Lyme disease in horses Cornell University – College of Veterinary Medicine News, July 3, 2023 Two horses in paddock. Photo: Claudia Desjardins. Many horses are infected with Borrelia burgdorferi, the organism that causes Lyme disease – though clinical signs appear to be uncommon. Board-certified internist and emergency and critical care specialist Dr. read more Cornell University College of Veterinary Medicine Resource: Lyme disease in horses