We recommend annual vaccination against Rabies for your horse. This is in accordance with the AAEP guidelines for core vaccinations for your horse. This means that ALL horses in the USA should be vaccinated against rabies. Eleven States reported 40 rabid horses, mules, and donkeys in 2011 though many cases in the USA are under-reported due to death of the horse or lack of an accurate diagnosis.
Rabies is caused by a virus and is usually spread by the bite of an infected animal, although it can enter the body through an abrasion in the skin. Wild life such as raccoons, foxes, skunks and bats are the most common reservoirs for the disease and transmit it to horses most often by biting the muzzle, face or lower legs. The virus is excreted in the saliva of the infected animal during a bite and then migrates via the horse's nerves to its brain where it initiates rapidly progressive, fatal encephalitis. Most raccoons, opossums, foxes and bats are not seen during the day. Instead, they are nocturnal animals and spend more time at night in your barn and pastures than you will ever know.
In horses, there are two clinical forms of the disease; dumb or paralytic and furious. Symptoms vary between the two forms. In the dumb form, the horse is not aggressive but exhibits signs like loss of appetite, neurological symptoms, stumbling and other symptoms similar to sleeping sickness. Often, the horse is noted to have excessive drooling saliva because the horse cannot swallow due to paralysis of the throat muscles. Unfortunately, humans can become exposed to rabies when the horse is exhibiting the dumb form because many people will reach back in the horse's throat thinking that the horse is choking on feedstuffs or similar.
In the furious form, the rabid horse will become very aggressive and may attempt to bite or attack other animals and people. In the horse, symptoms include unpredictable behavior, muscular incoordination, seizure and death from progressive paralysis. Death usually occurs within 7 days.
There are other disease that produce similar clinical signs as rabies: EEE, WEE and VEE (encephalitis), West Nile Virus, traumatic brain injury, traumatic spinal cord injury, poisoning, and equine encephalomyelitis or EPM.