Imagine your muscles in such a state of spasm, that you cannot stand or maintain your balance. Imagine not being able to breathe and then suffocating to death, because the muscles for breathing are also in spasm. This is what happens to horses suffering from tetanus.
The situation is not helped by the fact that horses are the most susceptible to the tetanus toxin of all animals in the world, followed by humans and then sheep and goats. Other mammals and birds are susceptible, but in varying degrees, and much less so.

Tetanus, or lockjaw, as it is occasionally known, is caused by bacteria called Clostridium tetani. This bacteria is an anaerobic type of bacteria which means it grows in tissue that is poorly oxygenated (no air). The spores of Clostridium tetani are present in faeces and soil, and can survive for a long time. They become really dangerous when they are in a low oxygen environment such as a deep, infected wound.

The problem

And this is where the problems start – often the wound via which the bacteria gained access to the body is very small, and by the time signs of tetanus are seen, the wound might have healed already. Deep, penetrating wounds, such as a nail in the hooves of horses, provide the ideal environment for the bacterial spores to release a very potent toxin that is either absorbed into the blood stream or lymph system, or the toxin travels along the nerves.

The toxin is a neurotoxin, which means it affects the nervous system. That is why the animal develops the typical signs: After an incubation period of about 12 days (this varies between three days and three weeks – thus the ability for a wound to heal before symptoms are first seen) one may notice flared nostrils; a clenched jaw; severe muscle spasms; a wide, stiff stance; twitchy, erect ears; a rigid, upright tail position; wide-open, staring eyes and the third eyelid membrane also protrudes across the eye somewhat.

Affected animals eventually go down on their side and because of their muscles being in spasm, they don’t often get up again. Their diaphragm (which is the main breathing muscle) also goes into spasm, thereby resulting in the horse suffocating to death. A similar pattern of symptoms and events occurs in humans as well.

Treating tetanus

Generally speaking, the deeper and dirtier the wound, the better the conditions for C. tetani because they need a low oxygen environment. Treatment may often prove unsuccessful. It is also very costly as it involves administrating copious quantities of expensive tetanus anti-toxin which only really works before symptoms set in. Treatment also involves antibiotics, pain killers, muscle relaxants, and very intensive and aggressive nursing care.

Once horses have started showing symptoms of tetanus, they have a mere 20% chance of surviving, despite treatment. Those that do survive, can take up to six weeks to fully recover. So what should be done if your horse sustains a penetrating wound?

First consult your vet. He or she will then decide whether or not it is necessary to come out or not. If the tetanus vaccination status of your horse is not known, then the tetanus anti-toxin MUST be given, especially if tetanus is known to occur on your property or in your area. A 1 500-3 000 IU of antitoxin should be given ASAP.

A course of penicillin should also be injected at the recommended dosage (also ASAP). Another important aspect of penicillin usage is that it is better to use a short-acting penicillin once or twice daily instead of a long-acting penicillin.

The wound should also be cleaned with tap water, a mild disinfectant solution may also be used, but ensure that it is not too strong because very strong, or worse, undiluted disinfectant may very well kill the bacteria. But it also damages and kills healthy tissue, and dead tissue isn’t well-oxygenated and this is exactly what anaerobic bacteria love!

Once the above has been carried out, it is also important to inject the tetanus vaccine at the same time, because the anti-toxin only protects for 2-3 weeks. Just to stress the difference between the vaccine and the anti-toxin: The vaccine is exactly that – after it is injected it will, over time, stimulate the body to produce antibodies against the disease (in this case tetanus); the anti-toxin, however, is, simply put, ready-made anti-bodies that have been extracted from the blood of another animal and then bottled – therefore it is a short-term protector.

Simply vaccinate

As mentioned above, the routinely administered antitoxin is only effective very early, because it is designed to bind the toxin while it is in the blood stream – once the nervous system is affected, it is too late.

All of the above could be prevented to a large degree by simply vaccinating your horses! All horses should be vaccinated twice (four weeks apart) initially. Thereafter a yearly booster is necessary.

If the tetanus vaccine status on your property is unknown or non-existent, it is best to vaccinate all horses twice (four weeks apart) after which the horses can fall into a yearly vaccination programme (see July 2006 edition of SA Horseman, or contact the author for a complete programme).
Some vaccines on the market also include equine influenza, which adds to the convenience. It is also important to realise that not all vaccines are the same. Once you get an honest, unbiased opinion, the differences will become clear. Therefore, base your decision on science and not price!

(References available from the author)