Millions of sterile screwworm flies released, and counting

As Key deer deaths stemming from New World screwworms slow down, the number of sterile screwworm flies being released goes up on Big Pine Key and neighboring islands.

Vessels containing sterile screwworm flies unable to produce the parasitic larvae sit in 25 wooded locations. Twice a week, 76,000 pods containing screwworm pupae are placed in each container.

Florida Commissioner of Agriculture Adam H. Putnam said Thursday morning at a release site on Big Pine that since Oct. 11, when the first release took place, 13 million flies have been released.

The releases take place on Tuesdays and Thursdays, after the chambers have been cleaned and the empty pods left behind by the pupae are emptied.

In the wild, pupae hatch from their casing in the ground, search for a mate and lay their eggs in the open wounds of warm-blooded animals. Then the maggots feed for five days, after which they fall to the ground and pupate, repeating the cycle.

But the eggs from sterile flies never hatch, as they have been sterilized with radiation. The sterile insect technique was created by the U.S. Department of Agriculture in the 1950s.

Screwworm flies have also been confirmed by entomologists with the U.S. Department of Agriculture on Summerland, Big Torch, Middle Torch, Little Torch, Cudjoe and Ramrod keys. Chambers carrying sterile flies from the USDA breeding location in Panama have been placed in all locations.

Putnam said he does not know how long it will take before the screwworms that feed on live tissue in warm-blooded animals is eradicated. Earlier in the month, he and other USDA officials said it could take six months.

The Key deer population was estimated at about 1,000 before the deaths and euthanizations of infected deer started. The deer, just 3 feet high, are found only in the Florida Keys and are on the Endangered Species List. Since the screwworm infestation was confirmed on Big Pine and No Name keys on Sept. 30, 119 Key deer have had to be euthanized.

Officers and volunteers at the National Key Deer Refuge on Big Pine have been treating as many deer possible with doramectin, an antiparasitic medicine that serves as a preventive measure and treatment for screwworm. It has been helping, as the number of Key deer having to be euthanized has been dropping.

Kevin Lowry, chief public information officer with the U.S. Fish and Wildlife Service at the National Key Deer Refuge, said officials had been euthanizing multiple deer a day earlier in the month. Now, they are putting down anywhere from two a day to none.

Still, Lowry said residents are not reporting deer because they’re afraid it will result in euthanization.

“That couldn’t be further from the truth. We want people to know that if there are early signs, those deer can be treated and the only reason we put them down is if we absolutely have to,” Lowry said.

To report an infected Key deer, call (305) 470-6863, Ext. 7.

This story was originally published October 29, 2016 at 9:04 AM with the headline "Millions of sterile screwworm flies released, and counting."