Molecular detection of tick borne bacteria in questing Ixodes ricinus ticks in Northern Italy

Introduction Ixodes ricinus ticks are major competent vectors for a range of microbial pathogens, several of which are of medical importance.The occurrence of bacteria such as Rickettsia spp., Borrelia spp. and Anaplasma phagocytophilum in questing ticks is yet a relevant question. Objectives Our objectives were to identify the prevalence of Rickettsia spp., Borrelia spp. and Anaplasma phagocytophilum in questing ticks in the Province of Trento, establish co-infection rates, and compare infection levels of selected pathogens. Materials & methods In 2011-2013 ticks were collected by dragging. All the ticks were identified, DNA was extracted and a nested PCR was carried out for the analysis of Rickettsia spp., Borrelia spp. and Anaplasma phagocytophilum. A PCR targeting the ompA gene was performed to detect the presence of Rickettsia monacensis. All positive samples were sequenced and a Blast search was performed. Results We collected and analyzed 2,133 questing ticks (1,794 nymphs and 339 adults) belonging to Ixodes ricinus. Nine tick-borne bacteria were detected: B. garinii (7.2%), Rickettsia helvetica (5.6%), B. afzelii (4.6%), B. valaisiana (4.6%), Borrelia burgdorferi s.s. (4.3%), R. monacensis (3.5%), Anaplasma phagocytophilum (1.9%), B. lusitaniae (0.8%) and R. slovaca (0.04%). 32% of the ticks resulted infected with at least one pathogen and 2.1% with two. Conclusion The high percentage of ticks found positive to at least one of the bacteria detected poses serious concerns regarding the potential of transmitting pathogens to humans. Carriage of multiple pathogens was observed, demonstrating the risk of acquiring multiple infections as a consequence of a tick bite.