued Rollins.

USDA's APHIS teams communicate daily about how to improve the strategy toward eradication. Livestock currently in holding to enter the U.S. will be processed normally, including an inspection exam and treatment by an APHIS port veterinary medical officer to ensure they are not carrying NWS.

Read more on DTN:

-- "NWS Agreement Keeps Cattle Imports Open," https://www.dtnpf.com/…

-- "Rollins Warns Mexico Over Screwworm," https://www.dtnpf.com/…

-- "APHIS Expands Biological Barrier Into Mexico to Help Prevent Screwworm Spread," https://www.dtnpf.com/…

Jennifer Carrico can be reached at jennifer.carrico@dtn.com

Follow her on social platform X @JennCattleGal

(c) Copyright 2025 DTN, LLC. All rights reserved.