The growth and cytopathogenicity of virulent and attenuated strains of canine distemper virus in dog and ferret macrophages

The in vitro growth of virulent and attenuated strains of canine distemper virus in dog and ferret lung, liver, spleen and peritoneal macrophages was examined. All virus strains tested grew in each type of macrophage culture. Cytopathic effects, consisting of cytoplasmic and nuclear inclusion bodies and polykaryocytosis, were found in all virus-cell combinations. The polykaryocytes were formed both by cell fusion and from single cells by amitosis. Marked nuclear abnormalities were found in alveolar macrophages infected with virulent virus strains. The role of lysosomal enzymes in the development of these cytopathic effects was discussed.