Farming Magazine - February, 2013


Working Horses: Ten-Dollar Tetanus

By Vicki Schmidt

Dirt: It grows our crops and hay and healthy grasses for our horses, but it also harbors the bacterium Clostridium tetani, which produces tetanospasmin, a neurotoxin. Almost all mammals are susceptible to tetanospasmin, with horses and humans being the most sensitive of all. Our barn cats are highly resistant and our farm dogs relatively so. Pigeons and chickens need more than 10 times the lethal dose for a horse to be affected.

Any location where such things as manure, old trees and wire are found is an area where tetanus toxins can also be found.
Photos by Vicki Schmidt.

The tetanus bacteria is an anaerobic pathogen found in soil, dust and manure. It survives best in a moist, warm environment that lacks oxygen. This is why any puncture-type wound, such as stepping on a nail (rusty or not), may result in a tetanus infection. Tetanus is a noncommunicable disease, and one that is easily prevented by vaccination.

While found worldwide, tetanus is now rare in the U.S. About 100 cases are reported every year in humans, with approximately 30 percent of those being fatal. Nearly all cases of tetanus occur in adults who were not vaccinated as children or those who have not had a booster vaccination in the last 10 years.

When it comes to you and your horses, do not allow the rarity of the occurrence of tetanus to lull you into believing vaccination is unnecessary. Tetanus is a disease that affects the central nervous system, causing violent and very painful muscular contractions. In horses it is nearly always a savagely fatal ending if the horse is not humanely and quickly euthanized.

Most of us grew up associating tetanus with rusty nails. Rust itself does not harbor tetanus, but rusty nails are often found in decaying environments, along with wire and old, splintered wood. These items, and any others that are capable of producing a puncture wound, can transport filth deep into our horses' flesh, where tetanus toxins can be deposited and thrive.

Working horses, especially logging horses working where old dumps of rusty cans and other debris may exist, and around old homesteads and barns, are often subjected to decaying environments where tetanus toxins thrive. There are also times when your horse is at greater risk from tetanus toxins, so it is imperative that your horse be up-to-date with a tetanus vaccination. High-risk situations include:

  • When undergoing invasive dental work, such as wolf teeth extraction
  • In the case of colts, when they are gelded
  • Any type of puncture wound, especially those of the foot
  • Wounds such as foot abscesses, wire punctures and wood splinters

Most young horses receive an initial vaccination against tetanus and should receive a booster four to six weeks later, and then annually. While vets in New England comment that they rarely see tetanus, most attribute this to the fact that most owners vaccinate their horses. Dr. Janelle Tirrell of Maine Equine Associates in central Maine has only seen one case in her career, but she stresses the importance of proper vaccinations for all horses. "Tetanus lives in a horse's environment. It is everywhere," Tirrell said. "Hopefully, through education of horse owners and diligent vaccination programs, tetanus will remain a rare condition. The vaccine costs around $10 per dose and is highly protective."

Working along stone walls requires looking out for old wires and other threats to both you and your horses. Injuries, even slight cuts that seem small, can harbor deadly tetanus toxins.

Horses are more prone to tetanus than other mammals due to the fact that the tetanus bacteria live harmlessly in a horse's intestinal tract and are passed to its environment through the manure. Tetanus can lie dormant in a horse's flesh for up to six months before they show any sign of the disease.

Another positive of the tetanus vaccination is that it is a quick and relatively inexpensive vaccination to administer. The tetanus vaccine can be given separately or in combination with other vaccinations. In the Northeast, it is most commonly given in combination with eastern and western encephalitis, often seen as EWT in vaccination form.

For additional information about the recommended tetanus vaccination routine for your horse, contact your local veterinarian. Contact your local family doctor about your tetanus vaccination. If the vaccine was given to you as a child, you most likely only need a tetanus vaccination once every 10 years to stay protected. For both you and your horse, it is a worthy investment.

Vicki Schmidt is owner and manager of Troika Drafts in Hebron, Maine. The working draft horse farm features Shires for work, sport and show. Visit them online at or contact them at