Species- and elevation-linked variation in the molecular occurrence of tick-borne pathogens in Phylloscopus warblers...

Tick-borne pathogens (TBPs) are increasingly reported from migratory passerines, yet data from the South Caucasus remain limited. Warblers of the genus Phylloscopus differ in migratory strategies and elevational distributions, providing an opportunity to examine host-associated variation in the molecular occurrence of TBPs. We screened blood samples from three sympatric species (Phylloscopus collybita, Phylloscopus lorenzii, and Phylloscopus nitidus) breeding in Armenia for TBP DNA using genus-specific PCR and reverse line blot hybridization targeting Anaplasma/Ehrlichia/Neoehrlichia, Babesia/Theileria, Borrelia, and Rickettsia. After excluding incomplete samples, 66 individuals were included in the analyses. Differences in molecular prevalence, elevation effects, and co-detection patterns were assessed statistically. Overall TBP DNA positivity differed significantly among host species, with the highest value in P. collybita. Among pathogens, Candidatus Neoehrlichia mikurensis showed the strongest host-associated pattern, whereas Rickettsia helvetica and Rickettsia slovaca showed weaker differences. The probability of TBP DNA detection decreased with elevation in a univariable model, but this effect weakened after accounting for host species. Multiple detections were relatively uncommon and were dominated by Candidatus N. mikurensis, R. helvetica, and R. slovaca, with only weak evidence of non-random co-occurrence. Our findings demonstrate species- and elevation-associated variation in the molecular occurrence of TBPs in Phylloscopus warblers in Armenia and highlight the need for broader sampling and integrated bird-tick studies to clarify the drivers and epidemiological meaning of pathogen DNA detection.