Conference reportTick-borne encephalitis (TBE): An underestimated risk…still: Report of the 14th Annual Meeting of the International Scientific Working Group on Tick-Borne Encephalitis (ISW-TBE)
Introduction
It has now been 14 years since the International Scientific Working Group on Tick-Borne Encephalitis (ISW-TBE) kicked off its first official meeting in 1998. Since then, no fewer than 760 expert scientists – including neurologists, general practitioners, clinicians, travel physicians, virologists, pediatricians, and epidemiologists – from 30 different European countries have convened to take the opportunity of exchanging late-breaking research, identifying obstacles to increasing vaccination rates, and shaping feasible strategies to overcome them. By publishing annual conference reports, the ISW-TBE wants to keep the scientific community updated about the latest developments (Kunze et al., 2004, Kunze et al., 2005, Kunze et al., 2006, Kunze et al., 2007, Kunze et al., 2008, Kunze et al., 2009, Kunze et al., 2010, Kunze et al., 2011).
The risk of getting TBE is still underestimated in many parts of Europe, and worldwide.
Therefore this year's conference was held under the title “tick-borne encephalitis (TBE): an underestimated risk…still”. The agenda was divided into the following parts: (i) underestimated risk, (ii) look more – find more, (iii) poster session: epidemiological update in Europe, (iv) TBE as a notifiable disease – status quo and the way forward, and (v) increased efforts in prevention.
Within this schedule, the working group discussed various themes, e.g. TBE – an underestimated risk in children, a case report in 2 Dutch travelers, the very emotional report of a tick victim, an overview of the epidemiological situation, investigations to detect new TBE cases in Italy, TBE virus (TBEV) strains circulation in Northern Europe, TBE Program of the European Centre for Disease Prevention and Control (ECDC), efforts to increase the vaccination rate in the Czech Republic, positioning statement of the World Health Organization (WHO), TBE in dogs. This meeting report presents some of the topics in detail.
In all these years, the main aims of the ISW-TBE have been promoting national and international scientific, medical, and regulatory collaboration on TBE, stimulating and co-ordinating applied and basic research, contributing to training and educational programs in the field, providing high-quality information and promoting appropriate distribution, promoting and aligning international standards on epidemiological surveillance, and defining and promoting proposals to harmonize national and international policies on prevention. Through these activities, the working group has gained recognition for the past years as an independent advisory committee to national and international health authorities as well as to scientific and medical professions. Table 1 shows an overview of ISW-TBE key activities.
Together with dengue virus, Japanese encephalitis virus, and yellow fever virus, the TBEV belongs to the genus Flavivirus in the Flaviviridae family. Due to the close antigenic relationship between TBEV and other flaviviruses, TBEV-binding antibodies may cross-react with antibodies induced by other flaviviruses, posing a diagnostic challenge in travelers either vaccinated against diseases (such as yellow fever, dengue fever, or West Nile encephalitis) or having acquired one of these infections. In patients with previous exposure to other flaviviruses, therefore, ELISA does not suffice to establish a diagnosis of TBE, and a neutralization test, the most specific serologic test measuring virus-neutralizing antibodies, has to be performed (presentation by F.X. Heinz).
The three TBEV subtypes have a similarity of about 95%, a relationship strong enough to not only cause cross-reactivity, but also cross-protection. Cross-neutralization between the European, the Siberian, and the Far Eastern TBEV isolates has been known to occur, but this was difficult to quantify (Hayasaka et al., 1999, Holzmann et al., 1992). Recent studies demonstrate that the TBE vaccine based on the European subtype strain Neudörfl induces equally potent protection against TBEV strains of the European, Far Eastern, and Siberian subtypes (Orlinger et al., 2010, Orlinger et al., 2011, Fritz et al., 2012).
Austria is a high-risk country for getting TBE, although the low incidence of 0.88 per 100,000 inhabitants may suggest otherwise. This seeming contradiction has been the result of a mass vaccination campaign initiated in 1981 and a vaccination rate that has meanwhile increased to 86% of the population, assuming that this percentage of people has received at least one shot (Heinz et al., 2007, Kollaritsch et al., 2011). Thus, whereas TBE case numbers in Austria in the prevaccination era were among the highest in central Europe (several hundred every year), case numbers have stayed at below 100 since 1997, with the single exception of 2011, when 113 cases were reported. There have also been significant changes in the locations of infection in the course of years, especially in valley regions of the Alps, new foci were detected. The western states of Austria (Tyrol and Vorarlberg) are now among those with the highest incidences. Attention must be paid to the fact that – despite fluctuating numbers of TBE cases and a high vaccination rate – the risk of getting a TBE infection for an unvaccinated person stays the same.
Section snippets
Evaluation of clinical manifestations in children
Recent findings from Sweden indicate that the incidence in children may be higher than previously thought. With symptoms mainly unspecific, TBE is unlikely to be found unless specifically sought. Accurate diagnoses are a precondition for elucidating the long-term effects of TBE in the very young.
In a study with 124 children (<18 years old) seeking medical attention for neurological complaints, anti-TBEV and anti-Borrelia serologies were performed (presentation by M. Sundin). All these children
Epidemiological situation in Europe
In the 20 years from 1991 to 2010, no fewer than 169,292 TBE cases were reported for Europe and Russia, 35% (n = 58,451) of these in Europe alone, reflecting an average of 2923 cases per year (presentation by J. Süss). The dynamics of TBE have differed greatly between countries and from year to year. Extensive fluctuations of TBE cases are a well-known phenomenon, which still lacks sufficient explanation.
When comparing the number of cases of 1991–2000 with those of 2001–2010, significant
TBE Program of the European Centre for Disease Prevention and Control
ECDC's mission is to identify, assess, and communicate current and emerging threats to human health posed by infectious diseases. An ECDC representative presented the ECDC TBE Program (presentation by H. Hrabcik). It is estimated that Europe-wide only 30–40% of TBE cases are reported. The objectives of ECDC are to strengthen the capacity of the EU Member States for surveillance and prevention of tick-borne diseases and to harmonize case definitions of TBE and Lyme borreliosis in order to draft
TBE as a travel-associated disease and TBE Travel Advisory Board
When it comes to travelers and travel medicine specialists, awareness of TBE at both the giving and the receiving ends is low. There are many different specialists involved in the field of TBE (mainly working on infectious diseases, virology, and epidemiology), however, the majority of travel medicine experts lack specific knowledge – therefore TBE in association with travelling is frequently neglected (presentation by M. Haditsch). The aim must be to bridge the gaps between these experts to
Conclusion
Sometimes, facing the true burden of a given illness requires a very close look, a keen awareness of the disease, tight surveillance, and international cooperation to look beyond natural foci and national borders. TBE is a good example. Reflecting the question “Is TBE still an underestimated risk?” the following answers can be given:
It is underestimated in children, in whom symptoms are often unspecific and unlikely to be correctly diagnosed unless serology is routinely performed in those with
Acknowledgements
We thank Ms. Gabriele Berghammer for assistance in writing and translation.
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Horst Aspöck, Maria Avdičová, Eric Caumes, Lidia Chitima, Roman Chlibek, Claus Bohn Christiansen, Natalie Cleton, Hanna Czajka, Hans Dautel, Gerhard Dobler, Mona-Lisa Engmann, Irena Grmek Košnik, Martin Haditsch, Mats Haglund, Yves Hansmann, Franz Xaver Heinz, Marika Hjertqvist, Terje Hoel, Hubert Hrabcik, Krista Jaago, Anu Jääskeläinen, Zsuzsanna Jelenik, Eva Jilkovà, Olaf Kahl, Peter Kimmig, Herwig Kollaritsch, Thomas Krech, Michael Kunze, Karl-Johan Lidefelt, Ute Mackenstedt, Rastislav Madar, Egon Marth, Aukse Mickiene, Emanuele Montomoli, Rainer Oehme, Olivier Péter, Branislav Petko, Martin Pfeffer, György Póta, Roman Prymula, Maurizio Ruscio, Gerold Stanek, Robert Steffen, Mikael Sundin, Jochen Süss, Pille Taba, Elina Tonteri, Karl Turk, Antti Vaheri, Jukka Vakkila, Rosanne Wieten, Reinhard Würzner, Joanna Zajkowska, Kai Zilmer, Milda Zygutiene.