Ott et al.
Tick-borne encephalitis virus (TBEV) prevalence in field-collected ticks (Ixodes ricinus) and phylogenetic, structural and virulence analysis in a TBE high-risk endemic area in southwestern Germany
Parasit Vectors 2020, 13: 303. Doi: 10.1186/s13071-020-04146-7

The Odenwald hill region (OWH) is a well-known TBE risk area in south-western Germany – located east and north of the city of Heidelberg. From September 2011 to May 2013, a total of 17,893 ticks have been collected in this territory of 3532 km2 by a crowd sourcing approach. The OWH was divided into 5 x 5 km2 grid squares and 61 lay people were recruited and trained as collectors (supported by local hunters), who then flagged ticks in their assigned district (136 in total and 78% of the total OWH). Nearly all collected ticks (99.46%) were identified as Ixodes ricinus. In addition, 84 ticks (0.54%) collected in the county „Kreis Bergstraße“and belonging to the ecotype of alluvial forest were Dermacentor reticulatus .

In six pools of I. ricinus nymphs and in one D. reticulatus specimen, TBE virus specific gE sequences were detected by PCR. Thus, the OWH is the second region in Germany where TBE virus was detected in D. reticulatus (seeSnapshotweek27/2019). The deduced overall minimum infection rate was low, 0.4%, (0.3% in nymphs and 1.4% in adults). The prevalence within TBE virus-positive grid square areas of 100 x 100 m was also low and varied from 0.6% up to 4.7%. All pools that tested positive for TBE virus were successfully sequenced for the whole gE gene. All OWH isolates belonged to the European subtype of TBE virus and showed a considerable heterogenicity. Mutations within the gE gene were associated with more frequent, severe and fatal TBE virus infections in the OWH risk region.

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