Genetic variability of Babesia parasites in Haemaphysalis spp. and Ixodes persulcatus ticks in the Baikal region and Far East of Russia

To study Babesia diversity in Ixodid ticks in Russia, Ixodes persulcatus, Haemaphysalis japonica, Haemaphysalisconcinna, Dermacentor silvarum, and Dermacentor nuttalli ticks collected in the Far East and Baikal region were assayed for the presence of Babesia spp. using nested PCR. In total, Babesia DNA was detected in 30 of the 1125 (2.7%) I. persulcatus, 17 of the 573 (3.0%) H. concinna, and 12 of the 543 (2.2%) H. japonica but was undetectable in any of the 294 analyzed Dermacentor spp. Partial 18S rRNA gene sequences were determined for all of the positive samples. Among the positive ticks, nine I. persulcatus were infected by Babesia microti 'US'-type, five I. persulcatus were infected by Babesia divergens-like parasites, and 11 I. persulcatus were infected by Babesia venatorum. For all three of these species, the determined 18S rRNA gene sequences were identical to those of the Babesia genetic variants found previously in I. persulcatus in Russia. In addition, five I. persulcatus from the Baikal region and all of the positive Haemaphysalis spp. ticks carried 13 different sequence variants of Babesia sensu stricto belonging to distinct phylogenetic clusters. Babesia spp. from 29 ticks of different species collected in distinct locations belonged to the cluster of cattle and ovine parasites (Babesia crassa, Babesiamajor, Babesiamotasi, Babesiabigemina, etc.). Babesia spp. from four H. japonica ticks in the Far East belonged to the cluster formed by parasites of carnivores. One more Babesia sequence variant detected in an I. persulcatus tick from the Baikal region belonged to the cluster formed by parasites of cattle and wild cervids (B. divergens, Babesiacapreoli, B. venatorum, Babesiaodocoilei, etc.).