Maine Issues Warning on Eastern Equine Encephalitis and West Nile Virus Cases

October 17, 2023

For more information contact: Jim Britt at:

AUGUSTA, Maine - The Maine Department of Agriculture, Conservation and Forestry's (DACF) Division of Animal Health and the Maine Center for Disease Control and Prevention (Maine CDC) have confirmed new cases of Eastern Equine Encephalitis (EEE) in several emu flocks and multiple horses across Piscataquis, Penobscot, Somerset, and Waldo counties in the past few weeks. A West Nile Virus (WNV) case has been identified in a horse from York County. Routine and enhanced mosquito surveillance has also pinpointed EEE in Kennebec and Penobscot Counties.

Ratites, including emus and ostriches, and game birds like pheasants, are particularly susceptible to these mosquito-borne diseases. Equines and camelids are not exempt from this risk. DACF's State Veterinarian's Office strongly urges all owners of sensitive species to take immediate precautions, which include environmental modifications to eliminate potential mosquito breeding grounds, vaccination of equines, booster vaccinations for horses if more than six months have passed since the last immunization, and consideration of off-label vaccination for camelids and susceptible bird species.

This is the first year that the Maine CDC has reported EEE, WNV, and Jamestown Canyon Virus (JCV) in mosquito pools in Maine in a single season. Maine CDC has not reported any human case for any of these viruses in Maine, so far this year.

Although a frost capable of killing mosquitoes may occur in many areas of Maine, the current risk persists in multiple state regions. With ongoing reports of suspected cases over several weeks, precautions must be taken to safeguard humans and at-risk animals.

Maine people and visitors should protect themselves and eligible animals from mosquito bites during the fall months. This includes:

  • Vaccinating horses against EEE and WNV and booster vaccination of equines if more than 6 months has elapsed since vaccination. A vaccine is not available for JCV. Discuss off-label vaccination with a veterinarian for camelids and susceptible bird species.
  • People should wear long sleeves and long pants when outdoors where mosquitoes are active.
  • Use an EPA-approved repellent on skin and clothes.
  • Take extra precautions at dusk and dawn when mosquitoes are most active.
  • Use screens on windows and doors.

Many people infected with a mosquito-borne disease have no symptoms. Others experience fever and flu-like illness. Severe symptoms can occur, including encephalitis, meningitis, and death. If you experience any of these symptoms call a health care provider.

DACF collaborates closely with public health partners at the Maine CDC and its Health and Environmental Testing Laboratory to share information and assist in diagnostic testing.

For more information and guidance, please visit the DACF Animal Health and the Maine CDC's Vector-Borne Disease webpages:

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