Diagnostics used to rule out neuroborreliosis in a seropositive 14 year old Paint gelding

A 14 year old Paint gelding presented to Cornell University Equine and Farm Animal Hospital (EFAH) on referral for evaluation of ongoing ataxia originating around the time of a falling episode. He was evaluated by his rDVM and deemed unsafe to ride. Blood was drawn at the time and submitted for an equine Lyme Multiplex. The patient had been obtained by the owner about three years prior with no history of injury or trauma. However, he did have a history of ringbone in both forelimbs that was diagnosed by radiograph. The patient was current on vaccines (EEE/WEE, WNV, Rabies, Tetanus) and recently dewormed with appropriate dewormer. He was regularly trimmed and shod and lived on a farm with three other horses, all in relatively good health. On presentation, moderate muscle wasting was noted over his topline. No ataxia or weakness was noted in the stall, however, generalized weakness and incoordination, especially on the hind limbs was noted on neurologic exam. On lameness examination, the patient moved with an overall stiff gait and appeared reluctant to flex forelimbs when walking and trotting. Diagnostics were performed and acute equine Borreliosis infection was diagnosed with neuroborreliosis suspected. Further diagnostics did not support neuroborreliosis. After 6 weeks treatment with Minocycline, the gelding was reexamined and despite improvement in demeanor and gait, the gelding was deemed still unsafe to ride at this time. Borrelia burgdorferi infection in horses is relatively common in specific areas of America; however, equine Borreliosis or Lyme Disease (LD) remains controversial due to inconsistent presenting clinical signs and difficulty determining current infection. Moreover, associating clinical disease and current infection has proved extremely challenging for the diagnostician especially in the face of multiple ongoing disease processes. The following case report reviews the differential list and diagnostic plan for an insidious peripheral ataxia and discusses the disease process, treatment options, and prognosis for horses affected with LD and especially neuroborreliosis