US Might Restrict Livestock Imports From Mexico Over Screwworm Concerns: USDA

‘We are now at a critical inflection point in our shared campaign against this pest, and I am very concerned about our collaboration,’ the secretary said.

A drone view shows livestock in pens before being exported to the U.S. through the Jeronimo-Santa Teresa border crossing, as the U.S. allowed Mexican cattle imports to resume after lifting a temporary suspension due to the detection of the New World screwworm, at the Chihuahua Regional Livestock Union facility, outside Ciudad Juarez, Mexico, Feb. 10, 2025. Jose Luis Gonzalez/Reuters

The U.S. Department of Agriculture (USDA) said on April 27 that it will restrict livestock imports from Mexico if it does not ramp up its fight against a threatening pest known as New World screwworm.

Agriculture Secretary Brooke Rollins sent a letter on April 26 to Mexican Secretary of Agriculture Julio Antonio Berdegué Sacristán, warning that the United States would “restrict the importation of animal commodities,” including live cattle, bison, and equine, 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.

“The outbreak in southern Mexico continues to expand, and every day that passes without full deployment of sterile insect technique operations represents a lost opportunity to contain this pest and prevent its spread beyond the Isthmus of Tehuantepec.”

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.

Signs and symptoms of infestations include irritated behavior, head shaking, and the smell of decay, according to the USDA.

In the letter, 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 parts required to keep its planes in the air.

Rollins’s letter was sent during heightened trade tensions between the United States and Mexico after the Trump administration levied 25 percent tariffs on its southern neighbor earlier this year over its failure to stem the trafficking of deadly opioids into the United States.

Goods subject to the U.S.-Mexico-Canada Agreement are exempt from the tariffs.

The screwworm is endemic in Cuba, Haiti, the Dominican Republic, and South American nations. In recent years, cases have also spread to Costa Rica, Nicaragua, Honduras, Guatemala, and now Mexico.

Before the discovery of screwworm, Mexico was the largest supplier of cattle to the United States. In March, 24,000 head of cattle were imported from Mexico, down from roughly 114,000 in March 2024, according to the USDA.

The agency temporarily blocked Mexican livestock shipments in November 2024 after the pest was discovered. At the time, the USDA said it was working with Mexico to implement measures to continue the normal flow of the nation’s exports.

The restriction was lifted in February after “extensive discussions between representatives from the countries” and the implementation of a “comprehensive pre-clearance inspection and treatment protocol to ensure safe movement and mitigate the threat of [screwworm].”

On April 26, Rep. Tony Gonzales (R-Texas), thanked Rollins for her letter in a post on social platform X and said he would “continue to fight for our farmers and ranchers.”

He linked to a March 11 announcement in which the congressman had led in producing a bipartisan letter with 43 congressional colleagues that urged the USDA to “expand eradication and containment efforts relating to the New World screwworm (NWS).”

“Left unchecked, an outbreak could cost livestock producers millions of dollars per year and inflict detrimental economic losses on the national economy,” Gonzales wrote in a statement.

“To address this growing concern across our livestock, farming, and wildlife industries, we urge the USDA to work with state, local, and relevant industry stakeholders to proactively address this emerging threat—including considering the feasibility of establishing a sterile fly production facility in Texas or the Southwest.”

Katabella Roberts contributed to this report.