Incidence and occurrence of tick-borne encephalitis and neuroborreliosis in Germany

Abstract

Given the nationwide distribution of the vector, Ixodes ricinus, both neuroborreliosis and tick-borne encephalitis (TBE) might be expected to occur throughout Germany. However, cases of neuroborreliosis and TBE have so far only been reported in certain German states and counties. The aim of this survey therefore was to investigate the possible occurrence of TBE in regions not designated as known risk areas and the spread and incidence of neuroborreliosis throughout Germany. Data were collected by means of a questionnaire which was sent to 305 neurological clinics in Germany. Only twenty-two of them (7.2%) participated in a prospective, and 52 (17%) in a retrospective survey, therefore the significance of the study is limited. Cases of TBE were detected in five counties (Barnim, Dessau-Roßlau, Western Pomerania-Ruegen, Saarbruecken, Uckermark) that were not known so far as areas of risk according to the definition of the German Robert-Koch-Institute (RKI). The median incidence of TBE in various counties was 1.24 cases with a range from 0.19 to 20 cases per 100,000 inhabitants/year. Illnesses from neuroborreliosis were reported from all 61 counties, where clinics participated in the study. The incidence here varied between 0.19 and 23.4 cases with a median of 3.0 cases per 100,000 inhabitants/year. In areas where both diseases occurred, their incidence differed greatly from each other. The survey shows the occurrence of TBE in several counties in eastern Germany that are not defined as risk areas by the RKI and an incidence of neuroborreliosis in Germany that is significantly higher than reported to the public health authorities.