Update: Eastern equine encephalitis reported in Michigan horses

Thomas Guthrie<guthri19@msu.edu> and Taylor Fabus, Michigan State University Extension -

Updated from an original article written by Updated from an article originally authored by Tom Guthrie, Judith Marteniuk and Taylor Fabus.

Vaccinate your horse to protect it from getting sick from eastern equine encephalitis.

Foal
Young horses are often more susceptible to eastern equine encephalitis (EEE).

The Michigan Department of Agriculture and Rural Development (MDARD) recently confirmed the first horse case of Eastern Equine Encephalitis (EEE) virus in 2021, in a two-year-old Standardbred filly from Livingston County. MDARD reports that in 2020, Michigan experienced 41 cases of EEE in animals and four cases in humans. This serves as a reminder for horse owners/caretakers to take precautions to protect themselves as well as the horses they care for.   

Facts about EEE

  • Transmission of EEE is by infected mosquitoes.
  • Birds can serve as a host after having been bitten by an infected mosquito.
  • The virus spreads through the body and attacks the central nervous system (brain and spinal cord).
  • All horses are at risk. However, younger horses (six months to two years of age) are more vulnerable.
  • The virus is not spread by direct contact between horses.
  • Death of horses infected with EEE is relatively high (90 percent of cases).

Michigan State University Extension suggests that horse owners/caretakers take the following steps to protect horses against EEE:  

  • Vaccinate your horse(s) for EEE annually. This is ultimately the most important and effective step to prevention. Vaccination for EEE typically provides protection for six to nine months and is included in the annual core vaccinations that the American Association of Equine Practitioner’s recommends for all horses. Your veterinarian will be your best resource for determining vaccination schedules for your respective area.
  • Keep horses indoors around dawn and dusk when mosquitoes are most active.
  • Remove sources of standing water in your pasture and around the barn.
  • Use fly masks, fly sheets and/or fly leggings when horses are on pasture.
  • Spray horses with insect repellent that is appropriate for use on horses.
  • Utilize fans or open windows to create a breeze in the barn for stalled animals.

Signs or symptoms of EEE include

  • High fever (temperature higher than 103 degrees Fahrenheit)
  • Depression and lack of appetite
  • Pressing the head into corners
  • Walking around aimlessly, often in circles
  • Blindness
  • Uncoordinated gait, staggering
  • Recumbency, unable to get up
  • Seizures
  • Death

If your horse is having any of these symptoms or issues, contact your veterinarian immediately. If EEE or West Nile virus (WNV) is suspected to have infected your horse, it should be reported to MDARD at 800-292-3939 (daytime) or 517-373-0440 (after-hour emergencies).

For more information on equine diseases, visit MDARD’s website at www.michigan.gov/equinediseases. Updates on EEE and WNV cases in Michigan will be posted to the Equine Disease Communication Center’s Outbreak Alerts. For more information on how EEE may impact human health, please visit the Centers for Disease Control and Prevention website.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).

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