The Eastern equine encephalitis (EEE) virus killed a Vermont man earlier this week in what the state Department of Health confirmed is the first human death ever in the state from the mosquito-borne illness.
The virus took the life of Richard Hollis Breen, 87, of Brandon, a former Otter Valley Union High School principal, on Tuesday. The Addison County Independent reported that the virus also hospitalized a Salisbury man.
These are the first two documented cases of humans contracting EEE in Vermont.
Earlier this year, state officials first discovered traces of EEE in mosquitos in the Addison and Rutland County towns of Whiting and Brandon. To address the issue, the Agency of Agriculture and the Department of Health (DOH) called for the aerial application of pesticides last night.
For the first time ever, the Agency of Agriculture took to the skies just after 8 p.m., aiming to spray large swathes of mosquito habitat in Whiting and Brandon with the pesticide known as Anvil. Due to lightning and poor visibility, however, the pesticide crew had to halt its activity.
A joint press release from the two state agencies indicates that the spraying will pick up again tonight at 7:30 p.m. and likely continue until 11 p.m. If the weather cooperates, the Brandon area will be sprayed in its entirety, as well as a portion of Whiting that was missed last night.
The DOH is instructing residents in those areas to stay inside until about 11:30 p.m. Residents should close windows and doors on their homes and kids’ toys and pet food should be brought inside. The DOH also advises that livestock not graze on sprayed pastures this evening and that homeowners with small organic gardens might consider covering them.
The pesticide Anvil
The chief ingredient in the pesticide Anvil is a synthetic chemical called sumithrin. It is classified as a pyrethroid insecticide, which according to the U.S. Environmental Protection Agency is adapted from chrysanthemum-derived insecticides categorized as pyrethrins.
CDC spokeswoman Candice Hoffmann said the application of Anvil is a common method to control outbreaks of EEE-infected mosquitos. The chemical specifically targets the adult mosquito population. Thus far, she said, Vermont officials have followed federal protocol to a tee.
But Anvil is neither benign, nor guaranteed to work.
A Vermont DOH fact sheet on the pesticide explains that exposure to this type of chemical can cause vomiting, central nervous system failure and tremors, among other complications.
When Vermont Deputy Commissioner of Agriculture Jolinda LaClair was asked about the effectiveness of Anvil, she spoke frankly.
“There’s a 10 to 90 percent rate of efficacy,” she said.
To assess the effects of the spraying, the state will need to heavily survey the mosquito populations of those areas. Funds for such surveillance, however, are shriveling up.
Erica Berl, Vermont infectious disease epidemiologist, said that the state mosquito surveillance program is working with nearly a quarter of the federal funds it had a year ago.
“We received $190,000 last year, and we got $50,000 this year,” she said about cuts to the federal “arbovirus” surveillance program, which is administered by the CDC. Arbovirus stands for arthropod-borne virus.
Tasked with capturing mosquito samples and meticulously analyzing them on a shoestring budget is state entomologist Alan Graham of the Agency of Agriculture. Over a 15-year period, he has sampled more than 1 million mosquitos in Vermont for EEE and the mosquito-borne West Nile virus.
But it wasn’t until this year that he came across EEE in Vermont mosquitos.
In 2010, the DOH and the Agency of Agriculture teamed up to test deer blood samples from across the state for EEE. When the results came in, Berl said she was surprised to find that 10 percent of the ruminants were carrying the virus.
That was the first time EEE’s presence was detected in the state.
That autumn, roughly 500 hunters brought their trophies to state officials, who then blood samples. The deer, however, posed no risk of spreading the virus. In mammals, the virus doesn’t build to levels high enough to infect others, said Berl.
“Mammals are pretty much dead-end hosts. The virus either kills them or it gets fought off,” she said.
The first case of EEE in Vermont domesticated animals was detected last September on an emu farm in Brandon. More than a dozen emus died as a result of the virus. That farm was the home of Richard Breen, the man who died from the virus earlier this week.
What is EEE and how does it spread?
The EEE virus has an incubation period of four to 10 days and can result in two types of illnesses.
The first illness is a systemic infection spread throughout the body. It’s characterized by cold-like symptoms such as chills, fever, stiffness of the joints and muscle pain. The second form is full-on encephalitis and can result in coma, convulsions, vomiting and, in severe cases, death.
According to the Centers for Disease Control and Prevention (CDC), there is no known treatment for EEE.
On average, the CDC reports that there are six documented cases of EEE in the United States each year. Before this week, there were only three this year: one in Massachusetts, one in Virginia and another in Florida. Massachusetts health officials reported today that a man died of EEE in August, and another resident was just diagnosed with the virus.
The disease tends to concentrate around wet mosquito breeding areas, like the Atlantic Ocean, the Gulf of Mexico, the Great Lakes and the St. Lawrence Seaway.
Graham found seven instances of EEE in mosquito samples taken by swamps in Whiting and Brandon. In one of the Whiting samples, Graham also found the West Nile virus, which was discovered in a hospitalized Franklin County patient earlier this week.
EEE mainly spreads between Culiseta Melanura mosquitos and perching songbirds. A mosquito carrying the disease might infect a bird, such as a robin, which may in turn infect another mosquito, which could then infect another bird and so the cycle goes.
But, said Berl, neither the birds nor the mosquitoes tend to die from the disease.
“The best sort of hosts are the ones that aren’t killed by the virus,” she said. “If it kills all the animals, it’s harder to transmit.”
Of the 45 identified species of mosquito in Vermont, Graham said that the disease has only been found in Culiseta melanura, and the chances of this type of mosquito spreading the virus to a mammal are slim.
Graham pointed to a three-year study completed in 2006 by the Connecticut Agricultural Experiment Station. The experiment found that only 4.2 percent of the 100-plus mosquitos sampled had a tendency to feed on mammalian blood. Another 89.6 percent of the mosquitos fed on birds. (PDF can be located here: http://www.ct.gov/caes/lib/caes/documents/biographies/molaeietalajtmh2006.pdf)
The CDC also points out that this type of mosquito feeds mainly on birds and is not likely to pass the EEE virus along to humans. As the CDC puts it, “Transmission to humans requires mosquito species capable of creating a ‘bridge’ between infected birds and uninfected mammals.”
Graham has never found a “bridge” mosquito in Vermont carrying the virus.
And as the heightened need to search for such mosquitos grows, Berl said extra funds to support this work are not currently available.