EPIDEMIOLOGICAL CHARACTER OF TICK-BORNE VIRAL ENCEPHALITIS EXTENSION IN THE ARKHANGELSK REGION

Abstract

The regional characteristics of the epidemic process and the incidence rates of tick-borne encephalitis (TBE) in the Arkhangelsk region have been examined in the paper. In the period 2005 -2015 the annual TBE incidence rates per 100 thousand population were from 2,0 to 5,4 times higher as compared to the corresponding averages reported for the whole population of the Russian Federation. The most possible causes of the increased incidence rates of tick-borne viral encephalitis in the Arkhangelsk region and temporal trends in its changes as well as potential risk factors of TBE extension have been stated. The vectors of viral encephalitis in the Arkhangelsk region are represented by two types of ixodic ticks: Ixodes persulcatus (the "taiga" tick) and Ixodes ricinus ("forest" tick), the Ixodes persulcatus constitutes over 99 % of their total number. Spring-summer season is typical for TBE cases occurrence which is associated with higher tick activity in this area. The average tick infection rate for the period was 7.8 %. The cases of TBE are reported to occur mainly in urban citizens; and lethality rate due to TBE reached 4.3%. Since 2010 decrease in the TBE morbidity has being observed in the Arkhangelsk region. Reducing morbidity can be connected to the increase in the proportion of vaccinated persons, which reached 6.3 % of the total population of the Arkhangelsk region. The main indices of the acaricide treatment volume which increased since 2005 nearly 6 times, from 128.2 to 740.0 hectares have been stated. Considering the fact that the area of acaricide treatment in the region increases every year, and the number of persons seeking medical advice concerning tick bites remains high it is necessary to control the effectiveness of acaricide treatment regularly. Core measures to decrease the tick-borne viral encephalitis conducted by the Regional Office of Federal Service for Consumers' Rights Protection and Human Wellbeing as well as ways for further research have been introduced.