The disease progresses through stages of neurological decline: Fever, depression, and lack of appetite.

Vision loss, circling, head pressing, and eventually paralysis or recumbency. Mortality rates in horses can range from 20% to 50% . Diagnosis and Management

The disease is caused by the Western Equine Encephalomyelitis Virus (WEEV) , a member of the Alphavirus genus in the Togaviridae family.