Page 285 - TBE_Book_V2_2019

Chapter 12b

TBE in Finland

Anu Jääskeläinen and Heidi Åhman

History and Current Situation

Finland is at the northernmost edge of the TBE The northernmost tick samples were from
endemic area in Europe. Here TBE is focally latitudes of 67°, but it is unclear whether ticks
endemic. An aseptic encephalitis disease has there are from stable populations or are
been known in Kumlinge Island in Åland stragglers transported there with animals.
1
Islands since the 1940s. TBE is also known in However, populations have established in new
Finland by name Kumlinge disease. locations, i.e. the Bothnian Bay coast and the
eastern part of central Finland. In addition,
According to a legend, tick-borne encephalitis TBEV RNA has been detected or TBEV isolated
–like disease was known in the Åland Islands from ticks in areas formerly unknown to be
2
already in the 18th century. However, this is TBE endemic and areas where only sporadic
apparently a misunderstanding due to a TBE cases have been reported.
11
doctoral thesis of archipelago fever in the
Turku region published 1781, which describes Both TBEV vector tick species, Ixodes ricinus
3
malaria, not TBE. and Ixodes persulcatus, are distributed in Fin-
land. 5,11 I. persulcatus is more abundant than I.
TBEV foci were determined in the 1960s by ricinus in certain areas, such as in northern
screening TBEV antibodies in cattle from all Finland where it is the dominant tick species.
4
over the country. The endemic areas Both species have been shown to transmit
remained the same throughout decades until TBEV-Eur and TBEV- Sib in Finland.
7,9
the 1990s, when Isosaari Island at the
archipelago of Helsinki was found to be TBE The overall prevalence of TBEV in ticks in
6
11
endemic. Since then, sporadic human cases Finland is reported to be 1.6%. TBEV pre-
have appeared in new areas, like in Närpiö on valence was higher in I. persulcatus (3.0 %)
the western coast and in eastern Finland in than in I. ricinus (0.2 %) in 2015 based on ticks
11
Varkaus, in the Kuopio region and in the Kotka sampled by crowdsourcing but varies greatly
7
archipelago. 2008 human cases were traced within Finland.
to Simo, the world’s northernmost TBE en-
9
demic foci in Finnish Lapland, which is nowa-
days a high endemic focus where residents are
vaccinated against TBE in national immu-
nization program.

Tick distribution in the country was studied in
10
11
1950s and 2015 using crowdsourcing.
Compared with the nationwide distribution
map drawn in 1960s, the distribution of ticks
11
has extended up to 200 km northwards.

280