Harvard Zika Expert: Naled Aerial Spraying Doesn't Work, Could Worsen Problem

Harvard scientist Dr. Michael Callahan, one of the world's preeminent experts on the Zika virus, has said in a video interview that aerial spraying to combat the Zika virus likely does not work to kill disease-carrying Aedes aegpyti mosquitoes.

Callahan, who works at the world-renowned Massachusetts General Hospital and Harvard Medical School, also runs the Zika Foundation, which likely has the largest clinical experience with the Zika virus in the world. Callahan says he has treated more than 1,700 Zika patents, as well as more than 10,000 people with the mosquito-borne dengue virus. Yesterday he appeared on a web show hosted by Dr. David Perlmutter, a Naples-based adviser for the Dr. Oz Show.

Callahan says he is "emphatic" that aerial spraying for the Aedes aegpyti mosquito simply does not work. Instead, he says, the spraying could make the problem worse because it kills insects that eat mosquitoes, such as dragonflies. (He begins discussing aerial spraying at the 30-minute mark in the clip above.)

"There has been a lot of money spent in Singapore, Thailand, Japan, and several Central American countries trying to control Aedes aegpyti with aerial spraying," he said. "It does not work."

The remarks come as residents are pushing back against Miami-Dade County's decision to aerially spray naled, a controversial pesticide banned in the European Union, over most of South Beach. After the county chose to spray naled to combat the outbreak in Miami Beach, residents swarmed city hall demanding the spraying stop. Though Gov. Rick Scott announced today the virus has been eradicated in Wynwood for now, the "active transmission zone" in Miami Beach was made larger Friday.

The county says it does not yet have plans to extend aerial naled spraying to a larger section of Miami Beach. The U.S. Centers for Disease Control and Prevention says aerial naled spraying was a crucial tool to eradicate the virus in Wynwood.

Callahan, meanwhile, has served as a special adviser on infectious diseases to two presidents, the U.S. secretaries of Defense and of Health and Human Services, and the Office of the Commissioner of the U.S. Food and Drug Administration. He has also been deployed to seven "mass-casualty" disease outbreaks, including those during the ebola and bird flu epidemics.

(Perlmutter, the host, does have some dubious scientific beliefs. He's authored a largely panned book claiming there's a link between wheat gluten and neurological disorders. He also works with Oz, who is routinely called a snake-oil salesman. But those facts don't take away from Callahan's expertise.)

In his interview with Perlmutter, Callahan explained that Miami-Dade's decision to blanket Zika-affected areas with pesticides, especially naled, stems from the county's preexisting plan to beat back the West Nile virus.

But, he stressed, the type of mosquito that carries West Nile — the Culex genus of mosquito — is easily killed using aerial spraying because those insects fly high in the air to bite birds. The Zika-carrying Aedes mosquito, however, instead flies low to the ground and often indoors, because it bites only humans. He said 60 to 70 percent of Aedes aegypti mosquitoes live indoors. This, he stressed, makes aerial spraying highly inefficient.

Aerial spraying for Zika has "proven systematically to be less effective," he said. He then explained that instead, mosquito-control experts must concentrate on removing nests and standing water on the ground.

"You need yard-to-yard control, with backpack-mounted sprayers, and you need to work on your biologic controls," he said.

Other scientists, including Emory University Dr. Barry Ryan, have said that while naled can be dangerous, it is the lesser of two evils in Miami's fight against Zika.

Harvard Zika Expert: Naled Aerial Spraying Doesn't Work, Could Worsen Problem
Zika Foundation via YouTube

Perlmutter also asked why the county was choosing to spray early in the morning and late at night, past 10 p.m. Callahan said he couldn't comment. He said the aerial spraying was a "highly visible public health decision," which simply "helps to promote trust that things are being done."

This isn't the first time a mosquto-control expert has questioned Miami-Dade's decision to spray. Last month, a mosquito-control supervisor in Palm Beach County also hinted to New Times that Miami-Dade might have chosen to spray simply to make it look like the county was doing something.

"There's a certain aspect of mosquito control that's somewhat psychological," Palm Beach County Environmental Program Supervisor Gary Goode said.

Regardless, that decision has not reflected well on the county or the CDC. Residents near the naled spraying have complained about feeling ill and have posted images of bees, birds, and fish that they say died from pesticide exposure.

Though some might say a few dead animals are necessary collateral damage to fight Zika, Callahan said the county can't afford to kill bugs such as dragonflies because they eat mosquitoes.

Aerial spraying "does a disservice by wiping out mosquito-eating insects," he said. Nations hit hard by mosquito-borne diseases, he said, know this fact already — instead of blasting pesticides through the air, Callahan says, countries such as Thailand and Singapore take great care to preserve natural mosquito killers and maintain a "judicious use of pesticides, only where the mosquitoes are."


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