The detection of a New World screwworm (NWS) case 70 miles from the U.S. border last week is testing the nation's animal disease preparedness, sparking a race against time for regulators to ramp up preventative measures against a pest not seen in the United States in decades.

The discovery of a single infected animal in a Nuevo Leon, Mexico, feedyard has put the American livestock industry on high alert for a parasite eradicated from the country more than 60 years ago. 

Reports indicate that the affected animal had recently been moved to a feedlot in Nuevo Leon from a region in southern Mexico with known active NWS cases.

The potential link to animal movement underscores the need for Mexico to fully implement and...