Parallel isolation of calicivirus and reovirus from lethal co-infected mink during a potential epidemic of farmed mink infections

Abstract

Mink has been identified as an animal with susceptibility to SARS-CoV-2 and also as the only animal with evidence to transmit the virus back to humans. Thus, the surveillance of viruses among high-density farmed minks has a significant meaning for the control of zoonotic emerging diseases in humans. Within anal swabs of minks that died of unknown causes in a mink farm, mink calicivirus (MCV) and mammalian orthoreovirus (MRV) were detected and simultaneously observed within MDCK cell culture from the sample of the same lethal mink. The parallel isolation was successfully performed by utilizing cell lines from different host sources with distinct viral sensitivities, i.e. Mv.1.Lu and Vero-E6 and the two viruses were independently separated. The prevalence of the virus among the minks and its genomic characteristics were investigated through deep sequencing technology. Phylogenetic analysis of the viral genome showed a close relationship of the newly isolated MCV-GCCDC8-2020 with MCV strains belonging to the genus Vesivirus, but with unique mutations derived from the major structural protein (VP1). The reovirus MRV-GCCDC9-2020 isolated from the same mink belongs to serotype 3 mammalian orthoreovirus and genome analysis showed a potential reassortment derived from reoviruses in different species. This study provides a beneficial reference on viral co-infection within disease investigation in farmed minks and raises the concern for the virus surveillance among the high-density fed animal farms.