Abstract
The prevalence of eosinophilic granulomatous pneumonia (EGP) is well known in Brown Norway (BN) rats. In this study, age-related changes in the incidence and severity of EGP in 4 to 20 weeks old BN rats were examined under two different housing conditions (isolator cages without woodchips and common cages with woodchips for bedding) in a SPF animal room in Charles River Japan Inc. A routine microbiological survey gave negative results to any specific pathogens tested. As a result of histopathological examination, there were no lung lesions observed at the age of 4 weeks. EGP developed at and after the age of 7 weeks, but the incidence and severity of EGP showed no age-related changes under both housing conditions. These findings suggest that EGP in BN rats may be a hypersensitivity response of strain-specific nature as reported by Albers and Clifford.
