Pathogenesis of Demyelinating Encephalopathy in Dogs with Spontaneous Acute Canine Distemper

So far, the pathogenesis of demyelination caused by canine distemper virus (CDV) in the central nervous system has remained unclear, although a lot of studies have been done extensively. To further investigate the relation of variety cells in brain to demyelination, this study was performed on 15 dogs with spontaneous acute canine distemper and 2 controls. According to anatomical relation, the brain was divided into cerebrum, cerebral stem and cerebellum. The sections with no, mild, moderate, or severe demyelinating lesions were selected respectively and stained by HE and immunohistochemistry. Immuno-localisation of CDV antigen was used to confirm CDV infection. The brain was examined for co-localisation of the CDV antigen with either an astrocyte-specific marker, glial fibrillary acidic protein (GFAP), or an oligodendrocyte-specific marker, galactocerebroside (GalC). Apoptotic cell was detected by TdT-mediated nick end-labeling assay (TUNEL). The results demonstrated that the local disturbance of blood circulation mainly included congestion, edema, thrombosis, and disseminated intravascular coagulation (DIC). The CDV neucleocapsid protein positive reaction, metabolic disorder and apoptosis of oligodendrocytes were observed in demyelinating areas. Lots of astrocytes displayed CDV antigen-positive, especially in their process. Some of them became apoptotic cell confirmed by TUNEL staining. Fibrous astrocytes showed more intense GFAP-positive in mild and moderate demyelinating area. Some of nervous cells located in pyramidal cell layers and nucleus nervi were in degeneration, necrosis. Satellitosis, neuronophagia and apoptotic neurons were examined by hematoxylin and eosin (HE) and TUNEL staining. The results suggested that the demyelinating changes in brain tissues infected with CDV mainly related to the metabolic disorder and apoptosis of ogliodendrocytes and astrocytes; also involved with the local disturbance of blood circulation and some neuron lost.