Infections and Coinfections of Questing Ixodes ricinus Ticks by Emerging Zoonotic Pathogens in Western Switzerland
ABSTRACTIn Europe,Ixodes ricinusis the vector of many pathogens of medical and veterinary relevance, among themBorrelia burgdorferisensu lato and tick-borne encephalitis virus, which have been the subject of numerous investigations. Less is known about the occurrence of emerging tick-borne pathogens likeRickettsiaspp.,Babesiaspp., “CandidatusNeoehrlichia mikurensis,” andAnaplasma phagocytophilumin questing ticks. In this study, questing nymph and adultI. ricinusticks were collected at 11 sites located in Western Switzerland. A total of 1,476 ticks were analyzed individually for the simultaneous presence ofB. burgdorferisensu lato,Rickettsiaspp.,Babesiaspp., “CandidatusNeoehrlichia mikurensis,” andA. phagocytophilum. B. burgdorferisensu lato,Rickettsiaspp., and “CandidatusNeoehrlichia mikurensis” were detected in ticks at all sites with global prevalences of 22.5%, 10.2%, and 6.4%, respectively.Babesia- andA. phagocytophilum-infected ticks showed a more restricted geographic distribution, and their prevalences were lower (1.9% and 1.5%, respectively). Species rarely reported in Switzerland, likeBorrelia spielmanii,Borrelia lusitaniae, andRickettsia monacensis, were identified. Infections with more than one pathogenic species, involving mostlyBorreliaspp. andRickettsia helvetica, were detected in 19.6% of infected ticks. Globally, 34.2% of ticks were infected with at least one pathogen. The diversity of tick-borne pathogens detected inI. ricinusin this study and the frequency of coinfections underline the need to take them seriously into consideration when evaluating the risks of infection following a tick bite.