Lamsal et al.
Prevalence of tick-borne encephalitis virus in questing Ixodes ricinus nymphs in southern Scandinavia and the possible influence of meteorological factors
Zoonoses Public Health. 2023;10.1111/zph.13049. doi:10.1111/zph.13049

The incidence of TBE has been increasing in Scandinavia (Denmark, Norway, Sweden) in the last few decades. As part of the ScandTick Innovation project, a total of nearly 30,000 ticks were collected at 50 sites in Denmark, southern Norway, and southern Sweden.

Of the 50 sites tested, 20 (40%) were found positive for TBE virus. In total, 2,957 tick pools (each pool contained 10 nymphs) were tested of which 29 pools were found positive resulting in an overall TBE virus prevalence of 0.1% in questing I. ricinus nymphs in southern Scandinavia.

In Sweden, positive pools were detected in northern Skåne county, Blekinge, Kalmar and Jönköping. In Norway, positive pools were identified in the Oslofjord and in Agder county. In Denmark, TBE areas were detected in Jutland, Zealand, Falster, and Bornholm. The results confirm that TBE virus is more widespread in Denmark than previously anticipated and new TBE foci were found along the Oslofjord in Norway.

The authors did not find any geographical clustering of TBE foci in southern Scandinavia. Study data suggest that humidity might play an important role in TBE virus prevalence.

Overall, this study confirms that TBE virus is circulating in many locations in southern Scandinavia, pointing out that people acquiring tick bites in these areas are at risk of developing TBE.

TBE Book