Officials say mosquito spraying for eastern equine encephalitis at least 60 percent effective

Mosquito. Photo by Arthur Chapman.

For the first time ever, a horse in Vermont was diagnosed with the potentially fatal eastern equine encephalitis virus.

The Agency of Agriculture received news about the Whiting horse on Friday.

On Sept. 4, EEE killed Richard Hollis Breen, 87, of Brandon and hospitalized a Salsibury man in what are the first two documented instances of humans contracting the virus in Vermont. This year, alone, the state has identified seven instances of EEE in mosquitos in the Addison and Rutland county towns of Whiting and Brandon.

To address the rise of EEE, the Department of Health (DOH) teamed up with the Agency of Agriculture and called for the aerial application of the synthetic pesticide Anvil in Whiting, Brandon and parts of Leicester, Cornwall, Shoreham and Salisbury. The night of Sept. 6 marked the first time the state has ever targeted mosquitos with pesticides from the air. More Anvil was then sprayed on Sept. 7 due to weather complications the night before.

This past Friday, state entymologist Alan Graham and Cary Giguerre, chief of the agency’s pesticide program, finished assessing the pesticide’s efficacy. According to their test results, the block over Whiting, Salisbury, Leicester, Cornwall and Shoreham reduced mosquito populations by 69 percent. And the block over Brandon cut mosquito populations by 60 percent.

These results pertain only to salient mosquito species, which include the primary carrier of the EEE virus — the mosquito known as Culiseta melanura.

While overall mosquito populations were down, a section of Whiting held an extremely high population of Culista melanura.

“The high number of Culiseta melanura in Whiting is of concern to me,” said Graham, who has sampled more than one million mosquitos for EEE over a 15-year period. This is very unusual and something I have never seen before in the many years I have been trapping in Vermont.”

By the end of Friday, Giguere still had not received the EEE results for the mosquitos were captured after the spraying. The mosquito samples were categorized by date and region and then sent to a lab in New York on Wednesday, which crushes their bodies and tests for traces of EEE.

If the tests come back positive, the DOH would analyze the data and make a decision about whether to spray again, said DOH spokesman Robert Stirewalt.

An organic exception

On the Wednesday morning before the state started spraying the synthetic pesticide, Jeremy Gildrien, owner of the Leicester crop farm Gildrien Farm, called the Agency of Agriculture.

He asked to be placed on a no-spray list for organic producers, but his request was denied.

Gildrien had purchased his farmstead less than a year prior and he was converting the farm to conform with USDA organic standards. The process, he explained, takes three years, and he was only in the first year. Since Gildrien Farm was not USDA certified organic, the state would not place it on the no-spray list.

The decision, said Giguere, had nothing to do with environmental risk and everything to do with finances.

“The organic farms were buffered for economic reasons. They have a value-added crop,” he said. “A lot of farmers in the area have put the extra cost into raising those products organically, and for them to lose the ability to sell those products organically would have damaged their businesses.”

The organic farms also would have lost their organic certifications, and the spraying of Anvil doesn’t impede the USDA organic certification process that Gildrien has begun.

The main ingredient in Anvil is a chemical called sumithrin. Anvil is classified as a pyrethroid insecticide, and it is a synthesized version of a class of chrysanthemum-derived organic insecticides called pyrethrins.

According to Giguere, the state chose to use Anvil because it is less harmful than organic pyrethrins, which would have remained in the atmosphere and damaged the state’s fragile bee population.

“Had we used the organic … pyrethrins … we’d still be killing bees today from the spray last week,” he said. “The pesticides that organic farms are allowed to use on organic farms are much more harmful than the ones we did use, so it wasn’t a risk-based decision. It was purely financial.”

Anvil dissipates very quickly and most of it doesn’t make it to the ground, said Giguere. The state was targeting adult mosquitos that were flying, as Anvil is classified as an “adulticide” pesticide.

“Once (the pesticide) lands on the ground and vegetation it dissipates very quickly,” said Giguere. “Half of it was gone by the time the sun came up the next morning. You cannot detect any (sumithrin) now, and we can detect down to parts per trillion.”

Gildrien, who has a degree in biology, said that once he learned about the nature of the pesticide, he was OK with the state’s decision.

“The Agency of Ag people were great and really helpful,” he said. “A guy died from EEE and that was pretty close to us. I’m not upset about the whole thing. It was an emergency, so it seems fine to me that they sprayed what they did. It’s not like people were just annoyed with mosquitos.”

A Vermont DOH fact sheet for the insecticide explains that sumithrin can cause vomiting, central nervous system failure and tremors, among other health complications.

The legal basis for spraying

Jordan Benjamin is a Cornwall resident and student at Vermont Law School. He wishes he had known earlier about the spraying because of the potential health risks it might have posed for his 11-month-old child.

Although notice of the spraying was published and broadcasted via news outlets across the state, and the town of Brandon held a public meeting about the incident, it wasn’t until a Cornwall official called Benjamin several hours before the state took to the air that he said he knew about the aerial application of pesticides.

“I’m concerned that we didn’t have more notice,” he said on Friday. “Being a law student it made me question just how much of an emergency this was.”

Giguere said the state did everything it could to get word out to area residents that pesticides would be sprayed over large swaths of land.

The legal basis for the state spraying pesticides over hundreds of private properties stems from DOH Commissioner Harry Chen’s determination that the recent episodes of EEE were a “significant public health risk.”

Under title 18 of the Vermont statutes, “‘Significant public health risk’ means a public health risk of such magnitude that the commissioner or a local health officer has reason to believe that it must be mitigated. The magnitude of the risk is a factor of the characteristics of the public health hazard and the degree and the circumstances of exposure to such public health hazard.”

According to Pat Parenteau, former commissioner of the Vermont Department of Environmental Conservation and law professor at Vermont Law School, that language gives the commissioner an extraordinary amount of power.

“That’s what I’d call unbridled discretion,” he said. “That basically commits the decision to the discretion of the commissioner. There are no objective standards there at all.”

Parenteau said he doesn’t know of any firm legal grounds by which to challenge decisions made by the commissioner during such an event. The Legislature made a rule, he said, that put an enormous amount of faith in the abilities of a health commissioner to make quick and crucial decisions during an emergency.