West Nile virus encephalitis in a dog

In November 2002, a 2-year-old, spayed Maltese Terrier in central Mississippi was presented for an acute illness characterized by uncontrolled hyperactivity that rapidly progressed to generalized tremors, ataxia, and intermittent hyperthermia. Postmortem examination after a 2-week course revealed mild, multifocal, nonsuppurative meningo encephalitis, with focal necrosis in the medulla. Reverse transcriptase-nested-polymerase chain reaction for West Nile virus (WNV) was positive on brain and negative on other tissues. Immunohistochemistry was negative on all tissues. The clinical, postmortem, and laboratory findings are consistent with acute encephalitis due to WNV infection. WNV infection should be considered in dogs showing signs of encephalitis when and where WNV and mosquito vectors occur.