The bicolored white-toothed shrew Crocidura leucodon (HERMANN 1780) is an indigenous host of mammalian Borna disease virus.
Authors: Dürrwald Ralf, Kolodziejek Jolanta, Weissenböck Herbert, Nowotny Norbert
Journal: PloS one
Summary
# Editorial Summary: Borna Disease Virus Reservoir Host Identified in European Shrews Borna disease has long puzzled equine practitioners with its restricted geographic distribution across central Europe and distinctive seasonal peaks that don't align with direct horse-to-horse transmission patterns, pointing towards an unidentified wildlife reservoir. Ralf Dürwald and colleagues conducted a five-year systematic survey of shrews in German Borna disease-endemic regions, identifying 14 bicoloured white-toothed shrews (*Crocidura leucodon*) harbouring the virus out of 107 shrews from five species examined, with genetic sequencing confirming these isolates matched the regional viral cluster. Critically, immunohistological examination revealed that infected shrews carried substantial viral antigen in oral epithelial cells and skin keratinocytes—without developing clinical disease—establishing a potential transmission pathway to horses and other susceptible species through direct contact or environmental contamination. The detection of high proportions of infected shrews at single locations across multiple consecutive years demonstrated a self-sustaining infection cycle within this species, whilst the shrews' behavioural ecology and population dynamics supported their role as a genuine wildlife reservoir rather than incidental hosts. This finding fundamentally reshapes our understanding of Borna disease epidemiology and suggests that integrated pest management, biosecurity protocols targeting shrew contact, and surveillance of shrew populations in endemic areas may warrant consideration alongside conventional disease monitoring in equine practice.
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Practical Takeaways
- •Shrews may be a natural reservoir for Borna disease virus in endemic regions of central Europe; horses in these areas should be monitored for seasonal disease peaks in spring
- •The presence of virus in oral cavities and skin of infected shrews suggests potential indirect transmission routes to horses and sheep worth investigating
- •Identification of shrew populations as BDV reservoirs could help explain the endemic patterns and seasonal variations in equine and ovine Borna disease that have previously been unexplained
Key Findings
- •Borna disease virus was identified in 14 bicolored white-toothed shrews (Crocidura leucodon) from BD-endemic areas in Germany
- •Viral antigen was present in oral epithelial cells and skin keratinocytes, suggesting these shrews may serve as a transmission source
- •Genetic analysis showed close relationship between shrew-derived BDV sequences and regional equine/ovine BDV clusters
- •High percentage of BDV-positive shrews persisted at one location over four consecutive years, indicating a self-sustaining infection cycle