Eastern Equine Encephalitis Virus
Deer and Moose Serosurvey Project

Since 2010, the Vermont Department of Health has been working with the Vermont Agency of Agriculture, Food and Markets and the Centers for Disease Control and Prevention on a deer and moose serosurvey project.

The purpose of this project is to determine if Eastern equine encephalitis (EEE) virus is present in Vermont, and where the virus is circulating. The serosurvey is done by collecting blood from harvested deer and testing the samples for antibodies to the virus. The presence of antibodies means that the deer were exposed to the virus at some point in their lives.

Deer are good for this purpose because they get bitten by a lot of mosquitoes, they stay in a relatively small area during mosquito season, and blood samples are readily available during hunting season. Since deer are relatively scarce in the northeastern part of the state, blood samples were collected from moose that were harvested during fall hunting season.

Learn more: Deer and Moose Serosurvey Project FAQ

Results to date

Prior to 2010, EEE virus had never been detected in Vermont. However, it had been found in neighboring states and the Provence of Quebec, so the virus was likely in Vermont as well.

The results of the 2010 serosurvey were remarkable. Approximately 10% (50/489) of the deer and 29% (6/21) of the moose tested positive for antibodies against EEE virus. Deer from many different parts of the state tested positive and there was not any detectable clustering of positive deer near wetlands or other bodies of water.

In 2011, 6.5% (12/184) of deer and 2.5% (1/40) of moose tested positive. In 2012, positive results were found in 12.1% (35/288) of deer and 2.4% (1/42) of moose. Deer and moose samples are being collected in 2013, and may also be collected in 2014.

Now that we know EEE virus is present in Vermont, the data will be combined to see if we can detect any patterns in the distribution of positive deer and moose. This may help us to focus future surveillance efforts.

map of vermont

Click map for larger version (PDF)


Eastern Equine Encephalitis in Moose (Alces americanus) in Northeaster Vermont. Journal of Wildlife Diseases: October 2012, Vol. 48, No. 4, pp. 1109-1112.

Serological Evidence for Eastern Equine Encephalitis Virus Activity in White-Tailed Deer, Odocoileus virginianus, in Vermont, 2010. Am. J. Trop. Med. Hyg., 88(1), 2013, pp. 103–107

More information

Call the Health Department's West Nile virus/EEE information line:
1-800-913-1139 • Monday through Friday • 8:00 a.m.- 4:30 p.m.

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