Contemporary prevalence of infectious agents in laboratory mice and rats

Abstract

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.

Indirect ELISA and Indirect Immunofluorescent Antibody Assay for Detecting the Antibody against Murine Norovirus S7 in Mice

“…In this study, we demonstrated that the prevalence of MNV was higher than those of MHV and M. pulmonis, which was consistent with serological survey data that indicates that MNV is the most prevalent viral pathogen in contemporary mouse colonies [13,15]. We found that some serum samples were negative for antibodies to MHV and M. pulmonis but positive for antibody to MNV-S7.…”

“…In these cases, a molecular detection technique such as PCR/RT-PCR is efficacious. A microspherebased, multiplexed fluorescent immunoassay has been recently developed as a high-throughput, automated screening test to complement traditional ELISA in laboratory animal medicine [7,15]. The antibody response judged by ELISA was correlated with the titer measured by the IFA assay during acute MNV-S7 infection.…”

“…The results suggest that MNV infection is more prevalent than mouse hepatitis virus (MHV) and Mycoplasma pulmonis (M. pulmonis) infections in conventional mouse colonies in Japan, as is the case in other areas of the world [13,15].…”

A Pitfall in Mouse Norovirus (MNV) Detection in Fecal Samples Using RT-PCR, and Construction of New MNV-Specific Primers

“…This virus is highly prevalent among laboratory mice, and it is symptomless in immunologically normal mice [3,9,10,14,17,18,23]. Karst et al showed that susceptibility to this virus is not substantially increased by deleting the recombination activating gene 1 (Rag1) or Rag2 gene-dependent specific immunity [7].…”

“…serological [5,6,9,18] and rT-PCr assays [2,5,6,10,14] have been widely used to detect MnV infections. in particular, the use of rT-PCr has shown that mice experimentally inoculated with an MnV strain (MnV-2, MnV-3, or MnV-4) have detectable viruses in the feces from day 2 to week 8 post infection [5], revealing that mice can become persistently infected and shed virus in the feces for prolonged periods.…”