Abstract
BackgroundSquirrels (family Sciuridae) are globally distributed members of the order Rodentia with wildlife occurrence in indigenous and non-indigenous regions (as invasive species) and frequent presence in zoological gardens and other holdings. Multiple species introductions, strong inter-species competition as well as the recent discovery of a novel zoonotic bornavirus resulted in increased research interest on squirrel pathogens. Therefore we aimed to test a variety of squirrel species for representatives of three virus families.MethodsSeveral species of the squirrel subfamilies Sciurinae, Callosciurinae and Xerinae were tested for the presence of polyomaviruses (PyVs; family Polyomaviridae) and herpesviruses (HVs; family Herpesviridae), using generic nested polymerase chain reaction (PCR) with specificity for the PyV VP1 gene and the HV DNA polymerase (DPOL) gene, respectively. Selected animals were tested for the presence of bornaviruses (family Bornaviridae), using both a broad-range orthobornavirus- and a variegated squirrel bornavirus 1 (VSBV-1)-specific reverse transcription-quantitative PCR (RT-qPCR).ResultsIn addition to previously detected bornavirus RNA-positive squirrels no more animals tested positive in this study, but four novel PyVs, four novel betaherpesviruses (BHVs) and six novel gammaherpesviruses (GHVs) were identified. For three PyVs, complete genomes could be amplified with long-distance PCR (LD-PCR). Splice sites of the PyV genomes were predicted in silico for large T antigen, small T antigen, and VP2 coding sequences, and experimentally confirmed in Vero and NIH/3T3 cells. Attempts to extend the HV DPOL sequences in upstream direction resulted in contiguous sequences of around 3.3 kilobase pairs for one BHV and two GHVs. Phylogenetic analysis allocated the novel squirrel PyVs to the genera Alpha- and Betapolyomavirus, the BHVs to the genus Muromegalovirus, and the GHVs to the genera Rhadinovirus and Macavirus.ConclusionsThis is the first report on molecular identification and sequence characterization of PyVs and HVs and the detection of bornavirus coinfections with PyVs or HVs in two squirrel species. Multiple detection of PyVs and HVs in certain squirrel species exclusively indicate their potential host association to a single squirrel species. The novel PyVs and HVs might serve for a better understanding of virus evolution in invading host species in the future.
Highlights
Squirrels are globally distributed members of the order Rodentia with wildlife occurrence in indigenous and non-indigenous regions and frequent presence in zoological gardens and other holdings
Schulze et al Virology Journal (2020) 17:42 (Continued from previous page). This is the first report on molecular identification and sequence characterization of PyVs and HVs and the detection of bornavirus coinfections with PyVs or HVs in two squirrel species
We extracted the large T-antigen (LTAg) and VP1 (PyV) or DNA polymerase (DPOL) and glycoprotein B (gB) (BHV and GHV) coding sequences from these genomes as well as from the novel viruses we identified in squirrels using Geneious v11.1.5 [55]
Summary
Squirrels (family Sciuridae) are globally distributed members of the order Rodentia with wildlife occurrence in indigenous and non-indigenous regions (as invasive species) and frequent presence in zoological gardens and other holdings. Squirrels (family Sciuridae) are members of the order Rodentia, and with the exception of Antarctica, distributed globally on all continents They occur both in the Old and in the New world, and squirrel species diversity is high in Africa and Asia [1]. Squirrels are generally distinguished as ground, flying (gliding) or tree squirrels With respect to the latter, the Eurasian red squirrel (Sciurus vulgaris) is the dominant squirrel species across the Palaearctic [2, 3]. The multiple introductions and subsequent translocations had devastating consequences for local Eurasian red squirrel populations in deciduous and mixed forest landscapes in Great Britain, Ireland and Italy leading to large-scale declines as a result of competition for resources and introduced pathogens [6,7,8]. Squirrel adenovirus has been known for many years, it was only recently that the complete genome of squirrel adenovirus 1 (SqAdV-1) was determined and found to indicate a close relationship between British and Continental European red squirrel populations [11, 13]
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