Abstract
The epidemics of Sendai virus characterized by snuffles occurred repeatedly at intervals of 8 to 10 months in a rat breeding colony of approximately 500 animals.
Outbreaks spread out over the whole colony rapidly and persisted for 2 to 3 weeks, but sometimes a limited incidence of snuff les was observed at 2 to 6 weeks after the termination of epidemics. During each epidemic, the delayed growth of youngs and the decreased weaning rate were observed. At autopsy of rats having shown snuffles the red consolidation was found in the lungs, from which a hemagglutinating virus was isolated and identified as Sendai virus by HI test. In animals exposed to the infection, there was a significant elevation of Sendai virus HI antibody titer coincidentally with each outbreak and the antibody was detectable even one year later. The rats born after the termination of an epidemic, however, had no antibody until the next outbreak. Mycoplasma was isolated from the lungs in one epidemy during a 2 year period. These findings might represent an epidemiological pattern of Sendai virus in a rat breeding colony where susceptible animals attain periodically a population large enough to provoke a new outbreak.
