Climatic prerequisites for changing activity in the natural Crimean-Congo hemorrhagic fever focus in the South of the Russian Federation

Subject of study. Examining an impact of the contemporary climatic changes on the natural CCHF focus as well as CCHF incidence in the South of the European part of the Russian Federation. Materials and methods. Annual Epidemiological Report on CCHF Incidence provided by Departments of the Russian Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing in the subjects of the Southern and the North-Caucasian Federal Districts, CCHF Epizootologic Monitoring Report on the territory of the Volgograd Region, Rostov Region and Stavropol Region were used in the study. Hydrometeorological data were obtained from the database of the All-Russian Research Institute of Hydrometeorological Information — World Data Center, weather station archives as well as The 2011—2016 National Report on the State of Environment in the Stavropol Region. Results. For the first time, climatic factors affecting each phase of the life cycle of ixodid tick Hyalomma marginatum which is the main CCHF virus vector in the South of the European part of the Russian Federation were identified. A direct correlation between seasonal air temperature fluctuations determining ixodid tick count and CCHF incidence was demonstrated. It was found that the average air temperature and accumulated precipitation collectively affect H. marginatum population (e.g., in Stavropol Region). Peak CCHF incidence was demonstrated to correlate with temperature conditions favorable to developing ixodid ticks. In contrast, air temperature fluctuations were noted to negatively impact in the years preceding decreased CCHF incidence. A relation between CCHF incidence and degree of wetting during preceding spring-and-summer as well as autumn seasons affecting vital activity, metamorphosis in preimaginal stages and count of the next-generation H. marginatum was revealed. Moreover, CCHF virus tended to expand geographic range northwards due to an effects of climatic changes. Virus-carrying Ixodidae found on the territory of the administrative districts of the Volgograd Region adjacent to the Volga Federal District evidence about a risk of CCHF virus spreading outside the Southern Regions of the Russian Federation.