Epidemiological and clinical characteristics of cases and detection of pathogens’ markers of tick-borne infections in the Tomsk region

BACKGROUND: Among the spectrum of the tick-borne infections, Lyme borreliosis and tick-borne encephalitis are most often recorded in the Tomsk region, however it is obviously that possible range of the pathogens is not limited to these ones.

AIM: To make epidemiological and clinical characteristics of cases and detect frequencies of pathogen’s markers of tick-borne infections among adult patients applying serological and molecular genetic techniques in the Tomsk region during 2020–2023.

METHODS: A single-center prospective sample study was conducted applying a comprehensive approach in peripheral blood specimens obtained from 197 patients with suspected tick-borne infections hospitalized during 2020–2023. To verify the diagnoses of tick-borne encephalitis or Lyme borreliosis, specific immunoglobulins of classes M and G to the antigens of virus of tick-borne encephalitis and Borrelia burgdorferi s.l. were determined in paired blood serum samples applying enzyme-linked immunosorbent assay. Additionally, the polymerase chain reaction was used to detect genetic markers of virus of tick-borne encephalitis, B. burgdorferi s.l., B. miyamotoi, Rickettsia spp., Coxiella burnetii, and Francisella tularensis. Epidemiological surveillance data of incidence rates of tick-borne infections obtained from official reports were analyzed as well. MS Office Excel 2010 software was used to calculate frequency morbidity measures.

RESULTS: We verified the final diagnosis of tick-borne encephalitis in 52 (26.4%) patients, Lyme borreliosis in 116 (58.9%) patients, co-infection of tick-borne encephalitis and Lyme borreliosis 15 (7.6%) patients, hard tick relapsing fever caused by B. miyamotoi in 8 (4.1%) patients, coinfection of Q fever caused by C. burnetii with tick-borne encephalitis or Lyme borreliosis in 4 (2.0%) patients, and coinfection of tularemia with tick-borne encephalitis or Lyme borreliosis in 2 (1.0%) cases. We identified markers of tick-borne encephalitis and Lyme borreliosis pathogens by polymerase chain reaction in 3.6% and 4.1% of the patients. Most number of individuals with tick bites, and the highest incidence rates of Lyme borreliosis and tick-borne encephalitis were recorded in the suburbs of Tomsk. The age groups of 40–59 years, and elderly people 60 years and older were predominated among the patients.

CONCLUSIONS: It was found out that, in addition to Lyme borreliosis and tick-borne encephalitis, there were such tick-borne infections as tick relapsing fever, Q fever, and tularemia in the Tomsk region in the 2020–2023 period.