Keeping your equine partner “as healthy as a horse” takes a little strategy and fine-tuning. This is even more important when you are responsible for multiple horses on the same property, and especially when some of those horses are owned by others. Several times each year you are faced with deciding which vaccines to use and when. It is your responsibility to ensure you understand the facts behind vaccinations, and that you enforce vaccination policies at your facility.

Rumors and inaccurate information seem to circulate each year, which confounds facts of what to give and how often. Work with your veterinary partner to ensure the horses in your care are properly vaccinated. This is doubly important when you are managing horses for other people, when outside people are exposed to your horses and when your horses are exposed to outside horses.

Cost Benefit of Vaccines

Luckily, there are vaccines available for many viral and bacterial diseases of horses. Some diseases, like encephalomyelitis, West Nile virus and tetanus, have potentially fatal consequences. Rabies is not only fatal, but also a huge public health concern as it is transmissible to humans. Protection against these specific diseases is considered essential. All horses should receive each of these core vaccines as an annual immunization: Eastern and Western encephalitis, West Nile virus, tetanus, and rabies.

Respiratory viruses, such as influenza, rhinopneumonitis and rhinovirus--as well as respiratory bacterial diseases such as strangles--may not necessarily be fatal, but they impact performance and cause lost time in training and competition as well as potentially long-lasting respiratory effects. For horses traveling out and about and those in active athletic or breeding ventures, respiratory viral vaccines are highly recommended--along with good biosecurity measures--to protect resident horses on the farm.

Vaccines have also been developed for specific high-risk situations and are administered on a special needs basis for diseases such as anthrax, equine viral arteritis, botulism, Potomac Horse fever, rotavirus and against snake bite.

Most equine vaccines are relatively inexpensive, especially when compared to the costs incurred if a horse should contract a disease.

Vaccination Strategy

Vaccines contain protein components of specific viruses or bacteria, but don’t contain the entire organism that creates disease. It is important that horses are immunized with a primary series early in life, then given boosters per the manufacturer’s recommendations. For a horse that has never received vaccines before, the first series of shots simply “primes” the horse’s immune system by telling the body to recognize specific proteins contained in the vaccine. Then the immune cells gear up to manufacture antibodies to counter those foreign proteins.

It is the second (or in some cases the third) in the series of primary injections that prompts cellular machinery into action to produce sufficient and protective levels of antibodies. Usually, you shouldn’t expect a horse to be covered against a specific disease until about two weeks after the second booster has been given.

Once the primary series is on board, your horse will need a booster 1–2 times per year to minimize the chance of developing an infection. The frequency depends on the disease type, geographical and seasonal factors, relative risk of exposure and the duration of protective coverage incurred by each vaccine. Horses that have received regular boosters all their lives are able to generate the best protective response within a couple weeks following a booster. The best strategy is for your horse to receive a booster vaccine 2-4 weeks prior to intended travel or competition. This also gives a horse time to get over any adverse vaccine-related reactions should they occur.

Why Get Your Vet Involved?

There are some particular features about vaccines that are important to recognize to ensure proper use. Vaccines must be kept under consistent refrigeration at all times to maintain their efficacy. Buying vaccines from a reputable source implies that they are kept appropriately under refrigeration and have not lost their potency. Warehouse or wholesale outlet companies, feed stores, or veterinary bulk supply outlets won’t necessarily guarantee proper handling of these products. While you may feel like you are getting a financial bargain by purchasing from such sources, your well-meant intentions could backfire--you can’t be assured that your horse will receive adequate immune coverage if you vaccinate with a poorly maintained product. There is rarely any visible evidence that a vaccine has lost its efficacy and so there is no real way to know what you’re getting.

It is best to have your veterinarian involved with your vaccination program so you can be assured that your horse is properly immunized. Having your veterinarian vaccinate your horse ensures that:

The vaccine is sourced from a reputable outlet.
The vaccine has been handled properly and kept at proper temperatures during the multiple transfers from manufacturer to distributor to the veterinarian’s office to your horse.
The vaccine is not outdated.
The choice of vaccines is the most appropriate for your unique geographic location and competition pursuits.

Safe techniques used by your vet for administering vaccines incur the least risk to your horse and protect you from being injured by a horse that objects to a needle. Even with excellent injection technique and proper handling of vaccines, transient side effects-- muscle soreness, fever, malaise or an uncommon post-injection abscess--can occur. Such transient adverse reactions are usually a consequence of the horse’s immune response to a particular antigen (protein) or may be caused by reaction to the adjuvant (carrier agent) in individual vaccines; some vaccine products are more reactive than others.

Adverse post-vaccination signs usually resolve within 48-72 hours. When the purest vaccine products available are used, fewer than 2% of horses even notice that they have received a shot. Based on the sheer numbers of horses your vet immunizes each year, he or she has knowledge of which manufacturers produce vaccines with the least likelihood of adverse reactions.

If your horse ever develops an adverse reaction following any immunizations, let your veterinarian know so he/she can put it in that horse’s records. For sensitive individuals, administration of an anti-inflammatory (NSAID) medication at the time of immunization is effective in warding off possible side effects. In some cases, it works best to separate administration of vaccines and give them at different times rather than immunizing with multiple vaccine products all at once.

There is another important point to consider for why it is important to have your vet involved with your immunization program--if your horse is insured and you administer any medications, including vaccines, that induce a health problem or a life-threatening or fatal anaphylactic reaction, the insurance company might not honor your insurance claim.

Take-Home Message

Discuss the appropriate vaccination program with your vet and set up an immunization frequency that works for your particular situation. Prevention through immunization is a far better cost-saving strategy than not vaccinating, and it confers excellent health advantages for the horse.

Nancy Loving, DVM