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Molecular characterisation of microorganisms within the stump-tailed lizard tick, Amblyomma albolimbatum, in Western Australia

Elliot, Samuel (2021) Molecular characterisation of microorganisms within the stump-tailed lizard tick, Amblyomma albolimbatum, in Western Australia. Honours thesis, Murdoch University.

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Ticks pose a major threat to the health and wellbeing of humans, domesticated animals and wildlife. Recently, a bacterial community study (16S rRNA) on the stump-tailed lizard tick, Amblyomma albolimbatum, removed from bobtails, Tiliqua rugosa, in Western Australia (WA), revealed the presence of Coxiella, Francisella and Rickettsia DNA sequences. However, resolution to species level could not be achieved due to the short sequences generated through next generation sequencing. In addition, oocytes proposed to be Hemolivia sp. have been identified within the gut epithelium of A. albolimbatum; however molecular data confirming the species is lacking. Here we present for the first time, molecular data supporting the presence of Coxiella burnetii, Francisella sp. nov., Rickettsia spp. and Hemolivia mariae within A. albolimbatum in WA. Three hundred and six ticks, morphologically identified as A. albolimbatum, were removed from 88 T. rugosa lizards at the Kanyana Wildlife Rehabilitation Centre, Perth, WA from 2013 to 2015. A subset of 142 ticks were subjected to genomic DNA extraction and screened for Coxiella, Francisella, Rickettsia using genus-specific assays and haemoparasites using a nested 18S rRNA assay followed by Sanger sequencing. Coxiella burnetii was found in a single A. albolimbatum based on 16S and GroEL genes. Coxiella burnetii is the causative agent of Q fever and coxiellosis in people and animals, respectively, and therefore, its presence is of major concern. Secondly, a Francisella sp. nov. based on a concatenated alignment of 4,230 bp (16S, tpiA, prfB, rpoA, dnaA) was generated with a 3% genetic distance to F. persica, a known soft tick endosymbiont. Interestingly, there was evidence of three Rickettsia spp. which warrants further investigation as two were closely related to the Spotted Fever Rickettsia spp. group. Lastly, two samples had a 100% genetic identity to H. mariae at the 18S gene, which is consistent with the previous report of Hemolivia within A. albolimbatum and that ticks have an important role for the sylvatic lifecycle of this parasite. Further research is required to determine the prevalence of these microbes within questing A. albolimbatum ticks and the role they play in the health of T. rugosa and wildlife rehabilitation workers.

Item Type: Thesis (Honours)
Murdoch Affiliation(s): Medical, Molecular and Forensic Sciences
Supervisor(s): Oskam, Charlotte, Austen, Jill and Barbosa, Amanda
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