Novel viruses in hard ticks collected in the Republic of Korea unveiled by metagenomic high-throughput sequencing analysis.

Ticks are vectors of a wide range of zoonotic viruses of medical and veterinary importance. Recently, metagenomics studies demonstrated that they are also the source of potentially pathogenic novel viruses. During the period from 2015 to 2017, questing ticks were collected by dragging the vegetation from geographically distant locations in the Republic of Korea (ROK) and a target-independent high-throughput sequencing method was utilized to study their virome. A total of seven viruses, including six putative novel viral entities, were identified. Genomic analysis showed that the novel viruses were most closely related to members in the orders Jingchuvirales and Bunyavirales. Phylogenetic reconstruction showed that the Bunyavirales-like viruses grouped in the same clade with other viruses within the Nairovirus and Phlebovirus genera, while the novel Jingchuvirales-like virus grouped together with other viruses within the family Chuviridae. Real-time RT-PCR was used to determine the geographic distribution and prevalence of these viruses in adult ticks. These novel viruses have a wide geographic distribution in the ROK with prevalences ranging from 2% to 18%. Our study expands the knowledge about the composition of the tick virome and highlights the wide diversity of viruses they harbor in the ROK. The discovery of novel viruses associated with ticks in the ROK highlights the need for an active tick-borne disease surveillance program to identify possible reservoirs of putative novel human pathogens.