Epidemiological Situation on Tick-Borne Encephalitis in the Russian Federation in 2014–2023 and Short-Term Forecast of the Incidence for 2024

The aim of the review was to conduct a comparative analysis of the epidemiological situation on tick-borne encephalitis (TBE) over 2014–2023 in the constituent entities of the Russian Federation located in the European and Asian parts of the country and to give a forecast of incidence for 2024. The incidence of TBE in 2023 only marginally decreased as compared to the peak values in 2022, which leveled down the ten-year trend towards reduction. Grouping of the entities of the Russian Federation according to the average incidence of TBE over a decade made it possible to classify 17 of them as regions of low, 15 – of medium, and 17 – of high epidemiological risk. In general, the epidemiological situation regarding TBE is more unfavorable in the Asian part of the country. A list of species of Ixodidae ticks, the main vectors of the tick-borne encephalitis virus, is provided, as well as subtypes and genetic variants of the latter, identified in the European and Asian parts of the country. The peculiarities of the epidemiological situation on TBE and the scope of preventive measures undertaken in Russia in 2023 are considered. It is shown that there are no clearly outlined trends in the nature of changes in the incidence of TBE in endemic federal districts and entities of the country, and the expected incidence rates in 2024 will remain at the long-term average level.

1. Erber W., Schmitt H.-J., Vuković-Janković T. TBEepidemiology by country – an overview. Chapter 12a. In: Dobler G., Erber W., Bröker M., Chitimia-Dobler L., Schmitt H.-J., editors. The TBE Book. 6th ed. Singapore: Global Health Press; 2023. DOI: 10.33442/26613980_12a-6.

2. Süss J. Tick-borne encephalitis 2010: epidemiology, risk areas, and virus strains in Europe and Asia – An overview. Ticks Tick Borne Dis. 2011; 2(1):2–15. DOI: 10.1016/j.ttbdis.2010.10.007.

3. Korenberg E.I., Pomelova V.G., Osin N.S. [Natural-Focal Infections Transmitted by Ixodidae Ticks]. Moscow: “Commentary”; 2013. 463 p. 4. Andaev E.I., Nikitin A.Ya., Tolmacheva M.I., Zarva I.D., Yatsmenko E.V., Matveeva V.A., Sidorova E.A., Kolesnikova V.Yu., Balakhonov S.V. [Epidemiological situation on tick-borne viral encephalitis in the Russian Federation in 2022 and forecast of its development for 2023]. Problemy Osobo Opasnykh Infektsii [Problems of Particularly Dangerous Infections]. 2023; (1):6–16. DOI: 10.21055/0370-1069-2023-1-6-16.

4. Rudakova S.A., Pen’evskaya N.A., Blokh A.I., Rudakov N.V., Trankvilevsky D.V., Savel’ev D.A., Teslova O.E., Kaneshova N.E. [Review of the epidemiological situation on ixodic tick-borne bor- reliosis in the Russian Federation in 2010–2020 and prognosis for 2021]. Problemy Osobo Opasnykh Infektsii [Problems of Particularly Dangerous Infections]. 2021; (2):52–61. DOI: 10.21055/0370-1069-2021-2-52-61.

5. Sirotkin M.B., Korenberg E.I. [The influence of abiotic fac- tors on pathogens, ecologically associated with Ixodidae ticks (for example, borrelia and encephalitis virus)]. Uspekhi Sovremennoi Biologii [Advances in Modern Biology]. 2019; 139(2):126–46. DOI: 10.1134/S0042132419020091.

6. Pogodina V.V., Ishmukhametova A.A., еditors. [Evolution of Tick-Borne Encephalitis (from the Discovery of the Pathogen to the Present)]. Moscow: LLС “TFP”; 2021. 344 p. DOI: 10.48359/978-5-6046253-0-9.2021.29.63.001.

7. Eliseeva I.I., Yuzbashev M.M. [General Theory of Statistics: Textbook]. Moscow: “Financial Accounting”; 2006. 656 p.

8. Savilov E.D., Astafiev V.A., Zhdanova S.N., Zarudnev E.A. [Epidemiological Analysis: Methods of Statistical Processing of Data]. Novosibirsk: “Science-Center”; 2011. 155 p.

9. Kolpakov S.L., Yakovlev A.A. [About methodology for assessment of epidemiological situation]. Epidemiologiya i Infek¬ tsionnye Bolezni [Epidemiology and Infectious Diseases]. 2015; 20(4):34–9.

10. Zlobin V.I., Rudakov N.V., Malov I.V. [Tick-Borne Transmissible Infections]. Novosibirsk: “Nauka”; 2015. 224 p.

11. Dai X., Shang G., Lu S., Yang J., Xu J. A new subtype of eastern tick-borne encephalitis virus discovered in Qinghai-Tibet Plateau, China. Emerg. Microb. Infect. 2018; 7(1):74. DOI: 10.1038/s41426-018-0081-6.

12. Adelshin R.V., Sidorova E.A., Bondaryuk A.N., Trukhina A.G., Sherbakov D.Yu., White III R.A., Andaev E.I., Balakhonov S.V. “886-84-like” tick-borne encephalitis virus strains: Intraspecific sta- tus elucidated by comparative genomics. Ticks Tick Borne Dis. 2019; 10(5):1168–72. DOI: 10.1016/j.ttbdis.2019.06.006.

13. Tkachev S.E., Babkin I.V., Chicherina G.S., Kozlova I.V., Verkhozina M.M., Demina T.V., Lisak O.V., Doroshchenko E.K., Dzhioev Yu.P., Suntsova O.V., Belokopytova P.S., Tikunov A.Yu., Savinova Yu.S., Paramonov A.I., Glupov V.V., Zlobin V.I., Tikunova N.V. Genetic diversity and geographical distribution of the Siberian subtype of the tick-borne encephalitis virus. Ticks Tick Borne Dis. 2020; 11(2):101327. DOI: 10.1016/j.ttbdis.2019.101327.

14. Andaev E.I., Nikitin A.Ya., Yatsmenko E.V., Verigina E.V., Tolmacheva M.I., Ayugin N.I., Matveeva V.A., Balakhonov S.V. [Trends in epidemic process development of tick-borne encephali- tis in the Russian Federation, laboratory diagnosis, prophylaxis and forecast for 2021]. Problemy Osobo Opasnykh Infektsii [Problems of Particularly Dangerous Infections]. 2021; (1):6–16. DOI: 10.21055/0370-1069-2021-1-6-16.