Infection of Ixodidae Ticks with Pathogens of Tick-Borne Infections in Trans-Baikal Territory

Trans-Baikal Territory is endemic for tick-borne encephalitis virus, borreliosis, and rickettsiosis. Cases of human granulocytic anaplasmosis and human monocytic ehrlichiosis are also reported. The aim of this study was to analyze the prevalence of tick-borne diseases and assess epidemiological risks in the Aginsky, Dul’durginsky, Kyra, Kalgansky, Nerchinsko-Zavodskoj districts of Trans-Baikal Territory. Materials and methods . During a period of three years (2022–2024), 2095 ticks of three species ( Ixodes persulcatus , Haemaphysalis concinna , and H. japonica ) were collected from five districts of the Territory and 60 small mammals from two districts. Results and discussion . In a PCR study of 2071 tick suspensions for four pathogen groups, markers for one or more pathogens were detected in half of them. Two or more pathogens were found simultaneously in 19.8 % of arthropod suspensions. Markers for Anaplasma, Ehrlichia, and TBEV were found two times more often in combinations than as mono-variants. The opposite pattern was observed when detecting DNA of Borrelia, which was more common in single variants. Borrelia markers were identified in average in 51.1 % of the ticks studied, Anaplasma markers – in 16.9 %, Ehrlichia markers – 9.7 %, and TBEV – 3.2 %. RNA isolates of the Baikal subtype from the Alkhanay National Park are genetically close to previously studied TBEV strains, confirming the continued circulation of the virus in this area over a long term. In a study of small mammals, markers of one or more pathogens were detected in six of them, using PCR for four pathogen groups. The Baikal subtype of the TBEV was detected in one Myodes rufocanus . The epidemiological situation on tick-borne infections in the Trans-Baikal Territory remains tense.