Central nervous system lesions in suckling mice and rats inoculated intranasally with sialodacryoadenitis virus

Suckling CD-1 and CFW mice and WI Wistar rats were inoculated intranasally with sialodacryoadenitis virus. In animals inoculated during the first week of life, there was an acute necrotizing encephalitis with malacia and minimal inflammatory cell response. In mice and rats which survived for up to 12 days post inoculation, loss of brain substance, gitter cells and occasionally mineralized debris were seen. Viral antigen was readily demonstrated in neurons and nasal epithelium in trypsin-treated, paraffin-embedded sections, and corresponded with the presence of lesions. There was no compelling evidence that sialodacryoadenitis virus invaded the central nervous system directly via the cribriform plate, and hematogenous spread was considered to be a likely route of spread to the brain. An age-related resistance to the encephalitic form was evident beginning at 10 days of age in both species. Thus it is conceivable that encephalitis could occur in young suckling rats exposed during naturally-occurring epizootics of sialodacryoadenitis.