Lyme disease in the horse, due to infection with Borrelia burgdorferi, is very prevalent in some areas of North America (mid-Atlantic and northeastern states, MN, WI, southern Canada, CA, central VA, for ex.). According to the author of a recent article, the incidence of clinical disease has not been determined, “which makes Lyme disease in the horse controversial.” Progress is being made in defining the different clinical presentations of Lyme disease in adult horses. Blood tests currently in use can detect antibodies to B. burgdorferi but may not be able to distinguish between previous or current infections (an antigen test would be needed for this). Treatment protocols, most commonly using the drugs oxytetracycline, doxycycline or minocycline, are available for Lyme disease in the horse, but the success of these treatments in eliminating the organism, especially with chronic infections, remains questionable.
Prevention of B. burgdorferi infection in horses includes avoiding tall grasses and other areas where ticks are commonly found, the use of sprays and topical preparations to repel ticks, and canine Lyme vaccines. Vaccination, like many other aspects of Lyme disease in the horse, “remains controversial, although the canine-approved vaccines have the potential to prevent infection based upon vaccine studies in ponies and other animals.”
Review Article: Divers, Thomas J., DVM, DACVIM, DACVECC “Equine Lyme Disease,” The Practitioner, published by FAEP. Issue 2, 2015, pp. 21-24.