USDA: Screwworms That Eat Humans and Livestock Alive, Nearing U.S. Border

New World Screwworm larvae. Credit: USDA

The New World Screwworm, a foreign maggot species that feeds on the living flesh of animals and humans, that briefly infested the Florida Keys in 2016,  is rapidly nearing the U.S. border through Mexico, according to the the USDA.

In response, U.S. Secretary of Agriculture Brooke L. Rollins announced on Sunday the suspension of live cattle, horse, and bison imports through U.S. ports of entry along the southern border, effective immediately.

The screwworm has been recently detected in remote farms with minimal cattle movement as far north as Oaxaca and Veracruz, about 700 miles away from the U.S. border.

The U.S. previously and successfully led the eradication of NWS in the U.S. and Mexico, however this cost billions of dollars and took decades.

Screwworms most often enter an animal through an open wound or, in the case of newborns, the navel. They feed on the animal’s living flesh and, if not treated, infestations can be fatal. The New World screwworm (Cochliomyia hominivorax) has not been widely present in the United States since the 1960s, but is still found in most of South America and in five Caribbean countries.

Over the last two years, screwworm has spread north throughout Panama and into Costa Rica, Nicaragua, Honduras, Guatemala, El Salvador, Belize, and now Mexico.

The first case of NWS in Mexico was reported to the U.S. in November 2024.

In 2016, more than 50 endangered Key deer were in such deteriorated conditions after being eaten alive by the maggots in the Florida Keys that euthanasia was necessary.