The role of cervids and wild boar in the prevalence of tick-borne encephalitis in Sweden
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Roe deer have been historically considered the main large mammal host for Ixodes ricinus ticks and its population levels have been related to the current distribution and prevalence of tick-borne encephalitis virus (TBEv) in Sweden. It was thought that the increases in this disease were due to the roe deer population peak and a series of mild winters in the nineties. The roe deer is now at levels similar to the seventies, but the incidence of both TBEv and ticks are increasing. The role Swedish Association for Hunting and Wildlife Management, 2013 that other large mammal species play on this could be important to understand the current situation. We analysed the presence or absence of tick-borne encephalitis virus antibodies on blood samples from 259 individuals of fallow deer, moose, red deer, roe deer and wild boar from blood samples collected by hunters during the hunting seasons of 2010 to 2013 in 31 municipalities in south-central and southern Sweden. We found antibodies for tick-borne encephalitis in all five species, with the highest prevalence in roe deer (50% of positives), followed by moose (42%), red deer (42%), wild boar (32%) and fallow deer (25%). The prevalence was not significantly different between the species. However, age and sex significantly affected the probability of infection. This study demonstrates that not only roe deer, but the other four species analysed are important hosts for tick-borne encephalitis virus. The increase of these populations may cause an increase of Ixodes ricinus population and the incidence of TBEv, and they should be taken into account in the management of the wild populations to prevent an increase in human infections.
Master i anvendt økologi. Evenstad 2014