A horse in Oxford County was euthanized last week after contracting Eastern equine encephalitis, state officials announced Wednesday.

The horse displayed neurological symptoms of the disease and tested positive for EEE, according to a press release from the the Maine Center for Disease Control and Prevention and the Maine Department of Agriculture, Conservation and Forestry.

The EEE virus is carried by mosquitoes, which pick it up from infected wild birds. The virus replicates in birds, which act as natural reservoirs for the disease. EEE can cause serious illness in humans, large animals such as horses and some species of birds.

The virus sometimes leads to encephalitis, or inflammation of the brain, resulting in death in one out of every three human cases. Last fall, a Vermont man died of EEE.

“The virus can affect human beings if they are bitten by mosquitoes that carry the virus,” Dr. Michele Walsh, state veterinarian, said in the release. “People cannot acquire EEE infection from sick animals, only from the bite of an infected mosquito.”

So far this year, eight pools of mosquitoes at collection sites in York County have tested positive for EEE. EEE has not been detected in humans in Maine. It reappeared in the state after killing 15 horses in 2009.

The horse euthanized last week in Oxford County was vaccinated a year ago against both EEE and West Nile virus, another disease spread by mosquitoes, but had not received a booster dose, according to the press release.

Signs of the disease in horses include stumbling or poor balance, unusual behavior and lethargy. Other symptoms include head pressing, circling, tremors, seizures and eventual coma.

“EEE is preventable in horses through vaccination,” Walsh said in the release. “If more than six months has elapsed since a horse has been vaccinated, a booster vaccination may be needed.”

The virus also can affect specialty livestock such as llamas, alpacas, emus, ostriches and other farm-raised birds, including quail and ducks. In 2012, a flock of 30 farm-raised pheasants in Lebanon died from Eastern equine encephalitis.

Vaccination can protect horses against West Nile virus, which has not been detected in Maine so far this year but was present in 2012 and has been confirmed in neighboring states this year.

Maine recorded its first human case of West Nile virus in a Cumberland County man in 2012.

EEE is more rare than West Nile, but more deadly. Symptoms range from mild flulike illness to encephalitis, coma and death. Approximately half of people who display symptoms of EEE will suffer mild to severe permanent neurological damage.

“This EEE activity in mosquitoes and horses should serve as a reminder to health care providers that humans are at risk from this disease, as well,” Dr. Sheila Pinette, director of Maine CDC, said in the release. “Although many persons infected with EEE have no apparent illness, those who develop symptoms do so usually three to 10 days after the bite of an infected mosquito.”

Maine CDC recommends the following preventive measures to protect against EEE, West Nile virus and other mosquito-borne illnesses:

— Wear long sleeves and long pants.

— Use an EPA-approved repellent on skin and clothes.

— Take extra precautions at dusk and dawn.

— Use screens on your windows and doors.

— Drain artificial sources of standing water where you live, work, and play.

— Vaccinate horses against EEE and West Nile.

Jackie Farwell

I'm the health editor for the Bangor Daily News, a Bangor native, a UMaine grad, and a weekend crossword warrior. I never get sick of writing about Maine people, geeking out over health care data, and...