Vaccination roundup

While your veterinarian will recommend the best vaccination schedule for your region and travel plans, here’s a quick summary of common vaccines and where they’re needed:


This virus is transmitted by a bite from a rabid animal. With horses, we often cannot tell they’ve been bitten until serious symptoms develop. Rabies is universally fatal and there is no treatment, so all horses should be vaccinated against it. The vaccine is 100% effective and can be given annually or every three years, depending on the product.


Tetanus is an infection caused by bacteria in the soil, which can invade deep wounds and punctures. When the bacteria colonize in the wound, they release a toxin that circulates in the bloodstream and causes death in horses. Vaccinate annually, and if your horse suffers a deep wound six months after vaccination, give another dose of tetanus anti-toxin.

Equine influenza and equine herpesvirus 1 (EHV-1)

At show grounds, race tracks and auctions, influenza and EHV-1 can spread like wildfire. They can lay a horse up for weeks or cause pregnant mares to abort their foals. Depending on the severity of the infection, the viruses can even cause death. While vaccinations are not 100% effective, they do provide a measure of safety. Your veterinarian may recommend you vaccinate several times a year if your horse is going to be exposed to crowds.

West Nile

This virus affects the horse’s brain and neurological system, and it is often fatal. West Nile virus is spread by mosquitoes, so if you live in a buggy region, you should administer this vaccine annually. Most West Nile vaccinations are 95% effective.

Eastern and Western Encephalitis (EEE and WEE)

Photo from Wikipedia

Photo from Wikipedia

Infected flies and mosquitoes transmit these diseases to horses via the bloodstream. It can also be spread by infected needles. Eastern and Western Encephalitis is often fatal as there is no treatment available, and horses that do survive suffer permanent damage to the central nervous system. Annual vaccination is 100% effective.

Potomac Horse Fever (PHF)

Horses that live near rivers and streams or irrigated pastures are susceptible to PHF ever during warm weather. They can ingest the bacterium by drinking from natural water sources, or aquatic insects like dragonflies can carry the bacterium from water sources to the horses’s pasture. The disease attacks the gastrointestinal tract and can be mild to life-threatening. While the vaccine is not completely effective, it will reduce the severity of the illness if the horse contracts it.

Strangles (distemper)

This highly-contagious disease is caused by a bacterial infection. Most horses will recover with the proper care, but they need to be quarantined to control the spread of infection. Backyard horses that don’t travel and aren’t exposed to large groups of horses are unlikely to contract strangles and may not require a vaccination, which is good because the vaccine must be administered intra-nasally. This type of administration requires a lot of finesse, but it results in stronger protection.

Equine Infectious Anaemia (EIA or Swamp Fever)

Photo from Wikipedia

Photo from Wikipedia

Once a horse contracts this virus, the disease can affect him on and off for the rest of his life. During flare ups, the horse will experience fever, weight loss, depression, weakness, anaemia and edema. This episodes can be fatal. There are no treatments or vaccines for Swamp Fever, but it can be detected with a Coggins test. The blood test is required annually for international travel and many competitions.

Rhinopneumonitis (Rhino or EHV-4)

Rhino is a highly-contagious disease that can cause abortion in pregnant mares and seriously respiratory infections in young horses. Affected horses can often be nursed back to health with the right care, but they must be quarantined and stable owners should sanitize all clothing and equipment to prevent an outbreak. Annual vaccinations are very effective at preventing rhino.

Three-way vaccine

This combination vaccinates for Eastern and Western Encephalitis and tetanus.

Four-way vaccine

This can refer to a few different combinations, but in Canada, it most often means Eastern and Western Encephalitis, tetanus and West Nile Virus vaccines.



Equine Canada Stable Management Manual, 2009
“Vaccines prevent horse fatalities,” Western Producer, 2012
EHV Fact Sheet, University of Connecticut
“Potomac Horse Fever: Cause and Treatment,” The Horse, 2007


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