Eastern Encephalitis is a neurologic disease caused by a virus that can infect horses and humans. This disease is spread by mosquitos. It cannot be spread from horse to horse or horse to human.

The eastern strain of encephalitis has a mortality rate near 100% in non-vaccinated horses. Humans rarely develop symptoms, but when they do symptoms range from mild flu-like to fatal.

In horses the symptoms are off feed, pacing, off balance, blindness, or inability to stand. There is no treatment, only supportive care.

The vaccine is very effective and protective, however. There have been thirty one (31) documented cases in northern Wisconsin. Three of these cases have survived and had all been previously vaccinated. Twenty eight of these horses died-none of these were vaccinated.

The vaccine for Eastern Encephalitis is usually in a combination vaccine called "three way".  Western Encephalitis and Tetanus Toxoid are also in the vaccine.