There is a growing body of evidence that suggests that we do not need to vaccinate our dogs and cats as frequently as the vaccine label and convention would suggest. Does this apply to horses? Should we be vaccinating less? Should we be testing for vaccine titers in individual horses?
Ideally yes—but here’s the real world situation
Most anti-vaccination articles are not scientific studies, but opinion in very biased, anti-vaccine publication with a lot of fear-mongering anti-Veterinarian language. Nearly all claim that vaccines weaken the immune system, which is absurd because they stimulate and strengthen the immune system against specific diseases.
While I personally would not mind if I never gave another vaccine in my practice—it's not my primary focus—I don't want to see my patients acquire preventable diseases. We all want the best for our horses and as a Vet, for my patients. As Doctors, we take individual patient status into consideration such as age, illness, surgeries, risk of exposure, etc. and do our best to vaccinate appropriately.
What about older horses?
Aged horses develop something called immunosenescence, meaning their immune system weakens with age and will not fight off disease as well and will not respond to vaccines as well as when younger. This is in direct contrast to the false assumption that older horses do not need to be vaccinated. They are more susceptible both because they have a weakened immune system and they are not as capable of mounting an immune response to the vaccines.
Preventable Disease—Risk Assessment
My concern over not vaccinating is that unvaccinated / unprotected horses will become ill and some will die. 30% of horses that come down with West Nile Virus die. I have only seen West Nile Disease in unvaccinated horses. It’s tragic, and very preventable.
For those not wanting to vaccinate I recommend doing a basic risk analysis to try to determine the likelihood of exposure and give the minimum reasonable number of vaccines. The likelihood of exposure of all horses to Tetanus and West Nile Virus is high. Respiratory virus (EIV and EHV) exposure varies but is relatively high in boarding situations, especially in enclosed barns. EEE and WEE and VEE is rare in New Mexico.
So should we do vaccine titers in horses?
Proponents of vaccine titers in horses show a lack of understanding of the equine species in regards to vaccination effectiveness. It is well established how long vaccination remains protective in horses for most of the diseases we vaccinate against.
- Horses are very sensitive to tetanus and have been known to develop the disease if it has been more than 6 months since vaccination.
- Encephalitis vaccines tend to remain protective for 9-12 months (West Nile, EEE, WEE, VEE)
- Respiratory Virus vaccines remain protective for 3-6 months.
- Rabies likely lasts longer than the 1 year it is labelled for.
- Strangles is likely longer but with the Intra-Nasal Vaccine and localized immunity it needs to be evaluated.
Vaccine titers are not likely to be helpful for Intra-Nasal vaccines because they are targeting a local immune response as opposed to systemic immunity.
Another problem is that we have never been able to establish what level of titer is protective for these diseases.
The link between vaccination and immune mediated disease is still very tenuous and conflicting reports abound.
And one more thing
These types of publications and authors love to espouse that Veterinarians want to give vaccines for the financial gain. To that I would say:
- I do not profit from giving vaccines and would be perfectly happy to have a practice focused more on lameness and other health issues. If I have to drive 30 minutes to a farm and give 2 horses vaccines I will have lost money on the transaction considering my overhead for digital equipment, staff, facility, etc. costs me several hundred dollars per hour.
- I probably could offer to do titers on horses and then I would profit from doing unnecessary expensive vaccine titers, especially knowing that the levels are meaningless and that we already know how long the immunity last in horses.
- That being said, I am not against doing vaccine titers as long as it is understood that we already know the ones that have a short duration of immunity and don't know what level is protective.
Another great article on this subject, written by Dr. David Ramey DVM, is Vaccinosis (and other dopey assertions about vaccines)