Virome analysis reveals ORF7 sequences of type 2 porcine respiratory and reproductive syndrome virus (PRRSV) for the first time in a rodent host (Microtus pennsylvanicus)

The lung virome of meadow vole (Microtus pennsylvanicus) from six neighbouring locations in New York State, USA was investigated using metagenomics to determine the circulation of potentially zoonotic viruses in a common wild rodent. This study provides the first evidence of the occurrence of Type 2 Porcine Respiratory and Reproductive Syndrome Virus (PRRSV2) in a rodent, or indeed in any species apart from wild and domestic pigs (Sus scrofa). PRRSV has the highest economic impact on the pig husbandry industry of any pathogen, but up to now, farm-to-farm transmission of this virus has been assumed to be associated with movement of and contact with infected pigs and fomites. Our results showing the natural occurrence of this virus in potential transmission hosts other than wild or domestic pigs challenge this scenario. Phylogenetic analysis of assembled partial genomes from four of our pooled samples and all other nucleocapsid protein (ORF7) sequences available in Genbank showed that the sequences recovered from meadow voles unambiguously clustered within the PRRSV2 clade together with sequences derived from wild and domestic pigs. Historical research suggests that spillover from voles to domestic pigs may be the most parsimonious explanation for these results; however, we cannot rule out the reverse: that the source of PRRSV2 in these wild voles derives from pigs. From a One Health perspective, our results reinforce the importance of characterizing wildlife viromes to survey possible sources of zoonotic pathogens, which is vital for making evidence-based decisions regarding potential threats to the health of humans, livestock and wild fauna.