Fighting Screwworm with Sterile Flies
October 28, 2016

Since a screwworm infestation was identified in the Lower Keys of Florida, more than 10 million sterile screwworm flies have been released on eight islands.

Sterile flies are the proven technology to eradicate screwworms. The flies are zapped with gamma radiation, making them sterile. Then those sterile flies are released to breed with wild flies. That stops reproduction, preventing more fly larvae.

Those larvae are the problem. Screwworm flies lay their eggs in open wounds. When the larvae hatch - those larvae are the actual "screwworms" - they feed on the living flesh of the host.

So far most of the victims of the screwworms have been Key deer, an endangered species that lives only in the Lower Keys. After screwworms were found in Lower Keys, the USDA began bringing in sterile flies from its lab in Panama.

The USDA and the Panamanian Ministry of Agriculture breed the flies and irradiate them there to maintain a sterile fly barrier in the Darien Gap between Colombia and Panama.

"As of yesterday, we have 25 sites in the field and we do this rain or shine for as long as it takes to eradicate this," said John Welch, who works with the USDA's Animal Plant Health Inspection Service.

The U.S. Fish and Wildlife Service has also begun treating Key deer with an anti-parasitic medicine to prevent infections or knock back minor cases.

The state of Florida is also trying to keep the screwworms from reaching the mainland, declaring an animal quarantine in the Keys and setting up a checkpoint on the Overseas Highway in Key Largo.

Officials say they can't tell yet how long it will take to eradicate the screwworms - or to figure out where they came from.