Skeptics are questioning the value of aerial spraying to combat mosquitoes that carry the EEE virus, even as state officials douse Massachusetts with 1,450 gallons of pesticide designed to kill the pesky, infectious insects.
“You’re doing very little good – that’s my concern,” said David Pimentel, a retired professor of entomology at Cornell University. “In most of these treatments there is no data on the number of mosquitoes present before spraying and the number after spraying. In a lot of ways this is a political decision to make the people happy.”
The deadly virus known as triple E, which is spread by mosquitoes, has hit two horses in Massachusetts this summer, and levels of the virus are at their highest in years, the Department of Public Health says. About six cases of EEE are reported in humans nationally each year. It can be fatal.
To combat the threat, the Department of Public Health began plane runs to spray the chemical Anvil – similar to what is used in flea collars – across almost 30 towns in Massachusetts.
“We expect it to be effective in reducing a significant amount of the adult mosquitoes in the spray area,” DPH chief Joel Auerbach said. “The exact percentage of the population of adult mosquitoes is difficult to calculate.” Auerbach said the state would measure the treatment’s effectiveness. He said it could kill more than 50 percent of the mosquito population.
The first aerial runs were completed Thursday night. The state plans to spray about 290,000 acres.
Anvil contains sumithrin, a mildly neuro-toxic agent that degrades rapidly in sunny conditions. Since its use became common in 2000, residents of other states have reported that the chemical caused health problems such as nausea and sight damage.
New York was a hotbed of complaints, with dozens of people saying Anvil led to breathing problems or other ailments. No such incidents were reported in Massachusetts this year or after Anvil spraying in 2006, Manley said.
The planes fly between 8 p.m. and 3 a.m., when there is the smallest likelihood of human exposure.
For the spraying to work, mosquitoes must be hit in-flight. Mosquitoes are less likely to fly in rain and wind, so the spraying was delayed last week. Under perfect conditions, there is less than a .01 percent chance the chemical will hit a mosquito, Pimentel said