Bank voles show high seropositivity rates in a natural TBEV focus in Hungary.

Rodents captured in a known tick-borne encephalitis virus (TBEV) focus were serologically surveyed for 4 years, with 28 visits. The collected sera were analysed by virus neutralization test. Bank vole (Myodes glareolus) had a significantly higher incidence rate of antibodies to TBEV (20.5%) than Apodemus flavicollis (3.7%) and Apodemus agrarius (4.6%). In all species, rates were higher in adults (6.8%) than in juveniles (1.7%). A higher incidence rate was observed in female A. flavicollis individuals (6.7%) than in males (1.5%). Smaller bank vole population coincided with lower (1.2-4.8%) seropositivity in all small rodents, while more abundant bank vole population meant higher (17.9%) total seropositivity. The TBEV focus originally had only Apodemus mice, bank voles appeared later, reached 20.5% positivity and raised the positivity in small rodents from 4% to 10.2% in 3 years. The results highlight the role of M. glareolus and of adult rodents in maintaining the TBEV in nature.