The South Florida mosquito season has hit the misery zone, spreading clouds of pesky marsh mosquitoes and bringing the first local case of dengue fever.
Shifting summer winds have swept the prolific Aedes taeniorhynchus, an annoying but largely harmless species, from the brackish and salty waters of Everglades National Park eastward, intensifying a season that officially began with seasonal rains in May. Predictably, the more dangerous yellow-fever and tiger mosquitoes, which carry dengue and the latest mosquito hazard, chickungunya, have also spread.
On Wednesday, state health officials announced the first case of locally acquired dengue. The victim, a 50-year-old woman, has fully recovered, state health officials said in a press conference to raise awareness about mosquito-borne illnesses.
No locally contracted cases of chickungunya, a mostly eastern hemisphere virus that appeared in the Caribbean for the first time last year, have been confirmed among 66 cases statewide. Nine were in Miami-Dade. But officials warn the virus will almost certainly turn up in South Florida’s abundant yellow-fever and tiger mosquitoes. Unlike marsh mosquitoes, these species breed in fresh water, can’t be controlled by aerial spraying and multiply in almost any standing water, from a drop in an upturned bottle cap to the rim of a flower pot.
“It’s clear that chickungunya has emerged as a major global public health threat,” University of Miami public health professor John Beier said, referring to the rapid spread through the Caribbean. “I think it’s the tip of the iceberg we’re seeing here.”
Until last weekend, the mosquito season had been nearly tolerable. But unpredictable summer winds carried clouds of marsh mosquitoes from the national park, where spraying insecticides is prohibited. At Bill Baggs Cape Florida State Park, rangers dialed their mosquito-warning sign up to the misery zone, park manager David Foster said. On Friday, more than 240 calls, or one every other minute, flooded the Miami-Dade County Mosquito Control Office.
“We’re getting calls not just because of the number of mosquitoes but because people are scared,” Miami-Dade County mosquito control operations manager Chalmers Vasquez said. “Luckily, the black salt marsh mosquito does not transmit any disease to humans. Luckily, because we get them in the billions.”
The county, which tracks mosquitoes through traps at potential breeding spots as well as the number of complaints it receives, has been fogging some neighborhoods with spray trucks since the season started, Vasquez said. But Friday’s spike in calls triggered an aerial spraying — the first since 2012 — over the Redland area, Homestead, Florida City and West Kendall.
The spraying might bring relief to residents, but it also reignited debate over the harm aerial spraying causes to wildlife.
“You know the expression when your only tool is a hammer, every problem becomes a nail? There’s a real mismatch between mosquito control solutions and the real problem,” said Florida International University biologist Phil Stoddard, who is also mayor of South Miami. At Tuesday’s City Commission meeting, he hopes to declare his city off-limits to spraying by designating it a biologically sensitive area.
Among the insecticides used by the county in aerial spraying are Naled. That was used in pet flea collars until about 2002, when the Environmental Protection Agency deemed it hazardous to animals and people. Truck foggers use a synthetic version of Pyrethrin, which comes from chrysanthemums.
Both chemicals kill not only mosquitoes but fish, honeybees, moths, butterflies — some of which are endangered — and other insects. The deaths of the insects can creep up the food chain to endangered bats, birds and other wildlife. The chemicals can also kill mosquitoes’ natural predators, like dragonflies and bats, said Tom Emmel, director of the McGuire Center for Lepidoptera and Biodiversity at the University of Florida.
“This is nontarget wildlife, and they’re the ones that get hit and usually the spray is much more toxic to something like a butterfly than mosquitoes,” he said. “Miami, I don’t want to say is behind the times, but they’re choosing an easier way to respond to public complaints and weather events. Marsh mosquitoes aren’t going to breed in 99 percent of Miami.”
Just dumping water from birdbaths, recycling bins and other containers or spraying bromeliads with cooking oil can make a difference, he said. There are also larvicides that attack mosquito eggs and nontoxic alternatives like sugar traps. Monroe County has considered genetically modified mosquitoes that keep eggs from hatching. Educating residents can also be a significant defense, Emmel said.
Aerial spraying also fails to reduce the more dangerous freshwater mosquitoes, Stoddard said, because they repopulate so quickly.
“You have a short-term solution. But you’re making the long-term problem worse,” he said. “It’s like drinking saltwater when you’re thirsty.”
But these measures cost money Miami-Dade doesn’t have, said Manuel Garcia, the county’s Road, Bridge, Canal and Mosquito Control Division Chief.
Neither Miami-Dade nor Broward counties has a mosquito-control district with taxing authority like the Florida Keys and Lee County near Fort Myers, which maintain fleets of airplanes and helicopters and employ staffs of 70 or more each. Miami-Dade’s mosquito control office has just 12 employees with a budget of about $1.8 million, Garcia said. Last year, Monroe’s taxing district collected more than $14 million and Lee County about $22 million.
“So that gives you my challenge in a nutshell,” Garcia said. “We look at every possible way of combating mosquitoes and to date, the [Florida] Department of Agriculture and Consumer Services says the best method is using EPA-approved insecticides.”
Part of the problem in budgeting is the inability to predict the severity of a season, Garcia added. In 2011, 300,000 complaints flooded the office. In 2013, just over 10,000 calls trickled in.
Mosquitoes “are like tornadoes. They’re here and that’s it. Then you react,” Garcia said. “It’s hard to forecast mosquitoes. I wish they were like hurricanes, where you have five days to prepare. But it’s not like that.”