In the summer season the danger lurks almost everywhere

Since last year, with the exception of the cantons of Geneva and Ticino, the whole of Switzerland has been considered a TBE risk area. In the Swiss Vaccination Plan 2020, vaccination is recommended for all adults and children 6 years of age and older residing in the relevant regions. The risk group for a severe course with permanent damage or fatal consequences includes the age group over 60 years.

Tick-borne diseases are on the rise in Central Europe, with an increase in the number of cases in recent years. In Switzerland, the number of reported cases is between 100-300 annually [1]. Tick-borne diseases occur seasonally in this country. The season in which ticks are particularly active begins in March and ends in November, depending on the weather. Among the infectious diseases transmitted by ticks, Lyme disease and early summer meningoencephalitis (TBE) are of particular importance in our latitudes. The TBE virus is one of the human pathogenic flaviviruses.

Almost all of Switzerland is a risk area

In connection with a marked increase in cases of TBE in previous years, the FOPH has issued a warning against TBE infection from tick bites for the spring and summer months of 2019. With the exception of the cantons of Geneva and Ticino, the whole of Switzerland has been declared a risk area [2]. In the Swiss Vaccination Plan 2020, vaccination is recommended for all adults and children aged 6 years and older who reside or temporarily reside in a risk area [3]. The costs for these indications are covered by the health insurance (mandatory basic insurance). In children under 6 years of age, serious illnesses are rare, so the situation in children who are younger must be examined individually. Transmission occurs through infected ticks, approximately 1-10% are carriers of the virus [4]. TBE is one of the notifiable infectious diseases. From April to November, the FOPH publishes a situation report with the case numbers of early summer meningoencephalitis (TBE) in the first week of each month [5]. Diagnosis is serological by culture or sequence analysis (e.g. PCR, sequencing, NGS) or antibody detection (IgM, titer rise ≥4× or seroconversion).

Vaccination as the most important protective measure

In contrast to Lyme disease, there is currently no causal therapy for TBE in Switzerland, but a highly effective vaccination is available. The TBE vaccines approved in Switzerland are inactivated vaccines (killed viruses). The effect is supported by an aluminum salt. Three doses of vaccination are required for complete basic immunization (≥95% vaccine protection), and time-limited protection is achieved after only two doses of vaccination [2]. The specific vaccination schedule varies depending on the vaccine: when ^TBE-Immun® [12] is used, vaccinations are given at intervals of 0, 1 and 6 months. For ^Encepur® [14], the intervals are 0, 1 and 10 months. For both vaccines, a booster vaccination every 10 years is recommended in the Swiss Vaccination Plan 2020 [3]. Vaccination is possible at any time of year, but the preferred vaccination date for the first and second partial vaccinations is during the cold season so that vaccine protection is already in place at the onset of seasonal tick activity. The third partial vaccination should then take place in the spring of the following year. If basic immunization is not started until the warm season, a rapid immunization procedure can be used in which the 2nd partial vaccination is administered as early as 14 days after the first partial vaccination so that a protective antibody titer can be built up as quickly as possible [12]. The third dose should be given 5-12 months after the second vaccination. Whether or not a rapid immunization procedure should be used depends, among other things, on the availability of vaccines.

Risk group for severe course

Longer-term rehabilitation is required in >40% of TBE patients [6]. Risk factors for severe progression include immunosuppressive therapy, age >60 years, and male sex [7–9]. The prognosis of the meningitic course is best, with frequent inconsequential remission. In meningoencephalitis, neurasthenic symptoms may persist for several weeks and permanent sequelae occur in about 20% [10]. Encephalomyelitis has the worst prognosis. In an observational study over a ten-year period (n=57), only one-fifth of patients recovered completely, 50% retained permanent deficits, and 30% died as a result of the disease [11].

Literature:

1. Federal Office of Public Health (FOPH): Notifiable infectious diseases 2020, www.bag.admin.ch
2. Federal Office of Public Health (FOPH): Early summer meningoencephalitis (FSME). Bulletin 6/19; 12-14.  
3. Federal Office of Public Health (FOPH): Swiss Vaccination Plan 2020, www.bag.admin.ch
4. Krause M: Lyme disease and TBE. Slide presentation, Prof. Martin Krause, MD. FOMF WebUp, Zurich, 16.05.2020.
5. Federal Office of Public Health (FOPH):  Tick-borne diseases, www.bag.admin.ch/bag/de/home/krankheiten
6. Karelis G, et al: Tick-borne encephalitis in Latvia 1973-2009: epidemiology, clinical features and sequelae. Eur J Neurol 2012; 19: 62-68.
7. Czupryna P, et al: Sequelae of tick-borne encephalitis in retrospective analysis of 1072 patients. Epidemiol Infect 2018; 146: 1663-1670.
8. Lenhard T, et al: Predictors, Neuroimaging Characteristics and Long-Term Outcome of Secere European Tick-Borne Encephalitis: A Prospective Cohort Study. PLoS One 2016; 11: e0154153.
9. German Society of Neurology (DGN): S1 Guideline Early Summer Meningoencephalitis  (FSME) 2020, www.awmf.org
10. Bogovic P, et al: The long-term outcome of tick-borne encephalitis in Central Europe. Ticks Tick Borne Dis 2018; 9: 369-378.
11. Kaiser R: Long-term prognosis of patients with primary myelitic manifestation of tick-borne encephalitis: a trend analysis covering 10 years. Neurologist 2011; 82: 1020-1025.
12. Swiss Drug Compendium: ^FSME-Immun®, https://compendium.ch
13. Infovac.ch www.infovac.ch
14. Swiss Drug Compendium: ^Encepur®, https://compendium.ch

GP PRACTICE 2020; 15(6): 24