EPIDEMIOLOGICAL FEATURES OF IXODES TICK-BORNE BORELIOSES IN THE KRASNOYARSK TERRITORY IN THE CONTEXT OF SEARCHING FOR THE CASES OF INFECTION CAUSED BY BORRELIA MIYAMOTOI

Aim. Estimation of the prevalence of Ixodes tick-borne borreliosis (ITBB) without erythema migrans in the Krasnoyarsk Territory in comparison with the prevalence of ITBB with erythema, that is Lyme disease (LD). Detection of cases of «new» infection caused by Borrelia miyamotoi (ITBB-BM) among patients with suspected tick-borne infection, primarily among patients with ITBB without erythema (ITBB-W/O-E). Materials and methods. We analyzed the database of Rospotrebnadzor containing individualized information about cases of ITBB officially registered in the Krasnoyarsk Territory in 2011 — 2016. Blood samples from 18 patients with suspected of tick-borne infection hospitalized in the Krasnoyarsk Emergency Hospital in 2017 were collected and studied. ITBB-BM was diagnosed if B. miyamotoi DNA was found in patient’s blood and/or the antibodies to specific antigens of B. miyamotoi were detected. Results. With an average annual incidence rate of ITBB of about 10 cases per 100,000 population, the proportion of ITBB-W/O-E among all ITBB in the Krasnoyarsk Territory is about 45%. Epidemiological characteristics of ITBB-W/O-E and LD are similar, but these diseases are very different clinically. All cases of ITBBW/O-E and some cases of tick-borne infections of unknown etiology, subjected to our enhanced laboratory diagnostics, were caused by B. miyamotoi. Conclusion. ITBB-W/O-E is a widespread disease in the Krasnoyarsk Territory, caused mainly by B. miyamotoi. The results of the study significantly expand the known geographic area of the ITBB-BM.