title: The High Diversity and Global Distribution of the Intracellular Bacterium Rickettsiella in the Polar Seabird Tick Ixodes uriae.
abstract: Obligate intracellular bacteria of the Rickettsiella genus are emerging as both widespread and biologically diverse in arthropods. Some Rickettsiella strains are highly virulent entomopathogenic agents, whereas others are maternally inherited endosymbionts exerting very subtle manipulations on host phenotype to promote their own spread. Recently, a variety of Rickettsiella strains have been reported from ticks, but their biology is entirely unknown. In the present study, we examined the incidence and diversity of Rickettsiella in 11 geographically distinct populations of the polar seabird tick Ixodes uriae. We found Rickettsiella in most tick populations with a prevalence ranging from 3 to 24 %. 16S ribosomal RNA (rRNA) and GroEL gene sequences revealed an unexpected diversity of Rickettsiella, with 12 genetically distinct Rickettsiella strains present in populations of I. uriae. Phylogenetic investigations further revealed that these Rickettsiella strains do not cluster within a tick-specific clade but rather exhibit distinct evolutionary origins demonstrating frequent horizontal transfers between distantly related arthropod species. Tick rearing further showed that Rickettsiella are present in eggs laid by infected females with no evidence of abortive development. Using this data set, we discuss the potential biological significance of Rickettsiella in seabird ticks. Most notably, we suggest that these organisms may not be pathogenic forms but rather use more subtle adaptive strategies to persist within tick populations.
authors.affiliation: Laboratoire MIVEGEC (Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle), Centre National de la Recherche Scientifique (UMR5290)-Université de Montpellier-Institut pour la Recherche et le Développement (UR 224), Montpellier, France. olivier.duron@ird.fr.
authors.forename: Olivier
authors.initials: O
authors.lastname: Duron
authors.affiliation: Laboratoire MIVEGEC (Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle), Centre National de la Recherche Scientifique (UMR5290)-Université de Montpellier-Institut pour la Recherche et le Développement (UR 224), Montpellier, France.
authors.forename: Julie
authors.initials: J
authors.lastname: Cremaschi
authors.affiliation: Laboratoire MIVEGEC (Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle), Centre National de la Recherche Scientifique (UMR5290)-Université de Montpellier-Institut pour la Recherche et le Développement (UR 224), Montpellier, France.
authors.forename: Karen D
authors.initials: KD
authors.lastname: McCoy
mesh_terms: D000818:Animals; D044822:Biodiversity; D001715:Bird Diseases / Q000382:microbiology* / Q000469:parasitology*; D001717:Birds / Q000382:microbiology / Q000469:parasitology; D044125:Coxiellaceae / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D005260:Female; D018884:Ixodes / Q000382:microbiology*; D008297:Male; D010802:Phylogeny
keywords: Endosymbiosis; Ixodes uriae; Rickettsiella; Seabird tick