Contemporary Prevalence of Infectious Agents in Laboratory Mice and Rats

Laboratory Animals. Apr, 2009  |  Pubmed ID: 19015179

Periodic health screening of rodents used in research is necessary due to the consequences of unwanted infections. One determinant of the risk of infection for any given agent is its prevalence; other factors being equal, a prevalent agent is more likely than a rare one to be introduced to a research facility and result in infection. As an indicator of contemporary prevalence in laboratory populations of rats and mice, the rate of positive results in the samples received at a major commercial rodent diagnostic laboratory was compiled for this paper. Although samples from laboratory rodent vendors have been excluded, results are tabulated from samples from more than 500,000 mice and 80,000 rats submitted over several years from pharmaceutical, biotechnology, academic, and governmental institutions in North America and Europe, allowing meaningful determination of which agents are common in the research environment versus which agents are rare. In mice, commonly detected infectious agents include mouse norovirus, the parvoviruses, mouse hepatitis virus, rotavirus, Theiler's murine encephalomyelitis virus, Helicobacter spp., Pasteurella pneumotropica, and pinworms. In rats, commonly detected infectious agents include 'rat respiratory virus', the parvoviruses, rat theilovirus, Helicobacter spp., P. pneumotropica, and pinworms. A risk-based allocation of health-monitoring resources should concentrate frequency and/or sample size on these high-risk agents, and monitor less frequently for the remaining, lower-risk, infectious agents.

Euthanasia of Neonatal Rats with Carbon Dioxide

Journal of the American Association for Laboratory Animal Science : JAALAS. Jan, 2009  |  Pubmed ID: 19245746

Exposure to CO(2) is a common method used to euthanize rodents in biomedical research and rodent production. The purpose of this study was to determine the length of CO(2) exposure required to euthanize neonatal rats (0 to 10 d old). Multiple groups of rats were exposed to 100% CO(2) for 5 to 60 min. After CO(2) exposure, rats were placed in room air for 20 min to allow for possible recovery. No difference was found in comparing 1 inbred strain and 1 outbred stock of rats. Time to death varied inversely with the age of the animals, requiring as long as 35 min on the day of birth. The time to death decreased steadily with increasing age, with 100% of the rats euthanized after 5 min of CO(2) exposure at 10 d of age. The time required for 100% mortality decreased by 3 min for every 1 d increase in age between days 0 and 10.

Breeding and Housing Laboratory Rats and Mice in the Same Room Does Not Affect the Growth or Reproduction of Either Species

Journal of the American Association for Laboratory Animal Science : JAALAS. Sep, 2009  |  Pubmed ID: 19807969

Few data exist regarding the effects of long-term housing of rats and mice in the same secondary enclosure. Historical reproductive and growth data were compared for colonies of mice and rats maintained in open-topped cages in either single-species or dual-species barrier rooms. This analysis included reproductive parameters (litter size at birth, litter size at weaning, and pups missing at weaning) collected from 33 colonies of mice comprising 500 to 38,500 breeding females and 28 colonies of rats totaling 350 to 4,600 breeding females, and representative samples from 28 colonies of each species were analyzed for weight gain from weaning to adulthood. The presence or absence of the other species was not associated with statistically significant differences in weight gain or any of the reproductive parameters. These results suggest that breeding colonies of rats and mice of the same health status can be housed in the same room without a negative effect on the growth and reproduction of either species.

Method of Feed Presentation Affects the Growth of Mongolian Gerbils (Meriones Unguiculatus)

Journal of the American Association for Laboratory Animal Science : JAALAS. Jan, 2010  |  Pubmed ID: 20122314

The Animal Welfare Regulations, which define legal requirements for the care and use of gerbils in research and testing, and the Guide for the Care and Use of Laboratory Animals describe feeding practices for several species of rodents but not Mongolian gerbils (Meriones unguiculatus). To investigate whether the method of feed presentation affected reproduction and growth of gerbils, we compared the reproductive performance and rate of growth of gerbils fed on the cage floor, by hopper (J-feeder), or by wire-bar cage lid. Reproductive parameters of 10 breeding pairs for each method of feeding were followed for 63 d and did not differ between methods. To investigate the effect of feeding method on weight gain in juvenile gerbils, groups of 80 male and 80 female weanling gerbils per feeding method were fed for 5 consecutive weeks after weaning and weighed weekly. Gerbils fed on the cage floor and by means of J-feeders were significantly heavier than were those fed by using a wire-bar top. Our findings indicate that feeding gerbils by using J-feeders or on the cage floor are both acceptable practices.

Retinal Lesions and Other Potential Confounders of Ocular Research in Inbred Mice

Investigative Ophthalmology & Visual Science. Jun, 2012  |  Pubmed ID: 22736716