A re-emerging arbovirus in livestock in China: Early genomic surveillance and phylogeographic analysis

Viruses in livestock represent a great risk to public health due to the close contact of their hosts with humans and the potential long-range transportation though animal trade. Here, we show how to predict outbreaks of potential zoonotic pathogens and use spatially-explicit phylogeographic and phylodynamic approaches to provide estimates of key epidemiological parameters. First, we use metagenomic next generation sequencing (mNGS) to identify a Getah virus (GETV) as the pathogen responsible for a re-emerging swine disease in China. The GETV isolate is able to replicate in a variety of cell lines including human cells and shows high pathogenicity in a mouse model suggesting a potential public health risk. We obtained 16 complete genomes and 78 E2 gene sequences from viral strains collected within China from 2017 to 2021 through large-scale surveillance among livestock, pets and mosquitoes. Moreover, phylogenetic analysis reveals that three major GETV lineages are responsible for the current epidemic in livestock in China. We identify three potential positively selected sites and mutations of interest in E2, which may impact the transmissibility and pathogenicity of the virus. We then reconstruct the evolutionary and dispersal history of the virus and test the impact of several environmental factors on the viral genetic diversity through time and on the dispersal dynamic of viral lineages. Of note, we identify temporal variation in livestock meat consumption as a main predictor of viral genetic diversity through time. Finally, phylogeographic analyses indicate that GETV preferentially circulates within areas associated with relatively higher mean annual temperature and pig population density. Our results highlight the importance of continuous surveillance of GETV among livestock in southern Chinese regions associated with relatively high temperatures, and the need to control mosquitoes in the livestock farms. Our analyses of GETV also provide a baseline for future studies of the molecular epidemiology and early warning of emerging arboviruses in China.