TBE in Estonia

Kuulo Kutsar

E-CDC risk status: endemic

(last edited: date 22.04.2024, data as of end 2023)

History and current situation

The first cases of tick-borne encephalitis (TBE) in Estonia were identified in 1949. Today, Estonia is  a  TBE- endemic country. A TBE-endemic area in Estonia is defined as an area with circulation of the TBEV between ticks and vertebrate hosts as determined by detection of the TBEV or the demonstration of autochthonous infections in humans or animals within the last 20 years.

Euro-Asian genotypes of TBEV – the Western or European (TBEV-EU), Siberian (TBEV-Sib), and Far-Eastern (TBEV-FE) subtypes are co-circulating in Estonia. Vectors of TBEV, the tick species Ixodes ricinus and Ixodes persulcatus, are distributed throughout the country.

The high-risk season for infection coincides with the period of biological activity of ticks and lasts for 7 months from April to November, peaking in June to August.

Most TBE cases are diagnosed in persons ≥60 years of age and the incidence among the rural population is 1.8 times higher than among the urban population.

Overview of TBE in Estonia

Table 1: TBE in Estonia
Viral subtypes, distributionCo-circulation of European (TBEV-EU), Far-Eastern (TBEV-FE), and Siberian (TBEV-Sib) subtypes
Reservoir animalsRodents, ruminants, game
Infected tick species (%)2011: I. persulcatus 8%, I. ricinus on mainland 0.6% – 0.8% and Saaremaa 3.0%.
2013: Estonia: I. persulcatus 4.23%, I. ricinus 0.42%.
2018: Tallinn 0.44% – 2.7%
2023: Estonia 1.1% – 8.3%: Valga county 6.1% and Viljandi county 8.3%.
Dairy product transmissionDocumented but rare
Mandatory TBE reportingReporting: neurologists, infectious disease specialist

Case definition
Clinical criteria: a person with symptoms of the central nervous system (meningitis, meningoencephalitis, encephalomyelitis, encephaloradiculitis)

Laboratory criteria for case confirmation:
At least 1 of the following:
– TBE-specific IgM and IgG antibodies in blood
– TBE-specific IgM antibodies in CSF
– Seroconversion of 4-fold increase of TBE-specific antibodies in paired serum samples
– Detection of TBE viral nucleic acid in a clinical specimen
– Isolation of TBEV from clinical specimens. Probable case: detection of TBE-specific IgM antibodies in a unique serum sample

Epidemiological criteria
Exposure to a common source (unpasteurized dairy product). Case classification:
– Possible case: not applicable
– Probable case: a person meeting the clinical criteria and the laboratory criteria for a probable case OR a person meeting the clinical criteria and with an epidemiological link
– Confirmed case: a person meeting the clinical and laboratory criteria for case confirmation
Other TBE surveillanceLaboratory and epidemiological surveillance
Special clinical featuresBiphasic disease: meningitis, meningoencephalitis, or meningoencephalomyelitis. Risk groups: people who often spend time outdoors (in nature)
Available vaccinesENCEPUR CHILDREN, ENCEPUR ADULTS, TICOVAC CHILDREN, TICOVAC ADULTS (Table 2)
Vaccination recommendations and reimbursementVaccination recommendations 1998. No reimbursement; self-paid
Vaccine uptake by age group/risk group/general populationVaccine uptake by general population (vaccinated and revaccinated): 2018 – 3.1%; 2019 – 3.7%; 2020 – 3.4%; 2021 – 2.6%, 2022 – 4,1%, 2023 – 5,8%. (Table 2)
Name, address/website of TBE National Reference CenterHealth Board, Tallinn Paldiski St 81; https://www.terviseamet.ee

Figure 1: Age and gender distribution of TBE cases in Estonia, 2023

Source data
Age (years)MalesFemalesAll
0 - 917724
10 - 1915520
20 - 29639
30 - 39141226
40 - 4951217
50 - 59142337
60 - 69131932
70 - 79162137
80 and older257
Total102107209

TBE seasonality: case numbers, Estonia 2023
January – 1, February – 1, March – 0, April – 0 , May – 3 , June – 20 , July – 19, August – 49, September – 45, October – 56, November – 11, December – 4 cases
TBE total cases 209 and incidence 15.6 per 100 000 population in Estonia 2023


Figure 2: Age distribution of TBE in Estonia, 2005–2023

Source data
Year0-910-1920-2930-3940-4950-5960≥
200517222026232135
200614222215253142
200710151425211837
20086101114131422
200917232022322441
201018242219333451
201112202828314784
201212281227242154
20138111212141937
2014711710161122
20151011719171537
20168858181123
20171661013101121
201861231315729
2019711512121026
20202879101024
20219975131423
2022158615242347
20232420926173776

Figure 3: Sites of TBEV-infection in Estonia, 2023

Source data
CountiesCases
Tallinn (capital)31
Harjumaa25
Hiiumaa2
Ida-Virumaa3
Järvamaa5
Jõgevamaa4
Läänemaa3
Lääne-Virumaa8
Pärnumaa45
Põlvamaa5
Raplamaa4
Saaremaa15
Tartumaa30
Valgamaa4
Viljandimaa13
Võrumaa12
Total209

Contact

Kuulo Kutsar
kkutsar@hotmail.com

Author

Kuulo Kutsar

Citation

Kutsar K. TBE in Estonia. Chapter 13. In: Dobler G, Erber W, Bröker M, Chitimia-Dobler L, Schmitt HJ, eds. The TBE Book. 7th ed. Singapore: Global Health Press; 2024. doi:10.33442/26613980_13-10-7

References

  1. Health Board of Estonia. [Nakkushaiguste esinemine ja immunoprofülaktika]. 2022. Accessed 9 April, 2024.
  2. https://www.terviseamet.ee/sites/default/files/Nakkushaigused/Haigestumine/epid_ulevaade_2022_0.pdfKatargina O, Russakova S, Geller J et al. Detection and characterization of tick-borne encephalitis virus in Baltic countries and Eastern Poland. PLoS One. 2013;8(5):e61375
  3. Geller J, Vikentjeva M. [Ticks as disease carriers in the green areas of Tallinn and the surrounding area]. 2020. Accessed 30 March, 2024. https://www.tai.ee/sites/default/files/2021-03/159852954118_Pealinna%20rohealade%20puugid%20ja%20puugihaigused.pdf
  4. Vikentjeva M, Geller J. Linnapuugid 2023 – puukide levimus ja puugihaiguste oht Eesti linnade avalikel haljasaladel. Tervise Arengu Instituut. 2023. Accessed 30 March 2024. https://tai.ee/sites/default/files/2023-09/Linnapuugid_2023.pdf

TBE Book