US Halts Cattle, Horse, and Bison Imports From Mexico Over Screwworm Spread

Mexican Agriculture Secretary Julio Berdegue said that he disagrees with the move.

Cattle are held in a corral before being exported to the United States through the Jeronimo-Santa Teresa border crossing after U.S. Agriculture Secretary Brooke Rollins announced an agreement with Mexico on the management of the New World screwworm at the Chihuahua Regional Livestock Union facility, outside Ciudad Juarez, Mexico, on April 29, 2025. Reuters/Jose Luis Gonzalez/File Photo

The United States will halt imports of live cattle, horses, and bison across the southern border due to the spread of the New World screwworm in Mexico, the Department of Agriculture (USDA) said on May 11.

In a statement, Agriculture Secretary Brooke Rollins said the decision was made following the detection of screwworm on remote farms as far north as Oaxaca and Veracruz, about 700 miles from the U.S. border.

“The protection of our animals and safety of our nation’s food supply is a national security issue of the utmost importance,” she said. “This is not about politics or punishment of Mexico, rather it is about food and animal safety.”

The USDA stated that it will restrict imports of live animal commodities originating from or transiting Mexico on a month-by-month basis “until a significant window of containment is achieved.”

“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,” Rollins stated.

The United States and Mexico reached an agreement last month to eradicate screwworm. But the USDA said that these efforts were not enough to contain the northward spread of the pest.

Mexican Agriculture Secretary Julio Berdegue said that he had spoken to Rollins and was informed that the border would be closed to live cattle exports for 15 days for a safety review.

“We don’t agree with this measure, but we’re confident we'll reach an agreement sooner rather than later,” Berdegue stated on social media platform X.

Screwworms are known to infect livestock, wildlife, and, in some rare cases, humans. Screwworm fly maggots burrow into the skin of living animals and can sometimes inflict serious or fatal damage.

The Centers for Disease Control and Prevention states on its website that people who travel to South America and the Caribbean with an open wound are at higher risk of becoming infested with the pest.

Signs and symptoms of infestations include irritated behavior, head shaking, a decaying odor, and evidence of fly strike, according to the USDA.

“NWS [New World screwworm] infestations are very painful,” the CDC states. “If you have an NWS infestation, you may see maggots (larvae) around or in an open wound.”

The National Cattlemen’s Beef Association (NCBA) supported the move to halt livestock imports along the southern border, though it acknowledged the potential economic impact of the measure.

NCBA CEO Colin Woodall said in a statement that the costs would be “far less” than if the pest were to spread inside the United States. He blamed Mexico for creating “unnecessary bureaucratic hurdles” that have hindered prevention efforts at the border.

“USDA’s border closure was entirely avoidable,” Woodall stated. “U.S. government officials, NCBA and leaders from affiliated state cattle industry associations have been sounding the alarm for months.”

Rollins had previously notified Mexico that its restrictions on USDA aircraft—which are used to eliminate the screwworm population—and customs duties were hindering efforts to eradicate the pest.

The U.S. official warned that the USDA would restrict the importation of animal commodities along the border if the issues are not resolved by April 30.

“We are now at a critical inflection point in our shared campaign against this pest, and I am very concerned about our collaboration,” Rollins wrote in a letter to Berdegue on April 26.

Rollins said that Mexico had allowed only one of the companies hired to carry out aerial spraying for killing the pest to fly six days a week while also imposing “burdensome customs duties” on equipment required to keep its planes in the air.

Screwworm is endemic in Cuba, Haiti, the Dominican Republic, and South American nations. In recent years, cases have spread to Costa Rica, Nicaragua, Honduras, Guatemala, Belize, El Salvador, and Mexico, according to the USDA.

Jacob Burg contributed to this report.