The Board recently announced the first West Nile virus (WNv) case in a horse for the 2022 season. Mosquitoes are active around the state and risk is elevated for Eastern and Western Equine Encephalitis (EEE & WEE) and WNv. These viruses are transmitted from birds to horses or people through the bite of infected mosquitoes. These viruses can cause encephalitis, an inflammation of the brain and spinal cord.

Vaccines for horses are widely available and have been proven to be effective in preventing infection. Steps can also be taken to reduce the risk of these diseases by reducing mosquito populations.

Positive test results for equine encephalitis or West Nile virus must be reported to the Board of Animal Health.

Horse owners are encouraged to work with their veterinarian to make sure their animals are up to date on vaccines to reduce the risk of illnesses from disease carrying insects. Additionally, owners can take these steps to reduce disease risk by reducing mosquitoes and other biting insects (see detail on horse and deer flies below).

  • Change water in drinking troughs every week.
  • Mow long grass.
  • Drain stagnant water puddles.
  • Remove items mosquitoes use for breeding grounds, like old tires and tin cans.
  • Place and maintain screens over windows and stable doors.
  • Use mosquito repellents to protect horses and people from mosquito bites.

These measures are especially important for Equine Infectious Anemia (EIA), which is primarily spread through horse and deer fly bites.