Vaccinating your horse for every disease you can is costly and unnecessary. Several factors enter into the decision about which vaccinations to perform. These include:
• Severity of the disease. Is it life-threatening (like tetanus), or more of a nuisance (Rhinopneumonitis)’
• Risk of exposure.
• Effectiveness of available vaccines.
• Vaccine-associated dangers.
Severity Of Disease
When considering severity of disease, the program is built around the most dangerous ones. ”Core” vaccines are ones that address life-threatening diseases and therefore shouldn’t be skipped in most cases. Tetanus tops this list. Next are the encephalitis viruses: Eastern, Western, Venezuelan and West Nile. EEE, WEE and VEE have higher mortality rates than WNV, but even 50% mortality is unacceptable if you can prevent it. Last on the list of core vaccines is rabies, definitely fatal, but also relatively rare.
The risk of exposure comes into play for both core vaccines and others. All horses are at equal risk of tetanus. The organism is everywhere. Horses on the East Coast don’t need WEE protection, and vice versa. West Nile is in all the states now, although it’s much more active in some areas than in others.
Since timing vaccination to occur shortly before your horse’s high-risk exposure season is wise, you may choose to keep track of mosquito-surveillance data for your state (available online) to note activity in mosquitoes and birds before vaccinating. However, this does put your horse at some risk of being infected and you should discuss the timing thoroughly with your veterinarian.
Of all the potentially fatal diseases, rabies poses the lowest risk. Equine cases do occur, but they’re infrequent. The coyote strain of this disease has been eliminated in the United States as of 2007. Focus is now turning to the raccoon and skunk strains in hopes of also eliminating those from Canada and U.S. by a similar program of oral vaccine-loaded baits for wild animals.
Most rabies cases are in wild animals, and they are clustered heavily along the Eastern states. Although there are approximately 10 million horses in the United States, typically less than 10 per year are infected with rabies. For details on rabies prevalence in your state, you can contact your state’s health department.
Botulism is another disease with a high fatality rate, but it’s not included in the core vaccines because it’s not common. Sporadic botulism, usually from contamination of hay or grain with dead animals, can occur anywhere, but outbreaks in pastured horses occur in some areas. Your veterinarian is your best source of information as to the relative risk of botulism in your area.
Exposure risk is a big factor in vaccinating against the respiratory diseases. Influenza is much more severe than the Rhinopneumonitis virus.
Furthermore, an estimated minimum of 60% of horses are chronically infected with the Rhinopneumonitis virus, which has come to a truce with the immune system.
Rhinopneumonitis vaccines don’t have a very good track record for preventing respiratory disease or abortions either, but they do reduce shed virus so are a social service in a group environment.
The modified live vaccine, Rhinomune, may provide some protection against the neurological form, but this is from limited experimental data. Influenza is primarily an issue for horses on high-traffic farms or traveling extensively.
Potomac horse fever causes a serious disease, but it’s not a problem in all areas. In any case, it’s probably a moot point since the vaccine performs poorly under field conditions and most vets agree it’s not very useful.
An EPM vaccine exists, but it’s never been granted FDA approval and again is of questionable value.
Another vaccine with poor efficacy is the intramuscular Strangles vaccine, which also has a high rate of serious injection site abscesses. If you need to vaccine for Strangles, the intranasal vaccine is best. We also like the intranasal influenza vaccine.
There is risk associated with vaccines, but it’s not what some people would lead you to believe. There’s no evidence to support the idea that equine vaccines are toxic to the immune system. In fact, they pose much less of an immune-system challenge than a full-blown infection would. That said, there’s no point in challenging your horse’s immune system for no reason. It has enough to do as it is.
Common vaccine reactions include mild fever, going off feed and injection site soreness for a day or so. More severe reactions are extensive vaccination site swelling and/or abscesses, high and/or prolonged fevers, even laminitis. In rare instances, a body-wide inflammatory/allergic reaction may occur, which can be fatal if not immediately treated. Risk vs. benefit is primarily an issue for horses with severe vaccine reactions.
The first step in eliminating repeat severe reactions starts with never using that particular brand of vaccine again. Reactions to an individual vaccine’s adjuvant are just as likely, if not more likely, than reactions to the disease agent. Adjuvants, which are in a vaccine to enhance the body’s response to it, vary by manufacturer.
If that doesn’t eliminate the problem, work out a strategy with your vet. Pretreatment with anti-inflammatories can block the reaction in some horses. This will vary by the individual situation but generally includes protecting the horse from exposure to disease as much as possible and drastically reducing vaccinations, e.g. giving tetanus only if the horse receives a wound.
Once you have determined the vaccines your horse really needs to have, the next question that arises is usually should you do your own vaccinations’ It’s no secret that many owners do, and it’s legal (except for rabies), with vaccines widely available in farm stores and through the Internet. There are pros and cons.
A serious con is the small, but real, risk of a life-threatening reaction. These occur within minutes of giving the vaccine and must treated immediately with prescription drugs like epinephrine and corticosteroids. Horses that panic can become violent.
If you’re giving your own vaccines, consider networking with other owners doing the same, as this can save a good bit of money if you buy multi-dose vials or multi packs of single doses of vaccine.
Compare prices from both Internet sources (factor in the overnight shipping) and local farm stores. Needles and syringes can be purchased at most farm-supply stores in most states. It’s fine to use the same syringe to hold multiple doses of vaccine for different horses (as long as it can be read accurately), but you should never reuse needles between horses.
We’re not strong advocates of giving your own vaccines. We believe the way to cut vaccine cost is to decide which injections your horse truly needs. Weigh your horse’s chance of exposure, the severity of the disease if he gets it, and the proven effectiveness of the vaccine itself.
Take into consideration your relationship with your vet. Many of us only see the veterinarian once a year, and annual vaccination is one way to remain an established client who will get immediate help in the event of an emergency.
If you still want to vaccinate your own horses, be up front about it with your vet. Let him or her know, and be sure make sure you know what you’re doing, especially with a severe reaction.
Article by Eleanor Kellon, VMD, our Veterinary Editor. She has extensive experience with high-performance horses. With her husband, she breeds, races and trains Standardbred harness horses in Pennsylvania. She has written countless articles and several books, including ”The Older Horse” and ”Horse Journal Guide to Equine Supplements and Nutraceuticals.”