In Europe, ixodid ticks are important arthropod vectors of human and animal pathogens, but comprehensive studies of the prevalence of all relevant pathogens in Central Europe are scarce. As a result of ecological changes, the incidences of tick-borne infections are expected to increase. In this study, 1,394 nymphal and adult Ixodes ricinus ticks sampled monthly during the active season from 33 ecologically distinct collection sites throughout Luxembourg were screened for all human tick-borne pathogens relevant in Central Europe. Species were identified by sequence analysis of detection PCR amplicons. Mean infection rates of ticks were 11.3% for Borrelia burgdorferi sensu lato, 5.1% for Rickettsia sp., 2.7% for Babesia sp., and 1.9% for Anaplasma phagocytophilum. No tick was found to be infected with Coxiella sp., Francisella tularensis subsp., or Tick-borne encephalitis virus (TBEV). A total of 3.2% of ticks were infected with more than one pathogen species, including mixed Borrelia infections (1.5%). Seasonal variations of tick infection rates were observed for Borrelia, Babesia, and Anaplasma, possibly reflecting a behavioral adaptation strategy of questing ticks. A positive correlation between the grade of urbanization and Borrelia infection rate of ticks was observed, suggesting an established urban zoonotic cycle. We also found Hepatozoon canis (0.1%) and Bartonella henselae (0.3%), which so far have not been found in questing Ixodes ricinus ticks in Central Europe.In Western Europe, the hard tick Ixodes ricinus is the main arthropod vector of various human and animal pathogens, causing several tens of thousands of severe infections in humans every year (25, 37). The most common tick-borne infection is Lyme borreliosis. This multisystemic disorder is caused by spirochetes of the Borrelia burgdorferi sensu lato complex, which is comprised of at least 12 species worldwide (45). Among the 6 European species, only Borrelia garinii, Borrelia afzelii, and Borrelia burgdorferi sensu stricto are known as human pathogens, whereas the significance of Borrelia valaisiana, Borrelia spielmanii, and Borrelia lusitaniae for human health is not clear (24). In a metaanalysis of 154 European studies, a mean of 13.7% of ticks were found to be infected with Borrelia spp., predominantly with B. afzelii and B. garinii. However, the prevalence of Borrelia species varies from 2 to 49% between different regions (43).Other tick-borne bacteria which cause disease in humans are Rickettsia sp., Anaplasma phagocytophilum, Bartonella henselae and Bartonella quintana, Coxiella burnetii, and Francisella tularensis subsp., all of which show only relatively low prevalence rates of 0.1 to 4.8% for European ticks (16,23,26,42,48,52). In addition, three species of the parasitic protozoan Babesia are known to infect humans, namely, B. divergens, B. microti, and the newly described Babesia sp. EU1 (5). Also, in Western Europe, Tick-borne encephalitis virus (TBEV) has a relatively low prevalence; however, this pathogen deserves special attention b...