Tetanus is often regarded as rather an old-fashioned disease that is seldom seen in horses as there is now a highly effective vaccine against it. The bacterium that causes tetanus is however still out there and very much alive. In fact, my friend’s little dog was struck down with it last week. The vets were astounded; in 40 years of practice, the senior vet had never seen a case of tetanus in a dog.

My friend is a riding instructor and her dog spends the day running around the yard and a favourite pastime is eating hoof offcuts when the farrier has been. The vet thinks this is how she might have ingested the bacterium. People are also susceptible to tetanus and you should get yourself vaccinated if you spend a lot of time working around horses.

Horses are especially susceptible to tetanus because of their environment and their tendency to become injured. Unfortunately, the disease is usually fatal so it’s really important to have your horse immunised.

What causes tetanus?

Clostridium tetanii is a bacterium that is found in soil and horse droppings. It can survive in the environment for long periods, entering the horse’s body through wounds. One of the most common infection sites are puncture wounds in the sole of the horse’s foot although bacteria can enter the body via the intestines if contaminated soil is ingested. Even newborn foals can be infected through the umbilicus (navel).

Tetanus bacteria are classified as anaerobic bacteria; i.e. they don’t need oxygen to survive and multiply. The bacteria multiply rapidly amongst the damaged tissue of the injury site and, as they do so, produce a potent neurotoxin.

What are the symptoms?

The tetanus toxin attacks the horse’s nervous system, specifically the nerves that control the muscles. The horse’s muscles become stiff and go into spasm making it difficult for the animal to move and eat, hence the old name for the disease; ‘lockjaw’. The third eyelid begins to encroach across the eye, especially if the horse is startled. Sometimes the horse will hold its tail out straight and muscle spasm will cause an anxious expression to develop.

Any sort of external stimulus like loud noises, bright lights or touch can make the horse worse. In severe cases where the condition has become advanced, the horse will collapse; suffer spasms, convulsions and death may result from respiratory failure.

Can tetanus be treated?

If the condition is diagnosed early enough, large doses of antibiotics used in conjunction with tetanus antitoxin can be successful although most tetanus cases result in the death of the horse. The aim of the treatment is to reduce the amount of toxin being produced and to kill the bacteria which are causing it.

How can tetanus be prevented?

No horse should be at risk from tetanus these days as the disease is very easily preventable. An extremely effective vaccine is available which should be boosted every two years. Foals can be vaccinated once they reach four months of age; prior to this, some immunity is passed from the mare via the first milk (colostrum) provided the mare is fully vaccinated.

Good stable management goes a long way towards preventing the disease. Paddocks, stables and other areas in which the horse is kept or worked should be kept clean and safe. Don’t leave potentially dangerous items such as bits of metal or old building materials lying around that could cause injury and always check stables and field fencing for protruding nails or screw-heads.

If your horse does sustain a wound, clean it thoroughly as soon as you can and monitor it closely for signs of infection. In the case of a particularly deep wound or a puncture, it’s always best practice to call your vet who will prescribe antibiotics to kill off any deep infection.