Abstract
ABSTRACTBackground: The causes of the recent rise of tick-borne encephalitis (TBE) incidence in Europe are discussed. Our objective was to estimate the impact of air temperature change on TBE incidence in the European part of the Russian Arctic.Methods: We analysed the TBE incidence in the Komi Republic (RK) over a 42-year period in relation to changes in local annual average air temperature, air temperature during the season of tick activity, tick abundance, TBE-prevalence in ticks, tick-bite incidence rate, and normalised difference vegetation index within the area under study.Results: In 1998–2011 in RK a substantial growth of TBE virus (TBEV) prevalence both in questing and feeding ticks was observed. In 1992–2011 there was 23-fold growth of the tick-bite incidence rate in humans, a northward shift of the reported tick bites, and the season of tick bites increased from 4 to 6 months. In 1998–2011 there was more than 6-fold growth of average annual TBE incidence compared with 1970–1983 and 1984–1997 periods. This resulted both from the northward shift of TBE, and its growth in the south. In our view it was related to local climate change as both the average annual air temperature, and the air temperature during the tick activity season grew substantially. We revealed in RK a strong correlation between the change in the air temperature and that in TBE incidence. The satellite data showed NDVI growth within RK, i.e. alteration of the local ecosystem under the influence of climate change.Conclusions: The rise in TBE incidence in RK is related considerably to the expansion of the range of Ixodes persulcatus. The territory with reported TBE cases also expanded northward. Climate change is an important driver of TBE incidence rate growth.
Highlights
Tick-borne infections are an increasing burden on healthcare in many countries
It is necessary to study the impact of air temperature at the boundary of the region inhabited by tick-borne encephalitis (TBE) vectors, as both air temperature and TBE incidence have increased in recent years in the north of European Russia
Earlier we have shown that the increase in average annual air temperature and “effective” temperature has a significant impact on the northward expansion of ixodid ticks and the rise in TBE incidence in Arkhangelsk Oblast of Russia.[16]
Summary
Tick-borne infections are an increasing burden on healthcare in many countries. In the EU in 2012 tickborne encephalitis (TBE) was included in the list of notifiable diseases,[1] and since it is notifiable in 17 European countries.[2]. Immediate causes of TBE incidence growth and the distribution of Ixodidae ticks, the main vector of TBE virus (TBEV), are still not understood and depend on a number of factors,[7,8,9,10,11,12] the impact of climate change being one of them.[13,14,15]. It is necessary to study the impact of air temperature at the boundary of the region inhabited by TBE vectors (ixodid ticks), as both air temperature and TBE incidence have increased in recent years in the north of European Russia. In 1998–2011 there was more than 6-fold growth of average annual TBE incidence compared with 1970–1983 and 1984–1997 periods This resulted both from the northward shift of TBE, and its growth in the south. The satellite data showed NDVI growth within RK, i.e. alteration of the local ecosystem under the influence of climate change
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