09/15/2026
DATCP confirms that an unvaccinated six-year-old Quarter Horse mare in Brown County has tested positive for West Nile Virus (WNV).
West Nile Virus (WNV) can cause inflammation of the brain (encephalitis). Symptoms of WNV in horses include fever, loss of coordination, hind-end weakness, depression, loss of appetite, muscle tremors, teeth grinding, inability to swallow, head pressing, excessive sweating, and going down with an inability to rise. The disease can cause brain inflammation in horses and people, and it is fatal in 30-40% of horses showing signs of illness.
WNV is transmitted by mosquitoes. Horses cannot transmit WNV to humans, but mosquitoes can. Implement mosquito control and mosquito bite prevention to protect your horses and yourselves!
There is a very effective vaccine to prevent WNV in equines. Please talk with your veterinarian about equine vaccination.
Learn more at: https://datcp.wi.gov/Pages/BrownCountyHorseConfirmedwithWestNileVirus.aspx.