Ixodes ticks are important vectors of a variety of tick-borne diseases. Recent studies suggest that Ixodes ticks have been expanding their distribution and increasing their abundance over the last few decades in the northern part of Europe and America. These studies include surveys that rely on the memories and impressions of the participants as to whether human-tick encounters have increased in the affected regions. Thus obtaining historically accurate data on tick range expansions remains a major challenge.
One approach to test if ticks are expanding their range is to use wildlife serums and test for antibodies against tick-transmitted pathogens like Borrelia burgdorferi sensu lato (the causative agent of Lyme disease) and tick-borne encephalitis virus (TBEv).  Temporal increases in wildlife antibody titres against those pathogens indicate higher host-tick encounter rates and provide indirect evidence of tick range expansions.
For my Master project, I will use an immunological approach (ELISA) to test whether there has been a temporal increase in the titre of antibodies against tick-borne pathogens (B. burgdorferi s.l. and TBEv) in Scandinavian populations of the brown bear, Ursus arctos. I will use bear serum samples that have been collected over the last 17 years by a team of Scandinavian wildlife biologists.
An increase of tick-borne infections in brown bear sera during those 17 years would suggest that Ixodes ticks are increasing their range and abundance in northern Europe.