Global Health Press - Tick-Borne Encephalitis
TBE News

TBE News

Global Health Press

TBE in children

October 2018
TBE is a serious health risk in many regions of Europe and Asia. An increase of TBE has been observed over the last two decades in many TBE endemic regions. Most infections occur after a tick bite, while a minority of infections are caused by the consumption of unpasteurized milk or milk products. Severity of disease increases with age and in the past, TBE in children was often regarded as benign. The author of this newsletter very well remembers the attitudes of some physicians, when he gave a lecture about TBE and TBE vaccines about 20 years ago on the Aland islands: A natural TBE infection in children is harmless and one should not vaccinate them to achieve protection against a more severe TBE infection in older age by natural infection in early childhood. In the current review, Robert Steffen asked the question, if such an attitude still is justified.

Broad cross-protection by different TBE vaccines against various TBE virus subtypes

September 2018
TBE is a disease caused by the TBE virus of which at least three subtypes have been described, the European (EU), the Siberian (Sib) and the Far-Eastern (FE) subtype, and newly phylogenetic virus groups have been described like the Transbaikal and the Himalayan strains (see e.g. Snapshot week 25). TBE vaccines have been developed either based on EU strains Neudörfl (marketed by Pfizer; Vac3) and strain K23 (marketed by GSK; Vac4) or on FE strain Sofjin (marketed by Chumakov FSC R&D IBP RAS, Russia; Vac1), strain 205 (marketed by Virion Company, Microgen, Russia; Vac 2) and Senzhang (produced by a Chinese company). All these TBE vaccines are inactivated whole virus vaccines, and they differ not only regarding the antigen subtype but also in antigen amount, inactivation process and excipients. However, all these TBE vaccines have shown immunogenicity in clinical trials and induce neutralizing antibodies not only to the homologous strain but also to other strains of the same subtype and to strains from other subtypes. The informative value about cross-protection is nevertheless still limited because in most studies only a few heterologous strains have been tested, sometimes only one representative of a certain subtype.

2018 – an unusual TBE year in Germany
and what it will finally bring

August 2018
While 2017 was already a year with high numbers of TBE in Germany, the year 2018 seems again to exhibit an increase in human TBE cases in Germany. So far (23 August 2018), more than 400 human TBE cases have been recorded by the Robert Koch Institute, Berlin. If the TBE virus transmission season would stop now, this would be already the year with the fifth highest number of human TBE cases in Germany recorded during the last 18 years (Fig. 1).

Is there a correlation between the level of TBE viremia and the severity of the disease?

July 2018
After a tick bite, TBE virus replication starts locally in dendritic skin cells. From there, the virus migrates to other organs, e.g. the spleen, liver and bone marrow. It is generally assumed that a high-level production of the TBE virus in these organs is the prerequisite for the virus to cross the blood-brain barrier where it induces neurological symptoms. What is yet not known is the level of TBE virus RNA in patients and if the RNA concentration correlates with clinical parameters including severity of the disease.

TBE cases reported in Europe and Asia, 2013-2017 – an update

June 2018
A considerable increase in TBE morbidity has been observed in Europe over the last 30 years, although a significant fluctuation of the number of yearly reported cases occurs. The countries with the highest incidence rates in Europe are Estonia, Latvia, Lithuania, Slovenia and the Czech Republic. The European Centre for Disease and Control (ECDC) has included TBE in the list of notifiable diseases in the European Unit in September 2012. However, diagnostic procedures vary, and surveillance and notification schemes are not uniform and not mandatory in all European countries, e.g. in Belgium, France and the Netherlands TBE are not notifiable although TBE cases have been reported from these countries.

Deadly TBE cases caused by Siberian and European subtypes reported from Finland

May 2018
According to phylogenetic studies, the TBE virus is usually classified into three subtypes – the European (Western) subtype (TBEV-EU), the Siberian subtype (TBEV-Sib) and the Far-Eastern subtype (TBEV-FE). In Western, Central, North, South and Eastern Europe, TBEV-EU is prevalent, while TBEV-Sib has been detected in most parts of Russia, including Western and Eastern Siberia, the Far East, Mongolia, Kazakhstan and Kyrgyztan. However, TBEV-Sib is expanding to the western direction and has been found in the Baltic countries and Finland. The principal vector for TBEV-EU is Ixodes ricinus, while TBEV-Sib is usually found in I. persulcatus.

Alimentary TBE infection in Germany

April 2018
The main route of TBE infection is by tick bite and in Germany some 200 to 500 TBE cases are reported annually. Most cases occur in southern Federal States. TBE can also be acquired by consumption of unpasteurized milk and milk products and most food-borne TBE infections have been reported from eastern Europe and the Baltic states. So far, no alimentary TBE infection had been reported in Germany, but recently a cluster of two human TBE cases caused by the consumption of unpasteurized goat milk and cheese has been reported.

Short report on the "Fourth Southern German Tick Congress", Stuttgart-Hohenheim (Germany), March 12-14, 2018

March 2018
The Fourth Southern German Tick Congress was held in the lovely atmosphere of the rococo auditorium of the palace of Hohenheim. 30 lectures were presented (mostly in German) and 13 posters dealing with various aspects including taxonomy of ticks (also ancient ticks), physiology of ticks, vaccine development, pathogens transmitted by ticks, ecology of ticks, control of ticks, spreading of ticks and pathogens.

Immune response to TBE infection or TBE vaccination? Differential serological analysis

February 2018
The protection rate of TBE vaccination has been estimated at more than 95% according to field studies. However, vaccine failures occur – often despite IgG antibodies being present in patients. Mostly, viral RNA cannot be detected at the onset of symptoms, and therefore, serological discrimination between vaccine-induced antibodies and those elicited by acute infection and measuring the immune response following vaccination is important. Non-structural protein 1 (NS1) is synthezised in TBE virus infected cells, but is not incorporated into TBE virus particles. Thus, NS1 is not present in (inactivated whole virus) TBE vaccines. Therefore, vaccinees should not develop NS1 antibodies and as a result serological response to NS1 should be a useful tool to distinguish between an immune response caused by an infection vs. antibodies induced from vaccination.

Increase of TBE cases in France

January 2018
France is the westernmost European country, where TBE occurs. However, only a low number of TBE cases has been reported in France during the last decade. In France, since 1968, a total of 171 TBE cases have been reported. About 10 TBE cases occurred annually, mainly in the Alsace region (north-eastern France, close to Germany). In addition, one or two cases were reported each year in the French Alpine region since 2003, and one TBE case has been notified in Southwestern France near Bordeaux.