Veterinarians at Rood and Riddle Equine Hospital answer your questions about sales and healthcare of Thoroughbreds. Email us at [email protected] if you have a question for a veterinarian.
QUESTION: Some vaccines seem to have significant failure rates. Why should I give my horse vaccines that may not prevent their contracting an infectious disease?
DR. DALE BROWN: Before discussing the various factors that can contribute to vaccine failure, it is important to understand that no single vaccine can guarantee 100 percent protection against that particular disease. Vaccinations serve to minimize the risk of infection and aid in the prevention of certain diseases, but do not prevent disease in every circumstance.
There are several factors that can play a role in a vaccine's effectiveness and lead to perceived failure: proper handling, following recommended timing of vaccination, the horse's age, immune status, and stress level. If the vaccine is not kept at the proper temperature, it can become inactivated and thus provide no protection. Most vaccines require a primary dose and a series of boosters to mount the proper immune response. If a booster is skipped, oftentimes the horse's immune system will not produce adequate antibodies post vaccination to aid in prevention of disease.
It is important to also understand that not every horse will mount the same immune response to the exact same vaccine. Horses that are immunocompromised (already sick, or under stressful conditions like traveling or showing/training) may not mount a normal immune response to a vaccine given at that time and lead to inadequate protection.
Finally, the particular disease that you are vaccinating against may change its genetic make-up over time (antigenic drift), especially true of viruses such as herpes and influenza, thus making the current vaccine less effective in preventing disease.
There are other vaccines that may be viewed as having high failure rates because the horse can still contract the disease when exposed, however, the vaccinated individuals have much less severe clinical disease or duration of sickness compared to the unvaccinated horse. You should always discuss your vaccination program with your veterinarian to decide which vaccines are most beneficial for your horse based on the risk of exposure and effectiveness. However, there are five core vaccinations every horse should receive no matter the age, breed, or discipline based on the AAEP guidelines: Rabies, Eastern Equine Encephalitis, Western Equine Encephalitis, West Nile, and tetanus. These vaccines have proven over the years to be highly efficacious in preventing these severe, potentially fatal diseases.
Dr. Dale Brown was raised on a cow/calf farm in Girard, Kan. He obtained his veterinary medical degree in 2006 and completed his ambulatory internship with Rood & Riddle in 2007. He joined Rood & Riddle as an associate in 2007 and in 2013 he became a shareholder. Dr. Brown's special areas of interest include reproduction, neonatal medicine, herd health, and public yearling sales
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