Diagnosis of eastern equine encephalitis by immunohistochemistry in two flocks of Michigan ring-neck pheasants

The diagnosis of eastern equine encephalitis (EEE) virus infection in avian species is relatively difficult when compared with other species. There ar e no characteristic histologic lesions in the avian brain that would serve to distinguish EEE from infections with, for example, Newcastle disease or highly pathogenic avian influenza virus. Traditionally, virus isolation (VI ) and/or hemagglutination inhibition (I-II) has been used for a definitive diagnosis of EEE in birds. Recently, we developed an immunohistochemistry ( IHC) technique for confirmatory diagnosis of EEE infection in equine brain. This test also detected EEE virus in formalin-fixed avian brain. VI confir med II-IC finding in two cases of EEE in ring-neck pheasants. IHC is a rapi d, sensitive test for confirming and differentiating a histopathologic diag nosis of EEE in avian species and should be considered as an alternative re st to VI or HI.