Survey on tick-borne pathogens in ticks removed from humans in Northwestern Italy

Ticks are able to transmit several pathogens to the host while feeding, and thus are considered the most important vectors of infectious agents together with mosquitos. The global incidence of tick-borne diseases (TBDs) is rising, due to increased interactions between pathogens, hosts and vectors, linked to global changes. Given that information about the prevalence of tick-borne pathogens in ticks removed from humans in Italy are scarce, the aim of the present study was to identify the species of ticks biting humans in Northwestern Italy and tick-borne pathogens they harbour. An overall number of 128 ticks from 92 patients were collected from April to October 2018, almost 98% of which belonging to the Ixodes ricinus species. Molecular analysis showed the presence of Babesia spp. in 29 out of 93 analysed tick pools, with a Minimum Infection Rate (MIR) of 31.18% (29/93; CI95% 22.67-41.19%), while 1 out of 93 pools tested positive for SFG Rickettsiae (MIR = 1.08%; CI95% 0.19-5.84%). No samples tested positive for A. phagocytophilum and Borrelia spp. Sequencing revealed the presence of Babesia venatorum (28 pools), Theileria buffeli/orientalis complex (1 pool) and Rickettsia monacensis. Among these, B. venatorum and R. monacensis are zoonotic pathogens able to cause from moderate to severe infections in humans. These data highlight the importance of passive surveillance to assess the epidemiology of TBDs that pose a threat to human health.