Lyme Disease

Lyme disease in horses is a controversial entity in veterinary circles. There is still not much evidence based medical data to establish that Lyme infection causes a definite set of pathologic signs in affected horses, even though many of them are treated for infections determined by serologic laboratory testing. Highly recognizable syndromes like those seen in human and canine Lyme disease patients are infrequent in horses. Resolution of perceived symptoms following treatment does appear to occur in some cases, but making that determination is subjective and often not definitive.

Nevertheless, protection of horses against infection by the causative bacterium Borrelia Burgdorferi is a worthwhile cause in dealing with the problems arising from the confusing clinical recognition and treatment of the disease.

Testing and Vaccination Protocol:

We have been vaccinating a significant number of our equine patients against Lyme disease in the past five years. Although there is still no official approved vaccine for horses, the experience of most equine veterinarians has shown that canine vaccine has produced high levels of vaccine antibodies against lyme disease when used in horses. These protective antibodies can help to protect vaccinated animals against infection if the immunizations are kept current.

It is not required to check your horses Lyme titer before vaccinating if they are not displaying clinical signs. If it is the first time your horse is receiving the vaccine, they will need a 2 vaccine series, 3 weeks apart, and then a booster every 6 months to maintain protection. If you would like to check your horse’s titer we recommend doing so at the first 6 month booster so that we can assess response to the vaccine as well.

Treating for Lyme Disease:

As Stated above, clinical Lyme disease in equines is rare even in the presence of a positive serum titer. If you are concerned your horse may have Lyme disease, discuss with your veterinarian whether testing and/or treatment may be the best option for your horse. Listed below are the standard approved treatments for Lyme disease in equines and your veterinarian can help determine which protocol would be best suited for each case based on you and your horse’s situation.

  1. 21 days of IV Oxytetracycline
  2. 7 Days of IV Oxytetracycline followed by 21 days of oral Doxycycline
  3. 28 days of oral Doxycycline
  4. 28 days of oral Minocycline
  5. No Treatment- Not treating your horse even though they have an above normal Lyme titer may be an acceptable option. This is especially true if they are not displaying clinical signs of Lyme disease.

Post treatment we recommend rechecking a serum titer at 4-6 months as it takes time for the level of antibodies in your horses system to change.


Whether or not you decide to vaccinate your horse against Lyme disease, keeping the ticks off your horse is key in preventing infection! Topical preventatives include:

  1. Vectra3D, a topical liquid applied once a month.
  2. Fly sprays containing Permethrin.
  3. Applying Swat above the chin area and Show Sheen to the lower limbs and tail to prevent ticks from climbing aboard while grazing.
  4. Using a lint roller to remove ticks from your horse before they can attach.