TBE in Switzerland and Liechtenstein

Daniel Desgrandchamps and Klara M. Posfay-Barbe

E-CDC risk status: endemic

(data as of end 2022)

History and current situation

The first serological reports of tick-borne encephalitis (TBE) in Switzerland date back to the early 1970s [T. Krech. Dissertation, University of Berne, 1980]. Surveillance started in 1984, and TBE became a notifiable disease in 1988. Most cases are reported between April and October with a tick bite exposure below an altitude of 1500–2000 meters.1,2

Tick-borne encephalitis virus (TBEV) has been identified in ticks from almost all regions of Switzerland and in Liechtenstein. Accordingly,  human cases are found in almost all regions. Most cases occur in the northeastern, central, and midwestern regions of the country, but in recent years, new endemic regions have been detected in western, and southern Switzerland. TBE has thus become endemic almost in the entire country.

In 2013, a procedure allowing for the definition of regions with a local TBE vaccination recommendation was adopted for Switzerland and Liechtenstein.3 Data from cases notified over the previous 12 years (“high risk areas”, Fig. 3a) were combined with data from the historical map of Swiss endemic regions and “natural clusters”. The resulting Swiss map was used until 2018 for the definition of regions where TBE vaccination is recommended for exposed people (Figure 3b).

However, in view of the increasing numbers of reported TBE cases in recent years, Swiss and Liechtenstein health authorities decided in 2019 to consider the entire countries – except for the cantons of Geneva and Ticino – as an at-risk area in which TBE vaccination is recommended for all individuals with possible exposure (both as residents or as visitors)2, see Figure 3c.

Currently, vaccination is recommended and reimbursed by health insurance for individuals older than 6 years of age living in or visiting endemic regions. In children aged 1–5 years, the indication shall be based on individual considerations. Unlike in other countries and in contrast to the label, a booster dose is recommended only every 10 years.3

As elsewhere in Europe, the proportion of “mild cases” is lower and the number of more serious cases higher with increasing age. However, more serious disease patterns like meningoencephalitis have also been reported in children below the age of 6 years over the later years (E. Altpeter, FOPH, personal communication). Less than half (45%) of symptomatic patients have reported a tick bite within 4 weeks of onset.5 Less than 2% of cases experienced tick bites outside of Switzerland.

Approximately 80% of all symptomatic patients are hospitalized.1 The mean duration for hospitalization was 9 days (interquartile range 5–11 days), and duration increased linearly with age (5 days in children less than 14 years old to 14.6 days for patients older than 70 years).5

Overview of TBE in Switzerland

Table 1: Virus, vector, transmission of TBE in Switzerland
Viral subtypes, distribution European subtype; 97%–98.4% similar to the reference Neudoerfl strain, strain Genbank = U27495; mostly: strain NET-BE7, HQ883372 & NETBE8 (HM450136, HM450137, HM450138, HM450140, HM450141)6,7
Reservoir animals Small mammals such as rodents, birds6,7
Infected tick species (%) Ixodes ricinus. 1.6%–9.9% in areas <2000 meters altitude6,8
Dairy product transmission Not documented

Table 2: TBE reporting and vaccine prevention in Switzerland

Mandatory TBE reporting

Notifiable disease since 1988

Tick bites and Lyme borreliosis have been reported via a sentinel group
(general practitioners and pediatricians in the entire country) since 20085,9

Categorization5 Case classification Laboratory criteria Clinical criteria
Not a case Positive IgM serology No ILI & no neurological symptoms
Possible case a) Positive IgM serology ILI or non-specific neurological signs & symptoms
  b) Positive IgM + positive IgG serology* Any
Probable case a) Positive IgM Meningitis, meningoencephalitis, encephalomyelitis or pareses
  b) Positive IgM + positive IgG serology* ILI or non-specific neurological signs or symptoms
Confirmed case a) Positive IgM Meningitis, meningoencephalitis, encephalomyelitis, or pareses
  b) Positive IgM + positive IgG serology* Meningitis, meningoencephalitis, encephalomyelitis, or pareses

IgG, immunoglobulin; IgG, immunoglobulin; ILI, influenza-like illness; PCR, polymerase chain reaction

*Or anti-TBE IgG serum antibody seroconversion or =4-fold rise in anti-TBE IgG serum antibodies

Special clinical features No Swiss data
  % with sequelae: 25%; mortality: 1%
Available vaccines10 Encepur N® (Bavarian Nordic);

FSME-Immun® (Baxter/Pfizer)

Number of doses sold: not available

Vaccination recommendations and reimbursement10 Recommendations and reimbursement for vaccination in 2006
Vaccine uptake by age group/risk group/general population11 Average national vaccination uptake (3 doses), 2014–2016:

8 years old: 22%–31%

16 years old: 33%–45%

High-risk area (canton of Thurgau):

8 years old: 40%–53%

16 years old: 64%–75%

Name, address/website of TBE National Reference Center National Reference Center for Tick-borne Diseases, SPIEZ LABORATORY is a division of the Federal Office for Civil Protection LABOR SPIEZ

Austrasse

3700 SPIEZ – Switzerland

https://www.labor-spiez.ch/de/die/bio/dediebionrz.htm

nrzk@babs.admin.ch

Figure 3a: High risk areas3

(local clusters of TBE notifications over the last 10 years, as per March 2022).

Figure 3b: Defined risk areas in Switzerland3, where vaccination was recommended for exposed people until end of 2018.

Figure 3c: Extended risk areas with recommended TBE vaccination for all exposed individuals (residents and visitors) as per March 20222

Latest update: Click here

Acknowledgments

Unpublished data and advice on data interpretation were kindly provided by Dr Ekkehardt Altpeter, Federal Department of Home Affairs FDHA, Federal Office of Public Health FOPH, Division of Communicable Diseases, Bern, Switzerland.
Updates for 2022 cases provided by Dr Kyra Zens, University of Zurich, Institute for Experimental Immunology, Switzerland.

Contact:

daniel@desgrandchamps.ch

Citation:

Desgrandchamps D, Posfay-Barbe, MK. TBE in Switzerland and Liechtenstein. 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_12b33-6

References

  1. FOPH. Vaccination protects against TBE: declarations for Switzerland from 2002 to 2015. [Impfen schützt vor Frühsommer-Meningoenzephalitis (FSME): Meldedaten Schweiz, 2002 bis 2015]. FOPH Bulletin. 2016;41:622-26.
  2. FOPH. Tick-borne encephalitis (TBE): Extension of risk areas. [Frühsommer-Meningoenzephalitis (FSME): Ausweitung der Risikogebiete]. FOPH Bulletin. 2019;(6):12-14.
  3. FOPH. Recommendation of vaccination for TBE: update and new presentation of the map from April 2013. [Aktualisierung und neue Darstellung der Karte mit Impfempfehlung für Frühsommer-Meningoenzephalitis per April 2013]. FOPH Bulletin. 2013;18:305-7.
  4. FOPH. Available at: https://www.bag.admin.ch/bag/de/home/zahlen-und-statistiken/zahlen-zu-infektionskrankheiten.exturl.html/aHR0cHM6Ly9tZWxkZXN5c3RlbWUuYmFnYXBwcy5jaC9pbmZyZX/BvcnRpbmcvZGF0ZW5kZXRhaWxzL2QvZnNtZS5odG1sP3dlYmdy/YWI9aWdub3Jl.html
  5. Schuler M, Zimmermann H, Altpeter E, Heininger U. Epidemiology of tick-borne encephalitis in Switzerland, 2005 to 2011. Euro Surveill. 2014;19.
  6. Rieille N, Bressanelli S, Freire CC, et al. Prevalence and phylogenetic analysis of tick-borne encephalitis virus (TBEV) in field-collected ticks (I. ricinus) in southern Switzerland. Parasit Vectors. 2014;7:443.
  7. Lommano E, Burri C, Maeder G, et al. Prevalence and genotyping of tick-borne encephalitis virus in questing Ixodes ricinus ticks in a new endemic area in western Switzerland. J Med Entomol. 2012;49:156-64.
  8. Burri C, Korva M, Bastic V, Knap N, Avsic-Zupanc T, Gern L. Serological evidence of tick-borne encephalitis virus infection in rodents captured at four sites in Switzerland. J Med Entomol. 2012;49:436-9.
  9. FOPH. Ticks: 2014, a medium year [Tiques: 2014, une année dans la moyenne]. Bulletin de l’OFSP. 2015;16:237-9.
  10. FOPH. Recommendations for vaccination against TBE [Empfehlung zur Impfung gegen Zeckenenzephalitis]. Bulletin de l’OFSP. 2006;13:225-31.
  11. FOPH. https://www.bag.admin.ch/dam/bag/de/dokumente/mt/i-und-b/durchimpfung/tabelle-durchimpfung.xlsx.download.xlsx/tabelle-durchimpfung-191216-de.xlsx

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