Evidence for Borrelia bavariensis Infections of Ixodes uriae within Seabird Colonies of the North Atlantic Ocean

The first report of members of the spirochete genusBorrelia in the seabird tick,Ixodes uriae , and seabird colonies occurred during the early 1990s. Since then,Borrelia spp. have been detected in these ticks and seabird colonies around the world. To date, the primary species detected has beenBorrelia garinii , with rare occurrences ofBorrelia burgdorferi sensu stricto andBorrelia lusitaniae. During our research onBorrelia andI. uriae in seabird colonies of Newfoundland and Labrador, Canada, we have identifiedBorrelia bavariensis inI. uriae . To our knowledge,B. bavariensis has previously been found only in the Eurasian tick speciesIxodes persulcatus andIxodes ricinus , and it was believed to be a rodent-specificBorrelia ecotype. We foundB. bavariensis withinI. uriae from three seabird colonies over three calendar years. We also reanalyzedB. garinii sequences collected fromI. uriae from Eurasian seabird colonies and determined that sequences from two Russian seabird colonies likely also representB. bavariensis . The CanadianB. bavariensis sequences fromI. uriae analyzed in this study cluster with previously described sequences from Asia. Overall, this is an important discovery that illustrates and expands the range of hosts and vectors forB. bavariensis , and it raises questions regarding the possible mechanisms of pathogen dispersal from Asia to North America.IMPORTANCE To our knowledge, this is the first documentation ofB. bavariensis outside Eurasia. Additionally, the bacterium was found in a marine ecosystem involving the seabird tickI. uriae and its associated seabird hosts. This indicates that the epizootiology ofB. bavariensis transmission is much different from what had been described, with this species previously believed to be a rodent-specific ecotype, and it indicates that this pathogen is established, or establishing, much more widely.