A few weeks ago, I told you about 18-year-old Dorado's spring check-up (more technically called a wellness exam). But today, I want to focus on one specific part of that check-up: vaccines.

Vaccines are important to help protect horses against potentially deadly diseases, which is why Dorado receives vaccines in both the spring and fall.

Photo: Erica Larson

Vaccines are an important part of every horse's preventive care program, and the American Association of Equine Practitioners (AAEP) divides these inoculations into two groups: core and risk-based.

The AAEP's core vaccines include Eastern/Western equine encephalomyelitis (EEE/WEE), rabies, tetanus, and West Nile virus (WNV). These vaccines are considered core because they're designed to protect against a common disease that all horses are at risk of developing (regardless of how frequently or infrequently they leave their home farms) and if the disease is often or always fatal if contracted. The AAEP recommends all horses receive all the core vaccines at least once per year, and possibly more frequently (depending on the horse's geographic location).

The AAEP classifies anthrax, botulism, equine herpesvirus-1 (EHV-1, or rhinopneumonitis), equine viral arteritis, influenza, Potomac horse fever, rotavirus, snake bite, and strangles as risk-based. Not all horses require all—or any—risk-based vaccines; these inoculations are chosen by—or in very close consultation with—a veterinarian and administered based on the horse's situation and lifestyle.

At last week's Ask the Vet Live on spring wellness exams and vaccines, Drs. Dale Brown (DVM) and Rob Keene (DVM) shared lots of important information on vaccinating horses of all age, but had some especially great points on vaccinating older horses. If you weren't able to tune in, I'd highly recommend you take a listen.

I always enjoy checking out the questions for these events as they come in, partly because some owners have queries about things I'd never considered myself.

On interesting question from last week's event dealt with vaccinating older horses against rabies, which is an AAEP core vaccine. A New Jersey owner had heard that rabies vaccines could kill older animals and was concerned about vaccinating her 23-year-old Quarter Horse.

"That's a great question," Dr. Keene said, "but in New Jersey I would be more concerned about rabies killing my horse than the rabies vaccine." He pointed out that rabies is bad news for horses: There's no cure, it's difficult to keep away from in some parts of the country, and there's no way to diagnose in a horse that might have it without sending their head to a laboratory for brain tissue evaluation. But, the rabies vaccine is highly effective in protecting horses against the disease.

"Any time you have a disease that's fatal and difficult to diagnose, that's a good one to think about vaccinating against," he relayed.

My family and I have always vaccinated our horses—regardless of their ages—against rabies because we've always lived in areas in which rabies occurs in wild animals, and none of our older horses have ever exhibited any kind of adverse reaction. And, taking Dr. Keene's points into account, it's one I think I'll continue vaccinating Dorado for.

Another interesting older horse owner asked about vaccinating her 20-year-old Oldenburg, who has PPID, because a group of show horses recently moved to her barn, and she wanted to ensure her Cushingoid horse received protection from the proper immunizations.

"Cushing's does have some effect on horses' immune systems," Dr. Brown explained. "But there's a decent amount of data and studies that have been done … that show that these horses do still mount an appropriate immune response, and it doesn't generally affect their antibody response to the vaccine. So, they're protected when you do vaccinate them."

Dr. Brown said an older horse in this situation will likely have an elevated risk of disease, since he or she resides with horses that travel regularly. So he recommended that owners and veterinarians start with the core vaccines, and then consider adding influenza and rhinopneumonitis—both diseases show horses could encounter and bring back to the farm.

Since Dorado is that old horse who continues to travel and commingle with other horses, as do several of his barn mates, he receives both flu and rhino each spring in addition to his core vaccines. We've been very lucky so far and haven't faced actual disease (knock on wood).

Another owner asked a great question about whether there are special protocols for vaccinating insulin-resistant horses. Both veterinarians concurred that the protocol should be similar to vaccinating other horses with some immune system issues.

And finally, Dr. Keene shared some insight on the future of vaccinating senior horses: "As horses get older, we're able to do a better job creating disease when we challenge them (in research settings)." So, in the future and once more data comes in, he said, we might end up adjusting the protocol to keep senior horses as appropriately vaccinated.

Make sure your senior horse is getting the best care with the latest horse health information from TheHorse.com’s FREE Senior Horse monthly e-newsletter!

The spring wellness exam and vaccinations visit is a perfect time to discuss concerns or questions about your individual horse's vaccine protocol with your veterinarian. Even though some of our readers had their questions addressed by our panelists last week, you can have all your questions and concerns about vaccines, your horse's health, and anything else addressed when your veterinarian visits. It's just an added perk that I try to take full advantage of each spring and fall.

What vaccinations do your senior horses receive? Do you have any questions on vaccines you're planning to ask your veterinarian this year?