Genomic Characteristics of a Novel Yezo Virus Identified in the Virome of <i>Ixodes pavlovskyi</i> Ticks from Tomsk, Russia (2024)

Ixodid ticks are blood-sucking ectoparasites of vertebrates. They are an integral part of any natural foci and are responsible for the worldwide transmission of infections to humans, which can result in severe symptoms. For instance, the Tomsk region, where three abundant tick species (Dermacentor reticulatus, Ixodes pavlovskyi, I. persulcatus) are found, is an endemic area for tick-borne encephalitis virus (TBEV). An increasing number of novel infectious agents carried by ticks are being identified using metagenomic sequencing. A notable example is the Yezo virus (Orthonairovirus yezoense, YEZV), which was discovered in people with fever symptoms after tick bites in Japan and China from 2014 to 2025. For the first time, we performed metagenomic sequencing of the virome of ticks collected in the Tomsk region. In a sample obtained from a pool of I. pavlovskyi ticks, all three segments of the YEZV genome were detected. The subsequent phylogenetic analysis demonstrated that the newly identified isolate formed a sister group to previously described virus isolates, indicating the presence of a new genetic variant. These findings expand the geographic range and the number of vector species for YEZV and highlight the importance of molecular monitoring of viral agents circulating among ticks in Western Siberia.