Page 417 - TBE_Book_V2_2019

Chapter 12b: TBE in Sweden

known TBEV-endemic region, Torö island, ii) The roe deer population gradually declined
southeast of Stockholm, the TBEV prevalence after its peak in the late 1980s and early
was 0.51% in nymphs and 4.48% in adult ticks. 1990s.
iii) During the decline of the roe deer
In a review of the ecology and epidemiology of
population, a gradually larger proportion of
TBE in Sweden, Jaenson and colleagues
the tick larvae and nymphs probably fed on
analyzed the possible reasons behind the small mammals, which are reservoir-
gradually increasing incidence of human TBE competent hosts for TBEV. Consequently,
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during the last 20 years. The authors made
since the mid-1990s, a larger proportion of
the following conclusions:
the tick population became infected with
i) Due to a large roe deer population during TBEV.
the 1980s and 1990s, the Swedish tick iv) Climate change and weather events
population gradually increased. At the turn associated with higher temperatures
of the century, the tick population in
further influenced the infection prevalence
Sweden was probably larger than ever.
in the tick population and therefore also

the annual incidence in humans.
Overview of TBE in Sweden

Table 1: Virus, vector, transmission of TBE in Sweden

Only western/European TBEV (TBEV-EU), southern part of the
Viral subtypes, distribution 1-6
country
Reservoir animals Not documented

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Infected tick species (%) I. ricinus, 0.23% to 4.48%
Dairy product transmission Not documented

Figure 2: Age and gender distribution of TBE cases in Sweden (2018)

Latest raw data can be found at https://id-ea.org/tbe/tbe12b32/#data2

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