Nina Kravinsky

More than a year after Mexico's first reported case of the New World screwworm, the deadly parasite has been discovered in a cow in the Mexican state of Tamaulipas.

The United States closed the U.S.-Mexico border to cattle for much of 2025 in an effort to protect its herds from the parasite, which so far has not been reported in the U.S.

The new world screwworm has largely spread in southern Mexico, but there have been cases closer to the U.S.

border.

Mexico says this most recent case in a border state has only been detected in a single animal.

Mexican ranchers have been advocating for months for a phased reopening of the border so they can return to exporting their cattle to the United States.

For NPR News, I'm Nina Kravinsky in Hermosillo, Mexico.