Michigan confirms first 2021 case of mosquito-borne EEE in Livingston County horse

On Thursday, Michigan confirmed the first Eastern Equine Encephalitis case this year.

The mosquito-borne virus was found in a Standardbred filly from Livingston County.

Related: First 2021 case of West Nile virus confirmed in horse

Mosquitoes can transmit the illness to animals and humans. Michigan usually sees cases of EEE in late summer and early fall.

With a 90% fatality rate among horses and a 33% fatality rate among humans, it is one of the most dangerous mosquito-borne diseases in the United States. Horses cannot pass the virus to other horses or humans. Humans can get sick if they are bitten by an infected mosquito. 

Signs of EEE in humans include the sudden onset of fever, chills, and body and joint aches. 

It can cause severe encephalitis, resulting in headaches, disorientation, tremors, seizures, and paralysis. Permanent brain damage, coma, and death could occur in some cases.

"The Livingston County horse was never vaccinated against EEE, and it developed signs of illness—including fever, lethargy, and depression—which progressed to the animal exhibiting neurologic signs and being down on the ground with an inability to get up. The horse was euthanized due to her declining condition," said Dr. Nora Wineland, a veterinarian with the Michigan Department of Agriculture and Rural Development. "It is critically important for horse owners to reach out to their veterinarian to discuss how to best protect their animals from this disease."

Officials offered tips for protecting animals:

  • Talking to a veterinarian about vaccinating horses against EEE.
  • Placing horses in a barn under fans (as mosquitoes are not strong flyers) during peak mosquito activity from dusk to dawn.
  • Using an insect repellant on the animals approved for the species.
  • Eliminating standing water on the property—i.e., fill in puddles, repair eaves, and change the water in buckets and bowls at least once a day.
  • Contacting a veterinarian if a horse shows signs of the illness: mild fever and stumbling, which can progress to being down and struggling to stand.

"This equine case indicates the EEE virus is here in Michigan and provides a warning that residents could also become infected by a mosquito," said Dr. Joneigh Khaldun, MDHHS chief medical executive and chief deputy director for health. "Michigan residents are urged to take precautions and protect themselves from mosquito bites."

The state also offered tips for humans:

  • Applying insect repellents containing the active ingredient DEET (or other U.S. Environmental Protection Agency-approved products) to exposed skin or clothing, and always following the manufacturer’s directions for use.
  • Wearing long-sleeved shirts and long pants when outdoors. Applying insect repellent to clothing to further prevent bites.
  • Maintaining window and door screening to help keep mosquitoes outside.
  • Emptying water from mosquito breeding sites around the home, such as buckets, unused children’s pools, old tires, or similar sites where mosquitoes may lay eggs.
  • Using nets and/or fans over outdoor eating areas.