title: Paraparesis in a polar bear (Ursus maritimus) associated with West Nile virus infection.
abstract: A polar bear (Ursus maritimus) housed at the Toronto Zoo presented with acute-onset, nonambulatory paraparesis. Physical examination 24 hr after onset was otherwise unremarkable, spinal radiographs looked normal, and blood tests indicated mild dehydration. With continued deterioration in its general condition, euthanasia was elected a day later. Necropsy did not reveal a cause for the major presenting clinical signs. Serum collected at the time of initial examination was positive for West Nile virus (WNV) antibodies in a serum neutralization assay and at the time of euthanasia was positive in both a competitive enzyme-linked immunosorbent assay and in a plaque reduction neutralization assay. The major microscopic finding was a mild-to-moderate nonsuppurative meningoencephalomyelitis. WNV was not detected by immunohistochemistry in brain or spinal cord or by real-time reverse transcription-polymerase chain reaction (RT-PCR) and cell culture of brain and kidney, but it was isolated and identified by RT-PCR in second passage cell culture of spleen. Retrospective immunohistochemistry on spleen revealed rare antigen-positive cells, probably macrophages. Prevention of exposure to potentially WNV-infected mosquitoes or vaccination of captive bears against WNV should be considered.
authors.affiliation: Toronto Zoo, 361A Old Finch Avenue, Scarborough, Ontario M1B 5K7, Canada. cdutton@torontozoo.ca
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Dutton
authors.forename: Mark
authors.initials: M
authors.lastname: Quinnell
authors.forename: Robbin
authors.initials: R
authors.lastname: Lindsay
authors.forename: Josepha
authors.initials: J
authors.lastname: DeLay
authors.forename: Ian K
authors.initials: IK
authors.lastname: Barker
mesh_terms: D000818:Animals; D000836:Animals, Zoo / Q000821:virology; D000914:Antibodies, Viral / Q000097:blood*; D017809:Fatal Outcome; D007150:Immunohistochemistry / Q000662:veterinary; D008297:Male; D009500:Neutralization Tests / Q000662:veterinary; D020335:Paraparesis / Q000209:etiology / Q000662:veterinary* / Q000821:virology; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D001503:Ursidae / Q000821:virology*; D014901:West Nile Fever / Q000150:complications / Q000175:diagnosis / Q000662:veterinary*; D014902:West Nile virus / Q000276:immunology* / Q000302:isolation & purification
chemical_list: D000914:Antibodies, Viral