U.S. halts cattle imports via southern border over screwworm pest

Jose Orozco, Bloomberg News on May 11, 2025

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The U.S. said it is suspending imports of live cattle, horse, and bison via ports along the southern border because of the spread of the screwworm pest in Mexico.

The suspension is effective immediately, U.S. Agriculture Secretary Brooke Rollins said on Sunday. “There has been unacceptable northward advancement” of the New World screwworm, which is actually a flesh-eating fly, and further action is needed to slow its spread, according to a U.S. Department of Agriculture statement.

Safeguarding the nation’s livestock is “a national security issue of the utmost importance,” Rollins said, adding that the measure “is not about politics or punishment of Mexico, rather it is about food and animal safety.”

The screwworm is a parasitic fly whose larvae eat the living tissue of warm-blooded animals, including livestock and wild animals. It was eradicated in the U.S. in the 1980s after a successful biological barrier program carried out with Mexico and Central American nations.

But in 2023, screwworm detections in Panama exploded from an average of 25 cases per year to more than 6,500 cases in one year, according to the U.S. Department of Agriculture. Since then, it has been detected in Costa Rica, Nicaragua, Honduras, Guatemala, Belize, El Salvador, and Mexico.

Its possible return to the U.S. has worried ranchers. Mexico and the U.S. will review the imports suspension in two weeks, though the measure will continue on a monthly basis until there is significant containment, the Department of Agriculture said.

Mexico Agriculture Secretary Julio Berdegue, writing on X, said his government disagrees with the measure, but trusts that an agreement will be reached soon.