Tick-borne encephalitis virus in Dermacentor reticulatus ticks, Poland

Abstract

We report the detection of tick-borne encephalitis virus (TBEV) in Dermacentor reticulatus ticks collected in Poland during the 2022 season. Both Ixodes ricinus and D. reticulatus ticks were surveilled. There was limited TBEV detection found in one pool out of 106 pools (418 ticks) that were shotgun genome sequenced. The TBEV positive tick pool consisted of N = 3 adult D. reticulatus ticks. Additional hybrid-capture sequencing of this pool resulted in the first full-length genome sequence of TBEV from this tick species. The assembled genome was classified as the European subtype through phylogenetic analysis. The new TBEV sequence is phylogenetically placed closest to a 2019 Hungarian isolate, suggesting potential viral migration or shared ancestry across nearly 1,000 km. These findings expand the known geographic range of TBEV circulation in Poland and highlight the role of D. reticulatus as an important vector of TBEV.