A semi-nested RT-PCR assay for detection of norovirus in rat fecal samples.

Norovirus is a highly prevalent pathogen that can infect a wide range of host species. Thus far, there have only been two reports of norovirus infection in rats. Diagnostic assays for the detection of norovirus are well established, but a specific molecular assay for the diagnosis of norovirus infection in laboratory rats has not yet been reported. In this study, we describe the development of a sensitive, semi-nested RT-PCR assay for detection of norovirus in fecal samples from Rattus norvegicus, reared in animal facilities under different sanitary barrier conditions. Additionally, we describe the first report of the presence of norovirus in rat colonies from Brazilian animal facilities.

Murine norovirus infection in Brazilian animal facilities.

Murine norovirus (MNV) is a single-stranded positive-sense RNA virus of the Caliciviridae family. MNV has been reported to infect laboratory mice with the ability to cause lethal infections in strains lacking components of the innate immune response. Currently, MNV is considered the most prevalent infectious agent detected in laboratory mouse facilities. In this study, mice in 22 laboratory animal facilities within Brazil were analyzed for MNV infection. Using primers targeting a conserved region of the viral capsid, MNV was detected by RT-PCR in 137 of 359 mice from all 22 facilities. Nucleotide sequencing and phylogenetic analysis of the capsid region from the viral genome showed identity ranging from 87% to 99% when compared to reported MNV sequences. In addition, RAW264.7 cells inoculated with a mouse fecal suspension displayed cytopathic effect after the fifth passage. This study represents the first report of MNV in mouse colonies in Brazilian laboratory animal facilities, emphasizing the relevance of a health surveillance program in such environments.