Investigation of Genotypes of Borrelia burgdorferi in Ixodes scapularis Ticks Collected during Surveillance in Canada

ABSTRACTThe genetic diversity ofBorrelia burgdorferisensu stricto, the agent of Lyme disease in North America, has consequences for the performance of serological diagnostic tests and disease severity. To investigateB. burgdorferidiversity in Canada, where Lyme disease is emerging, bacterial DNA in 309 infected adultIxodes scapularisticks collected in surveillance was characterized by multilocus sequence typing (MLST) and analysis of outer surface protein C gene (ospC) alleles. Six ticks carriedBorrelia miyamotoi, and one tick carried the novel speciesBorrelia kurtenbachii. 142 ticks carriedB. burgdorferisequence types (STs) previously described from the United States. Fifty-eight ticks carriedB. burgdorferiof 1 of 19 novel or undescribed STs, which were single-, double-, or triple-locus variants of STs first described in the United States. Clonal complexes with founder STs from the United States were identified. SeventeenospCalleles were identified in 309B. burgdorferi-infected ticks. Positive and negative associations in the occurrence of different alleles in the same tick supported a hypothesis of multiple-niche polymorphism forB. burgdorferiin North America. Geographic analysis of STs andospCalleles were consistent with south-to-north dispersion of infected ticks from U.S. sources on migratory birds. These observations suggest that the genetic diversity ofB. burgdorferiin eastern and central Canada corresponds to that in the United States, but there was evidence for founder events skewing the diversity in emerging tick populations. Further studies are needed to investigate the significance of these observations for the performance of diagnostic tests and clinical presentation of Lyme disease in Canada.