Equine encephalomyelitis and West Nile virus, two diseases of the central nervous system, have garnered headlines in recent decades. These two diseases were discussed earlier in this chapter. However, there are some other less publicized central nervous system disorders that are just as deadly. For example, most people have heard of tetanus and rabies, two diseases that have been around for ages and that terrorized people long before the age of vaccines finally reined them in.

Horses are quite susceptible to tetanus, a deadly disease caused by bacteria living in the soil. Their environment — old barns, rusty nails, dirt, manure — readily supports the bacteria that affect the nervous system and for which successful treatment is difficult at best.

When the bacteria enter the bloodstream, usually via a bad cut or a deep puncture wound, they release a toxin that targets the horse's nervous system. Afflicted horses display extreme stiffness and muscle paralysis, especially around the neck and face, hence the origin of the common name for the disease, lockjaw.

Like encephalomyelitis, tetanus has a high mortality rate, roughly 80 percent. Fortunately, the disease is easily prevented by vaccination and annual boosters. As a precaution, most veterinarians will also rebooster a vaccinated horse that suffers any serious wound, especially a deep puncture wound.

Rabies is a problem throughout most of the continental United States. This horrible disease of the central nervous system has an outcome of certain death. It is not one to mess with — for your horse's sake and for yours, as rabies is communicable to humans from contact with the saliva of an afflicted animal to an open wound. Statistics are not high for horses contracting rabies, but those living in open situations with access to pasture are prime candidates because they come in contact with skunks, raccoons, foxes, bats, and other common rabies carriers. Furthermore, horses are curious animals, likely to go up and sniff a sick or dying animal that wanders into the field and end up getting bitten on the nose.

In most localities, rabies vaccinations are required by law for dogs, and in some places, even for cats. As more and more cases crop up, horse owners have taken notice and begun to vaccinate their animals routinely as well. It is a commonsense precaution, a small investment that could save you lots of grief if you were ever faced with the situation.

An animal suspected of having been exposed to rabies is either quarantined and observed for symptoms or destroyed and tested for the virus. Medical authorities, not the animal's owner, choose which option is best to take, depending on whether any human life has been placed at risk.

If your horse contracts the disease from a chance encounter, he will surely die or have to be put down. If that isn't reason enough to get your horse vaccinated, consider this. A rabid horse can spread rabies to anybody who handles him via a bite or by licking a wound. People exposed to animals even suspected of having rabies are usually given antirabies shots as a precaution. As the horse owner in this scenario, you would be responsible for any medical expenses, or worse, any human fatalities incurred as a result.

Because of the legal ramifications, always have your veterinarian give the rabies shots to your horse so there will be a documentation trail. Some savvy horse owners learn how to give their horses their shots themselves, to save money. This is perfectly legal in most cases. But with a suspected case of rabies, you want to be able to prove with legally recognized medical records when and how your horse was vaccinated. Even if you give your horse all his other shots yourself, leave the rabies shot for your vet to do.

EPM is sometimes misdiagnosed as West Nile Virus because it affects the brain and spinal cord and causes similar symptoms. The disease is often difficult to diagnose because the symptoms mimic other health problems. Testing is the only way to be sure which disease you're dealing with, although an astute veterinarian can distinguish the two more readily if one side or one part of the horse is affected more than the other.

While West Nile is caused by a virus, EPM is caused by an entirely different organism called a protozoan. This organism is transmitted to the horse via the opossum, which acquires the protozoan from infected birds. Because of the source, EPM is often called the possum disease. Symptoms may include abnormal gait, lameness, stiffness, incoordination, weakness, muscle paralysis (especially around the face), head tilt, and unusual sleepiness. Treatment is long-term, expensive, and not always successful.

A vaccine is in the works but not yet widely available. As a means of prevention, you can discourage possums and other wild animals from coming around the stable at night by keeping all feeds in tightly closed containers and behind closed doors. This goes for cat and dog food, too, as possums love to find a steady source of these delectables; don't leave food out in the barn for Fido and Fluffy to munch on at will.