The first genetic study of Babesia caballi, Theileria equi, and Babesia occultans in Dermacentor spp. in Russian Siberia.

Equine piroplasmosis (EP) is a worldwide infection of Equides caused mainly by Theileria equi and Babesia caballi. Recently, these agents have been found in horses in the Republic of Altai. To identify probable vectors for EP agents in Western Siberia, 443 adult questing Dermacentor spp. (199 D. silvarum, 236 D. nuttalli, and 8 D. marginatus) were collected from vegetation in four districts of the Republic of Altai and examined for the presence of Piroplasmida DNA. Three Piroplasmida species were identified. Babesia caballi was found in ten (2.3%) Dermacentor spp., including eight D. silvarum and two D. nuttalli, indicating that these species are probable vectors of B. caballi in Siberia. The determined 18 S rRNA gene sequences of B. caballi from ticks were identical to those previously found in equine blood from the same region, which demonstrated their involvement in common transmission cycles. Another agent of EP, T. equi, was found in only one D. silvarum, indicating that in studied region Dermacentor spp. hardly can efficiently transmit T. equi transstadially. In addition to EP pathogents, the agent of bovine mild piroplasmosis, Babesia occultans, was identified in one D. marginatus; this is the first detection of this agent in Russia.