Encephalitis in suckling rats induced with rat cytomegalovirus.

Encephalitis has been induced in suckling rats by intracerebral inoculation of rat cytomegalovirus. This agent has been carried through five animal passages without changes in virulence. Principal sites of viral attack were the meninges and ependyma with limited parenchymal invasion from these sites. Characteristic features of cytomegalovirus disease observed included cytomegaly, formation of nuclear and cytoplasmic inclusions, and polykaryocytosis. Fundamental tinctorial and optical differences were noted between nuclear and cytoplasmic inclusions, the latter being characterized by their phloxinophilia which contrasts with the hematoxylinophilia of nuclear inclusions. Differential interference microscopy improved visualization and photography of cytoplasmic inclusions. Hydrocephalus developed in a few of the animals and was studied in late phases of the disease.