COMPARATIVE SEVERITY OF RESPIRATORY LESIONS OF SIALODACRYOADENITIS VIRUS AND SENDAI VIRUS-INFECTIONS IN LEW AND F344 RATS

In several chronic diseases, lesions are more severe in LEW rats than in F344 rats. To determine whether or not acute viral diseases also ar e more severe in LEW rats than in F344 rats, we inoculated 6-7-week-ol d LEW and F344 rats with 10(7.2) cell culture infective units of sialo dacryoadenitis virus or 10(4.7) infective units of Sendai virus. Twent y-four rats of each strain were given each virus. Lesions in nasal pas sages, tracheas, intrapulmonary airways, and pulmonary alveoli in 6 or 12 rats inoculated with each virus were assessed by scoring 5, 10, an d 14 days after inoculation. Both viruses caused typical patchy necrot izing rhinitis, tracheitis, bronchitis, and bronchiolitis, with multif ocal pneumonitis, in rats of both strains. Mean lesion indices for LEW rats given sialodacryoadenitis virus were significantly different fro m those for F344 rats for nasal passages on days 10 (0.999 vs. 0.680) and 14 (0.736 vs. 0.278), bronchi on day 5 (0.479 vs. 0.361), and alve oli on day 5 (0.677 vs. 0.275). Lesion indices for LEW rats given Send ai virus were significantly different from those for F344 rats for nas al passages on days 10 (1.000 vs. 0.611) and 14 (0.778 vs. 0.583); tra chea on day 10 (0.625 vs. 0.028); bronchi on days 5 (0.476 vs. 0.331), 10 (0.123 vs. 0.013), and 14 (0.038 vs. 0); and alveoli on days 5 (0. 413 vs. 0.114) and 10 (0.185 vs. 0.020). Thus, at the tested doses, bo th viruses caused more severe respiratory tract lesions in LEW rats th an in F344 rats.