Pathological and Immunohistochemical Findings in American Crows (Corvus Brachyrhynchos) Naturally Infected with West Nile Virus

Twenty-one American crows were identified as being West Nile virus (WNV) infected by WNV-specific reverse transcriptase-polymerase chain reaction (RT-PCR) performed on fresh brain tissue (cerebrum and cerebellum of 16 crows) or by WNV-specific immunohistochemistry of various organs (21 crows). Consistent gross lesions attributable to WNV infection were not detected. Common histological lesions included necrosis of spleen and bone marrow. West Nile virus antigen was consistently detected in heart and kidney (100%). In addition, bone marrow (92%), duodenum (89%), proventriculus (87%), liver (86%), lung (85%), spleen (80%), pancreas (61%), and brain (45%) contained WNV antigen-positive cells. Infected cells included cardiomyocytes; neurons; endothelial cells and vascular smooth muscle cells; hematopoietic cells of bone marrow; and macrophages of spleen, liver (Kupffer cells), and lungs. Epithelial cells of renal tubules, duodenum, pancreas, and proventriculus were also infected. The diagnostic histopathologi...