A pest that had been considered eradicated from the U.S. has re-appeared in the Lower Florida Keys.

It's the first local infestation of New World screwworm in the U.S. in more than 30 years.

An adult screwworm fly.
CREDIT U.S. DEPARTMENT OF AGRICULTURE

Florida Agricultural Commissioner Adam Putnam on Monday declared anagricultural state of emergency in Monroe County and the state imposed an animal quarantine from the southern end of Key Largo  to Key West.

"The screwworm is a potentially devastating animal disease that sends shivers down every rancher's spine," Putnam said in a news release. "It's been more than five decades since the screwworm last infested Florida and I've grown up hearing the horror stories from the last occurrence."

Screwworms are fly larvae — or maggots — that can infest warm-blooded animals, including people. The flies lay eggs in an open wound or sore and the larvae feed on the animal's living flesh. Cases in humans are rare.

The infestations can be fatal if not treated. Treatment consists of cleaning the wound and applying a topical pesticide.

U.S. Department of Agriculture tests confirmed the presence of screwworms in three Key deer and up to 22 have died of the disease, according to the Florida Department of Agriculture. The department said that "a few pets in the local area" have also shown signs of screwworms over the past two months, although no larvae were collected or tested in those cases.

A screwworm fly lays eggs in an animal wound.
CREDIT U.S. DEPARTMENT OF AGRICULTURE

The state quarantine is intended to keep the infestation from spreading outside of the Florida Keys and reaching the state's $2.78 billion livestock industry. The quarantine area goes from the southern edge of Key Largo, at Mile Marker 91, through all islands of the Keys including Key West.

Bringing animals in or out of the area without state permission is prohibited. Livestock need an Official Certificate of Veterinary Inspection and proof of effective treatment against screwworm within 72 hours — or the owners must allow inspection and treatment by state inspectors.

Owners of pets like dogs, cats and birds who want to take their animals out of the Keys must allow inspection and treatment, if necessary. The state has set up an inspection station near Mile Marker 106.

State and federal animal health and wildlife officials are planning to trap flies to determine the extent of the infestation, release sterile flies to eliminate the screwworm fly population and to look for additional cases in animals.

Anyone who suspects the presence of screwworms or has questions or concerns can call the state Department of Agriculture at 1-800-HELP-FLA, or 1-800-435-7352. Non-Florida residents can call 1-850-410-3800.

The U.S. Department of Agriculture developed a sterile insect technique in Florida to combat screwworms and they were largely eradicated from the U.S. by 1966. Since then, the U.S.D.A. has worked with Mexico and Central American countries to eradicate screwworms and maintains a "permanent sterile fly barrier" at the Darien Gap between Panama and Colombia to prevent re-infestations.

According to the Florida Department of Agriculture, the screwworm flies are still found in most of South America and five Caribbean countries.