Abstract
The synergistic effect of Sendai virus on Mycoplasma pulmonis infection was investigated in ddY mice infected with the two agents. As the results, growth of M. pulmonis was remarkably enhanced in the lung by superinfection of Sendai virus, although not significantly affected in the trachea. The enhanced growth of M. pulmonis was most evident when the both organisms infected at the same time, and the less enhancement of the growth was observed in the longer time difference between infections of the two agents. Detection rates of pneumonia in mice infected with both M. pulmonis and Sendai virus were 80 to 100 per cent, remarkably higher than 12 per cent of control mice infected with M. pulmonis alone, and comparable to 80 per cent of control mice infected with Sendai virus alone. However, the lesions in the dually infected mice were more severe and persisted longer than those in the mice infected with Sendai virus alone. CF antibody against M. pulmonis persisted longer in the dually infected mice, as compared with that in control mice infected with M. pulmonis alone. Production of HI antibody to Sendai virus was considerably inhibited by combined infection with M. pulmonis.
