Use of immunohistochemistry and molecular assays such as RT-PCR for precise post mortem diagnosis of distemper-related encephalitis

The wide spectrum of neurological presentations of nervous distemper, granulomatous meningoencephalitis (GME), and necrotizing encephalitis (NE) may complicate their clinical diagnosis. In addition, although there are some differences, distemper encephalitis, NE, and GME share similar histological changes such non-suppurative inflammation. Further, necrotic lesions may be present in both distemper and NE. As nervous distemper may mimic other inflammatory conditions of the brain, CDV infection should be always excluded before making the definitive diagnosis of a neuropathological entity such as GME, NE, or other non-suppurative encephalitis of unknown etiology. However, immunohistochemical (IHC) assays routinely used for post mortem CDV antigen detection may cross-react with autoantigens, resulting in non-specific immunolabeling. Accordingly, in this mini-review a critical approach to the usefulness of IHC for definitive diagnosis of nervous distemper will be discussed. Additionally, the use of CDV gene detection by molecular assays such as RT-PCR for post mortem diagnosis of nervous distemper will be commented on.