Detection of Bartonella spp. in Ixodes ricinus ticks and Bartonella seroprevalence in human populations

Ticks are vectors for many bacterial, protozoan and viral pathogens and are potential vectors for Bartonella species. Hunters and foresters, therefore, may be regarded as high-risk groups for Bartonella infections. The aims of this study were (i) to identify Bartonella species in questing Ixodes ricinus ticks collected in all provinces of Austria, and (ii) to determine the prevalence of antibodies to Bartonella species in hunters and blood donors in eastern Austria. A total of 515 larval, nymphal and adult I. ricinus, collected throughout Austria in 2005, were selected from the tick library at the Institute for Hygiene and Applied Immunology of the Medical University of Vienna and screened in a specific real-time PCR that targeted a region of the ssrA gene of Bartonella species. The overall Bartonella infection rate was 2.1% (11/515) and the highest rate, 7.5% (4/53), was found in ticks from Vienna. This finding was confirmed by screening a further 60 I. ricinus collected from Vienna in 2013: of these, 6.7% (4/60) were positive for Bartonella spp. The rate of infection was always higher in adult ticks. Sequence analysis in the Bartonella-positive ticks identified several species, including B. henselae, B. doshiae and B. grahamii. To our knowledge this is the first time that these species have been identified in I. ricinus in Austria. Prevalence of IgG antibodies against B. henselae and B. quintana was determined in serum samples from hunters (100) and blood donors (100): in hunters 23% were positive for B. quintana and in 2 samples (2%), antibodies to both B. quintana and B. henselae were detected; in blood donors 22% were positive for B. quintana, 1% for B. henselae and 5% for both. These results indicate that exposure to ticks does not constitutes a relevant risk for Bartonella infection.