Kaiser, R.
Incidence and occurrence of tick-borne encephalitis and neuroborreliosis in Germany
Ticks Tick Borne Dis. 2022: 13(2):101867. doi: 10.1016/j.ttbdis.2021.101867

Different definitions for TBE risk areas exist in European countries. In Germany, a TBE risk area (a county) is defined since 2020 as a region where the incidence is at least one per 100,000 inhabitants. However, TBE cases are also reported outside of these official risk areas, and TBE virus is sometimes detected in ticks collected by flagging or in ticks picked from wild animals.

A survey has been conducted to investigate the possible occurrence of TBE in regions not designated as known risk areas and the incidence of neuroborreliosis throughout Germany. A total of 305 head physicians of neurologic clinics were contacted in 2020 and asked for participation in a prospective data collection to document cases of TBE or neuroborreliosis. Despite repeated letters, the participation rate remained low: 22/305 clinics (7.2%). An additional 52 clinics (17%) participated in a retrospective survey.

In five cases, TBE was recorded in the prospective study in regions outside of defined risk areas in various federal states of Germany – Barnim/Eberswalde, Dessau-Roßlau, Saarbrücken, island of Hiddensee and Templin. Of these five cases in areas not defined as risk areas, only the case in Barnim (federal state of Brandenburg) has been really new. In the other counties, isolated cases of TBE have already been recorded in the past. In the retrospective study, 129 cases of TBE were reported, but with limited data on the probable infection site. Six cases were reported from counties where patients became infected outside their home regions and which were not official risk areas – Bad Segeberg, Cologne, Neuwied, Siegerland, Wuppertal.

In summary, the survey demonstrated that there is a risk to acquire TBE virus infection in some eastern areas in Germany that are not yet defined as risk areas. Knowledge of all TBE virus endemic areas – and not just official TBE risk areas – would be helpful to neurologists who treat patients with febrile inflammatory diseases of the nervous system. Otherwise, cases of meningoencephalitis can be overlooked.

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