Core Horse Vaccines: Rabies, Tetanus, EEE/WEE, and West Nile

Author: Elliott Garber, DVM

Every horse, no matter where it lives or what it does, should get four core vaccines: rabies, tetanus, Eastern and Western equine encephalomyelitis (EEE/WEE), and West Nile virus. The American Association of Equine Practitioners (AAEP) defines these four as core because they protect against diseases that are widespread, often fatal, and in the case of rabies a threat to human health too. Everything beyond those four is risk based, meaning you and your veterinarian decide together based on where your horse travels, whether it boards or shows, and what circulates in your region.

The four core vaccines every horse needs

Core vaccines are the ones the AAEP recommends for essentially every horse in North America, regardless of use or location, because the diseases they prevent are serious, widespread, and in most cases have no reliable treatment once the horse is sick. Prevention is the whole game. Here is what each one covers.

Rabies

Rabies is rare in horses but always fatal once symptoms appear, and it is transmissible to humans, which makes it a public health concern as well as an animal one. A horse can be exposed by the bite of an infected wild animal such as a bat, raccoon, skunk, or fox. Because the outcome is death and the risk to people is real, the AAEP lists rabies as a core vaccine for all horses, typically boosted once a year. Your veterinarian will confirm the schedule that applies where you live, since some areas have specific requirements.

Tetanus

Tetanus is caused by a toxin from Clostridium tetani, a bacterium found in soil and manure almost everywhere horses live. Horses are especially susceptible, and puncture wounds, especially in the foot, are a classic route of infection. The tetanus toxoid vaccine is highly protective, and tetanus only rarely occurs in properly vaccinated horses. Adult horses are generally boosted annually. One important detail: if a vaccinated horse gets a serious or deep wound, the Merck Veterinary Manual notes a tetanus booster may be indicated at that time, so call your vet about any significant injury rather than assuming last year’s shot has it covered.

Eastern and Western equine encephalomyelitis (EEE/WEE)

EEE and WEE are viral diseases spread by mosquitoes that attack the horse’s nervous system. They cause fever, weakness, incoordination, and often death or the need for humane euthanasia. Eastern equine encephalomyelitis in particular carries a very high fatality rate. Both are usually given together in a combination vaccine and are boosted before mosquito season each year. In much of the country that means a spring booster, but in warm southern regions with a long mosquito season your vet may recommend vaccinating more than once a year.

West Nile virus

West Nile virus is also mosquito borne and also targets the nervous system, causing similar signs to EEE and WEE. It has been found across North America, and because its distribution is unpredictable from year to year, the AAEP recommends every horse be immunized against it. It is frequently bundled into the same combination product as EEE and WEE, so a single spring visit can cover all three mosquito borne diseases at once.

Timing: why spring matters for the mosquito borne three

Three of the four core vaccines (EEE, WEE, and West Nile) protect against diseases carried by mosquitoes, so the goal is to have your horse fully protected before mosquitoes become active. For most of the United States that means vaccinating in the spring, a few weeks ahead of the season, so immunity has time to build. The Merck Veterinary Manual describes the standard approach for adult horses in temperate climates as an annual booster within about a month before the start of the mosquito borne disease season.

Not every core vaccine follows the same calendar. Rabies and tetanus are not seasonal, so they can be given at any convenient point in the year, and many owners simply do them at the same spring visit for simplicity. In regions with long or year round mosquito activity, or for horses that travel and compete widely, your vet may space EEE/WEE and West Nile boosters more often than once a year. The specific intervals, and how many total visits your horse needs, are a decision to make with your veterinarian rather than a fixed rule.

Because these dates are easy to lose track of across a barn, it helps to log each vaccine with its date so the next due date is obvious. You can keep a running vaccination history on your horse’s Creatures profile using the health and medical records feature, and set reminders for upcoming care so a booster never slips past its window.

Risk based vaccines: the ones you choose with your vet

Beyond the four core vaccines, the AAEP recognizes a longer list of risk based vaccines that are recommended only after a risk versus benefit conversation with your veterinarian. Whether your horse needs any of them depends on its lifestyle: does it travel to shows, board where new horses come and go, live in a region where a particular disease is present, or is it a broodmare or a young foal. Common risk based vaccines include:

• Equine influenza. A contagious respiratory disease and one of the most common infections in horses that mix with others. Horses that travel, show, or board are the usual candidates.
• Equine herpesvirus (EHV, also called rhinopneumonitis). Causes respiratory disease and, in some forms, abortion in mares or neurologic disease. Boarding and breeding operations often vaccinate for it.
• Strangles. A highly contagious bacterial infection (Streptococcus equi) that causes fever and abscessed lymph nodes. Vaccination is a risk based decision, and the AAEP notes the killed injectable vaccine reduces but does not eliminate clinical cases and can carry a higher rate of injection site reactions, so it is used selectively.
• Potomac horse fever. A regional disease that can cause fever, diarrhea, and laminitis. Where it is present, vaccination may be worthwhile, though protection can be inconsistent, another reason to weigh it with your vet.

There are more on the full list (including botulism, leptospirosis, rotavirus, and others), but the point is the same: these are matched to your horse’s actual exposure, not given by default. A boarded show horse and a retired backyard companion can have very different, and equally correct, vaccination plans.

Foals and broodmares need their own schedule

Newborn foals and pregnant mares are handled differently from adult horses, and this is where working closely with your veterinarian matters most.

A foal cannot be protected by a single shot. It needs a primary series, a set of doses spaced out over several months to build lasting immunity. For the mosquito borne core vaccines, the Merck Veterinary Manual describes a three dose primary series beginning around 4 to 6 months of age, with later doses timed so the foal is protected before its first mosquito season. Rabies and tetanus follow their own foal schedules. The exact ages and intervals depend partly on whether the mare was vaccinated, because a foal that nursed good colostrum carries some borrowed immunity that affects when its own vaccines should start.

That is exactly why broodmares are boosted before foaling. Vaccinating the pregnant mare in the weeks ahead of birth (commonly around 4 to 6 weeks before foaling for the core vaccines, per the Merck Veterinary Manual) raises the antibodies in her colostrum, the first milk, so the newborn absorbs strong protection in its first hours of life before it is old enough for its own shots. If you are planning a foaling, sort out the mare’s booster timing with your vet well ahead of the due date. Our horse gestation guide and foaling guide walk through the surrounding timeline.

Keeping records straight

Vaccination is only as good as your ability to remember what was given and when. Missed boosters, uncertain dates, and horses that change hands with no paper trail are all common problems. Keeping a clear, dated history on each animal solves most of it: you can see at a glance what is current, what is overdue, and what the horse actually received rather than relying on memory.

On Creatures you can add each horse and log each vaccine as a record with its date, so the profile becomes the single source of truth that travels with the horse if it is ever sold or transferred. Naming a new foal for the barn records? Our horse name generator is a fun place to start.

Frequently asked questions

What are the four core horse vaccines?

Rabies, tetanus, Eastern and Western equine encephalomyelitis (EEE/WEE), and West Nile virus. The AAEP recommends all four for every horse in North America regardless of location or use, because the diseases are serious, widespread, and largely untreatable once the horse is sick.

When should horses be vaccinated?

Adult horses are generally boosted annually, with the mosquito borne core vaccines (EEE/WEE and West Nile) timed for spring, ahead of mosquito season, so immunity is in place before exposure. Rabies and tetanus are not seasonal and can be given at any convenient time, often at the same visit. Your veterinarian sets the exact schedule for your region and your horse.

Do foals need different vaccines than adult horses?

Yes. Foals need a primary series of several doses spaced over months rather than a single shot, and the timing depends on the mare’s vaccination status. Broodmares are boosted before foaling so their colostrum passes protection to the newborn. Both are best planned directly with your veterinarian.

Are influenza and strangles core vaccines?

No. Influenza, equine herpesvirus, strangles, and Potomac horse fever are risk based vaccines, chosen with your vet based on travel, boarding, showing, and regional disease. A horse that never leaves home may not need them, while a boarded show horse likely does.

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