Probable Herpesvirus Infection in an Eastern Cottontail (Sylvilagus floridanus)

One wild eastern cottontail(Sylvilagus floridanus) from Milwaukee County, Wisconsin was necropsied. The lungs contained numerous multifocal, circumscribed, tan foci; the spleen was markedly enlarged and had a mottledreddish tan color; and the brain had a red to tan friable tract in the left hemisphere. Microscopically, the lung had a severe bronchiolitisand pneumonia. The bronchiolitiswas characterized by epithelial cells containing eosinophilic intranuclear inclusion bodies. The encephalomalaciaof the left cerebral cortex featured tissue disruption and astrocytes or neurons containing intranuclear inclusion bodies. Herpesvirus particles were found within the bronchiolar epithelial cells. Based on histopathological and ultrastructural findings, a herpesvirus seemed the most likely etiologic agent.