A question I get asked a lot is what, if any, vaccines are necessary for horses that stay at home and don’t go anywhere. You know, for the pasture pal who lives out in the field whose idea of exercise is walking up to the barn for dinner each night. Does he really need vaccines every year?

There are several diseases with excellent, safe and proven vaccines available that are either already present on your farm, or can come to your farm and “find” your horse – in other words, your horse doesn’t have to leave home to contract these diseases.

The American Association of Equine Practitioners (AAEP) considers the vaccines for these diseases to be Core Vaccinations. The American Veterinary Medical Association (AVMA) defines Core Vaccinations as those “that protect from diseases that are endemic to a region, those with potential public health significance, required by law, virulent/highly infectious, and/or those posing a risk of severe disease. Core vaccines have clearly demonstrated efficacy and safety, and thus exhibit a high enough level of patient benefit and low enough level of risk to justify their use in the majority of patients.”

The following equine vaccines are considered to be Core Vaccines for horses by the AAEP, and why it is important to vaccinate all horses for these diseases.

Tetanus is caused by a neurotoxin released by the spore-forming bacteria, Clostridium tetani. C. tetani lives in the dirt, intestinal tract of horses, other animals and humans and in other areas of your horse’s environment. It is a very hardy and resilient bacterium, and can live in the environment for many years. The toxin enters a horse’s body through a wound, umbilicus or even the reproductive tract of a recently-foaled mare. Most commonly it is caused by deep puncture wounds to the foot or legs, and the bacterium and neurotoxin becomes trapped inside the wound. Tetanus is often deadly – treatment for tetanus is difficult, prolonged and expensive.

All horses should receive a tetanus toxoid vaccine once per year, and should also receive a booster if they sustain a wound or undergo surgery. If a horse has an unknown or overdue tetanus toxoid vaccine history, a tetanus antitoxin injection can be given to the horse at the time of injury, which provides short-acting protection against the neurotoxin. Tetanus antitoxin injections should not be used as a replacement for tetanus toxoid vaccines as they don’t provide the same kind of protection – it is important to be sure your horse is receiving the correct version if you are buying your own vaccines. Sadly, I have treated several cases of tetanus in person, and none of those horses had ever received a tetanus toxoid vaccine. I have not seen a case of tetanus in a horse that has been vaccinated appropriately.

Eastern Equine Encephalitis (EEE) and Western Equine Encephalitis (WEE) or “Sleeping Sickness” – carried by mosquitoes, this virus is endemic in several locations, particularly on the east coast of US. It causes neurologic disease in horses and is often fatal even with intensive treatment. West Nile Virus (WNV) is a virus that was new to the USA in the early 2000′s, and is also carried by mosquitoes. WNV also causes neurologic disease that resembles that of EEE and WEE. Horses that stay at home, and particularly those at pasture, are just as likely to be exposed to the mosquito-borne diseases, and maybe even moreso because they tend to spend more time outdoors. Vaccinations for EEE, WEE and WNV are available and effective when given correctly. The recommendation is to vaccinate adult horses once per year for these diseases, but some veterinarians will recommend a six month booster if you live in a particularly endemic mosquito-laden area.

Rabies is a virus carried by infected wildlife (raccoons, foxes, opossums, bats) or other animals that could enter your fields and barns and bite horses, infecting them with the virus. The virus travels slowly up the nerves to the brain, so it can be several weeks from the injury until the horse shows clinical signs. The virus makes the infected animal particularly aggressive, which is why they attack the horses whereas normally these animals would not approach a horse. Rabies is always fatal, there is no treatment.  Rabies is also zoonotic, which means humans can also contract it, and it is a public health hazard. Rabies vaccines are highly effective against preventing infection if a horse is bitten by a rabid animal. Horses should also receive a vaccine once per year for rabies.

These five diseases are all covered by readily-available vaccines. Even if you have a “closed herd” situation, where your horses are not leaving the property and are not exposed to other horses coming and going, these are the diseases that you should still be vaccinating your horses against.

Tanis MacDonald Walker, DVM graduated from the Atlantic Veterinary College on Prince Edward Island and currently practices both small animal emergency and equine medicine in Delaware. You can email her at tanis_macdonald@hotmail.com or visit her at www.drtanis.com. You can also write to her in care of InStride Edition.