Isolation of Canine Distemper Virus from Dogs with Chronic Neurological Diseases

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Abstract
Successful isolation of CDV [canine distemper virus] was accomplished from 2 of 6 dogs diagnosed as ODE [old dog encephalitis] and 2 of 6 dogs with chronic distemper encephalitis. Brain or bladder tissues obtained from diseased dogs and cultured in vitro yielded the cell-free virus. Cocultivation was not necessary for the transmission of the virus to susceptible ferrets. The brain from a dog with chronic distemper encephalitis, which had the earliest appearance of syncytium in culture, also showed CDV when triturated brain was assayed directly into ferrets. Direct isolation of CDV in ferrets was not possible from any other brain or tissues. CDV antigen was detected in brains of other dogs but viral isolation was not accomplished even after cocultivation, suggesting the presence of defective viruses. CDV antigen was not detected nor was virus isolated from kidney, lymph nodes, spleen, pituitary, lung and liver of any dog. All dogs showed CDV neutralizing antibody in sera and CSF. The antibody was primarily Ig[immunoglobulin]G rather than IgM, suggesting remote and not recent infections. Within the ODE group or within the chronic distemper encephalitis group, the clinical manifestations, histopathology of brains, antibody and IFA results were not measurably different whether CDV could be isolated or not.