Florida expects to win its fight against flesh-eating maggots that threaten small, endangered deer in a national wildlife refuge, the state agriculture commissioner said Thursday.
"It's too early to declare mission accomplished,” Commissioner Adam Putnam said, but he added that no wild screwworm flies have been found in the island chain known as the Florida Keys since Jan. 10.
That amounts to three life cycles of the parasite, and officials have decided it's safe to begin winding down efforts to keep the screwworms from spreading from the island chain onto the mainland, Putnam said.
New World screwworm can eat livestock and pets alive, and once cost the U.S. livestock industry millions every year. There hadn't been a U.S. infestation in over 30 years, until agriculture officials confirmed in September that screwworm was killing the dog-sized Key deer whose range is limited to a national wildlife refuge.
To kill the parasite's population, millions of male screwworm flies sterilized with radiation have been released since October over the Keys and agricultural areas south of Miami.
Putnam said those releases will end in late April. The last batches of sterilized flies will still offer protection through the deer's spring fawning season.
The state also plans as early as next week to shut down a highway checkpoint where animals leaving the Keys were inspected for screwworm infections. A stray dog found near Homestead in early January was the only animal on the mainland to show signs of screwworm.
The Keys' isolation helped control the infestation, Putnam said.
“We had better control of access to the Keys, because we had one road in and one road out,” he said. “Unfortunately, the most impacted species was one of the rarest, the Key deer.”
The infestation killed 135 Key deer, but none have died and no new infections have been reported since an infected deer was euthanized in early January, said National Key Deer Refuge Manager Dan Clark.
Only about 650 deer survive in the unique herd. Up to eight deer each day had to be euthanized during the infestation's peak, between October and December, but the infections slowed as sterilized flies saturated the area, Clark said.
“We were concerned with how fast we were losing deer, but things turned after that,” Clark said.
Monitoring of the deer will continue, but the animals likely will stop receiving anti-parasite medications over the next month.
It's still unclear where the screwworms came from. A traveler must have brought the parasite into the area around the refuge on Big Pine Key, but the genetic makeup of the flies in Florida doesn't match screwworm populations identified in the Caribbean, Putnam said.