06/12/2026
The United States Department of Agriculture confirmed the presence of New World screwworm in the United States this past week. The dangerous pest can seriously affect livestock, pets, and wildlife, and less commonly, birds and humans.
The name New World screwworm can be misleading, Rosslyn Biggs, DVM, OSU Extension beef cattle specialist, said.
They are not worms. Instead, the concern is with a specific type of fly. The fly will lay eggs in an open wound, and the resulting maggots will feed on live tissue, as opposed to more common maggots that eat dead or decaying tissue. Wounds as small as a tick bite can become infested.
New World screwworm flies look similar to other common flies, explains Jonathan Cammack, OSU Extension livestock entomology and parasitology specialist.
“We’ve got flies that are metallic green that are strongly associated with our livestock,” he said. “There is a fly that is very closely related to a house fly that only eats cow manure. Metallic-colored flies and non-metallic flies that feed on these rotting materials are there and have been there for quite some time, but they’re not screwworms,” Cammack said. Read the full story in today's Weekend Edition of the Miami News-Record.
