Screwworms are a type of fly named for the shape of its larvae, which are deadly to livestock, once costing U.S. farmers $100 million annually. The program to eradicate the screwworm in the U.S was completed in the 1960s and expanded into Mexico and further south in the following decades. Today, the U.S. airdrops 14.7 million sterile screwworms in Panama each week to disrupt reproduction and prevent reinfestation.