Equine Lyme Disease Vaccine: Protecting Your Horse’s Future

Lyme is known to be a concern amongst humans and dogs. But were you aware of the growing threat it holds in the equine world too.

Horses are located in the tick- prone areas and are at constant risk of exposure to Borrelia burgdorferi bacteria, which is a causative organism for Lyme disease.

So what do you think is the challenge? This is often misdiagnosed thereby postponing the treatment. As a horse owner, this is one important question: Can Lyme be prevented in equines?

There is no official equine Lyme vaccine yet. However, there are veterinary practices that provide off- label options and let us understand the science behind them.

What Causes Lyme Disease in Horses?

Lyme disease in horses is transmitted by the tick Ixodes bite. Due to the modulation of the surface proteins present; that causes the evasion of the immune system causing progression in the symptoms associated with Lyme disease.

1.Signs in Equines associated with Lyme disease:

• Majority of the horses are asymptomatic even when they are infected.
• The clinical signs and symptoms even if they appear, consists of–
  • Stiffness and inflammation in joints
  • Low- grade fever
  • Arthritic signs and muscle tenderness
  • Swollen lymph nodes
  • Fatigue and low- performance levels
  • Sensitivity to touch
  • Neurological symptoms (if infected by neuroborreliosis)
  • Ocular signs at tick bite site (rare in nature)

2.Missed or Delayed Diagnosis:

• Clinical presentations that are non- specific and varied in nature often lead to missed or delayed diagnosis. For instance signs such as lowered performance or stiffness is often associated with other equine illnesses. This makes clinical diagnosis quite challenging.
• Positive results in serology tests does not always mean an active disease. Due to high rates of subclinical exposure, many horses show less or no- show symptoms.
• Other diagnostic tests such as PCR detection are quite inconsistent in nature due to the lowered bacterial load in blood or tissues. This gives rise to potential false negatives and positive results.
• Equine Lyme Multiplex Assay

The Equine Lyme Vaccine: What You Need to Know

1.Types of Vaccines Available:

• There is no current equine- specific Lyme vaccine that is currently licensed.
• Use of canine vaccines is quite common for horses.
• Experimental equine vaccines show promising results in research settings.

2.How exactly does the vaccine work?

• Vaccines stimulate the production of anti- OspA antibodies.
• The antibodies work on the ticks in neutralizing Borrelia burgdorferi bacteria before it transmits to the horse.
• There are studies that suggest vaccinated ponies do show resistance to the infection even after the tick exposure.
• Cornell’s Lyme Multiplex Test aids in measuring OspA, OspC, and OspF antibodies.

3.Effectiveness:

• Provided full protection in vaccinated ponies is seen.
• Though there is a limitation with canine vaccines. They may produce weaker and short- lived immune responses in horses.
• There are no serious adverse reactions reported in controlled vaccine studies with horses.
• Mild, temporary injection- site swelling might occur.

Vaccination Protocol and Schedule for Lyme in Horses

(Based on current practices using off-label canine Lyme vaccines)

1. Ideal Age and Timing

• The minimum age for vaccination for horses begins after 3-6 months of age, which depends on the overall health and exposure risk.
• Initiate vaccination prior to the peak tick season. Ideally around early spring in endemic areas.
• High-risk cases (e.g. foals, performance horses, tick-heavy environments) may start earlier under veterinary supervision.

2. Initial Dosage and Booster

• Most veterinarians follow a three- dose series based on the canine vaccine protocols.
• Horses in high- risk areas do benefit from booster shots. This can be done every 6-12 months.

3. Incorporate with other Equine Vaccines

• Lyme vaccine can be administered with the core equine vaccines.
• Space vaccinations at least 2 to 3 weeks apart reduces immune stress.
• Common equine vaccines to consider timing around include–
  • Rabies
  • Tetanus
  • West Nile virus
  • Eastern/Western equine encephalitis
  • Influenza/Herpesvirus (EHV-1/4)
• Frequent wellness visits and annual health checkups are good opportunities to align Lyme vaccination with dental exams, tick prevention counseling, deworming, and so on.

Veterinarian Insights on Equine Lyme Vaccination

1.Survey of Equine Veterinarians: A German veterinary survey found:

• 51% of vets had seen clinical Lyme cases in horses.
• 41% regularly vaccinate horses (off‑label), 39% do not offer vaccination, and 20% may consider it under specific circumstances.

2.What Equine Vets Recommend

• Many vets in Lyme-endemic areas offer off‑label canine Lyme vaccines for horses, despite lack of equine-specific licensing.
• The protocol often follows-
  • A primary two-dose canine vaccine series (Day 0 and Day 3 weeks)
  • Frequent biannual boosters due to waning antibody responses.
• Veterinarians emphasize that- Most horses remain subclinical, so vaccination may suit performance or tick-exposed horses—but is not universal practice.

Conclusion

• Protecting your horse from Lyme disease is not just about managing symptoms. Stay ahead of this debilitating infection.
• Equine vaccine still lacks an FDA- approved solution. When combined with the smart- tick management and regular health checkups offer a practical defense layer.
• By working closely with your veterinarian, you can create a personalized plan that balances risk, response, and responsibility. Because when it comes to your horse’s long-term well-being, prevention is always more powerful than cure.

What’s Next for You?

Ready to explore a more complete path to recovery? Join the Lyme Support Network Community.

References

1. Guarino A, Flemming D, Dufresne L, et al. Evaluation of canine Lyme vaccines in horses. Vet Microbiol. 2017;205:60-66. doi:10.1016/j.vetmic.2017.04.006. Available from: Link.
2. Guarino A, Berger S, Nielsen S, et al. Comparison of vaccination strategies using the EquiLyme® vaccine in horses. Vaccine. 2019;37(23):3179-3185. doi:10.1016/j.vaccine.2019.03.062. Available from:Link
3. Guarino A, Riviere J, Flemming D, et al. Recombinant OspA vaccine in ponies: Protection against Borrelia burgdorferi infection. Vaccine. 1999;17(1):129-137. doi:10.1016/S0264-410X(98)00201-X. Available from:Link
4. Divers TJ, Toth M, George S, et al. Lyme disease in North American horses: A consensus statement. J Equine Vet Sci. 2018;67:1-6. doi:10.1016/j.jevs.2018.02.003. Available from: Link
5. Wagner B, Lucas S, Bouvier J, et al. Development of a Lyme multiplex assay for detecting antibodies to Borrelia burgdorferi in horses. J Vet Diagn Invest. 2011;23(4):726-733. doi:10.1177/1040638711412474. Available from: Link