Husbandry 13 of 13

What Vaccinations Should I Give My Horse?

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Before I can answer this question I must have information about you and your horse.

How old is your horse?

How healthy is your horse?

What diseases are present in your area?

Where and how is your horse stabled?

What activities do you and your horse participate in?

How fearful are you that your horse will get sick or die if you do not vaccinate?

Are you willing to change your management, if necessary, to prevent disease and support your horse’s immune system?

Once you answer these questions, you can work with your veterinarian to create a vaccination program that works for you and your horse. (Hopefully your veterinarian will be educated in or open to your holistic approach.) In addition to his professional input, it is also important for you to educate yourself about the common equine diseases so you can take an active and empowered role in the final decision. Here’s a quick-start guide to the more common equine diseases and their vaccines to help you get started.


I recommend vaccinating healthy horses for this disease as it can be fatal. Equine encephalitis comes in three forms; Eastern, Western and Venezuelan. All three are combined with tetanus toxoid in one vaccine. This is commonly referred to as a VEW-T or 4-way vaccine. Equine encephalitis is a viral disease transmitted to the horse by mosquitoes which pick up the virus from an intermediate hosts, such as birds, small rodents and reptiles. This means your horse does not get this infection from or give it other horses, so even a backyard horse that never travels is at risk. To my knowledge, no research has been done to determine length of immunity, but vaccine manufacturers suggest annual vaccination. Until further information is available, I would suggest initial vaccination at 5 and 6 months of age followed by a booster every 3 years. If an outbreak is occurring, the booster can be given sooner. I would not vaccinate any horse over 15 years of age unless there is an outbreak.

West Nile Encephalitis

Because of the current levels of alarm about West Nile, this vaccine cannot be ignored. However, we have to give careful consideration to the effects and effectiveness of this vaccine before giving it. West Nile is not fatal in most cases. It can cause jumpiness, lack of coordination, and some neurological dysfunction. When a patient of mine contracted West Nile (verified through titers), we were able to stop the progression of symptoms within 12 hours and restore the horse to normal health within 48 hours using several homeopathic remedies. I recommend that this vaccine be given once a year at most, and never to horses who are not in good health. The West Nile vaccine is currently available as a single injection from Merial or in combination with Eastern and Western encephalitis from Fort Dodge. Even though it means giving separate injections, I prefer the Merial vaccine—and hopefully Merial will soon make it available in a combination vaccine. I am not as concerned about giving combination Section Two: Husbandry and Basic Maintenance56 vaccines for several forms of encephalitis at once as I am about giving vaccines for several different diseases at once because the immune response is similar for all forms of encephalitis.


This disease can also cause death if it is not treated early and aggressively. Tetanus is caused by the bacteria, clostridium teteni, which generally infects the horse through contamination of a wound. Vaccine manufacturers recommend annual vaccination, but horses have been known to have protection for up to 10 years from their last vaccination. I would suggest the same schedule as encephalitis with a booster given if horse sustains an injury and has not been vaccinated within the last year.

Tetanus antitoxin

This is not a vaccine, but an antitoxin against the tetanus neurotoxin. It should only be given along with tetanus toxoid when the vaccination history is not known and a horse is injured, foaling, going into surgery, or having invasive dental work.


Horses can get rabies and it is fatal. To my knowledge there are no documented cases of a horse transmitting rabies to a person. To contract rabies, the horse must be bitten by a rabid animal. Wild animals such as skunks, fox, raccoons or bats are the usual sources of infection. Vaccine manufacturers recommend annual vaccination for horses, although the same vaccine is known to provide protection to dogs and cats for at least three years. There have been cases of rabies in vaccinated horses. I do not routinely advise vaccinating for this disease, but if you are concerned and choose to vaccinate, the manufacturer’s directions should be followed.

Influenza (Flu)

This is a respiratory disease caused by a virus. Symptoms include coughing, fever, loss of appetite and muscle soreness. It is rarely fatal. Uncomplicated cases recover in 1 to 3 weeks. It is acquired from other infected horses. The best treatment is rest and TLC. Immunity from vaccination is of very short duration, often less than 2 months. It is my opinion that vaccination causes more harm than good, and horses will become less susceptible as they mature. A healthy immune system is the best defense. In a study with racehorses, there was no difference in infection rates in vaccinated verses unvaccinated controls when the horses continued to work. In the same study, vaccinated horses that were taken out of hard training during the outbreak had lower infection rates. Unfortunately, this study did not include unvaccinated horses that were rested. I suspect they would have done just as well.

If you choose to give the influenza vaccine, give the intranasal version, which gives year-long immunity rather than just two-month immunity.

Rhinopneumonitis (Rhino)

This viral disease can take several forms. It is an equine herpes virus (there are two types, labeled “1” and “4”) and causes mild respiratory infection, primarily in young horses. Infection is acquired from other infected horses. Like influenza, the immunity the horse develops from vaccination can last less than two months, and horses can become latent carriers (with the virus present in the body but not active) of the equine herpes 1 virus. This means the horse stays infected but does not show symptoms or infect other horses unless stressed. Once stressed, however, the horse may or may not show symptoms, but can be a source of infection for other horses. Equine herpes 1 can also cause abortion in pregnant mares. When horses are shipped and congregated together there is more stress on latent carriers. These horses may then become viremic (meaning the virus has become active in the body) and cause abortions in the herd. For this reason, most brood mare farms require that mares be vaccinated for Rhino at five, seven, and nine months of pregnancy. Even this procedure does not always prevent abortion, and yet some mares will not abort even if they become sick.

Although I prefer to take my chances rather than give these vaccines, you may not have an option if you ship your mare for breeding. If you do not ship your mare, you can use good management to control exposure to the herpes virus. Keep pregnant mares separated from young stock and isolate all horses who have been brought in from other locations for 10 to 14 days before introducing them to the herd.

On rare occasions equine herpes 1 can cause neurological symptoms ranging from mild hind limb incoordination to quadriplegia. I have never seen this from actual infection, but I have often seen pain and persistent hypersensitivity in horses following vaccination. This usually appears about two weeks after the vaccination, and I do not know if the vaccine causes these symptoms directly or perhaps stresses the horse enough to cause a flare up of a latent infection. Despite all the varied disease states this virus can cause, it is rarely fatal with the exception of abortions. I believe that management is the most effective control measure, and that the vaccination may cause more harm than good. Vaccinating for this disease will not provide guaranteed protection. Ohio State University recently had a severe outbreak of the neurological form of herpes in a group of horses who had been routinely vaccinated.

Streptococcus Equi (Strangles)

This is a contagious bacterial infection of the upper respiratory tract that occurs primarily in young horses. It is characterized by inflammation in the nasal passages and throat, a nasal discharge, and abscesses in the regional lymph nodes. It is rarely fatal, although complicated cases do occur. Strangles is usually contracted through contact with infected horses, and this bacteria can live in the environment and become concentrated where large numbers of horses congregate. This strain of strep bacteria can also be transmitted by contamination of inanimate objects such as water or feed buckets. Infected horses may shed this bacteria for several months, which can then infect other horses. Unfortunately, there is no good vaccine for this illness, and I do not recommend vaccination with the current vaccines on the market.

Equine Monocytic Ehrlichiosis (Potomac Horse Fever)

This is a blood-borne disease caused by ehrlichia risticii. Clinical symptoms associated with this disease can include severe diarrhea, fever, anemia, leukopenia (low white blood cell count), edema (swelling) of the limbs and lower portions of the body, abortion, colic, and laminitis. Horses can die from this disease, but most recover following appropriate treatment. A study done at Cornell University in 1995 suggested the vaccine for Potomac Horse Fever did not lower rates of infection or severity of disease. I do not recommend vaccination for this disease.


Planning a vaccination program is an important part of horse care. Antibody titers can be measured by taking blood samples and this may help determine your horse’s current immune status for diseases such as encephalitis, influenza, rhinopneumonitis, tetanus, and rabies. After careful consideration of the seven questions at the beginning of this chapter and discussion with your veterinarian, you should be able to determine what is best for you and your horse.

About the Author

Madalyn Ward, DVM, owns Bear Creek Veterinary Clinic in Austin, Texas. She is certified in Veterinary Homeopathy and Equine Osteopathy.

Memberships include American Veterinary Medical Association, American Association of Equine Practitioners, American Holistic Veterinary Medical Association, Texas Veterinary Medical Association and the Academy of Veterinary Homeopathy.

She has authored several books and publishes at her blog.

Madalyn Ward DVM