Optic neuritis caused by canine distemper virus in a Jack Russell terrier.

A 9-year-old spayed female Jack Russell terrier was referred to the Ontario Veterinary College Veterinary Teaching Hospital (OVC VTH) with a 1-week history of neurological deficits, including blindness. One week prior to presentation, episodes of lethargy were noted. No coughing, ocular or nasal discharge, or abnormal lung sounds were reported by the referring veterinarian. There was a brief mention in the medical record of an “abnormal breathing pattern” with a normal respiratory rate, but this observation was not clarified and subsequent clinical examinations failed to identify any such abnormality. There was also mention of a mild pyrexia of 39.6°C (reference range: 38.4°C to 39.4°C) (1). Pyrexia was not noted on any subsequent examinations. Empirical treatment with orbifloxacin (3 mg/kg q24h) and meloxicam (0.1 mg/kg q24h) had been initiated prior to referral. Despite therapy, the dog’s clinical condition deteriorated to include circling, falling, seizuring and, eventually, blindness. Prior to referral, phenobarbital therapy was initiated (8.5 mg/kg once as a loading dose, then 2 mg/kg q12h).