Tick-borne encephalitis (TBE) virus is considered the medically most important arthropod-borne virus in Europe. Although TBE is endemic throughout central Europe, ticks and rodents determine its maintenance in small, difficult-to-asses, natural foci. We investigated the interrelation between the genetics of the main TBE virus (TBEV) vector tick (Ixodes ricinus), the most important reservoir host (Myodes glareolus, syn. Clethrionomys glareolus), and TBEV. Rodents and ticks were sampled on 15 sites within an exploratory study area, which has been screened regularly for TBEV occurrence in ticks for more than 10 years. On all 15 sites, ticks and bank voles were sampled, screened for TBEV presence via serology and RT-PCR, and genetically examined. Moreover, TBEV isolates derived from these analyses were sequenced.

In long-term TBEV foci bank vole populations show extraordinary genetic constitutions, leading to a particular population structure, whereas ticks revealed a panmictic genetic structure over all sampling sites. Landscape genetics and habitat connectivity modeling (analysis of Isolation by resistance) showed no landscape-related barriers explaining the genetic structure of the bank vole populations.

The results suggest that bank voles do not simply serve as TBEV reservoirs, but their genetic composition has a significant influence on establishing and maintaining long-term natural TBEV foci, whereas the genetic structure of TBEV´s main vector Ixodes ricinus does not play an important role in the sustainability of long-term TBEV foci.

Bank voles were sampled in 2019 using Sherman Traps.

Ticks were sampled in 2019 using the flaggin method.

TBEV isolates were dervied from positive samples.