Further characterization of infection mechanisms and transmission dynamics of rustrela virus in rodent in vivo models

Rustrela virus (RusV) is a newly discovered member of the genus Rubivirus . RusV causes a fatal, non-suppurative meningoencephalomyelitis in a variety of mammals. Various aspects of RusV biology remain poorly understood, e.g. the excretion of infectious virus and its transmission. To address these questions, we performed in vivo experiments including putative reservoir (wood mice) as well as potential dead-end hosts (Lewis rats). To investigate the natural route of RusV infection and transmission, subgroups of wood mice and Lewis rats were either inoculated intranasally or orally. Successful infection was only observed in animals inoculated via the intranasal route, leading to the assumption that the virus could enter via olfactory neurons and subsequently spread throughout the central nervous system. To gain an initial understanding of the mechanisms of viral transmission, we co-housed RusV-inoculated wood mice with non-infected sentinels. In addition, wood mice or Lewis rats were placed in cages previously occupied by infected wood mice as donor animals for indirect transmission via the environment. Successful RusV transmission was observed solely in co-housed sentinels. These findings suggest that RusV transmission requires direct contact with bodily fluids, such as saliva or nasal secretions or at least a higher infective dose. In contrast, indirect exposure to a presumably contaminated cage does not seem to be sufficient for transmission between reservoir animals or reservoir and dead-end hosts.