Borna disease virus infection: Retrospective case series of five horses and two donkeys in Switzerland

Summary Borna disease is an acute to subacute, rarely chronic non‐purulent meningoencephaylomyelitis affecting mainly horses and sheep. This case series describes the clinical signs, diagnosis, treatment, outcome and post‐mortem findings of five horses and two donkeys with this condition. The equids affected were geldings or mares of various breeds and aged from 1 to 15 years. Typical clinical signs included lethargy, obtundation, compulsive circular walking, ataxia, head pressing and arrested eating with chewing motions (‘pipe smoking’). The presumptive clinical diagnosis was made by considering the geographical location of the stable, clinical signs and exclusion of other causes, in conjunction with the detection of antibodies in serum and/or cerebrospinal fluid. All cases were treated with anti‐inflammatory drugs and supportive care. All equidae were euthanised due to progressive neurological deficits. Necropsy and histopathological evaluation revealed a non‐suppurative meningoencephalomyelitis, and Borna antigen detection by immunohistochemistry confirmed the presumptive clinical diagnosis.