Page 204 - TBE_Book_V2_2019

Chapter 11: General epidemiology of TBE

Table 1: Seroprevalence of anti-TBE anti- Table 2: Seroprevalence of anti-TBE
bodies in normal populations of different antibodies in high-risk populations
European countries of different European countries

Preva-
Country Prevalence (%) Literature Country Risk group Literature
lence (%)
Bornholm Bornholm Forest 71
17
(Denmark) 1.4 Kristiansen (Denmark) worker 16 Kristiansen
72
Estonia 0-5 Vasilenko et al. Forest 78
Aland Archipel Germany worker 5.6-7.2 Satz
73
(Finland) 5 Han et al.
Forest 79
74
Lithuania 3 Juceviciene et al. Alsace (France) worker 8 Collard et al.
75
Norway 2.4 Skapaas et al. Forest 78
Poland (North) 20-40 Satz
Poland (North) 4.8-6.5 Anonymous 1983 worker
76
Czech Republic 15-28 Gresikova 1988 Switzerland Forest 4.7 Matile et al.
77
77
Switzerland 0.5-5.0 Matile et al. 1979 worker
Forest 80
Hungary 3.3 Molnar
78
Hunchun (China) 10.9 Satz 2006 worker
clear picture of the ecological structure that is about 30,000 years ago in Central Africa. From
required for the development and mainten- there, the tick-borne flavivirus ancestors
ance of a TBE natural focus. migrated east and arrived in central Siberia
about 7,500 years ago. The virus ancestor

then divided into a western branch and an
The phylogeny and phylo- eastern branch. The eastern branch developed
into the Siberian and Far-Eastern subtypes
geography of TBEV plus also into potentially 2 newly identified
subtypes. This evolutionary development took
According to phylogenetic studies at least 3 about 3,000 years. The western branch spread
and possibly 6 subtypes of the TBEV can be to Central Europe and further evolved on the
genetically distinguished by molecular British Isles into Louping ill virus and on the
technologies. At present, 3 subtypes of Iberian Peninsula into the Spanish sheep
TBEV—the European (western) subtype encephalitis virus.
11
(TBEV- EU), the Siberian subtype (TBEV-SIB),
and the Far-Eastern subtype (TBEV-FE)—are In Western Europe, TBEV-EU is prevalent.
recognized. Russian virologists have claimed 2 However, in the Baltic countries and in parts
new subtypes, strain 178-19 and strain 886- of Finland, the Siberian and Far-Eastern
84, both isolated in the Lake Baikal region in subtype virus strains have been isolated and
10
Siberia. Also, a new putative TBEV Himalayan identified. So far, it is not clear whether the
84
subtype was claimed in China. The European Siberian subtype in particular moves in a
subtype differs by 4% to 6% from the other 2 western direction. However, identification of
subtypes (amino acid sequence). The Siberian virus strains in Siberia shows that a few of the
and Far-Eastern subtypes also differ by 4% to strains circulating in Siberia belong to the
6% in amino acid sequence from each other. European and Far-Eastern subtypes. According
to results from Russian investigators, the
Phylogenetic analysis shows that the TBEV Siberian subtype invaded the Baltic countries
group separated from the other flaviviruses

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199