Biological risk assessment related to intracerebral injection of TMEV-DA.

Theiler's murine encephalomyelitis virus (TMEV) is a natural enteric pathogen of mice that, when injected intracranially, induces a demyelinating disease resembling multiple sclerosis. However, data on viral shedding following intracranial infection are sparse for some strains and entirely absent for others, such as the Daniels strain, making it difficult to accurately assess the biological risks associated with infected animals. In our study, we used a combination of RT-qPCR and immunoassays to evaluate viral shedding and the associated infectious risk. We show that viral RNA is detectable in the feces of some mice and that the proportion of shedding animals varies by mouse line. Nevertheless, none of the sentinel mice exposed to soiled bedding from infected animals exhibited seroconversion, indicating that the viral particles are either present at levels below the minimum infectious dose or represent residual, non-infectious material rather than active, transmission-competent virus.