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Updated: Jul 13, 2026
Reverse Genetics Mediated Recovery of Infectious Murine Norovirus
Published on: June 24, 2012
Naturally occurring murine norovirus infection in a large research institution
Kathy A Perdue1, Kim Y Green, Michelle Copeland
1Comparative Medicine Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA. kperdue@niaid.nih.gov
Abstract:
Murine norovirus (MNV) is a recently discovered infectious agent in mice and may be the most common naturally occurring infection of laboratory mice in North America. In 2005, we surveyed the Swiss Webster female sentinel mice in our institute's research facilities. Of the 4 facilities surveyed, 3 had sentinel mice that were positive for MNV antibodies, whereas our largest facility (which only receives mice directly from select vendors or by embryo rederivation directly into the facility) was apparently MNV-free. However, testing of sentinel mice in this large facility 1 y later found that 2% of the animals had developed MNV-specific antibodies. In a recently opened fifth facility, a serologic survey in 2006 identified MNV-antibody-positive Tac:SW sentinel mice that had received bedding from experimental mice on the same rack quadrant. Reverse transcription- polymerase chain reaction analysis of feces from the cages of these mice showed evidence for shedding of MNV. These sentinel mice were used to study the fecal excretion, antibody development, gross lesions upon necropsy, histopathology, and immunohistochemistry of the viral infection. None of the MNV-antibody-positive sentinel mice exhibited clinical signs or gross lesions, but these mice excreted virus in feces and developed antibodies to MNV. Histopathologic lesions consisted only of a few hepatic inflammatory foci in each liver section, some of which were immunoreactive with antibodies to MNV. MNV viral antigens also were present in the mesenteric lymph nodes.
Insights
Murine norovirus (MNV) is a common infection in lab mice. Sentinel mice developed MNV antibodies and shed the virus, indicating transmission within research facilities.
Area of Science:
- Veterinary Virology
- Laboratory Animal Science
- Immunology
Background:
- Murine norovirus (MNV) is a prevalent infectious agent in laboratory mice.
- Understanding MNV transmission is crucial for maintaining research integrity.
- Previous studies indicated MNV presence in North American research facilities.
Purpose of the Study:
- To investigate the prevalence and transmission dynamics of Murine norovirus (MNV) in a research setting.
- To characterize the clinical and pathological outcomes of MNV infection in sentinel mice.
- To identify potential routes of MNV dissemination within animal facilities.
Main Methods:
- Serological surveys of Swiss Webster sentinel mice to detect MNV antibodies.
- Environmental sampling, including analysis of sentinel mouse bedding.
- Reverse transcription-polymerase chain reaction (RT-PCR) for viral detection in fecal samples.
- Histopathology and immunohistochemistry to assess tissue-associated viral presence and host response.
Main Results:
- Three out of four initial facilities surveyed had MNV-positive sentinel mice.
- A previously MNV-free facility became positive within one year, with 2% of sentinel mice developing antibodies.
- MNV shedding was confirmed via fecal RT-PCR in sentinel mice housed with infected animals.
- Infection was subclinical, with no gross lesions observed, but histopathology revealed hepatic inflammatory foci and MNV antigens in mesenteric lymph nodes.
Conclusions:
- Sentinel mice effectively detect MNV presence and transmission within research facilities.
- MNV can spread between experimental animals and sentinel populations, even in facilities with stringent controls.
- Subclinical MNV infections can lead to antibody development and viral shedding, necessitating ongoing monitoring.
