Mexican President Claudia Sheinbaum says the U.S. is over-reacting to the threat of a flesh-eating cattle parasite.

Sheinbaum on Thursday told reporters that the U.S. decision to close the border again to Mexican cattle imports is overblown. She said that decision was sparked by a single case of the New World screwworm.

The screwworm is a parasitic fly that the U.S. declared eliminated here in 1966.

New cases in Mexico prompted a shutdown of cattle imports from November to February, and again in May. A port of entry in Arizona was set to open Monday but now that’s been put on hold.

The U.S. Department of Agriculture has been working with Mexico to stop the insect.