Do you know anyone with a horse that has had tetanus? Probably not. Despite the fact that the organism responsible for the disease is often present in soil and horse manure, it is not a common disease. That is largely due to the widespread use of vaccination.

But that doesn't mean you can be complacent. Tetanus is an ever present threat to the health of your horse. In many cases the disease is fatal.

Tetanus is caused by a bacterium called Clostridium tetani. It produces spores, which are very resistant and can survive treatment with many disinfectants. In its active form, the organism thrives in conditions with little oxygen. So damaged tissue buried underneath the skin is an ideal habitat.

In horses, most cases of tetanus result from the organism getting into wounds. Contrary to what many think, it is not big gaping wounds that present the greatest risk. It is often the small puncture wounds that are the most dangerous. It takes between one and three weeks for signs of disease to develop after the animal has become infected. So the original wound has usually healed by the time the horse becomes unwell. Often the owner has not even noticed that their horse has had a injury.

Puncture wounds to the foot are a particular risk. They are often contaminated with soil - which is a good source of Clostridium tetani.

The nervous signs characteristic of the disease are caused by a neurotoxin that is released by the organism as it multiplies in the tissues. The toxin may be absorbed into the bloodstream and produce generalized signs. Less commonly it may be affect the nerves close to the wound and produce a localized spasm before spreading more generally.

The toxin causes progressive muscle rigidity. Affected horses often have a frightened expression because of spasm of the facial muscles. Their nostrils flare, their ears are held back and they have a wide-eyed appearance. They have difficulty chewing and opening their mouth. Often their tail is held up slightly. Affected horses walk stiffly (like a board) without bending their neck. The muscles of the jaw seize up and the horse is unable to eat. That is the characteristic that gave the disease its old name of lockjaw.

The spasms are made worse when the horse is stimulated. Any sudden noise or movement can be enough to set off bouts of muscle spasms. Often there is spasm of the muscle of the third eyelid, causing it to protrude across the eye. Eventually, horses with tetanus are unable to stand. Their respiratory muscles become affected and so they have difficulty breathing. Most cases will die.

What can you do if you think your horse has tetanus? Call the veterinarian straight away! Some affected animals may respond to treatment. But their chances of survival are much better if treatment is started as early as possible. Keep the horse in a cool dark stable. Avoid any sudden noises or movements. Putting plugs of cotton wool in the ears may help.

What is the likely outcome? Unfortunately many cases of tetanus will die. Some horses that only show mild signs when they are first recognized may respond to aggressive treatment. Even so, they will need careful nursing for two weeks or longer if they are to survive.

So how can you prevent your horse getting tetanus? An effective vaccine is available. There is initial course of two injections, followed by a booster after a year. Current vaccines require boosters at up to three year intervals. Tetanus is often included with the influenza vaccine. So horses that have been vaccinated against `flu will probably be covered against tetanus as well . But it is well worth checking to make sure.

In the vast majority of horses there are no adverse effects of vaccination. Occasional horses may develop a small lump after vaccination.

If your horse suffers an injury and has not been vaccinated, the veterinarian can administer tetanus antitoxin - the antidote to tetanus. But this only provides temporary protection for a couple of weeks. By far the most reliable way of protecting your horse from this frequently fatal disease is to make sure that he or she is fully vaccinated.

There is no excuse for any horse or pony not to be fully vaccinated against this disease. Prevention is always better than the cure - certainly for the horse - and for your pocket!