BRACING FOR A RETURN OF ZIKA
In Miami, officials prepare for mosquito season
MIAMI BEACH, Fla. - On a warm afternoon in March, Chalmers Vasquez walked through the streets of Miami Beach hunting for standing water.
Whatever he found, he dumped, each trickle of water sparkling in the sun as it rolled across the concrete. Vasquez, operations manager of Miami-Dade County Mosquito Control, peered into a puddle.
“There,” he said, pointing to the squirming larvae of the world’s deadliest animal. The mosquito. One year after the Zika virus arrived in Miami, South Florida is in the midst of a new mosquito season. And experts expect the virus to return.
The 2016 outbreak, while contained, brought lessons for Florida and other Gulf Coast states, including Texas, where Zika also appeared. Miami’s challenges — resistant mosquitoes, controversial pesticides and the difficulty of getting individuals to take action — remain.
“We read about Zika. There was Zika in Brazil. And to be honest with you, we did not see that train coming. Not really,” said Vasquez. “We had dealt with dengue fever and chikungunya, and we pretty much controlled the situation. It did not get out of hand.
“But Zika is a different beast.”
In his more than 25 years working in mosquito control, Vasquez has seen nothing like Zika: an infection with symptoms tough to identify and, therefore, difficult to track. In 80% of cases, victims do not show any symptoms at all.
In a way, the danger becomes less about the mosquito and more about the human carrier who fails to realize and report an infection. It’s hard to avoid spreading something if you don’t know it’s there.
The mosquito carrying the virus, Aedes aegypti, is equally sly. In addition to Zika, the species carries the tropical diseases yellow fever, dengue fever and chikungunya. A female can lay eggs in tiny amounts of water and is known for being hardy. The species has adapted to a common class of insecticide, rendering it useless.
Unlike in 2016, this year the department plans to test mosquitoes in the area on an ongoing basis for resistance.
“This mosquito is a formidable foe,” Vasquez said. “We did not realize how difficult it is to control.”
Longer, more intense mosquito seasons
In Miami, unseasonably mild winters are creating lengthy and intense mosquito seasons. Normally, trapping 25 mosquitoes in an area is considered a lot. One time last mosquito season, Vasquez said, they caught 180.
Even after the normal mosquito season, when the weather cooled, they were still catching the insects.
Officials now monitor 160 traps throughout Miami-Dade, a surveillance system that will continue “in perpetuity,” said Paul Mauriello, deputy director of Miami-Dade Department of Solid Waste Management.
The need for better mosquito surveillance goes well beyond Miami. A 2017 report in the Journal of Medical Entomology found that while local monitoring systems have expanded across the country since Zika’s arrival, records and reports are inconsistent.
In areas that have “no measurement of mosquitoes whatsoever,” the U.S. Centers for Disease Control and Prevention monitors disease but does not track the insects that carry it, said Dan Strickman, a senior program officer at the Bill & Melinda Gates Foundation, which is active in combating infectious diseases around the world.
“In some ways the United States has big holes in its ability to detect an outbreak to some extent and certainly to detect the insects that are associated with the outbreak,” Strickman said.
A simple approach
Experts suggest that the success of mosquito control efforts last year in Miami may have prevented a much larger outbreak. Keeping the insect at bay requires simple — though rigorous — tactics: kill the ones that are alive and prevent new births.
The mosquito control team spent last summer pouring water out of everything from upside-down frisbees to tiny bottle caps and asking neighborhood residents to do the same. A major source of standing water is the bromeliad, a common decorative plant that looks like the top of a pineapple. Mosquitoes lay eggs in the rainwater that pools where the waxy leaves converge.
The county uprooted any bromeliads on public land, but the battle against private ownership continues. If approved, a new ordinance will enable county officials to cite and fine property owners for standing water, including in bromeliads.
All the tasks take workers to accomplish.
When Zika arrived last summer, Miami-Dade’s mosquito control staff had 17 employees. This year, it will more than triple to 59. The department’s budget, which was increased, will cover new equipment, including 29 spray trucks.
Controversy over insecticides remains, especially naled, which was sprayed from airplanes last summer. A recent study in China, the first to analyze naled’s effect on human health, suggested a link between prenatal exposure to the chemical and delays in the motor skills of infants.
Naled is banned in Europe. It is approved in the U.S. by the CDC and the Environmental Protection Agency. Miami-Dade has used it for more than five decades.
The research, while validating concerns about naled and other chemicals, was met with caution from experts and scientists. Naled will be used aerially when mosquitoes pose a public health threat in Miami-Dade until the CDC and EPA change their stance, Mauriello said.
For now, the county keeps trying to catch up.
“The next piece of the puzzle is really changing from more of a reactive mode into proactive larvicide treatments,” Mauriello said.
Vasquez expects that the upcoming season will bring similar pockets of Zika but nothing more widespread.
“We’re prepared,” he said. “We have personnel, we have equipment and we have experience.”