Sterile screwworm flies now released in Marathon

Though the New World screwworm outbreak has been seen only in the Lower Keys, efforts to widen the buffer zone of the flies that produce the worms are underway.

There are 25 locations in the Lower Keys where containers holding sterile screwworm flies unable to produce the parasitic larvae sit and now four have also been set up in Marathon.

Twice a week, 76,000 pods containing screwworm pupae are placed in each container, shipped to from the U.S. Department of Agriculture’s breeding location in Panama. As of Tuesday, 304,000 had been released in Marathon since Oct. 25 and more than 13.5 million had been released in the Lower Keys since Oct. 11.

“We will continue to do sterile fly releases for up to three life cycles after the last wild fly or last positive case of screwworm infestation is identified,” said Yindra Dixon, public information officer for the USDA. It takes nine weeks for three life cycles of screwworm fly to occur and releases could continue for the next five to six months.

Preventive measures also continue at the National Key Deer Refuge on Big Pine Key. In an effort to prevent putting down more of the deer, which grow to only about 3 feet tall, veterinarians are tranquilizing and treating those reported to have infections.

“If they have an infestation, the maggots are pulled off by hand and the deer get some medication at the wound site,” said Dan Clark, refuge manager.

Screwworm flies lay their eggs in open wounds where larvae hatch and feed, basically eating the deer alive.

Temporary enclosures are being constructed should the need arise to sequester some of the deer and preserve the species, found only in the Florida Keys. One of the enclosures spans 36 acres on Big Pine while the other is 12 acres, located on Cudjoe Key.

“I’m actually pretty optimistic they’ll never get used,” said Clark, seeing as how the number of deer being treated for the parasitic larvae continues to rise, with 870 doses of antiparasitic medicine doramectin administered by refuge staff and volunteers as of Tuesday. “We’re not planning on enclosing any deer, but implementing the enclosures as a ‘what if.’ ”

Each enclosure has open gates where the deer can wander in and out freely. Those would be closed with deer inside if researchers determine the population has dropped below a certain threshold.

The herd of Key deer before the screwworm infestation was estimated at 1,000 prior to the screwworm outbreak and since July, 127 have died.

Deer on remote parts of the Lower Keys islands that may be inaccessible to U.S. Fish and Wildlife Service staff and local volunteers now have access to 10 medication stations.

The deer come to the contraption where food is and when they bend down to eat it, doramectin is automatically applied to the deer’s back with paint roller-like tools. The stations were constructed on Sunday and are being monitored with cameras to keep track of the number of deer receiving treatment.

Clark said deer euthanizations have gone down drastically because of the doramectin and the release of sterile screwworm flies, of which more than 13 million have been released by the U.S. Department of Agriculture.

This story was originally published November 2, 2016 at 9:13 AM with the headline "Sterile screwworm flies now released in Marathon."