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Vaccines: A Good Investment for a Healthy Horse

Hagyard Equine Medical Institute's Dr. Ernie Martinez talks you through core vaccines and risk-based vaccines

by Margaret Buranen | Sep 5, 2018, 3:08 PM EST

Whether your horse or pony travels to compete or is strictly a stay-at-home companion animal, you’ll need to talk to

It's important to discuss your horse or pony's vaccination plan with your veterinarian.
Photo: vchalup/Adobestock

your veterinarian about an annual plan and schedule for vaccinations—a key to horse health. When you do, be prepared to discuss both core vaccines (considered essential for the majority of horses) and risk-based vaccines (which may or may not be essential given your horse’s location and other potential factors).

The so-called “core vaccines” form the core of good health for virtually every horse. These vaccines protect horses from five terrible diseases: West Nile virus (WNV), Eastern and Western equine encephalomyelitis (EEE and WEE), rabies, and tetanus.

If a horse contracts one of these diseases, “treatment and recovery can be very difficult. The course of treatment is expensive and the horse may not fully recover, and rabies is a zoonotic disease and could be spread to humans,” explained Dr. Ernie Martinez of the Hagyard Equine Medical Institute in Lexington, Kentucky.

Before Vaccinating

If your horse or pony is taking steroids or some other anti-inflammatory drug, ask your veterinarian about stopping the drug a day or two before the horse will be vaccinated. This ensures that the horse develops the full level of immunity the vaccine delivers.

It’s always best to consult your veterinarian about what vaccines your particular horse or pony needs and when those vaccines and boosters should be scheduled. Martinez stressed that vets and horse owners are partners in keeping horses healthy and that owners should ask their vets to administer vaccinations. The vet has the opportunity to examine your horse prior to vaccinating him, and the vet’s vaccines are always properly stored. (Vaccines will lose their efficacy if they are not kept constantly at the correct temperature.) If your horse has an illness and is diagnosed with the disease and requires treatment after receiving a vaccination, the vaccine’s manufacturer may cover the costs of diagnosis and treatment, but only if the vaccine was administered by a veterinarian.

Before the vet arrives, the horse’s coat needs to be cleaned. The owner (or barn manager) should have records of past vaccinations available and keep records up to date.

The Core Vaccines

The core vaccines—West Nile, Eastern and Western equine encephalomyelitis, rabies, and tetanus—are recommended annually for every horse. As the American Veterinary Medical Association describes it, these vaccines protect from diseases that are endemic to a region, have potential public health significance, are required by law, are virulent/highly infectious, and/or pose a risk of severe disease.

“Core vaccines have clearly demonstrated efficacy and safety, and thus exhibit a high enough level of patient benefit and low enough level of risk to justify their use in the majority of patients,” according to the AVMA.

“These vaccines have a great track record. They work together well. They’re very efficacious,” said Martinez.

The rabies vaccine is given by itself. It can—but doesn’t have to be—given at the same time the combined vaccine for the other four diseases is administered.

The initial series of shots for each of the five diseases varies in number. When there is documentation that the horse has had all shots in each initial series, he needs only two annual booster shots. The two injections (one for rabies and one for the combined four other core vaccines) are commonly given on opposite sides of the neck .

“Timing is important,” cautions Martinez. “They should be given by the end of April at the latest.”

Giving the annual booster vaccines in spring is essential, because WNV, EEE, and WEE are transmitted by mosquitoes. Spring inoculation gives the horse’s immune system time to develop full protection before mosquito season starts.

Martinez recommends that the horse’s owner schedule the core vaccines as part of the spring wellness exam. That saves the expense of a second vet visit.

Horses who travel where mosquitoes are active during the winter can have a second booster shot later, but Martinez says that “isn’t necessarily recommended. The immunity lasts for 12 months. It would be more for the owner’s peace of mind.”

Pregnant mares should receive their core vaccine boosters in their 10th month of pregnancy. When a mare’s foal is born a month later, the mare’s immunity is transferred through colostrum, which should protect the foal until time for his or her first shots at four months of age.

For the older horse, Martinez says that the core vaccines “may be even more important. Their immune system doesn’t mount as strong a response, so the antibody levels produced may be lower. A lapse in these vaccinations puts the horse more at risk.”

The American Association of Equine Practitioners has more information on core vaccines here.

Risk-Based Vaccines

Risk-based vaccinations might or might not be appropriate for a particular horse or pony, depending on a number of factors, including the animal’s geographic location, level of contact with outside horses, travel schedule, and/or competition requirements. Under its rule GR845 (the Equine Vaccination Rule), the United States Equestrian Federation requires that horses and ponies competing at USEF-licensed competitions be accompanied by documentation confirming they’ve had equine influenza virus and equine herpesvirus (rhinopneumonitis) vaccinations within six months prior to entering the stables.

Vaccines for equine influenza and herpesvirus are “almost considered to be core vaccines,” Martinez said, particularly for horses that have the stress of traveling. A horse receives two annual boosters for each disease. Martinez notes that “the intranasal flu vaccine is very quick-acting.”

It’s important to ask your vet to assess your horse’s risk for contracting other diseases—like anthrax, botulism, equine viral arteritis, leptospirosis, Potomac horse fever, rotaviral diarrhea, and/or strangles—and the need for vaccinating against them. Such risks include traveling where disease outbreaks have happened or being around unknown horses at shows or at the horse’s home farm.

For anthrax, most horses are “at low risk,” Martinez said. But the vaccine can be indicated for horses pastured where anthrax is endemic, according to the American Association of Equine Practitioners.

Martinez said the vaccination for botulism is “recommended for broodmares and young foals. An adult horse may be at risk of botulism if he eats hay from round bales. These bales may have moisture and mildew [that allow botulism to develop].”

Martinez also noted that foals are the most at risk for equine rotavirus. The mare needs a three-shot series prior to foaling to boost the colostral antibody levels and pass on protection to the foal. For equine viral arteritis, Martinez said, “I wouldn’t worry about it unless the horse is involved in breeding.”

Horses may need the leptospirosis vaccine only if they are in an area where an outbreak of uveitis has occurred or where leptospirosis has been implicated in equine abortion or acute liver failure.

Horses are most at risk for Potomac horse fever in the eastern U.S. or if they routinely graze near freshwater creeks or rivers or in irrigated pastures. But Martinez said that there are many types of PHF and cautioned that the vaccine “is not always effective, as it only provides protection for one serotype.”

Martinez advised against vaccinating for strangles “unless the horse is at risk going where the disease is, because the products [vaccines] carry some risk, so discuss your needs with your vet.” If the horse already has been exposed to strangles, do not vaccinate; vaccinating during an outbreak can cause the horse potentially to develop a different disease, called purpura hemorrhagica, or bastard strangles.

“Good barn husbandry—keeping pitchforks, water buckets [and other tools] separate and doing a nasal wash screening on new arrivals, because they may be carriers—is important in preventing strangles. Biosecurity and isolation are the key,” he added.

The American Association of Equine Practitioners has more information on risk-based vaccinations here.

To Work or not to Work?

Martinez suggested that after a horse is vaccinated, his owner should “plan on [giving the horse] a day or two off. Perhaps have the vet give the shots before a weekend off.”

Horse owners sometimes worry about reactions to vaccines, but “some reaction is good,” said Martinez. “It shows that the vaccine is working.”

Soreness at the injection site varies with horses. Martinez recommended that owners “refrain from giving the horse anti-inflammatory medicine, because it will suppress the immune response and protection provided by the vaccine. Apply a warm compress or hot towel to the area instead.”

He added that if the lump at the injection site feels hot, the owner should let the vet know. Other reasons to call the vet include a lump that increases in size over two or three days or a horse not wanting to move his head in that direction.


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