Characterization of reptile-associated Borrelia sp. in the vector tick, Amblyomma geoemydae, and its association with Lyme disease and relapsing fever Borrelia spp.

The genus Borrelia is arthropod-borne infectious agents in vertebrates, and is classified into Lyme disease (LD) Borrelia spp. and Relapsing fever (RF) Borrelia spp. In addition to these Borrelia groups, we recently reported reptile-associated (REP) Borrelia spp. from reptiles and from hard-bodied ticks, which probably transmitted the REP Borrelia spp. In this study, we investigated the presence of REP Borrelia sp. in moulted ticks, and found that trans-stadial transmission of REP Borrelia sp. occurred in the midgut, while it was observed that REP Borrelia sp. entered the salivary gland during blood-feeding. This characteristic is also found in LD Borrelia spp., which are also transmitted by hard-bodied ticks. Although phylogenetic analysis demonstrated that REP Borrelia spp. are similar to RF Borrelia spp., the ecology of the spirochaetes within the vector ticks is different for REP Borrelia spp. and RF Borrelia spp. Elucidation of the evolutionary history of the genus Borrelia and its adaptation to ticks promises to be of great interest to researchers of vector-borne microorganisms.