TBE in Belgium

Marjan Van Esbroeck, Tinne Lernout, Vanessa Suin and Steven Van Gucht

E-CDC risk status: affected

(data as of end 2022)

History and current situation

In 2018, the two first human tick-borne encephalitis (TBE) cases with possible/probable autochthonous infection were diagnosed at the National Reference Centre (NRC) of Arbovirus (The Institute of Tropical Medicine, Antwerp, Belgium). Every year, some imported cases of TBE are also detected, infected in other European countries such as Germany,1 Scandinavia, Austria, Kyrgyzstan or Slovenia2 and Russia.

Several seroprevalence/prevalence studies in sentinel animals and ticks have been performed in Sciensano. Seropositive dogs, cattle, roe deer, and wild boar have been found in Belgium.3-7 Up to now, no positive tick has been detected in Belgium (on a total of ca. 1,600 ticks tested).8

  1. Serum samples of Belgian dogs were obtained from 3 diagnostic laboratories in Northern Belgium (n = 688) and Southern Belgium (n = 192). All samples were taken by local veterinary surgeons between March 15, 2009 and June 22, 2009. ELISA-positive and borderline samples were subjected to a tick-borne encephalitis virus (TBEV) sero-neutralization test. One dog was confirmed TBEV seropositive but the clinical history of the seropositive dog could not explain beyond doubt where and when TBEV infection was acquired.
  2. Based on a targeted, risk-based sampling design, serological screening was performed on Belgian cattle (n = 650), selected from the 2010 Belgian national cattle surveillance serum bank. All samples were subjected to a sero-neutralization test. Seventeen bovines were seropositive and 6 had borderline results. The overall bovine seroprevalence in the targeted area was estimated between 2.61% and 4.29%. This confirmed for the first time the presence of TBE foci in wild animals in Belgium.
  3. Roe deer sera collected between 2008 and 2013 (n =190) in Flanders were examined for antibodies against TBEV using a sero-neutralization test. Seroprevalence was 5.1%.
  4. As part of a Flemish wildlife surveillance in 2013, a serological screening was performed on sera from wild boar (Sus scrofa; n = 238) in order to detect TBEV- specific antibodies by using a sero-neutralization test. Ten wild boars were found to be TBEV-seropositive (2.9 % of tested wild boars). This study demonstrated the presence of TBEV-specific antibodies in wild boar and highlighted potential TBEV- foci in Flanders.

The above studies in animals suggest that TBEV has been circulating for at least several years in Belgium (at a low level), and infections in humans were expected to occur. In 2018, two human cases of TBE were reported, in people that were possibly/probably infected in Belgium. However, since they also traveled abroad during the incubation period, the autochthonous origin could not be confirmed. In 2019, a seroprevalence study among 195 forestry workers in Flanders revealed that none had antibodies showing evidence of an acquired infection.9

Three confirmed autochthonous cases have been diagnosed in Belgium during summer 2020. The patients had been exposed in geographically separate regions of the country, two of which were adjacent to an area with known TBEV seropositivity in animals.10 Two travel-associated TBE cases were diagnosed in 2021. One after travel to Austria while the other after travel to the Czech Republic. There was no autochthonous case in 2021.

There were also two travel-associated TBE cases diagnosed in 2022. One after travel to Sweden and the other after travel to Slovenia. No autochthonous cases were reported in 2021 and 2022.

Based on the current epidemiological findings, Belgium is classified as an affected country for TBE.

Overview of TBE in Belgium

Table 1: Virus, vector, transmission of TBE in Belgium
Viral subtypes, distribution No information available in humans yet. No virus-positive animals or ticks have been reported to date.
Reservoir animals Rodents: To date, no rodents seropositive for TBEV have been found in Belgium
(Study realized by Sciensano in 2014, not published). 

Seropositive cattle, roe deer, and wild boar have been identified (cattle in the Wallonia region and wild boar in Flanders).3-7

Infected tick species (%) No positive ticks have been detected 

(Sciensano project in 2018 – RNA detection, Institute of Tropical Medicine (ITM) project in 2018 – RNA detection).8

Dairy product transmission No information available.

Table 2: TBE reporting and vaccine prevention in Belgium
Mandatory TBE reporting None
Other TBE surveillance 1. A national reference center (NRC) for TBE has been established since 2011. This center performs laboratory confirmation in suspected human cases and reports to Sciensano. 
  • From 2011 to 2015: Sciensano, Brussels, Belgium
  • From 2016 to 2020: Institute of Tropical Medicine (ITM), Antwerp, Belgium
  • From 2021 to 2025: ITM, Antwerpen, Belgium

2. Human surveillance via NRC

  • From 2011 to 2015: Sciensano, Brussels, Belgium
  • From 2016 to 2020: ITM, Antwerpen, Belgium
  • From 2021 to 2025: ITM, Antwerpen, Belgium

3. Animal surveillance (2011 to present): Sciensano, Brussels, Belgium3-7

4. Tick surveillance (2018 to present): ITM, Antwerp, Belgium and Sciensano, Brussels, Belgium.

Case definition as described in https://eurlex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2012:262:0001:0057:EN:PDF.
Confirmed case: symptoms of TBE and immunoglobulin M (IgM) and/or ribonucleic acid-positive.

Special clinical features No information available
Available vaccines FSME-IMMUN 

(Purchased from Baxter by Pfizer in 2014)

Vaccination recommendations and reimbursement In 2019, the Belgian Superior Health Council published recommendations for 3 different epidemiological situations. In the current situation (sporadic cases possible), vaccination is only recommended for travelers to endemic regions doing outdoor activities in forested areas (such as hiking, camping, mushroom picking, …) during the tick season (spring, summer and autumn), and for people handling TBEV in a laboratory setting.10
Vaccine uptake by age group/risk group/general population No data available.
Name, address/website of TBE National Reference Center ITM, Antwerp, Belgium, www.itg.be

Note: No information available on TBVE burden or distribution as up to now there have been no TBE cases.
Also, no TBEV has been isolated to date and no autochthonous cases have been identified in Belgium.

 

Figure 1: Burden of TBE in Belgium over time

Click the image above to enlarge

Source Data:
YearNumber of Cases
20132
20143
20151
20161
20173
20182
20190
20203
20212
20222

Contact:

vanessa.suin@sciensano.be

Citation:

Van Esbroeck M, Lernout T, Suin V, Van Gucht S. TBE in Belgium. Chapter 12b. In: Dobler G, Erber W, Bröker M, Schmitt HJ, eds. The TBE Book. 6th ed. Singapore: Global Health Press;2023. doi:10.33442/26613980_12b3-6

References

  1. Gils S, Frans J, Ho E, et al. Case report: tickborne encephalitis (TBE) in a Belgian traveller returning from Germany. J Travel Med. 2018;25;(1); https://doi.org/10.1093/jtm/tay078
  2. Du Four S, Mertens R, Wiels W, De Keyser J et al. Meningoencephaloradiculitis following infection with tick-borne encephalitis virus : case report and review of the literature. Acta Neurologica Belgica, 2017; https://doi.org/10.1007/s13760-017-0873-9
  3. Roelandt S, Heyman P, De Filette M, et al. Tickborne encephalitis virus seropositive dog detected in Belgium: screening of the canine population as sentinels for public health. Vector Borne Zoonotic Dis. 2011;11:1371-6.
  4. Roelandt S*, Suin V*, Riocreux F, et al. Autochthonous tick- borne encephalitis virus-seropositive cattle in Belgium: a risk- based targeted serological survey. Vector Borne Zoonotic Dis. 2014;14:640-7. *Equal contribution
  5. Tavernier P, Sys SU, De Clercq K, et al. Serologic screening for 13 infectious agents in roe deer (Capreolus capreolus) in Flanders. Infect Ecol Epidemiol. 2015;5:29862.
  6. Roelandt S, Suin V, Van der Stede Y, et al. First TBEV serological screening in Flemish wild boar. Infect Ecol Epidemiol. 2016;6:31099.
  7. Roelandt S, Heyman P, Tavernier P, Roels S. Tick-borne encephalitis in Europe: Review of an emerging zoonosis. Vlaams Diergeneeskundig Tijdschrift. 2010;79:23-31.
  8. Lernout T, De Regge N, Tersago K, Fonville M, Suin V, Sprong H. Prevalence of pathogens in ticks collected from humans through citizen science in Belgium. Parasit Vectors. 2019;12(1):550.
  9. Lernout T. Personal Communication.
  10. Stoefs A, Heyndrickx L, De Winter J, Coeckelbergh E, Willekens B, Alonso-Jiménez A, et al. Autochthonous cases of tick-borne encephalitis, Belgium, 2020. Emerg Infect Dis. 2021 Aug; https://doi.org/10.3201/eid2708.211175
  11. Superior Health Council. Vaccination against Tick-Borne Encephalitis (TBE). Brussels: SHC; 2019. Report 9435. Available from: https://www.health.belgium.be/sites/default/files/uploads/fields/fpshealth_theme_file/shc_9435_tbe.pdf

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