Maine CDC Press Release

August 30, 2019

Eastern Equine Encephalitis confirmed in York County horse

Maine CDC reminds residents and visitors to protect themselves and their animals against mosquito-borne disease

AUGUSTA, Maine – Maine Center for Disease Control and Prevention (Maine CDC) was alerted late this afternoon of a positive test for Eastern Equine Encephalitis (EEE) in a horse in York County. The horse, which was not vaccinated against the disease, was euthanized. This is the first case of a horse contracting EEE in Maine since 2013.

EEE is a virus that is transmitted through the bite of an infected mosquito. "EEE, which is carried by mosquitoes, is a fatal, viral disease in horses. The virus can affect human beings if they are bitten by mosquitoes that carry the virus," said Dr. Michele Walsh, Maine State Veterinarian. "People cannot acquire EEE infection from sick animals, only from the bite of an infected mosquito."

"This positive result confirms that mosquitoes carrying the virus are present in Maine, which is the reason why Maine CDC urges the state's residents and visitors to take precautions to protect themselves and their animals from mosquito bites," said Nirav D. Shah, Director of Maine CDC. "We want everyone to take precautions while enjoying themselves this holiday weekend."

Public health officials in other northeastern states have seen evidence of a very active season for EEE and some evidence of mosquitoes carrying West Nile virus (WNV), another mosquito-borne illness. There have been no confirmed cases of EEE or WNV in humans in Maine this year. The last case of EEE involving a human in Maine was in 2015.

Maine CDC advises residents and visitors to protect themselves, their children, and animals by minimizing outdoor activity from dusk to dawn, when mosquitoes are most active. If outdoor activity is unavoidable, take personal precautions to prevent mosquito bites, including:

  • Use an EPA-approved repellent
  • Wear long-sleeved shirts and pants
  • Treat clothing and gear with Permethrin
  • Take steps to control mosquitoes around your property by emptying artificial sources of standing water, fixing holes in screens, and working with a pesticide control applicator.

Animal owners should be aware that:

  • An EEE/WNV vaccine for horses is available.
  • Horses that have not been EEE/WNV vaccinated in the past six months should get either an initial vaccine or a booster as soon as possible.
  • The virus cannot be transmitted from horses to humans.
  • The virus can also affect specialty livestock, such as llamas, alpacas, emus, ostriches, and other farm-raised birds, such as pheasants, quail and ducks. Owners should contact their herd or flock veterinarians to discuss available vaccines and should also take precautions to help reduce exposure to mosquitoes for both themselves and their animals.

Signs of EEE in horses include stumbling or poor balance, unusual behavior, and lethargy. Other symptoms include head pressing, circling, tremors, seizures and eventual coma. In some animal species, the first signs of the disease can be bloody diarrhea or sudden death. The fatality rate for infected animals is greater than 90%, and those that recover can have permanent brain damage. When approved for protection of a particular species, vaccination is the best way to prevent the disease.

The risk of mosquito-transmitted diseases such as EEE and WNV usually increases through the late summer and early fall. Mosquitoes are active until the second heavy frost.

Human infection with EEE virus can cause serious illness affecting the brain. Some persons infected with EEE have no obvious symptoms. In those persons who do develop illness, symptoms – which typically appear between three and 10 days after a bite – range from mild flu-like illness to high fever, headache, stiff neck, and decreased consciousness. Approximately one in every three individuals who are infected with EEE die and many of those who recover experience lasting health problems. Individuals with symptoms suggestive of EEE infection should contact their physician immediately. No human vaccine against EEE and WNV infection is available. There is no specific antiviral treatment for EEE or WNV infections.

Maine has many resources regarding mosquito-borne diseases: