Serological signature of tick-borne pathogens in Scandinavian brown bears over two decades

Background: anthropogenic disturbances are changing the geographic distribution of ticks and tick-borne diseases. over the last few decades,the tick ixodes ricinus has expanded its range and abundance considerably in northern europe. concurrently,the incidence of tick-borne diseases,such as lyme borreliosis and tick-borne encephalitis,has increased in the human populations of the scandinavian countries. methods: wildlife populations can serve as sentinels for changes in the distribution of tick-borne diseases. we used serum samples from a long-term study on the scandinavian brown bear,ursus arctos,and standard immunological methods to test whether exposure to borrelia burgdorferi sensu lato,the causative agent of lyme borreliosis,and tick-borne encephalitis virus (tbev) had increased over time. bears had been sampled over a period of 18 years (1995-2012) from a southern area,where ixodes ricinus ticks are present,and a northern area where ticks are uncommon or absent. results: bears had high levels of igg antibodies against b. burgdorferi sensu lato but not tbev. bears at the southern area had higher values of anti-borrelia igg antibodies than bears at the northern area. over the duration of the study,the value of anti-borrelia igg antibodies increased in the southern area but not the northern area. anti-borrelia igg antibodies increased with the age of the bear but declined in the oldest age classes. conclusions: our study is consistent with the view that ticks and tick-borne pathogens are expanding their abundance and prevalence in scandinavia. long-term serological monitoring of large mammals can provide insight into how anthropogenic disturbances are changing the distribution of ticks and tick-borne diseases. © 2015 paillard et al.