Analysis of pathogen co-occurrence in host-seeking adult hard ticks from Serbia.

Past studies in Serbia have reported concurrent infections of Ixodes ricinus ticks with Borrelia burgdorferi sensu lato genospecies, Anaplasma phagocytophilum and Francisella tularensis. As a step forward, this investigation included a broader range of microorganisms and five most common and abundant tick species in Serbia. Five tick species were identified (Dermacentor marginatus, D. reticulatus, Haemaphysalis punctata, H. concinna and I. ricinus) and analyzed for the presence of seven pathogens. Anaplasma ovis, A. phagocytophilum, Babesia canis, B. burgdorferi s.l., Coxiella burnetii, Rickettsia helvetica and R. monacensis were detected. Sequencing of samples positive for F. tularensis revealed the presence of Francisella-like endosymbionts. No Bartonella spp. DNA was amplified. Concurrent infections were present in three tick species (D. reticulatus, H. concinna and I. ricinus). The rate of co-infections was highest in I. ricinus (20/27), while this tick species harbored the broadest range of co-infection combinations, with dual, triple and a quadruple infection(s) being detected.