Vermont steps up mosquito tracking
By Lucia Suarez
STAFF WRITER | July 11,2013
BRANDON — State health and agriculture officials are increasing their monitoring of the population and movement of mosquitoes in the Brandon area.
They hope to be more proactive against the spread of the mosquito-borne diseases Eastern equine encephalitis, or EEE, and the West Nile virus.
State Health Commissioner Harry Chen said the state’s approach this mosquito season includes more robust monitoring in targeted areas which epidemiologists feel are higher-risk areas for the breeding of disease-carrying mosquitoes.
Chen was addressing a crowd Wednesday night at the Brandon Town Hall, where state officials unveiled an updated plan on how they will monitor mosquito movement and determine risk of exposure to humans and other mammals.
“The only way to prevent equine encephalitis is to prevent mosquito bites,” he said. “We can’t kill all mosquitoes — as much as we would like. I can tell you that we want to lower the risk of equine encephalitis.”
Prior to the meeting, Erica Berl, a state infectious disease epidemiologist, said the Health Department and the state Agency of Agriculture, Food and Markets started testing mosquitoes earlier this season and plan to collect mosquitoes on a weekly basis to test them for viruses.
“Agriculture hopes to do more trapping across the state,” she said. “Right now we only have enough manpower to do trapping in specific areas.”
Berl said they began testing mosquitoes in the region’s swampy areas a couple of weeks ago. The results received earlier this week came back negative for any virus.
Berl said the state’s surveillance plan, written in 2001 and updated periodically since, now includes information on the increased testing and a risk matrix that explains how the state determines which areas are at higher or lower risk for mosquito-borne diseases.
“The Brandon-Whiting swamp areas are moderate risk based on the evidence from last year,” Berl said.
The no-risk level, or baseline, includes areas across the state that have had no human or veterinary cases of mosquito-borne viruses and no mosquito surveillance is available.
Berl said most of the state currently falls under this category, but not the area including Brandon and its surrounding towns.
Low-risk areas include those where EEE in mosquitoes was detected within the last two years and have detected it in only a single trapping site in the current year. The region also cannot have had human or veterinary cases.
Moderate risk means there have been confirmed human or veterinary cases, or sustained viral activity in mosquitoes within the last two years. Regions also fall under this category if, in the current year, they have no human or animal cases but have sustained activity of mosquitoes carrying the disease.
At that point, the state would begin discussions about spraying the region against mosquitoes.
In 2012, two people — one in Brandon and one in Sudbury — died after being infected with EEE. Evidence of the exposure to the virus was recorded in deer as early as 2010 and in a flock of emu a year later.
Alan Graham, an epidemiologist with the state Agency of Agriculture, said at Wednesday’s meeting that the Brandon area is home to mosquitoes production because of the swamp areas. He said the hardwood swamps found here — the most across Vermont — is the perfect breeding area for mosquitoes that could be infected with EEE.
“We have more money this year and we are focusing our efforts in this area,” Graham told residents at the meeting.
High-risk areas are regions where, in the current year, there has been a confirmed case of EEE in humans or animals or there is a sustained or increasing activity of viral mosquitoes.
Berl said in Brandon, Pittsford and the southern parts of Addison County, the risk level can only go up because of the evidence of EEE in humans last year.
“After last year, there is a likelihood that (EEE) might be there, but we can’t confirm that,” she said.
Berl said the risk matrix and a subsequent risk map that illustrates the regions that fall under the matrix, are the state’s starting points for tackling the issue and learning more about the virus.
She said it would help the state determine if or when to spray areas to kill infected mosquitoes. She said there must be evidence of a “public health risk” before the state takes that next step.
“There is not a lot of information (about EEE in Vermont),” Berl said at the meeting. “We can’t spray until we have a good educated guess that it will do something.”
More information regarding EEE and the West Nile virus and the work being done to monitor mosquitoes can be found at www.healthvermont.gov.