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Intranuclear inclusions in neurons and glial cells of a dog with old dogence- phalitis had paramyxovirus nucleocapsid structures identical to those observed in distemper- infected CNS tissue. This finding further suggests that the distemper virus is involved in the pathogenesis of old dog encephalitis. Canine y-globulin (IgG) was demonstrated in frozen brain sections by means of the direct fluorescent antibody test. Although IgG occurred in the cyptoplasm of mononuclear cells and in the neural parenchyma in those areas where viral antigen was most abundant, it was not established if it was antibody to distemper virus. Old dog encephalitis, a disease of middle-aged dogs, is characterized by neurologic manifestations of progressive motor and mental deterioration and is ultimately fatal. It is typified pathologically by widely scattered perivascu- lar accumulations of mononuclear cells in the CNS and by intranuclear inclusions in neurons and glial cells (3). Although a viral cause has been sus- pected, only recently has a specific agent been implicated (8). Demonstration of viral antigen of canine distemper by fluorescent antibody staining in the brain of two dogs with encephalitis indicated a possible causal role of the dis- temper virus. Investigators have been unsuccessful in attempting to isolate an agent and to transmit the disease to other animals (3, 81. This paper extends our initial observations on the presence of a paramyxovirus and reports other immuno- histologic findings and transmission trials.

SummaryThe electrophoretic patterns of normal and Aleutian disease affected mink have been determined. The serum from diseased animals had increased total serum proteins, increased gamma globulin, and decreased albumin.