Murphy, S., Fortner, J., Adusumilli, S. 2014. A comparison of soiled bedding densities and stress in sentinel mice. American Association for Laboratory Animal Science [AALAS] Meeting Official Program, 609. (Abstract #P225).

Sentinel animals are used to monitor the health status of rodents used in research. It is important to screen for potentially pathogenic viruses, parasites, and bacterial organisms to detect and rapidly respond to unwanted pathogens that may adversely affect research outcomes. Soiled bedding exposure is the most common method of sentinel surveillance. However, standards and protocols for bedding transfer vary widely. In an effort to standardize surveillance programs with global colleagues, we proposed a change from our standard 50% soiled bedding protocol to 100% soiled bedding. At the request of the IACUC, a pilot study was conducted to investigate whether mice housed on 100% soiled bedding for a duration of 12 wk experienced greater stress when compared with those on 50% soiled bedding. Twelve adult CD1 female mice were housed in 2 groups (6 per group) and exposed to either bedding concentration. Body weights and clinical observations were recorded weekly. At weeks 0, 1, 4, 8, and 12 blood samples were collected for serum corticosterone analysis. At the completion of the study, 3 mice per group were euthanized and tissues submitted for histopathologic review. At week 12, all the mice in both study cohorts had continued to increase in body weight. No animals were reported for any clinical abnormalities, including abnormal behavior. Changes in serum corticosterone levels were not statistically significant. Histologic analysis did not reveal gross or microscopic changes in the mice from either cohort. Based on the results of this study we conclude that housing mice on 100% soiled bedding does not result in increased stress and does not induce pathologic or clinical abnormalities when compared with animals housed on 50% dirty bedding for a duration of 12 wk.