Sterile screwworms to be released on Florida mainland in effort to prevent outbreak

Sterile flies used to combat screwworm in Key Deer

In the coming weeks, swarms of sterile screwworm flies will blanket parts of the Middle Keys, an army of millions manufactured in Panama to combat an outbreak of the flesh-eating pest attacking the islands’ beloved Key deer.
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In the coming weeks, swarms of sterile screwworm flies will blanket parts of the Middle Keys, an army of millions manufactured in Panama to combat an outbreak of the flesh-eating pest attacking the islands’ beloved Key deer.

Agriculture officials will begin releasing sterile New World screwworms in Homestead on Friday after an infection was confirmed in a stray dog last week.

No screwworms have been detected on the mainland, but because so little is known about the dog — a German shepherd — or where it came from, officials want to act aggressively to prevent the spread of the grisly outbreak that has ravaged endangered Key deer. Since September, at least 135 deer, part of the last herd on the planet, have died in the Lower Keys.

As of Friday afternoon, Oct. 14, 2016, 83 endangered Key deer had been euthanized because of an infestation of the New World screwworm. The screwworm, not seen in the U.S. since the 1960s, is leaving open wounds on the deer and then eating the fle

“Given that Florida’s livestock industry is at stake, this sterile fly release is a precautionary move to ensure we’re doing everything we can,” Agriculture Commissioner Adam Putnam said in a statement Wednesday.

Since October, the U.S. Department of Agriculture has released more than 80 million sterile flies on 12 islands in the Keys and maintained an inspection checkpoint for pets on the Overseas Highway in North Key Largo. In recent weeks, it appeared the outbreak was largely under control, with only a handful of deer turning up infected after 130 died between October and November.

The outbreak is the first in the U.S. in more than 30 years and has been difficult to control because unlike livestock, many of the wild deer live in inaccessible scrub in remote parts of the National Key Deer Refuge. If the outbreak were to spread to the mainland, it could pose a significant threat to the state’s $1 billion cattle industry, U.S. Sen. Bill Nelson said in a letter Wednesday to federal officials urging for more control efforts.

Officials know little about the dog, which was spotted by a resident who called Miami-Dade County animal control, said USDA spokeswoman Donna Karlsons. The dog was taken to the county’s Homestead shelter on Southwest 210th Avenue before being turned over to a German shepherd rescue group, she said. Staff with the rescue group spotted the infection, isolated the dog and began treating it, she said. The dog is recovering.

It’s possible the dog came from the Keys, but so far officials have no way of knowing, Karlsons said. A scan turned up no identifying chip, and it had no tags. The checkpoint is voluntary. As of this week, 10,202 animals — mostly dogs, cats and birds but also horses, a pig, one ape and two sugar gliders — had been inspected.

Screwworms, a gruesome bug that feeds on living tissue by burrowing into open wounds, continue to pop up in South America but have been successfully contained in the U.S. over the years by using sterile flies. Screwworm flies only reproduce once, so outbreaks can typically be contained in a matter of months. The U.S. operates a lab to breed sterile flies in Panama, where it also maintains a barrier with the continual release of sterile flies at the Darian Gap, a swath of jungle between Panama and Columbia.

It’s not clear how the screwworms wound up in the Lower Keys. But once there, the flies targeted the herd, zeroing in on male deer who often suffer head and neck wounds from rutting during the fall mating season. As the season wound down, the number of infected deer dropped off sharply. But wildlife officials worry that infections could creep up during the spring fawning so last month began strapping radio collars on deer to monitor for infections.

Since confirming the infestation on the dog last week, agriculture officials have been conducting surveillance — although their preference for live flesh makes screwworm flies difficult to trap. They are asking the public to regularly check pets and livestock and report any suspected infections to 1-800-HELP FLA. Humans have been infected, but rarely, they said.

An earlier version of this story incorrectly reported the screwworm outbreak had spread across the Middle Keys.

Follow Jenny Staletovich on Twitter @jenstaletovich.