The good news is that there are answers, and the more knowledge you have, the more power you have to make the right decisions for your horse.

We sat down to chat with Ann Andrews, DVM, CVA, of Park Equine Hospital in Lexington, Ky., to answer your most-asked questions.

Photo by Christiane Slawik

Q: Does my horse need vaccinations?

As modern-day horse owners, it’s easy for us to take for granted the health advantages that vaccines now offer our equines. Not too many years ago, horses died from tetanus, rabies, Eastern and Western encephalomyelitis, and other diseases.

Nowadays, horses can be protected from these diseases with vaccinations; if not completely, at least with the resulting illness being less severe. The key is developing a program alongside your veterinarian that meets the individual needs of your horse.

Q: Is there a safe and essential minimum of vaccinations required?

Like many equine veterinarians, Andrews follows the guidelines of the American Association of Equine Practitioners (AAEP), which recommends a few core vaccines for all horses.

“The AAEP is a great resource for horse owners, and not just for vaccinations, but many health issues,” she says.

There are five diseases the AAEP’s core vaccines protect against: EEE, WEE, rabies, tetanus, and West Nile virus. Photo by peopleimages.com/Adobe Stock

Here’s a brief description of the diseases core vaccines protect against, and their recommended frequency.

◆ Eastern and Western equine encephalomyelitis (EEE/WEE) are viral diseases spread by mosquitoes that cause neurological damage or death. Vaccine frequency is annual in spring prior to the rise in vector season.

◆ Rabies is a fatal neurological disease that affects all mammals; it can be transmitted by raccoons, bats, skunks and foxes. Vaccine frequency is annual.

◆ Tetanus is a bacterial disease that is often fatal; it can be contracted through wounds or punctures. Vaccine frequency is annual.

◆ West Nile virus (WNV) is a neurological disease transmitted by mosquitoes; it can be fatal, and recovered horses may have abnormalities in behavior and gait. Vaccine frequency is annual in spring prior to vector season.

“Depending on your geographic location, regional prevalence, exposure risk, stabling environment and other factors, your vet may also recommend certain additional risk-based vaccinations,” says Andrews.

Commonly recommended risk-based vaccines include:

◆ Equine herpesvirus (rhinopneumonitis/EHV): EHV-1 and EHV-4 are viral diseases that can cause abortions in broodmares, neurological issues, and respiratory illness. Horses that travel, compete, or are kept in high-density environments are particularly susceptible.

u◆Equine influenza (flu) is a highly contagious viral disease that causes respiratory illness and impacts performance. Horses involved in activities that involve contact with other horses are at highest risk.

◆ Potomac horse fever (PHF) is a disease caused by the bacteria Neorickettsia risticii and transmitted to horses drinking from water sources where parasitic worms have infected aquatic insects. Vaccination is recommended in areas where the disease is prevalent, as well as for horses traveling to or through those areas. 

◆ Strangles (Streptococcus equi) is a highly contagious bacterial infection that causes swollen lymph nodes and respiratory issues. Horses in high-risk environments (for example, where new horses arrive frequently) are most susceptible.

Flu/rhino and strangles vaccines are a good idea to add to the list for horses that travel to competitions. Photo by Janet/Adobe Stock

Other risk-based vaccines include:

◆ Anthrax

◆ Botulism

◆ Equine viral arteritis

◆ Leptospirosis

◆ Rotaviral diarrhea

◆ Snake bite

◆ Venezuelan equine encephalomyelitis (VEE)

Q: Do vaccinations differ for horses that compete or are stabled in a large boarding facility versus a small herd or retirees that never travel?

“Even for older horses and those that live in a closed environment with no interaction with outside horses, the four core vaccines are always advised,” says Andrews. These provide protection from common diseases and illnesses, especially those that are spread by mosquitoes or chance encounters with wildlife.

“For horses that travel to competitions and/or live in large barns where lots of horses come and go, I’d also recommend additional vaccines to cover their exposure, including flu/rhino at least annually and perhaps a booster every six months, and strangles,” she adds.

Q: If my horse has reactions to vaccines, what can help minimize them?

Common reactions include swelling at the injection site, lethargy, going off feed, and sometimes colic and laminitis. The best solution might seem to be spreading out vaccinations over several days or weeks to avoid bombarding the horse’s system with multiple antibodies at the same time.

“The problem with this approach is that each vaccine can cause a reaction, even if it’s minimal,” says Andrews. “Then the horse’s system has to process, and potentially react to, each vaccine spread over many days instead of one episode with multiple vaccines.”

However, there are ways to work with your vet to help minimize reactions:

◆ Vary the injection sites for each vaccine, such as different locations on the neck and hip. “This also helps identify reactions to certain vaccines if there’s swelling at the injection site,” says Andrews.

◆ Allow the horse free movement after vaccinations to help his system process the antibodies.

◆ Devise a proactive approach, such as treating with Dexamethasone or Banamine the day before the injections, the day of, and a couple days after.

◆ Another benefit of having a client/vet relationship is the ability to dig deeper to find solution (see more below).

“One client’s horse had severe reactions to vaccines,” she recalls, despite trying the ideas above. “I decided to switch the brand of vaccines, and for whatever reason, that worked for him. Now we have an established protocol that we follow every time, and it’s helping keep his side effects as minimal as possible.”

If your horse has severe reactions to vaccinations, you might consider asking your vet about checking titers—the level of antibodies in the horse’s blood that are specific to a particular pathogen.

Q: Are there any differences for vaccines based on geography, weather, et cetera?

Certain diseases or illnesses can be more prevalent in some areas of the country than others, and your vet’s vaccination recommendations will reflect that.

For example, Potomac horse fever was first discovered in Maryland near the Potomac River. It’s since been reported in numerous states (including California), and it seems to peak in summer and fall in areas with bodies of water, like lakes, creeks, rivers, and ponds.

Botulism, a potentially fatal neurologic disease, is not a regional disease per se, but it’s more commonly found in horses that eat from large round hay bales as well as fermented haylage and silage feeds. If these forage types are common in your area and consumed by your horse, your vet may recommend this vaccination. 

Botulism is more commonly a threat for horses that eat from large round bales. Photo by pimmimemom/Adobe Stock

Horses in Florida and other areas with higher mosquito populations or longer mosquito seasons may be recommended to have boosters for Eastern/Western equine encephalomyelitis and West Nile virus.

Quarantine and Biosecurity Imagine this. After years of searching, your dream horse had finally arrived. You smile as he steps off the trailer and into his stall in the big barn.  A couple days later, he’s lethargic and has stopped eating. When you go to halter him, you notice the area under his jaw was swollen. You call the vet, sure that he has an abscessed tooth. The vet arrives and peeks over the stall door. “Your horse doesn’t have an abscessed tooth. He has strangles.” Within days, every horse in the barn is sick. The following weeks of treatment, mess, stress, and expense could have been avoided with a simple quarantine and biosecurity program. “I believe every horse owner should quarantine any new horse that comes to their property,” says Andrews. “At the client barns where we have a quarantine protocol, I’ve seen numerous times how it prevented huge outbreaks of illness and confined it to one horse.” Setting up a quarantine system is simple and well worth the time. Here’s how: ◆ Use portable panels to set up a corral that’s away from the barn and pasture fence lines. ◆ Keep the new horse in this area for a minimum of two weeks, and up to three. Monitor daily for elevated temperature and other signs of illness. ◆ Avoid cross-contamination with feed and water buckets, grooming tools, et cetera, and be sure all handlers wash their hands after contact with the quarantined horse. ◆ If the quarantined horse gets sick, use biosecurity measures when treating the horse, including separate (or disposable) clothing/gowns, gloves, hats, boots, and masks. ◆ When the horse is released from quarantine, thoroughly clean the area with a 5-10 percent bleach solution and allow to dry. If you don’t already have a separate area, use portable panels to set up a corral away from other horses during the quarantine period. Use brushes and water buckets that aren’t shared with any other equines. Photo by Christiane Slawik

For more on recommended vaccines, visit the American Association of Equine Practitioners.

This Q&A about vaccines for horses appeared in the March/April 2025 issue of Horse Illustrated magazine. Click here to subscribe!

The post Horse Vaccines Q&A appeared first on Horse Illustrated Magazine.

Photo by Clix/Shawn Hamilton

Horse owners often find it challenging to keep up with the latest vaccination recommendations, and some may not grasp their importance in keeping horses healthy and strong. Your horse needs certain “core” vaccines, and may also need non-core vaccines based on his usual activities, geographic location, and other considerations.

Although you might be hesitant to get your horse poked, it’s for his protection, and vaccines are generally safe. They have been well-tested, and many have been used for decades. Vaccination should be routine, so read on for current recommendations, potential side effects, and the overall importance of having your horse vaccinated.

Core Vaccines

One of the best measures to protect your horse’s health is a vaccination program. Core vaccines are often administered in an initial series of two to three shots, and then once or twice a year after that. Skipping core vaccinations could mean sickness or even death among your equine family.

The American Association of Equine Practitioners (AAEP) has established vaccination guidelines for horses. Core vaccinations are those recommended for all horses, regardless of age, sex or region where they live. These include any vaccines required by law and those that protect animals from diseases that are highly infectious, pose a risk of severe illness, are of potential public health significance, or are endemic to a region.

Kris Hiney, Ph.D., is an assistant professor and equine extension specialist for the Oklahoma State University Department of Animal and Food Sciences. She says the five core vaccines are Eastern and Western equine encephalomyelitis, West Nile virus, tetanus and rabies.

“We consider these ‘core’ due to the risk of fatality associated with these diseases,” she says. “And the human health risk with rabies, of course.”

5 Core Vaccines

The following are recommendations for core vaccines based on the guidelines provided by the American Association of Equine Practitioners. Always work with your veterinarian to develop the ideal vaccination schedule for your horse.

◆ Eastern & Western Equine Encephalomyelitis: EEE and WEE are primarily transmitted by mosquitoes, but they’re also infrequently transmitted by ticks, other insects, or nasal secretions. While EEE has been reported throughout North and South America, WEE is more common in the western United States. Both have a high mortality rate, and vaccinations are recommended for all horses in North America.

Combo shots include multiple core vaccines with one poke, like this one for EEE, WEE and tetanus. Photo by Clix/Shawn Hamilton

◆ Rabies: Rabies is transmitted through the bite of an infected animal, typically wildlife, and is endemic in every state but Hawaii. Although the incidence of rabies in horses is low, it presents a considerable public health risk, and it’s almost always fatal among horses, making it a core annual vaccination to all equines.

◆ Tetanus: Tetanus presents a risk to all horses and is often fatal. Although it isn’t contagious, horses can develop tetanus through a Clostridium tetani infection resulting from its entrance into a wound or from environmental exposure to the toxin—which resides in the soil—if a horse eats contaminated soil or droppings. The vaccines currently available are recommended for all horses.

◆ West Nile Virus: WNV is nearly always transmitted by mosquitoes that have fed on infected birds. It’s been identified throughout the continental United States, Mexico, and most of Canada, and is the leading cause of arbovirus encephalitis in horses. However, it’s not directly contagious from horse to horse or equine to human.

Non-Core Vaccines

One or more non-core vaccines also may be recommended following a risk-benefit analysis. Recommendations of non-core vaccines vary based on region and specific horse populations
within an area.

The risks of horses contracting non-standard diseases aren’t always easy to identify, which is one of the many reasons it’s important to consult a veterinarian. Equine vets understand what’s endemic in an area and which horses may be at higher risk for certain diseases, so they can recommend the appropriate non-core vaccines to add.

“Non-core—flu/rhino, strangles, Potomac—are considered risk-based more on the lifestyle of the horse and if they are endemic,” Hiney explains.

Some non-core vaccinations that may be recommended due to risk-based assessments include:
◆ Anthrax
◆ Botulism
◆ Equine herpesvirus (also called equine rhinopneumonitis, or “rhino”)
◆ Equine influenza (aka “flu”)
◆ Equine viral arteritis
◆ Leptospirosis
◆ Potomac Horse Fever
◆ Rotavirus
◆ Snake bite
◆ Strangles
◆ Venezuelan equine encephalomyelitis

Don’t Forget Boosters

Once your horse receives the initial series of a core vaccine, he’ll still require boosters. Many vaccines require an annual booster to maintain immunity, but some diseases may require more frequent action.

“Booster frequency depends on how endemic the disease is and your horse’s level of exposure,” Hiney explains. She says there isn’t a lot of research on how long vaccines last in horses, which is why they recommend annual boosters for all, and even more frequent ones in certain circumstances. She says they have a better idea of the duration of immunity in companion animals.

“To some degree, we’re probably over-vaccinating horses for tetanus,” says Garrett Metcalf, DVM, an equine veterinarian at Pine Ridge Equine Hospital in Glenpool, Okla. “However, horses are rather sensitive to the neurotoxin produced from Clostridium tetani that leads to the clinical signs of tetanus. Infected horses can be treated and saved, but up to 75 percent of them still die. It’s better to just over-vaccinate them, which won’t hurt them.”

Boosters help maintain a good protective level of antibodies, so if you forgo boosters, your horse may no longer be protected when exposed to a disease. If you allow his annual vaccinations to lapse longer than a couple of years, your vet may recommend that the primary series be administered again before recommencing annual boosters.

Injection Site

The best injection site for vaccinations is another area where a veterinarian’s extensive knowledge plays a key role. You must consider the possibility of adverse reactions when choosing injection sites.

For example, it’s not recommended to inject vaccines into the gluteal muscles or hip region of a horse because considerable tissue damage can occur should an abscess develop. If lesions erupt, they could require a long healing time.

“The neck is the usual site, in the ‘triangle,’” says Hiney. “But if a horse has an adverse reaction and his neck is stiff and sore, he may be more reluctant to move.”

The ideal vaccination site is the “triangle” of muscle in front of the shoulder above the neck vertebrae and below the fat and nuchal ligament of the neck crest. Photo by Clix/Shawn Hamilton

Metcalf says that some people still vaccinate their own horses, and some vaccines can be purchased at feed stores. He emphasizes that it’s always better to let your vet administer vaccines, but if he has a client who insists on doing it themselves, he always shows them at least once where to give the shot.

“The ideal spot is [the triangle-shaped area] about the size of your hand right in front of the shoulder blade, in the middle of the neck,” says Metcalf. “Too low and it’s too near the cervical spine. Too high and it’s in the fat within the nuchal ligament instead of the muscle.

“When it’s in the fat, the horse won’t have an immune response,” he continues. “Horses can also get really sore when vaccinated in this spot. They can’t lower their head to eat and can’t move their neck well. Be educated.”

Having a vet administer your horse’s vaccines will ensure they are stored and administered correctly to minimize the chance of any adverse reaction. Photo by Clix/Shawn Hamilton

While administering your horse’s vaccines yourself isn’t advisable, working with your vet also has the benefit of ensuring serious side effects can be quickly identified and handled properly. If you insist on administering vaccines yourself, realize that some manufacturers will not reimburse for adverse outcomes.

“The vaccine makers want a vet to administer vaccinations,” Hiney says. “Usually, they only guarantee vaccines administered by a vet and not purchased online or through a feed store.”

Adverse Reactions

Adverse reactions are an inherent risk of vaccination. Horses commonly experience local muscle swelling and soreness at the vaccination site. Transient, self-limiting clinical signs, which last only a short time and resolve without treatment, may include fever, lethargy, and lack of appetite.

Severe reactions at injection sites may require prolonged treatment and convalescence. Allergic-type reactions, such as hives, purpura hemorrhagica colic, or anaphylaxis can also occur and are particularly dangerous. Although unlikely to occur if proper procedure is followed, the potential for severe adverse reactions is one major reason why vaccines should be administered by a veterinarian.

“Some horses will react to the adjuvant, which is the ‘extra’ part that stimulates the horses’ general immune system,” Hiney says. “If that is the case, you may want to switch brands; it can make a difference.”

Metcalf advises horse owners who are concerned about adverse reactions to research the vaccine manufacturer, because the reactions can vary. However, he says usually less than 1% of horses have a severe reaction.

Administering multiple vaccines of both multiple antigens and adjuvants simultaneously may increase a horse’s risk of a reaction. When multiple products are needed, ask if your vet recommends staggering administration by three to four weeks between shots.

“If your horse has reactions, I would not give multiple [vaccines] at once,” Hiney says. “But many manufacturers now bundle vaccines together, sort of a ‘one and done.’”

If your horse has had a reaction in the past, you may need to avoid combo vaccines and stagger his shots.

“But then you have to worry about them developing a fever and other bad responses from having too many injections,” warns Metcalf. “Most companies mix vaccines with five, six or seven types all together to keep injection sites from getting sore. There are actually fewer problems with the mix of vaccines, which we use.”

Best Vaccination Practices

It’s important to develop a comprehensive vaccination program, but a one-size-fits-all version for all horses doesn’t exist.

“Talk to your vet,” Hiney stresses. “Remember biosecurity! Even if you take a vaccinated horse to a show and have others at home, you may be dragging pathogens back with you, so always think about good biosecurity protocols—don’t just rely on vaccines alone.”

This article about horse vaccinations appeared in the March 2022 issue of Horse Illustrated magazine. Click here to subscribe!

The post Horse Vaccinations 101 appeared first on Horse Illustrated Magazine.

• The core vaccines are recommended for all horses due to the widespread and serious nature of those diseases.
• Risk-based vaccinations vary depending on the horse’s age, use, and geographic location.

In the month of October 2018, the New York State Department of Agriculture reported three confirmed cases of Eastern equine encephalitis (EEE). All three were in unvaccinated horses, ranging in age from 3 months to 8 years. Two of the three were euthanized; the third horse was still alive, but showing neurological signs, despite medical care.

On November 2, 2018, the California Department of Food and Agriculture confirmed its eleventh case of equine West Nile virus in 2018. As of November 14, 2018, the state of Kentucky had confirmed 17 cases of West Nile virus so far for the year.

Texas reported two confirmed cases of rabies in horses in 2017, and in April of 2018, a horse in the Texas Panhandle tested positive for rabies and was euthanized.

In print, these are statistics. In real life, they are individual horses with unique personalities and abilities. Some lost their lives, and each one was impacted by a disease that could likely have been prevented with routine vaccination.

Unfortunately, not all horse owners take this simple precaution.

Protecting Against Serious Disease

The American Veterinary Medical Association (AVMA) defines equine core vaccinations as those “that protect from diseases that are endemic to a region, those with potential public health significance, required by law, virulent/highly infectious, and/or those posing a risk of severe disease.”

In light of that definition, the American Association of Equine Practitioners (AAEP) notes that the following equine vaccines meet those criteria and are identified as “core” in their vaccination guidelines. The five equine core vaccines include:

• Eastern equine encephalomyelitis (EEE)
• Western equine encephalomyelitis (WEE)
• Rabies
• West Nile virus
• Tetanus

These are not diseases you want to gamble with.

WEE is fatal in 50 percent of cases, while EEE has a 90 percent fatality rate; both are transmitted by mosquitoes. West Nile virus, which is transmitted by mosquitoes that feed on infected birds, is about 33 percent fatal, but 40 percent of horses that survive the acute disease are left with permanent neurologic effects. Rabies isn’t common in horses, but it is 100 percent fatal, and puts at risk the humans who have handled the horse.

AAEP recommendations are for all horses—regardless of where they live, their age or use—to be vaccinated against these five diseases every year.

“These are endemic diseases with high mortality rates—diseases that every horse should be vaccinated for every spring, no matter how old the horse, what he does, or where he lives,” says Jacquelin Boggs, DVM, ACVIM, an internal medicine specialist and senior technical service veterinarian with Zoetis.

“These diseases also tend to be ones that are the more difficult to mitigate [in terms of] risk of exposure to the disease-carrying vectors,” says John H. Tuttle, DVM, director of equine professional services at Boehringer Ingelheim Animal Health.

Tuttle refers to the various ways these core diseases are spread, including mosquitoes, bacteria in soil, rabid animals, et cetera. You can be the most careful horse owner in the world, but you can’t guarantee your horse won’t come in contact with one of these vectors that could introduce a potentially life-threatening disease.

Risk-Based Vaccines

Beyond the five equine core vaccines, there are a variety of risk-based vaccines, meaning your horse only needs them depending on his risk of exposure to those diseases. Examples of risk-based vaccines include:

• Influenza
• Equine herpes virus (also referred to as rhinopneumonitis)
• Equine viral arteritis (EVA)
• Strangles
• Potomac horse fever (PHF)
• Rotavirus
• Botulism
• Anthrax

Your veterinarian can advise you as to which, if any, of these risk-based vaccinations your horse should receive in addition to the five core vaccines. Recommendations vary widely, depending on your horse’s age, living accommodations and travel/show routine.
It can be difficult to limit your horse’s exposure to risk-based infectious diseases, which are often related to his use. For example, if your horse frequently travels to shows or events, his exposure to other horses increases his risk of respiratory disease, such as influenza.

“Risk-based respiratory vaccinations, such as influenza and equine herpes, should be considered for horses that are regularly exposed to outside horses,” says Tuttle. “Even if a horse ‘never leaves the farm,’ there may be other horses that do (or perhaps neighboring horses that do), and they may act as a carrier of infection for the horse that is considered a ‘homebody.’”

Protecting Your Horse

Your veterinarian knows your horse and your region, and therefore is the best person to evaluate the timing of vaccines and their frequency.

Some horse owners mistakenly think that certain diseases aren’t found in their part of the country, so they neglect vaccinating for them.

“Every year there are cases of horses contracting one of the core equine diseases, and these most often occur in unvaccinated horses,” says Boggs.

Occasionally, owners will neglect to vaccinate senior and retired horses.

“A common misconception is that as a horse gets older, his need for vaccination decreases [because] he may have been ‘exposed’ to the disease before, or previous vaccinations should be sufficient,” says Tuttle.

However, this isn’t the case. As a horse ages, his immune system experiences age-associated decline, a process known as “immunosenescence.” This may lead to decreased individual immune efficiency and should be taken into consideration when developing a vaccination protocol for senior equines.

Bottom line: Older horses should continue to be vaccinated against all five core diseases.

How Vaccines Protect

The antigens contained in a vaccine are considered foreign by the horse’s immune system. In response, his body takes defensive action by producing antibodies to neutralize the antigens, building defenses against that specific disease.

This doesn’t happen overnight. Generally speaking, it takes about two weeks after vaccination for the horse’s immune system to develop a sufficient level of protection against exposure to the actual disease. In the case of young horses or horses that have never been vaccinated, these inoculations will require boosters, often four to six weeks later.

After the initial vaccination, all horses require annual booster shots to maintain protective levels of immunity. Depending on where the horse lives and his exposure, a second booster may be advised each year.

For example, horses living in regions where mosquitoes are prevalent often receive boosters for core vaccinations in both spring and fall. Even if your horse is annually vaccinated for tetanus, you’ll want to give him another booster if he gets a wound and it’s been longer than six months since he had his last tetanus shot.

As horses age, their immune systems decline, so core vaccines are still very important for seniors.

Benefits of Working with Your Vet

Sure, you can buy equine vaccines at your neighborhood farm supply store or online, but should you?

A benefit of having your veterinarian out to vaccinate is feeling confident that they’ve properly handled, stored, and administered the vaccines.

“Just having your veterinarian’s eyes on your horse once a year is good practice,” says Boggs. “The USDA requires rabies vaccine be given by a veterinarian, so you can’t go buy it at your local feed store.”

And in the unlikely, but still possible, scenario that your horse has a negative reaction, your veterinarian is already familiar with the exact vaccine product that was given.

If you haven’t scheduled your horse’s spring vaccinations yet, now is the time to call your vet and set up an appointment. In the scheme of things, vaccinations are relatively inexpensive. Besides, you can’t put a monetary value on the peace of mind you get from knowing your horse is protected.

This article originally appeared in the March 2019 issue of Horse Illustrated magazine. Click here to subscribe!

The post Core Equine Vaccines appeared first on Horse Illustrated Magazine.