Thanks to Lucie Lecomte for alerting me to this CIDRAP report by Stephanie Soucheray: Experts warn spraying may not be very effective against Aedes.
On the heels of a federal recommendation to begin aerial spraying in Puerto Rico as a way to beat back Aedes mosquitoes, the hosts of the Zika virus, several vector control experts are voicing their concern over the plan.
"I consulted the CDC [Centers for Disease Control and Prevention] on this topic, and I recommended against it," said infectious disease and mosquito control expert Duane Gubler, ScD, MS. "It's uncharted territory. It's expensive. And it's temporary."
Gubler explained that while spraying is often used successfully against floodwater mosquitoes, the Aedes mosquito, which can spread Zika, yellow fever, dengue, and chikungunya, doesn't live in easy-to-reach places.
"The mosquito lives in closets, inside garbage, indoors," said Gubler. Those conditions are less than ideal for mass spraying campaigns, he added.
And Gubler has direct experience in this area. In 1987, he ran a study in Puerto Rico during the height of a dengue fever outbreak, using C-130s—the same airplane the CDC is recommending for Zika spraying—and the same insecticide, naled. Though Gubler found spraying was effective in decreasing mosquito populations, it did nothing to stop the transmission of dengue.
"Successful spraying against Aedes depends on too many factors. Do people have their windows open? What rate is the wind speed? What is the weather?" said Gubler. "Spraying doesn't kill larvae, and naled isn't a residual insecticide. You'd have to spray weekly to make an impact."
Gubler, like several other mosquito experts, says the CDC's recommendation was borne out of political pressure to assuage the public's fears about Zika virus. "The president, the Secretary of Health and Human Services, the director of the CDC are all responding to the pressure to do something, anything," he said.
Before considering spraying against Aedes again, Gubler said there need to be more studies and data that show updated spraying methods can target the mosquito where it lives.
Gubler, now retired, served as director of the CDC's Division of Vector-Borne Infectious Diseases for 15 years, and as chief of the agency's dengue branch for 9 years, as well as on numerous World Health Organization committees.
