Page 337 - TBE_Book_V2_2019

Chapter 12b

TBE in Lithuania

Auksė Mickienė

History and Current Situation

The first case of tick-borne encephalitis (TBE) TBEV seroprevalence in non-vaccinated
in Lithuania, diagnosed by clinical and healthy permanent residents in Lithuania is
epidemiologic criteria only, was reported in 3%. TBEV antibodies have been more
1953. A forest worker became ill with the frequently found in people who regularly visit
disease in April after a tick bite, had a typical the countryside or who consume
clinical presentation with shoulder girdle unpasteurized goat milk, and the risk for
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muscle paralysis and bulbar syndrome, and seropositivity increases with age. Also, a
died after 12 days from the start of clinical general correlation has been noted between
symptoms. Autopsy data were compatible seropositivity among domestic animals, TBEV
1
with viral encephalitis. Serological diagnosis prevalence in ticks, and cases of TBE in
9
2
of TBE in Lithuania was started in 1970. humans in some regions of Lithuania.
In Lithuania, Ixodes ricinus is the main vector The highest annual incidences of TBE are
of tick-borne encephalitis virus (TBEV), which recorded in the northern and central parts of
is spread throughout the entire country. In the country, mainly in the municipalities of
addition, Dermacentor reticulatus is also Kaunas, Panevėžys, and Šiauliai. In these three
3
found in Lithuania. In 1974, 142 of 13,726 regions, 17–32% of the total annual case
field-collected ticks in two northeastern numbers for the country have been registered.
districts of Lithuania (Rokiškis and Biržai) Three particular districts within these
located near the Latvian border were municipalities – Panevėžys, Šiauliai, and
4
identified as Ixodes persulcatus. However, Radviliškis – can be called the ‘hot-spots’ of
more recent entomologic studies have not TBE in Lithuania. Between 1998 and 2011,
detected I. persulcatus in any region of when the average incidence of TBE in
Lithuania. 5,6 Sequence analysis of Lithuanian Lithuania was 11.5 cases per 100,000 people,
TBEV strains isolated from humans and field- the average incidence rate in these three
collected ticks has shown that the virus districts was 52.1, 45.6, and 33.3, respectively
5,7
belongs to the European TBEV subtype. The (3–5 times higher than the average incidence
infection rate of I. ricinus ticks in Lithuania in the country). In 2012, 4.1% of the
5
varies from 0.1% to 1.7%. Lithuanian population lived in these three
districts (123,255 of 3,003,641 permanent
TBEV is found from ticks collected in all inhabitants of Lithuania); however, the total
administrative districts of Lithuania and in 3 number of TBE cases in these districts
3
urban parks in the country. The density of I. comprised 17% (1,230 of 7,409) of all TBE
ricinus ticks during the spring peak of activity cases registered in Lithuania between 1993
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increased three-fold from 1995 (19 ticks per 1 and 2011.
3
km) to 2008 (57 ticks per 1 km), and this
increase has been correlated to increased Presently, TBE is the most common viral
numbers of TBE cases in humans. infection of the CNS in Lithuania, with an
average number of 395 cases per year; a total

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