Parasite Outbreak Threatens Endangered Florida Keys’ Deer

A Florida Key deer pauses while grazing. An outbreak of screwworm among the deer marks the first resurgence of the parasite in the U.S. in over 30 years.Flickr/Murray Foubister

An agricultural emergency has been declared in the Florida Keys upon the return of the screwworm, a fly whose larvae feeds on living tissue. The Chicago Tribune reports that on Florida's Big Pine Key and No Name Key, three samples of screwworm have been confirmed in Key deer, an endangered whitetail subspecies.

The discovery marks the first case of screwworm in the U.S. in 30 years. The Washington Post reports that in an effort to slow the spread of the fully grown screwworm fly 40 Key deer were killed.

The screwworm was a menace to agriculture and wildlife before its eradication from the U.S. in the 1960s. Before the fly was killed off, at a Texas ranch, an estimated 80 percent of whitetail fawns died during years of substantial screwworm infestation.

According to a U.S. Department of Agriculture estimate, in each subsequent year following the screwworm's removal., the livestock industry saved $900 million. Adam H. Putnam, Florida's agricultural commissioner, said in a Florida Department of Agriculture press release that mentioning the screwworm "sends shivers down every rancher's spine," and "...poses a grave threat to wildlife, livestock, and domestic pets in Florida. Though rare, it can even infect humans."

To kill off the fly, in the late 1950s, a "fly factory" was erected in Sebring, Fla., breeding sterile flie—releasing as much as 50 million per week—to disturb the screwworms' mating cycle. This led to their elimination, and Putnam says the flies can be beaten twice. "We've eradicated this from Florida before," he said. "We will work with our partners in the federal, state, and local level to protect our residents, animals and wildlife by eliminating the screwworm from Florida."