The last known outbreak of Venezuelan Equine Encephalomyelitis in the United States occurred in Texas in 1971. Approximately two days after equine infection with encephalomyelitis, there is an inapparent infection and low-grade fever. The first apparent signs are at four to five days. At that time, the animal generally has a fever and rapid heart rate, is showing signs of anorexia, depression, and variable other neurological signs. As the illness progresses the brain stem and spinal cord are affected.
Muscle weakness becomes apparent and there are behavioral changes and dementia.
Notable symptoms aggression, head pressing, wall leaning, compulsive circling, and blindness. Other signs might include uncontrolled twitching of the eyeball, and facial muscle paralysis. As the disease progresses, a semi-comatose and convulsive state occurs. Death usually follows two or three days later. If the animal survives, residual nervous system problems result.