Viruses belonging to the genus Norovirus (NoV) of the family Caliciviridae are the major cause of acute viral gastroenteritis worldwide. NoVs are classified into 10 genogroups (GI-GX), and those belonging to the genogroup GV are able to infect several species of rodents. To evaluate the circulation of MNV among mice housed in an Italian facility, sampling was performed over two separate periods, in 2011, and 3 years later in 2014. During the two samplings, 75 fecal samples were collected from healthy mice housed in the animal facility and subjected to RT-PCR for viral detection. After the analysis, 41/75 animals (54.6%) resulted positive for the presence of MNV in feces. Nucleotide sequencing revealed the presence of two MNV variants co-circulating in both 2011 and 2014. One MNV strain was isolated on RAW264.7 cell line, and subjected to full genome sequencing. Our study showed that the murine noroviruses are widespread in the investigated animal facility, despite guidelines for animal care and maintenance. Full genome sequence analysis of the MNV strain described in this study showed a correlation with other strains circulating in Europe. Understanding the molecular epidemiology of this virus should give insight into its natural history and evolution in mice.
Keywords: MNV; Murine norovirus; facility; isolation; sequencing.