Equine Core Vaccine Basics

Core vaccines are those that veterinary authorities—the American Veterinary Medical Association and the American Association of Equine Practitioners—recommend as yearly must-haves, regardless of your horse’s activity level, use, or housing, said Elizabeth Davis, DVM, PhD, Dipl. ACVIM, section head of equine medicine and surgery at the Kansas State University’s Veterinary Health Center.

She explained that a panel of veterinary infectious disease and immunology experts have established core vaccines based on those diseases (think mosquito-borne diseases) that are endemic to a region, have a potential public health significance, require vaccination by law, are highly virulent (capable of causing disease), or cause very severe disease or even death, regardless of biosecurity measures taken.

On the contrary, veterinarians recommend risk-based vaccines based on a horse’s potential to develop certain diseases. “Risk-based vaccines are for diseases that horses might be more likely to develop based on interaction with other horses, geographic location, or climate,” Davis said.

All vaccines, she added, prime the immune system (which she compares to an army) with a very low level or portion of a pathogen (disease-causing organism—the enemy) so that if the horse is exposed to the actual pathogen, his immune system could call in the troops (pathogen-fighting immune cells and proteins) to ward off infection.

What Are the Core Vaccines?

Equine diseases for which veterinarians administer core vaccines include:

  • Eastern and Western equine encephalomyelitis (EEE and WEE) are named for their geographic distribution. These “sleeping sicknesses” occur mainly in the Eastern, Southeastern, Southern, and some Midwestern states (EEE) and the Western and some Midwestern states (WEE). Mosquitoes primarily transmit the viruses to horses from wild birds and rodents. The mortality rate for EEE and WEE varies from 50-90%.
  • West Nile virus also falls into the encephalitic (brain-inflammation-causing) category (along with EEE and WEE). It occurs throughout North America and spreads from birds mainly via mosquitoes to horses, humans, and other mammals. The fatality rate for horses that exhibit clinical signs is 33%.
  • Rabies, once signs appear, is 100% fatal in all mammals (including horses, humans, dogs, cat, skunks, foxes, and raccoons). “The primary reason the rabies vaccine is among core vaccines is that rabies is zoonotic (transmissible from animals to people),” Davis said.
  • Tetanus is caused by the bacteria Clostridium tetani, which are abundant in horses’ gastrointestinal (GI) tracts and feces, said Davis. “Things like penetrating (puncture) wounds, subsolar (inner hoof) abscesses, and even invasive medical procedures can put an unvaccinated horse at risk.” The disease is neurologic, causing extremely painful muscle spasms, and usually fatal.

Take-Home Message

Core vaccines protect your horse from frequently deadly diseases that biosecurity measures can’t prevent. Talk to your veterinarian to create a core and risk-based vaccine plan that meets your horse’s needs.