Health Surveillance

Surveillance for health quality is essential to detect unwanted and complicating spontaneously occurring mouse diseases. Health monitoring entails sampling of sentinel mice in the quarantine areas as well as any SPF mice in the colony. This can be done at intervals of 4 weeks in the quarantine area and every 12 weeks in the repository colony. Sentinel mice are often SW, 2-month-old females. These mice are free of all the agents that will be screened. In the barrier colony, sentinel mice are placed two per cage and placed on a cage rack so as to receive soiled bedding from about 70 cages each time cages are changed. In addition, foster mothers and retired breeders should also be sampled. Both types of surveillance are necessary, because not all infections in mice are spread by soiled bedding.

The skin should be examined for ectoparasites. The cecum and colon of mice should be examined for the presence of endoparasites. Mucosal scrapings from the duodenum, jejunum, cecum, and colon should be examined for pathogenic protozoa. In addition, every six weeks, a random sample of colony mice should be tested by anal tape test and fecal flotation for endoparasites, and the pelage examined by dorsal tape test for ectoparasites. Feces should be cultured to detect enteric pathogens (Salmonella sp., Citrobacter rodentium, enteropathogenic Escherichia coli, Pseudomonas sp., Campylobacter sp., and Clostridium sp.) PCR assay of the feces should be done for Helicobacter sp. (H. hepaticus, H. bilis, H. rodentium). A swab of the upper and lower respiratory tract should be cultured to detect respiratory pathogens (Pasteurella sp., Bordetella sp., Streptococcus sp., and Staphylococcus sp J. PCR assay of a smear from a nasopharyngeal swab should be done for CAR bacillus. Serology should be performed to detect the presence of various viral and mycoplasmal infections. Every six weeks, mice should be tested for MHV and MPV. On a quarterly basis, mice should be tested for MHV, MPV, TMEV, and rotavirus. In addition, mice should be tested semiannually for PVM, Sendai virus, reovirus-3, adenovirus, MTV, LCMV, MCMV, ectromelia and Mycoplasma sp.

Mice that die unexpectedly or spontaneously, or are identified through daily health screening in the quarantine or repository area as showing signs of poor health or disease, should be necropsied by a veterinary pathologist. This examination should consist of grossly visualizing major organ systems. This should be followed by a microscopic examination of all gross lesions within a subset of organs that include brain, heart, lungs, liver, kidney, adrenal glands, reproductive organs, gastrointestinal tract, pancreas, skin, and spleen. Where indicated, samples should be taken for microbial isolation, special diagnostic staining, or clinical chemistry determinations to aid in reaching a diagnosis. The lungs of immunodeficient mice can be silver stained and examined for Pneumocystis sp.

Helicobacter was initially recognized as a pathogen in rodents in 1994.10 Several species of Helicobacter (H. hepaticus, H. bilis, and H. rodentium) are increasingly being recognized as a serious problem in mouse colonies because of their ability to induce hepatitis, inflammatory bowel disease, and rectal prolapse, and function as an intercurrent variable in biomedical research studies.11 Also, some lines of mice generally do not breed well or thrive when infected with one or more Helicobacter species. A recent report detected Helicobacter hepaticus in 11 different genetically altered mouse lines.12 Infection was associated with rectal prolapse and inflammatory bowel disease, and such animals would not be expected to reproduce optimally. Helicobacter hepaticus is apparently widespread in commercial mouse colonies and only a few large suppliers are currently certifying their mice to be free of certain Helicobacter spp. Helicobacter organisms are infectious and can easily be detected in sentinel mice using dirty bedding.13

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