Novel Borrelia species detected in echidna ticks, Bothriocroton concolor, in Australia

Abstract

BackgroundTo date, little has been documented about microorganisms harboured within Australian native ticks or their pathogenic potential. Recently, a Borrelia sp. related to the Relapsing Fever (RF) group was identified in a single tick removed from a wild echidna (Tachyglossus aculeatus). The present study investigated the presence of Borrelia in 97 Bothriocroton concolor ticks parasitizing echidnas in Queensland, New South Wales, and Victoria, Australia, using nested PCR with Borrelia-specific primers targeting the 16S rRNA (16S) and flaB genes.ResultsBorrelia-specific PCR assays confirmed the presence of a novel Borrelia sp. related to the RF and reptile-associated (REP) spirochaetes in 38 (39 %) B. concolor ticks. This novel Borrelia sp. was identified in 41 % of the B. concolor ticks in Queensland and New South Wales, but not in any ticks from Victoria. The resulting flaB sequences (407 bp) were 88 and 86 % similar to the flaB sequences from Borrelia turcica and Borrelia hermsii, respectively. Of the ticks confirmed as Borrelia-positive following the flaB assay, 28 were positive with the 16S assay. Phylogenetic analysis of the 16S sequences (1097 bp) suggests that these sequences belong to a novel Borrelia sp., which forms a unique monophyletic clade that is similar to, but distinct from, RF Borrelia spp. and REP-associated Borrelia spp.ConclusionsWe conclude that the novel Borrelia sp. identified in this study does not belong to the Borrelia burgdorferi (sensu lato) complex, and that the phylogenetic analysis of the partial 16S gene sequences suggests it forms a unique monophyletic cluster in the genus Borrelia, potentially forming a fourth major group in this genus associated with monotremes in Australia. However, a thorough molecular characterisation will be required to confirm the phylogenetic position of this unique Borrelia sp. The zoonotic potential and pathogenic consequences of this novel Borrelia sp. are unknown at the current time.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1627-x) contains supplementary material, which is available to authorized users.

Division of the genus Borrelia into two genera (corresponding to Lyme disease and relapsing fever groups) reflects their genetic and phenotypic distinctiveness and will lead to a better understanding of these two groups of microbes (Margos et al. (2016) There is inadequate evidence to support the division of the genus Borrelia. Int. J. Syst. Evol. Microbiol. doi: 10.1099/ijsem.0.001717)

“…However, in the phylogenetic tree presented by Margos et al [7], which includes B. turcica and other related reptile-associated strains of Borreliaceae without taxonomic standing, these species/strains exhibit the same pattern of branching as described by Takano et al [8], which was acknowledged by Adeolu and Gupta [4]. It should be noted, however, that in other recent studies [9,10], the position of the reptile-associated Borrelia species with respect to its branching position was found to be variable. Thus, further studies based on whole genome data are needed to clarify the position of B. turcica and the 'reptile group' of strains.…”

There is inadequate evidence to support the division of the genus Borrelia

“…1) underscore our criticism and highlights the uncertainty around the proposed genus split. Presumably this is only the tip of the iceberg, as more RFlike and LB species continue to be detected and described every few years [3,6]. In this context, it is our opinion that it would be prudent to retain the generic name Borrelia for both LB and RF spirochaetes.…”

“…A major omission in the study published by Adeolu and Gupta [1] is the exclusion of a Borrelia clade containing RF-like species that utilize hard ticks as vectors and reptiles as reservoir hosts [3,4].…”

“…spirochaetes to humans likewise are the principal vectors of B. miyamotoi. Further RF-like and LB spirochaetes are being discovered and described [3,6], and the ecological and genetic differences between these groups will most certainly become even more blurred in the future.…”

A description of ‘Australian Lyme disease’ epidemiology and impact: an analysis of submissions to an Australian senate inquiry

“…The issues surrounding ‘Australian Lyme disease’ have been reviewed recently and recommendations for diagnosis have been published . There is no current evidence of B. burgdorferi sensu lato in non‐travelling Australian patients or Australian ticks …”