Population structure ofBorrelia gariniifromIxodes uriaecollected in seabird colonies of the northwestern Atlantic Ocean

AbstractThe occurrence ofBorrelia gariniiin seabird ticks,Ixodes uriae, associated with different species of colonial seabirds has been studied since the early 1990s. Research on the population structure of this bacterium in ticks from seabird colonies in the northeastern Atlantic Ocean has revealed admixture between marine and terrestrial tick populations. We studiedB. gariniipopulation structure inI. uriaecollected from seabird colonies in the northwestern Atlantic Ocean, in Newfoundland and Labrador, Canada. We applied a multi-locus sequence typing (MLST) scheme toB. gariniifound in ticks from four species of seabirds. TheB. gariniistrains found in this seabird colony ecosystem were diverse. Some were very similar to strains from Asia and Europe, including some obtained from human clinical samples, while others formed a divergent group specific to this region of the Atlantic Ocean.ImportanceThis study provides the firstB. gariniisequences from North American seabird ticks that were characterized using an MLST approach. This revealed new MLST sequence types and alleles, enhancing our knowledge ofB. gariniidiversity. Our findings highlight the genetic complexity ofB. gariniicirculating among seabird ticks and their avian hosts but also demonstrate surprisingly close connections betweenB. gariniiin this ecosystem and terrestrial sources in Eurasia. Genetic similarities amongB. gariniifrom seabird ticks and humans indicate the possibility thatB. gariniicirculating within seabird tick-avian host transmission cycles could directly, or indirectly via connectivity with terrestrial transmission cycles, have consequences for human health.