Comparison of strain susceptibility to experimental sialodacryoadenitis in rats

Wistar, Sprague-Dawley, and Long-Evans outbred rats, and the Fischer344 inbred strain were inoculated intranasally with 10(3) TCID50 of sialodacryoadenitis virus at approximately 9 weeks of age. Paired animals were killed at 2-day intervals post inoculation up to 2 weeks, then at 20 days. A comparison of strain susceptibility to sialodacryoadenitis virus was made using the following criteria: histopathology, immunofluorescent microscopy, serology and serum amylase activity. All four strains were susceptible to sialodacryoadenitis virus. The disease was frequently subclinical, although typical lesions were observed on histopathology. Focal bronchitis, bronchiolitis and pneumonitis were observed histologically during the acute stages of the disease. Immunohistochemistry was performed on trypsin-treated, paraffin-embedded sections, and viral antigen was readily demonstrated in salivary and lacrimal glands during the early stages of the disease. A rise in serum amylase was observed, and it was correlated with the first appearance of lesions in the salivary glands. Based on serology and immunofluorescence microscopy, the appearance of detectable antibody to sialodacryoadenitis virus, and the rate of viral clearance from infected glands, the course of the disease was similar in the four strains studied.