gms | German Medical Science

Small size, synanthropic behaviour and ubiquity are characteristics of small mammals that may facilitate the occurrence of spillover events. While rodents are known carriers of multiple pathogens with pandemic potential, less is known about insectivores, such as shrews.

We have investigated the pathogen presence in white-toothed shrews (Crocidurinae) from Central Europe. Almost 400 individuals of bicolored white-toothed shrews (Crocidura leucodon), lesser white-toothed shrews (Crocidura suaveolens) and greater white-toothed shrews (Crocidura russula) were tested for the presence of Leptospira spp., Coxiella burnetii, Brucella spp. and arthropod-borne pathogens (Anaplasma spp., Babesia spp., Neoehrlichia mikurensis, Bartonella spp.) with different PCR methods. Leptospira spp. were found with a prevalence of 12% with L. kirschneri (sequence type 100) in C. russula. Two C. russula tested positive for N. mikurensis, which is the first description in shrews. Crocidura leucodon is the known reservoir for Borna Disease Virus 1 (BoDV-1, species Orthobornavirus bornaense) causing lethal encephalitis in humans and domestic animals. We took the first ever detected geographic cluster (human n=2; death 2019 and 2022) in a municipality in Bavaria, Germany, as an opportunity for an interdisciplinary One Health investigation. We assessed the local small mammal community to narrow down possible infection sites and conducted a survey to evaluate potential shrew-human interfaces. Of all analysed small mammals, 9/21 Crocidura leucodon tested positive for BoDV-1 RNA. The results were presented to the public during a community meeting.

Overall, our study is the first to shed light on the virosphere of different crocidurine shrew species from Central Europe by implementing a metagenomic next-generation sequencing approach. RNA of individual organ pools from C. leucodon, C. suaveolens, C. russula and Suncus etruscus (Etruscan shrew), the latter from a husbandry, were extracted, further processed, and finally sequenced. Subsequently, RT-qPCRs were designed for newly detected viral sequences. Whole-genomes were obtained for several novel viruses of the families Nairoviridae, Paramyxoviridae and Hepeviridae. Some of them formed phylogenetic clusters closely related to highly relevant viruses such as Crimean-Congo haemorrhagic fever virus and henipaviruses. Our study has started as a regional investigation in Germany on a specific virus with enormous public interest, addressing important questions for the assessment of human-wildlife contacts and the establishment of preventive measures, and enabled us to identify novel viruses in white-toothed shrews with phylogenetic relationships to globally important diseases. Further investigations are needed to characterize these novel viruses and to assess their zoonotic potential, and to evaluate its significance in a global context.