Detection of a Borrelia species in questing Gulf Coast ticks, Amblyomma maculatum

Abstract

Borrelia spp. are agents of Lyme disease and relapsing fever, diseases which use Ixodes hard ticks and Ornithodoros soft ticks, respectively, as primary vectors. Some relapsing fever spirochetes, such as B. miyamotoi, are also found in hard ticks. To date, no Borrelia sp. is known to use the hard tick, Amblyomma maculatum, as a vector. However, both B. burgdorferi and B. lonestari were recently detected in A. maculatum removed from hosts. In our study, DNA extracts from 306 questing adult A. maculatum collected in Mississippi in 2009 and 2010 were tested for Borrelia spp. DNA by PCR amplification of flaB and 16S rRNA gene targets. An additional 97 A. maculatum collected in 2013 were tested by amplification of 16S rRNA gene target. Two ticks, one collected in 2009 and the other in 2010, were positive by PCR of the flaB and 16S rRNA gene targets; both were collected from the same location in central Mississippi. Interestingly, 16S rRNA gene amplicons from these two tick extracts were 98% identical to twelve Borrelia spp. including the reptile-associated spirochete B. turcica and Borrelia sp. “tAG158M”; flaB amplicons from these two ticks shared closest identity (89%) to the reptile-associated spirochete, B. turcica. These results demonstrate a Borrelia sp. in unfed A. maculatum ticks that is unique from other species in the NCBI database and in a clade with reptile-associated Borrelia species. Detection of a previously unrecognized Borrelia in a hard tick species generates additional questions regarding the bacterial fauna in these arthropods and warrants further studies to better understand this fauna.

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.…”

Frequency and Distribution of Rickettsiae, Borreliae, and Ehrlichiae Detected in Human-Parasitizing Ticks, Texas, USA

“…identified in Amblyomma maculatum ticks from Texas in this study (box) and from Mississippi ( 12 ) shares a closer phylogenetic relationship to B. turcica than to to other Borreliae groups. Analysis is based on flaB sequences (267 bp).…”

“…(accession no. KF395230) previously found in A. maculatum ticks in Mississippi and known to share a phylogenetic clade with B. turcica ( 12 ). Borrelia 16S rDNA primers produced nonspecific amplification with these 2 samples.…”

“…The results supported findings by Lee et al that the novel Borrelia sp. flaB sequences were more closely related to the reptilian Borrelia than the other 2 Borrelia groups ( 12 ). …”

Emerging borreliae – Expanding beyond Lyme borreliosis

“…Phylogenetic analysis of these Borrelia taxa has revealed that they are deeply divergent from both the Lyme disease-associated clade and those causing relapsing fever, justifying their inclusion as a separate cluster within the over-arching genus of Borrelia [50,51]. Intriguingly, these presumed reptile-associated species have subsequently been detected in Amblyomma maculatum collected in the Gulf Coast [52]. Similarly, related Borrelia have been detected in Amblyomma varanense collected from pythons in Thailand [53].…”