Detection of TBEV in feeding ticks
All the ticks collected on rodents in 2012 and 2013 were tested for TBEV. In 2012, a MIR of 1.1% [95% CI : 0.2 – 3.1] was found on larvae (n=283) and no nymphs (n=9) nor females (n=4) were found to be infected. No larvae were found positive in season 1. The MIR in larvae did not differ significantly between seasons 2 and 3 (season 2: 0.7% [95% CI: 0.0 – 3.7], season 3: 4.2% [95% CI:0.5 – 14.2], Fisher’s exact test, p-value=0.15). TBEV was detected in larvae feeding on three rodent-sessions (2.2% of rodent-sessions infested by ticks, n=137): one seronegative A. flavicollis captured in June (1/67 rodents infested by ticks during the June session) and two seronegativeM. glareolus captured in September (2/22 rodents infested by ticks during the September session). These animals were not re-captured later. None of the feeding ticks collected in 2013 were found to be infected. Overall, 31 larvae and one nymph feeding on eight TBEV-seropositive rodents were negative for TBEV.
The three sequences obtained from feeding ticks (collected in 2012) had 100% identity with each other. One sequence was deposited in GenBank (accession number: MT109186) and showed 100% homology with sequences obtained from questing ticks during our study, and 99% homology with reference sequences from European subtype strains isolated in ticks (Germany, GenBank KX268728 ; Finland, GenBank MK801808), and human cerebellum (Finland, GenBank MG589937).