Equine Fall Vaccines

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By Liana Wiegel, DVM, Pilchuck Veterinary Hospital 
Vaccines for horses are grouped as core vaccines and risk-based vaccines. 
A core vaccine means that all horses have the potential to be exposed to the disease regardless of their exposure to another horse (such as tetanus, which is a bacterial spore found in the soil). Core vaccines for horses are tetanus, eastern/western encephalomyelitis (EEE, WEE) and West Nile virus. 
Risk-based vaccines are given to horses based on their exposure to the disease and depend on the animal’s geographic location and lifestyle. The risk-based vaccines for horses in the Seattle area are  influenza (flu), rhinopneumonitis (rhino, equine herpesvirus-1 and -4), strangles and rabies.
Following is more information on selected vaccines: 

Influenza and Rhinopneumonitis

Disease symptoms: 

  • Infection of the respiratory tract, characterized by fever (>101.5), depression, lethargy, decreased appetite, nasal discharge and cough  
  • Abortion in pregnant mares from EHV-1  

Spread via aerosolized secretions of sick horses from direct contact or shared equipment, such as water buckets and tack, and aborted fetuses, placenta and fluids (EHV-1)

Low-risk horses:  

  • If no horses ever leave the property and there is no exposure to breeding mares, vaccination for flu/rhino is not critical.  
  • If horses leave the property infrequently over the summer, vaccinate once a year, in the spring with core vaccines.

High-risk horses:  

  • Includes horses that travel, horses housed at facilities with frequent equine travel, horses under 5 years old, and horses on breeding farms  
  • Adult horses: Recommendation is to vaccinate twice a year, once in the spring with core vaccines and again in the fall.  
  • Pregnant mares: Vaccinate for EHV-1 in the fifth, seventh and ninth month of pregnancy to prevent abortion, using vaccine approved for pregnant mares (regular flu/rhino combo will not protect mares against abortion). Vaccinate for flu/rhino with intramuscular vaccine four weeks prior to anticipated foaling date to transfer immunity to foal via colostrum.  

Vaccine options:

  • Flu/rhino combo: intramuscular vaccine of killed virus
  • Intranasal flu vaccine: modified live virus that has been shown to be more efficacious than the intramuscular vaccine
  • Rhino: intramuscular vaccine of killed EHV-1 virus; can be used in conjunction with intranasal flu and in pregnant mares 
  • Rhino: intramuscular vaccine of modified live of EHV-1; currently on long-term backorder  


Typically considered a core vaccine due to risk of severe disease and public health significance, but Washington has relatively low incidence of rabies-positive animals.

Disease symptoms: neurologic disease that ultimately leads to death

Exposure: In the Pacific Northwest, bats are the source of infection and infect animals through bites.  

Vaccine options: intramuscular vaccine of killed virus; done once a year; must be given by a veterinarian

From the young foal to the geriatric retiree, we recommend personalized vaccine protocols that are based on AAEP (American Association of Equine Practitioners) guidelines and tailored to each horse's particular circumstances. Please contact Pilchuck Veterinary Hospital for information on your horse’s specific vaccine recommendations: 360.568.3111

Article added December 5, 2013