Abstract
The generalist tick Ixodes ricinus is the most important vector for tick-borne pathogens (TBP), including Borrelia burgdorferi sensu lato, in Europe. However, the involvement of other sympatric Ixodes ticks, such as the specialist vole tick I. trianguliceps, in the enzootic circulations of TBP remains unclear. We studied the distribution of I. ricinus and I. trianguliceps in Central Finland and estimated the TBP infection likelihood in the most common rodent host in relation with the abundance of the two tick species. Ixodes trianguliceps was encountered in all 16 study sites whereas I. ricinus was frequently observed only at a quarter of the study sites. The abundance of I. ricinus was positively associated with open water coverage and human population density around the study sites. Borrelia burgdorferi s. l.-infected rodents were found only in sites where I. ricinus was abundant, whereas the occurrence of other TBP was independent of I. ricinus presence. These results suggest that I. trianguliceps is not sufficient, at least alone, in maintaining the circulation of B. burgdorferi s. l. in wild hosts. In addition, anthropogenic factors might affect the distribution of I. ricinus ticks and, hence, their pathogens, thus shaping the landscape of tick-borne disease risk for humans.
Highlights
The generalist tick Ixodes ricinus is the most important vector for tick-borne pathogens (TBP), including Borrelia burgdorferi sensu lato, in Europe
Of the Ixodes species that feed on rodents, I. ricinus, I. trianguliceps and I. persulcatus are found in Finland[24,25]
B. burgdorferi s. l. has been detected in I. trianguliceps ticks that have been removed from small mammals, suggesting that I. trianguliceps may contribute to the transmission of this pathogen as well[32,33]
Summary
The generalist tick Ixodes ricinus is the most important vector for tick-borne pathogens (TBP), including Borrelia burgdorferi sensu lato, in Europe. We studied the distribution of I. ricinus and I. trianguliceps in Central Finland and estimated the TBP infection likelihood in the most common rodent host in relation with the abundance of the two tick species. L.infected rodents were found only in sites where I. ricinus was abundant, whereas the occurrence of other TBP was independent of I. ricinus presence These results suggest that I. trianguliceps is not sufficient, at least alone, in maintaining the circulation of B. burgdorferi s. Other tick species may contribute to the circulation of these pathogens among wild vertebrate host species by increasing the infection prevalence in the wild hosts[1,19] These enzootic transmission cycles need to be characterised to estimate and predict the risks that tick-borne zoonotic pathogens pose to humans. In Europe, I. ricinus has been proposed to be the primary vector for B. burgdorferi s. l., but the role of I. trianguliceps in its natural circulation among rodent host populations remains unclear
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