Horses and humans are the most likely candidates to develop tetanus, a condition caused by contact with Clostridium tetani. This bacteria is commonly found in the soil in pastures, on metal or wood or virtually any dirty surface in a stable, trailer or barn that is not regularly disinfected and cleaned. The bacteria can enter the horse's body through any open injury, but cuts or burns are the most common form of entry to the body. Large or small puncture wounds are a source of entry to the body and these are most problematic as the bacteria are able to gain deep access to the body very quickly.
In order for the bacteria to live it must be kept in an anaerobic state, or away from oxygen. The soil or dirt on a surface is ideal, especially if the area is moist and dark. A common problem in horses are injuries to the foot, especially punctures with nails or sharp wire that may be in the soil, allowing the sharp object to enter into the wound along with some of the soil and the attached bacteria.
Once the Clostridium tetani is safely in the body away from oxygen, it immediately begins to reproduce. This in turn generates a toxin that affects the central nervous system by preventing muscles from relaxing after they are contracted. In horses tetanus is often known as lockjaw since the horse cannot relax the lower jaw to be able to eat. Muscle spasms, inability to move and hypersensitivity to light, sound and movement that trigger body muscle spasms are easily noted in the horse. Recovery from tetanus for horses is very poor with about 3/4 of all horses that develop tetanus dying from the disease every year.
Tetanus can be prevented in horses through a routine vaccination as well as immediate treatment of any wounds. Cleaning up stables and pastures and removing old nails, fences, wire and other sharp objects is easy and simple, often preventing many different injuries as well as decreasing the potential for tetanus. Routine cleaning and disinfecting of stables, stalls and equipment as well as removing any old or soiled bedding from stalls in a timely and daily fashion is essential in limiting the areas where anaerobic bacteria can live. Well ventilated stalls and air movement in barns is also critical in controlling the bacteria.
If your vaccinated horse has been injured, the vet may decide to provide a booster of the tetanus toxiod vaccine to increase the body's immunity. Even previously unvaccinated horses can be given the emergency vaccination, although it may not be as effective as in a horse with regular yearly vaccinations. Pregnant mares should be vaccinated for tetanus to provide their foals with protection from the bacteria until they can be vaccinated themselves.