Abstract
Pneumonia in 4-6 weeks old mice (ddY strain), used in the safety test of biological products, has been observed. This pneumonia occured in April and November for a few years, and the increase in body weight of pneumonic mice was slightly disturbed.
Studies have been made to find out the causative agent of the pneumonia, but the isolation of patho-genic bacteria or virus has not been successful though it seems to be an infectious disease.
The pneumonic mouse was not distinguished from other normal mouse easily. The response of the pneumonic mouse was severer than that of the normal mouse when pertussis vaccine was inoculated intraperitoneally.