Eastern Equine Encephalitis Identified in a Maine Horse

Maine people and visitors urged to take precautions during an active mosquito season

AUGUSTA—  The Maine Center for Disease Control and Prevention (Maine CDC) and the Maine Department of Agriculture, Conservation and Forestry (Maine DACF) announced today that a horse from Somerset County tested positive for Eastern Equine Encephalitis virus (EEE). This is the third domestic animal this year to test positive for the virus, which is spread through the bite of infected mosquitoes.

Maine is experiencing an active mosquito-borne disease season. Already this year, the Maine CDC has reported:

  • EEE in two emus and one wild bird
  • Jamestown Canyon virus (JCV) in 4 mosquito pools (groups of up to 50 mosquitoes regularly tested as part of routine surveillance)
  • West Nile virus (WNV) in 15 wild birds.

At this time, no human cases of EEE, WNV, or JCV have been contracted in Maine this year.

"Unfortunately, we have confirmed a case of EEE in a horse here in Maine, the third animal this season," said Dr. Stefanie Bolas, State Veterinarian, DACF. "This confirmation serves as a reminder of the importance of vaccinating horses against this deadly virus. While horses cannot transmit EEE to humans or other animals, the high mortality rate makes prevention critical. We urge horse owners to take immediate precautions, including ensuring that their horses are up to date on vaccines, using approved insect repellents, and minimizing exposure during peak mosquito activity hours, from dusk to dawn."

EEE, WNV, and JCV spread through the bite of an infected mosquito and can infect humans and some animals. The virus cannot spread from human to human, or between horse and human. However, ratites (mostly flightless birds including emus and ostriches) may spread the virus to other animals and people. Many infected people have no symptoms. However, mosquito-borne illnesses can be serious and sometimes fatal. About one in three people who get EEE die and most who recover have long-term physical or cognitive health effects.

"These positive cases of EEE and West Nile virus should prompt Maine people and visitors to take action to protect themselves whenever they go outside" said Maine CDC Director Dr. Puthiery Va. "The best way to keep yourself, your loved ones, and domestic animals safe from these serious viruses is to avoid mosquito bites as much as possible."

You can take these simple steps to protect yourself from EEE, JCV, and WNV: 

  • Wear long sleeves and long pants. 
  • Use an EPA-approved repellent on skin and clothes. Reapply as indicated. 
  • Take extra precautions at dusk and dawn when mosquitoes are most active.
  • Use screens on windows and doors.
  • Drain artificial sources of standing water around the home, such as bird baths, pet water dishes, wheelbarrows, etc. This is ideal habitat for mosquitoes to lay eggs. 
  • Take steps to prevent mosquito bites when traveling.

These illnesses usually start with flu-like symptoms in humans. Severe symptoms can include brain swelling (encephalitis) and spinal cord inflammation (meningitis). If you experience flu-like symptoms, severe headache, behavior changes, or serious drowsiness, call a health care provider, especially if a COVID-19 test is negative.

To help prevent mosquito-borne diseases in pets, talk to your veterinarian. Horse owners can protect horses with vaccines against EEE and WNV. Symptoms of mosquito-borne illness in horses include muscle tremors, incoordination, weakness, decreased awareness, and seizures. If you notice any of these symptoms in your horse, call your veterinarian.

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