Coding-Complete Genome Sequence of Murine Hepatitis Virus Strain 3 from Brazil.

Murine hepatitis virus (MHV) strain 3, one of the most important inducers of viral hepatitis, has been extensively studied as an organism to gain a better understanding of coronavirus biology and pathogenesis. Only one sequence is currently available. Another representative isolate has now been sequenced and added to the arsenal of MHV-3 variants.

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.

Theiler's murine encephalomyelitis virus in nonbarrier rat colonies.

Theiler's murine encephalomyelitis virus (TMEV), a member of the genus Cardiovirus, is an enteric pathogen of mice that causes acute encephalomyelitis followed by persistent central nervous system infection with chronic inflammation and demyelination after intracerebral inoculation. Although TMEV is a mouse pathogen, antibodies against TMEV strain GDVII have been detected in conventional rat colonies. Natural infection of rats by Cardiovirus has not yet been described. The purpose of this study was to demonstrate TMEV infection of rat colonies by using serologic assays, reverse transcription-polymerase chain reaction (RT-PCR) analysis, and clinical characterization. Indirect immunofluorescence assay of rat serum samples demonstrated antibodies against TMEV-GDVII in 86.3% of samples analyzed, and 77.2% of the antibody-positive samples had neutralizing antibodies. To determine whether rats can be infected experimentally with TMEV-GDVII, specific pathogen-free newborn mice and rats were inoculated intracerebrally with intestinal suspensions from seropositive rats. Both species showed the typical clinical signs of TMEV infection in mice, which is characterized by flaccid hindlimb paralysis and tremor. RT-PCR in brain tissue of experimentally infected animals detected RNA sequences corresponding to the 5' noncoding region of Cardiovirus known as the 'internal ribosome entry site.' These results suggest that rats can be naturally infected with TMEV and related Cardiovirus. Therefore, continued health monitoring for TMEV infection should be included in rat colonies mainly because these animals are used for various experimental purposes.