Western Equine Encephalomyelitis

Western equine encephalomyelitis (WEE) is a viral disease that primarily affects horses. Birds serve as the primary host for the virus, which is spread by mosquitoes and occasionally ticks. Although the disease may occur in other wild and domestic animals, horses and humans are most likely to develop symptoms.

Horses infected with WEE exhibit neurological symptoms. Most horses recover from the disease but some may have chronic neurological issues. The fatality rate for WEE is between 20-50 percent.

WEE is endemic throughout the Western Hemisphere including the western United States. The frequency of WEE has declined with no significant outbreaks in more than 20 years. Cases of WEE in Minnesota would most likely occur when mosquitoes are most active, usually throughout the summer months into mid-September.

Help prevent WEE in horses by taking the following steps:

• Vaccinate
• Eliminate "mosquito zones" by mowing long grass, draining stagnant water puddles, and removing items such as old tires and tin cans that can serve as breeding grounds for mosquitoes.
• Change water in drinking troughs at least once a week to prevent mosquito breeding.
• Use mosquito repellents and place screens in stables.

Any case of WEE in horses must be reported to the Board by calling 651-201-6804.