First report of clinical disease associated with canine distemper virus infection in a wild black bear (Ursus americana).
An approximately 1-yr-old black bear was discovered on the porch of a rural residence in southwestern Pennsylvania on October 26, 2011, where it remained during the day in spite of efforts to frighten it away. The bear exhibited periods of somnolence and sporadic tremors and seizures. It was euthanized by gunshot that evening. Immediately after euthanasia it was observed to have footpads that exuded fluid when compressed. It was submitted for necropsy the next day where roughened footpads were noted. Histologic examination of the brain demonstrated nonsuppurative encephalitis with eosinophilic intranuclear and intracytoplasmic inclusion bodies in neurons. The footpads were thickened and hyperkeratotic. Canine distemper virus (CDV) was detected by immunohistochemistry (IHC) in the brain and footpads, and by reverse transcription polymerase chain reaction (RT-PCR) from the brain tissue. Phylogenetic analysis indicated that the CDV cDNA from the bear had 98.2% nucleotide identity to the Rockborn-Candur vaccine and a canine isolate from 2004 in Missouri, USA, and 97.3% nucleotide identity to a raccoon CDV isolated in 2011 from Tennessee, USA. This represents a first report of CDV as a cause of encephalitis or footpad hyperkeratosis in a wild black bear.