The Lyme Disease Table Topic at this year’s American Association of Equine Practitioners (AAEP) Annual Meeting, held Nov. 18-22 in San Antonio, Texas, was facilitated by Amy Grice, VMD, partner at Rhinebeck Equine LLP, in Rhinebeck, N.Y., and Bettina Wagner, DVM, PhD, associate professor and Director of Serology/Immunology at Cornell University’s College of Veterinary Medicine. Lyme disease is caused by the spirochete Borrelia burgdorferi, and bacteria are transmitted to horses by infected ticks. Table Topic participants discussed clinical signs of disease, treatment options, diagnostic tests, and vaccination against Lyme disease. Behavioral changes and increased skin sensitivity, both with rapid onset, were the most common clinical signs seen in horses with potential Lyme disease. In addition, most practitioners observed weight loss and shifting leg lameness regularly. Attendees discussed special clinical conditions such as neuroborreliosis (a disorder of the central nervous system), a recently described pseudolymphoma (a benign disorder of lymphoid cells), and uveitis (inflammation of the uvea of the eye) cases as less frequently described clinical outcomes of infection with B. burgdorferi. Discussed briefly were differential diagnoses such as equine protozoal myeloencephalitis (EPM) and infection with Anaplasma phagocytophilum.

Most practitioners treat horses with clinical signs and a confirmed serological antibody titer to the pathogen with either oral administration of the antibiotic doxycycline for 30-45 days, intravenous (IV) administration of the antibiotic oxytetracycline for 30 days, or a combination of oxytetracycline IV for a variable period, followed by an oral doxycycline treatment for a total treatment time of 30-60 days. Very few practitioners reported adverse reactions to treatment; the most common side effect was soft manure. Many of the doctors treat concurrently with pre- or p