Tetanus

Tetanus - is your horse vaccinated?

Out of all domestic animals, horses are the most susceptible to tetanus toxin.  Combine this with the equine propensity to acquire wounds, hoof injuries and abscesses and tetanus becomes a significant risk.

Tetanus is a disease caused by the bacterium Clostridium tetani which is a common natural inhabitant of the intestinal tract of animals (including humans).  The bacteria produce spores which persist in the soil.  These spores are the infective form that invade wounds and hoof injuries, releasing a potent toxin that causes the disease tetanus.  Tetanus is not transmissible between horses.

Tetanus spores thrive in anaerobic (poorly oxygenated) environments.  Hence, deep penetrating wounds where tissue and blood supply have been destroyed provide the ideal environment for spore proliferation.  Toxin produced by spores travels via nerves to the brain and spinal cord, interfering with certain neurotransmitters.  The incubation period ranges from three days to three weeks.  Affected horses will show general muscle stiffness - especially affecting the jaw (‘lockjaw') spreading to the muscles of the neck, trunk and limbs.  As the disease progresses the horse experiences a lot of pain and becomes very distressed, will sweat and salivate and have difficulty chewing, swallowing and moving.  Death occurs when paralysis of the respiratory muscles prevents breathing.

Most horses that contract tetanus will die.  Early, aggressive treatment will save some.  Early diagnosis and treatment is critical to success.  Tetanus can look similar to conditions such as colic, laminitis and tying-up in the early stages of the disease. 

The disease tetanus is rare nowadays, largely due to vaccination and improved medical management of wounds.  The reduction in cases, however, is not due to a reduction in the number of environmental bacteria and every unvaccinated horse is still at risk.

Tetanus toxoid vaccine is used in routine vaccination programmes.  It contains an inactivated form of the tetanus toxin which stimulates the body to produce long-term immunity. 

If your horse is unvaccinated and receives an injury or infection, your vet will administer tetanus antitoxin.  Tetanus antitoxin contains pre-formed antibodies that immediately begin to neutralise any tetanus toxin present in the horse's body.  Antitoxin only lasts for about three weeks.

It is always better if a horse is fully vaccinated with tetanus toxoid prior to injury than to administer an antitoxin at the time.  Tetanus toxoid vaccination provides excellent
long-term immunity - it is one of the most effective equine vaccines available.  The disease tetanus progresses very quickly and by the time an injury is detected and antitoxin administered, it may be too late.  Most importantly, in many cases of tetanus no known injury has occurred.

Tetanus is a rare but devastating disease.  Horses are the most vulnerable species and as excellent vaccines are available, every horse should be vaccinated.

This photo is of a seven year-old show jumper with tetanus.  The owners called the veterinarian because the horse seemed to be showing signs of mild colic.  She had competed the day before and appeared normal.  The mare was not vaccinated against tetanus and had no known recent wounds.  The veterinarian diagnosed tetanus but despite intensive treatment the mare was euthanased 4 days later when her condition became so bad she could not stand.

If your horse is due for a tetanus vaccination, please contact Totally Vets.