Vaccines are a vital part of maintaining equine health.
Photo: Anne M. Eberhardt/The Horse
If you own a horse, one of the most important things you can do to maintain health is have your animal vaccinated. Everyone seems to have a strategy or recommendation, but the real question is: What is right for your horse? That depends on many factors including location, exposure to other horses, and general risk factors. Let's explore the options.
When evaluating vaccines and establishing a protocol, remember that each horse is an individual and that no one perfect protocol exists. It is generally not necessary to implement the same protocol in every horse just because they are in the same barn. Here are the main points to consider when establishing a vaccine protocol:
- Risk factors associated with the particular horse (including his housing situation, exposure to other horses, environment, age, and geographic location);
- The potential impact of the disease being targeted, including mortality/morbidity rate and risk of spread to other animals and species (including humans);
- Possible negative side effects of vaccine; and
- Cost implications to the owner.
Some basic considerations that we always need to remember include:
- No vaccine is 100% effective in preventing disease. Rather, vaccines are designed or intended to reduce morbidity or clinical signs of disease.
- No vaccines is 100% risk-free.
- Vaccines are not generally protective until 10 days or more following administration.
- Most vaccines require an initial booster series to build an antibody titer and establish protection.
- Many vaccines come combined with many antigens.
The core, as defined by the American Association of Equine Practitioners (AAEP), include:
- Eastern/ Western encephalomyelitis
- West Nile virus
The risk based vaccines, according to the AAEP, include:
- Rhinopneumonitis (equine herpesvirus, or EHV)
- Potomac horse fever
- Equine viral arteritis
The vast majority of horses should receive the core vaccines. Questions arise when it comes to determining if other vaccines are necessary. Risk factors include exposure to other horses such as at boarding facilities or competitions, frequent traveling, or issues involved with breeding. Also take the animal's age into consideration when developing a vaccine protocol.
How are vaccines administered and how often?
In most instances, vaccines are administered by intramuscular injection—usually in the neck, pectoral, or thigh muscles—and some vaccines can be administered intranasally (into the nose). In unvaccinated adult horses, it is generally recommended that they start their vaccination programs by receiving a series of injections, spaced apart by four to six weeks before annual vaccination beginning the following year. In foals, vaccines are generally started around four to six months of age and given as a series of three injections spaced about four weeks apart. Most of the core vaccines, once initiated, are administered on an annual basis. It's advisable to develop a vaccination schedule based on your horse's individual needs with the help of your veterinarians. He or she will be able to formulate a program to best protect your horse from diseases he's at risk for.
What are the side effects to the vaccines?
No vaccines are completely safe nor void of any risk. That said, most vaccines are administered without any problems. Some common side effects include general malaise, body aches, a slight fever 24 to 48 hours after administration, sore necks, and swelling at injection sites. In most cases, the signs resolve within a couple of days. More serious or adverse reactions have been noted included anaphylactic reactions (some life threatening), localized infection, scar tissue deposition, and generalized hypersensitivities.
Your veterinarian might prescribe a non-steroidal anti-inflammatory medication to be administered to help alleviate some clinical signs associated with vaccine administration.
Why do some horses respond differently to the vaccines?
To answer this, we first have to determine what a favorable response to a vaccine is. Ideally, it would be one void of any side effect and one that establishes a protective antibody titer. In an ideal world, we would perform antibody titers to determine who is and who is not responding well to the vaccines, but this is costly.
Remember that the purpose of a vaccine is to stimulate an immune response to a specific antigen. If a horse is sick or not feeling well, then not only would it be possible that their immune system might not respond appropriately. It is generally not a good idea to vaccinate a sick animal, and we are often better let them recover and then vaccinate when it is more appropriate. Other reasons that a horse might not respond appropriately include concurrent diseases impacting immune responses, such as Cushing's disease. Age also plays a role in the immune response and some older horses fail to respond appropriately for this very reason.
In the end, vaccines are a vital part of maintaining equine health. This being said, they are not without risk and consideration needs to be given to make sure they are administered appropriately, at the right time and at the right intervals, taking into consideration the many risk factors involved. Be an astute horse owner: Take into consideration the many variables when working with your veterinarian to decide what your horse should be vaccinated against.—Tom Schell, DVM, Dipl. ABVP
POLL: University Equine Hospitals