“Candidatus Neoehrlichia mikurensis, ” Anaplasma phagocytophilum, and Lyme Disease Spirochetes in Questing European Vector Ticks and in Feeding Ticks Removed from People

To estimate the likelihood of people coming into contact with the recently described tick-borne agent “Candidatus Neoehrlichia mikurensis, ” we compared its prevalence to those of Lyme disease spirochetes and Anaplasma phagocytophilum in questing adult Ixodes ricinus ticks collected in various Central European sites and examined ticks, which had been removed from people, for the presence of these pathogens. Whereas spirochetes infected questing adult ticks most frequently (22.3%), fewer than a third as many ticks were infected by “Ca. Neoehrlichia mikurensis ” (6.2%), and about a sixth harbored A. phagocytophilum (3.9%). On average, every twelfth encounter of a person with an I. ricinus tick (8.1%) may bear the risk of acquiring “Ca. Neoeh-rlichia mikurensis. ” Although a fifth of the people (20%) had removed at least one tick infected by “Ca. Neoehrlichia mikuren-sis, ” none displayed symptoms described for this pathogen, suggesting that its transmission may not be immediate and/or that immunocompetent individuals may not be affected. Because immunosuppressed patients may be at a particular risk of develop-ing symptoms, it should be considered that “Ca. Neoehrlichia mikurensis ” appears to be the second most common pathogen in I. ricinus ticks. In our survey, only Borrelia afzelii appears to infect Central European vector ticks more frequently. Ticks of the Ixodes ricinus complex serve as vectors for a varietyof pathogens in the temperate zones of North America, Asia, and Europe. The most common of these is the agent of Lyme disease, Borrelia burgdorferi sensu lato. Like Pandora’s Box, these ticks seem to reveal consistently novel pathogens. “Candidatu