Clinical signs and results of specific diagnostic testing among captive birds housed at zoological institutions and infected with West Nile virus

West Nile virus (WNV) infection can be difficult to diagnose antemortem in birds because clinical signs mimic those associated with other more common avian diseases. Antemortem diagnostic tests for WNV infection in birds include a plaque reduction neutralization test for antibodies in serum and a reverse transcriptase-polymerase chain reaction assay for viral RNA in oral swab specimens. Neither of these antemortem diagnostic tests is definitive for diagnosing WNV infection. For birds with clinical signs suggestive of infection, a combination of tests, including a CBC, serum biochemical testing, plaque neutralization reduction test, and reverse transcriptase-polymerase chain reaction assay, would likely be the best way to obtain a diagnosis of WNV infection and exclude other potential causes of the clinical signs. Early detection of WNV infection in animals in zoological institutions is critical to prompt initiation of medical treatment and implementation of measures to decrease exposure of other animals in the collection to the virus.