The impact of climate change on the expansion ofIxodes persulcatushabitat and the incidence of tick-borne encephalitis in the north of European Russia

Abstract

BackgroundThe increase in tick-borne encephalitis (TBE) incidence is observed in recent decades in a number of subarctic countries. The reasons of it are widely discussed in scientific publications. The objective of this study was to understand if the climate change in Arkhangelsk Oblast (AO) situated in the north of European subarctic zone of Russia has real impact on the northward expansion of Ixodid ticks and stipulates the increase in TBE incidence.MethodsThis study analyzes: TBE incidence in AO and throughout Russia, the results of Ixodid ticks collecting in a number of sites in AO, and TBE virus prevalence in those ticks, the data on tick bite incidence in AO, and meteorological data on AO mean annual air temperatures and precipitations.ResultsIt is established that in recent years TBE incidence in AO tended to increase contrary to its apparent decrease nationwide. In last 10 years, there was nearly 50-fold rise in TBE incidence in AO when compared with 1980–1989. Probably, the increase both in mean annual air temperatures and temperatures during tick active season resulted in the northward expansion of Ixodes Persulcatus, main TBE virus vector. The Ixodid ticks expansion is confirmed both by the results of ticks flagging from the surface vegetation and by the tick bite incidence in the population of AO locations earlier free from ticks. Our mathematical (correlation and regression) analysis of available data revealed a distinct correlation between TBE incidence and the growth of mean annual air temperatures in AO in 1990–2009.ConclusionNot ruling out other factors, we conclude that climate change contributed much to the TBE incidence increase in AO.

First evidence of established populations of the taiga tick Ixodes persulcatus (Acari: Ixodidae) in Sweden

“…In north-western European Russia I. persulcatus has extended its range and has also become more abundant [23, 24]. In Karelia, Bugmyrin and co-workers recorded a significantly increased abundance of I. persulcatus and a decrease in I. ricinus abundance since the 1950s [23].…”

“…This decision was based on the following facts: (i) it has been estimated that ≈ 7 million ticks are carried into Sweden each spring by migratory birds [32]; (ii) many of these ticks could originate from the Baltic countries and Finland, where I. persulcatus is present [7, 8, 21]; (iii) in 1992 we found a nymph of I. persulcatus on a warbler captured on a small island near the coast of northern Sweden [33]; (iv) I. persulcatus has recently expanded its range in northern European Russia [23, 24] and Finland; (v) and because climate change is likely to increase the possibility for I. persulcatus to become established in northern Sweden [26, 34]. …”

Detection of tick-borne encephalitis virus in I. ricinus ticks collected from autumn migratory birds in Latvia

“…The reason for these events is complex. Apart from anthropogenic factors, i.e., human activity, the main two levers on which the process relies is considered to be climate change -global increase of average temperature -and vector and host population expansion and distribution (Andreassen et al, 2012;Gray, 2008;Haemig et al, 2011;Jaenson et al, 2012;Pfeffer and Dobler, 2010;Porretta et al, 2013; Tokarevich et al, 2011). In order to survive TBEV relies on two types of hosts -ticks, which play the role of both virus vectors and reservoir hosts, and vertebrates, which act as a reservoir hosts (Süss, 2003).…”

Seroprevalence of Tick-borne Diseases in the Population of the European North of Russia

“…Firstly, in KR most Ixodes persulcatus ticks are infected with TBEV of the Far East genotype known for its high mortality rate [31]. The expansion of this virus genotype to other Russian regions and further to Scandinavian countries is possible.…”