Sidorenko M, et al. Phylogenetic characterisation of tick-borne encephalitis virus from Lithuania. PLoS One. 2024;19(2):e0296472. doi:10.1371/journal.pone.0296472

Different subtypes of TBE virus can circulate in the same natural area. In the Baltic countries, the European (Eu), the Siberian (Sib) and the Far Eastern (FE) subtypes coexist in Estonia and Latvia, and here, the vectors Ixodes ricinus and I. persulcatus overlap. However, in Lithuania, only the Eu-subtype has so far been documented even though I. ricinus and Dermacentor reticulatus coexist in this country.

A genotypic characterization based on sequences of the glycoprotein E gene and non-structural protein 3 of TBE virus has been carried out from 8846 ticks collected from 81 locations in Lithuania from 2017 to 2019. Sequence analyses revealed that all isolates belonged to the EU virus subtype with a maximum/minimum identity of 98.7%/98% and 97.4%/95.9% to the Neudörfl reference strain.

On the phylogenetic tree, Lithuanian samples split up into eight clusters. The identity of the determined NS3 gene sequences ranged from 95.5% to 100% and the genetic variation between isolates from different locations was small. TBE virus strains isolated from D. reticulatus in this study were not specific to this tick species and had a high degree of sequence homology with strains isolated from I. ricinus.

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