Equine Encephalomyelitis (Sleeping Sickness, Blind Staggers,
Brain Fever) is a viral disease that results in inflammation of
the brain's vascular system.
This seasonal disease is transmitted by mosquitoes and has
an acute onset that is fatal. If affects all ages and types of horses.
The horse is a dead end host and cannot pass this virus to another
horse. Birds and rodents serve as reservoirs for the virus.
The three common viruses are named by their geographical area
- Eastern (EEE), Western (WEE) and Venezuelan (VEE).
Within one to three weeks, symptoms begin with
a mild fever that progresses to loss of appetite, depression,
drowsiness, facial paralysis, incoordination and death in two to
In the cases of recovery, survivors have residual central
nervous system signs and are called "dummies" or "sleepers"
because of their unsatisfactory response to outside stimuli.
The vaccination schedule starts with injections for
foals at three months of age and again at four months. A booster
is given every year. Control of the mosquito population
reduces the transmission of the virus.