Pet Columns, Office of Public Engagement, College of Veterinary Medicine at the University of Illinois at Urbana-Champaign

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Equine Vaccinations: What Your Horse Really Needs


Pet Column for the week of February 1, 2010

Related information:

Related site - American Association of Equine Practitioners

Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Ashley Mitek
Information Specialist

Source - Dennis D. French, DVM, DABVP
There's a vaccine for almost everything these days. From West Nile to strangles to sleeping sickness, it's easy to not be certain what vaccines are truly essential, which ones may be needed, and which ones are a waste of time (and money).

Dr. Dennis French is a veterinarian at the University of Illinois Veterinary Teaching Hospital in Urbana. He says that for the average backyard horse that does not travel, "there really are just four 'core' vaccines a horse needs each year." They are:

  • West Nile Virus (WNV)
  • Tetanus
  • Eastern and Western Encephalitis (EEE and WEE)
  • Rabies


When deciding upon which vaccinations should be mandatory, and which are elective, Dr. French's explanation is simple. "These are the diseases of backyard horses that can kill them," he notes. Not that there aren't other deadly diseases to horses, but these four have the highest risk of being contracted.

Some equine veterinarians still debate about whether the risk of rabies to horses is worth vaccinating for. But in the end, the reason why it ended up on the American Association of Equine Practitioners (AAEP) 'core' list is because not only is it a serious risk to humans, but the only way to diagnose the disease is with a necropsy (an autopsy).

It's worth noting that some herds will vaccinate for various other ailments in addition to the four listed above. For example, any horse that travels to shows or races is at an increased risk of being exposed to certain other diseases, such as strangles, the flu, and herpes. For that reason, a veterinarian may recommend the horse be vaccinated for various other ailments.

Although the core vaccines should be given annually, there are exceptions to this rule. If you live in the southern part of the United States where the mosquitoes tend to stick around for longer, your veterinarian may recommend that your horse receive a booster for the diseases carried by these pests -- WNV and EEE/WEE. But in Illinois, vaccinating just once a year with the 'four core' provides sufficient protection.

A great time to schedule yearly vaccines for your horse is in the spring. That's when the mosquito population is not quite up to speed and you can get your horse immunized against the mosquito-borne diseases before they start to be a problem. An interesting finding has been that horses vaccinated during the mosquito season are more likely to come down with clinical signs. The reason for this is that their response to the vaccines compromises their ability to fight off the virus being transmitted by the mosquito.

But if the thought of vaccinating your horse with four vaccines at once sounds a bit traumatic, it really is not worth worrying about. Because certain vaccines are combined into one syringe, your horse may end up getting just two injections. Although in some species certain vaccines have a higher risk of causing a reaction, "the vaccines we have for horses are very innocuous," says Dr. French. The risk of a horse having an adverse reaction to any of the four core vaccines is incredibly small. In addition, research has shown that by vaccinating against all three of the encephalitis viruses there is an enhanced response that increases protective immunity.

For more information on what vaccines your horse needs, please contact your veterinarian.