Spatial pattern of risk exposure to pathogens transmitted by Ixodes ricinus in north-eastern Italy and the Italy/Slovenia transborder territory

The Friuli Venezia Giulia region (FVG) and the transborder territory Italy/Slovenia are endemic for Lyme borreliosis and, more recently, also for Anaplasma phagocytophilum infections. In the present study, we determined the density of questing Ixodes ricinus ticks and their infection rates with Borrelia burgdorferi and A. phagocytophilum in the four main biogeographical regions present in the study area. Within these regions, stations for collecting ticks were selected. The pathogens were detected by PCR methods specific for the two infectious agents. The prevalences of infection varied among different landscapes. The local potential risk of human infection through tick bite was drawn from tick abundance and prevalence of infection in ticks: The level of risk for B. burgdorferi infection was found to be highest in the transborder Karst territory. In that environment up to 45.5% of the ticks were infected. The prevalence dropped approaching the alpine environment (13.2%). Conversely, the potential risk to be bitten by ticks infected with Anaplasma was quite low: The annual average infection prevalence in ticks was 1.6%.