The New World screwworm, a parasitic fly that harms both cattle and humans and was once eradicated from the U.S. after more than three decades of effort, is raising new concerns amid an outbreak in Mexico. In response to the looming threat, the U.S. Department of Agriculture (USDA) has announced a halt on imports of cattle, bison, and horses through the southern border.
The New World screwworm produces larvae that feed on the flesh and blood of livestock, pets, wildlife, birds, and, in some cases, humans, causing painful infestations that can lead to potentially fatal damage to their hosts. It was eradicated in the U.S. in 1966 after billions of dollars were spent on an operation that involved releasing hundreds of millions of sterile adult flies, which would mate with wild females and ultimately prevent them from laying viable eggs.
