Eastern and Western Equine Encephalitis (EEE & WEE) and West Nile Virus are endemic diseases in the United States. Birds serve as the primary hosts for these diseases. 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. Infected horses may or may not show neurological symptoms and many recover completely from these diseases.
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. Practices such as changing water in drinking troughs every week, mowing long grass, draining stagnant water puddles, and removing items such as old tires and tin cans may help to eliminate mosquito breeding grounds. Horses and people can also be protected from mosquitoes by using repellents and placing screens over windows and stable doors.
Positive test results for equine encephalitis or West Nile Virus must be reported to the Board of Animal Health.
2018 West Nile Virus cases by county
Beltrami, Big Stone, Fillmore (2 cases), Hennepin, Meeker, Pine, Polk, Sherburne, Stearns (alpaca case), Todd, Waseca (mule case).
All cases were either unvaccinated or had no records of vaccination against West Nile Virus.
List updated: 09/17/2018
Click on the map below to view positive West Nile Virus cases by county.