Borrelia, which is transmitted by arthropod, is known as an infectious agent to vertebrate, such as Lyme disease (LD) Borrelia and Relapsing fever (RF) Borrelia. LD Borrelia is only transmitted by hard-bodied ticks classified into the Ixodes ticks. In contrast, almost of RF Borrelia was transmitted by soft-bodied ticks, Argasid ticks. Thus so far, the co-evolution was thought to be established between Borrelia and tick.
In this study, we found unknown borreliae from imported reptiles and its associated ticks (we preliminary named as ‘REP Borrelia’). Ticks were introduced into Japan with world-wide trading of reptiles. Ticks were classified into genus Amblyomma or Hyalomma. Out of 82 ticks, 76 were positive for PCR of tickmitochondrial gene for 16S rRNA, and we used these 76 ticks for our examination. From 57 ticks (75%), Borrelia turcica and unknown three Borrelia spp. were detected or isolated. In addition, we examined imported reptiles which were infested exotic ticks. A total of 15 reptiles including 5 of Testudo graeca, 1 of T. horsfieldii, 2 of Phelsuma dubia and 7 of Geochelone pardalis were used for isolation study of Borrelia. Borrelia was isolated from 11 reptiles (73.3%) as follows: T. graeca, T. horsfieldii, G. pardalis. It suggested that, these imported reptiles and exotic ticks were highly infected with Borrelia.
Phylogenetic analysis based on the DNA sequences of Borrelia, it was indicated that REP Borrelia constituted a cluster which was independent from RF and LD Borrelia. Surprisingly, this REP Borrelia was expected that was transmitted by hard-bodied tick, although it was thought to be diverged from ancestor RF Borrelia. From quantitative analysis of divergence based on 16S rRNA gene, it was expected that REP and RF Borrelia were differentiated around 50 million years ago (MYA). On the other hand, the oldest soft-bodied tick fossil from New Jersey amber was indicated that soft-bodied tick was speciated since ~92 MYA. In fact, soft-bodied tick was already diverged into genus level when RF and REP Borrelia were diverged. This may suggest that the vector switching event was occurred in ancestor REP/RF Borrelia.

• Ai Takano(Department of Bacteriology, National Institute of Infectious Diseases, Japan, United Graduate School of Agricultural Science & Veterinary Science, Gifu University, Japan)
• Hiroki Kawabata(Department of Bacteriology, National Institute of Infectious Diseases, Japan, United Graduate School of Agricultural Science & Veterinary Science, Gifu University, Japan)
• Haruo Watanabe(Department of Bacteriology, National Institute of Infectious Diseases, Japan, United Graduate School of Agricultural Science & Veterinary Science, Gifu University, Japan)
• Tei-ichiro Shino(AIDS Research Center, National Institute of Infectious Diseases, Japan)
• Koichi Goka(Global Environment Division, National Institute for Environmental Studies, Japan)
• Yumi Une(Laboratory of Veterinary Pathology, School of Veterinary Medicine, Azabu University, Japan)
• Hiromi Fujita(Ohara Research Laboratory, Ohara General Hospital, Japan)