Sharova et al.
Prevalence and genetic diversity of tick-borne encephalitis virus in ixodid ticks from specific regions of northwestern Russia. PLoS One. 2025;20(1):e0314385. doi:10.1371/journal.pone.0314385
Russia has a high incidence of tick-borne encephalitis (TBE) virus infections (see, for example, Snapshot Week 49/2024). In 2022, a total of 1,957 cases were reported, including 60 fatalities. Between 2015 and 2022, a study was conducted in northwestern Russia to assess TBE virus prevalence and identify relevant virus subtypes in ixodid ticks collected through flagging. A total of 2,812 ticks were examined.
In the Arkhangelsk and Leningrad regions, as well as the Republic of Karelia, Ixodes persulcatus was the dominant tick species. In contrast, in the Komi Republic, Pskov region, and St. Petersburg region, I. ricinus was more prevalent. The overall TBE virus prevalence in adult ticks was 2.4%, with a higher rate in I. persulcatus (3.2%) compared to I. ricinus (0.8%).
All identified TBE virus isolates belonged to the Siberian subtype, with distinct lineages showing specific geographical distributions. The exclusive detection of the Siberian subtype in northwestern Russia suggests a significant westward expansion, likely displacing the European subtype. This shift may be facilitated by the ability of the Siberian subtype to be transmitted by both I. persulcatus and I. ricinus.