A flesh-eating parasite known as New World Screwworm (NWS) has breached the long-standing biological barrier at the Darién Gap and is now rapidly advancing through Mexico, prompting an emergency livestock embargo along the U.S. southern border. The parasite, which infests wounds and mucous membranes with larvae that bore into living flesh, poses a grave threat to both public health and America’s already fragile cattle supply. USDA officials warn the outbreak could cripple domestic livestock production if not contained, calling it a national security crisis.