Allelic Variants of the p66 Gene Loci in Isolates from Ixodes persulcatus and I. trianguliceps Ticks, Vectors of the Causative Agent of Tick-Borne Borreliosis, Borrelia bavariensis

The aim of the study was to investigate the genetic variability of p66 gene loci in Borrelia bavariensis isolates obtained from adults and nymphs of Ixodes persulcatus ticks, as well as from nymphs of I. trianguliceps.

Materials and methods. 123 isolates of B. bavariensis from nymphs and adults of taiga tick and from nymphs of I. trianguliceps collected in 1993–2003 in the natural focus of Ixodid tick-borne borreliosis (ITBB) of Perm Territory were studied. Nucleotide sequences were obtained using polymerase chain reaction followed by sequencing of p66 gene loci amplicons. The results were analyzed applying BLAST service. The dendrogram was constructed using the maximum likelihood method in MEGA11 software (a bootstrap value of 1000 repeats).

Results and discussion. Among the studied isolates, 8 allelic variants of p66 gene loci of B. bavariensis were found, 6 of which were in the adult taiga ticks. Isolates from nymphs of I. trianguliceps have an almost similar set of such variants as isolates from nymphs and adults of I. persulcatus. In isolates from nymphs (70.0±7.2 %) and adults (67.2±6.2 %) of the taiga tick, allelic variants No. 1 and 2 were more frequent. They also prevailed among isolates from I. trianguliceps nymphs (76.0±17.4 %). In the studied natural focus, I. persulcatus and I. trianguliceps ticks maintain the circulation of various allelic variants of Borrelia bavariensis, which is confirmed by the presence of corresponding p66 gene loci in them. Variants No. 1 and 2 are identical to those previously detected in isolates B. bavariensis from humans with ITBB (Golidonova et al., 2022). The significant prevalence of the two identified allelic variants of Borrelia in tick vectors during circulation of the pathogen in the natural focus explains the most frequent infections of population with ITBB by these variants.

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