TDK conference 2016

Man-made barriers are well known for their effects on ecosystems. Habitat fragmentation, for instance, is a recognized consequence of modern day infrastructure. The aim of the present study was to investigate tick species diversity, abundance and risks of acquiring tick-borne infections in habitats adjacent to a freeway. Ixodid ticks were collected with the dragging-flagging method in four habitats of different types (including forest, grove, meadow) along both sides of a freeway. The ticks were collected on six occasions, at two-week intervals (March to June). Ixodes ricinus females were molecularly screened for tick-borne bacteria.

In the study period, 887 ixodid ticks were collected. These included: 704 I. ricinus (79.4%), 51 Dermacentor reticulatus (5.7%), 78 D. marginatus (8.8%), 35 Haemaphysalis inermis (3.9%) and 19 H. concinna (2.1%). There was no significant difference in the abundance of tick species between similar habitats separated by the freeway, however, the absence of Dermacentor spp. was noted on one side.

In I. ricinus females, the overall prevalence of Anaplasma phagocytophilum in rural biotopes evaluated here (1.9%) was significantly lower than in urban biotopes, approx. 40 km away (8.8%), and (in part due to this low rate) did not show significant difference between the two sides of the freeway. Rickettsia helvetica had significantly different overall prevalence between two distant habitats along the same side of the freeway (12.3% vs. 31.4%), but not between habitats in the opposite sides. Borrelia burgdorferi s.l. showed significantly different overall prevalence between habitats both on the same and on the opposite sides of the freeway (8.6-35.9%). In addition, the prevalence rate of the Lyme disease agent was highest in a forested resting area, and was significantly inversely proportional to the prevalence of A. phagocytophilum (apparently related to deer population density). Prevalence rates of these bacteria also differed significantly on single sampling occasions between: (1) closely situated habitats of different types; (2) distant and either similar or different habitat types; and (3) habitats in the opposite sides of the freeway.

No significant differences were found between similar habitats that were close to each other but separated by freeway, suggesting the absence of a "dramatic effect" of these man-made barriers. On the other hand, concerning habitat-related differences observed in the overall prevalence of B. burgdorferi s.l., the level of significance was higher if relevant habitats were also separated by freeway. This finding exemplifies that a freeway can contribute to differences in tick-borne pathogen prevalence, and this effect is most likely a consequence of the barrier role of freeway fences preventing deer movements.