One of the basic studies for improvement in quality of laboratory animals, histopathological observation and serological test of mouse hepatitis virus (MHV) were carried out to investigate subelinical infectious diseases in ICR, C59BL/6, CBA, C3H/He mice. Those mice, which were healthy in appearance and treated with cartisone ar not, were sacrificed in late-spring and late-winter season.
The results were as follows.
1. In the histopathlogical findings of liver, lung, kidney, spleen and heart, the lesions were observed in liver arid lung;
2. Vacuolar degeneration and hydropic degeneration were main lesions in liver, interstitial pneumonia and thickening of alveolar wall were in lung. These lesions were more severe in ICR strain, both cortisone treated group and non-cortisone treated group, than the others.
3. The MHV infection rates were 66.7∼95.8%. In the late-spring group, the positive rates were about two times than the late-winter group.
The rate of C57BL/6 strain was higher than other strains, but there was no difference in between cortisone treated group and non-cortisone treated group.
4. The above results suggest the histopathalogical lesions of liver caused by mixed infection of MHV or Tyzzer etc, the lesiotas of Lung by Sendai virus etc.
5. Then, when performs animal experiment, laboratory animal user has to select animals not infected because animals seem to be healthy, in spite of being infected subclinical infectious diseases which make important effects on interpreting the results of experiment.
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