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The prevalence and diversity of blood-borne parasites and ticks from Tasmanian devils

Munns, Sarah (2018) The prevalence and diversity of blood-borne parasites and ticks from Tasmanian devils. Honours thesis, Murdoch University.

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Tasmania’s apex predator the Tasmanian devil (Sarcophilus harrisii) is under threat from multiple sources including devil facial tumour disease (DFTD) and as a result is now classified as endangered. Thus, understanding other factors that can have an influence on health is vital as they can have ecosystem-wide effects. One such factor of interest is devil-parasite interactions. The present study analysed ticks and tick-borne protozoal pathogens of devils to gain an understanding of what haemoprotozoan pathogens are present in devils and ticks collected from them.

Specifically, the present study aims to detect the presence and distribution of haemoprotozoan pathogens in (1) populations of wild Tasmanian devils with and without Tasmanian devil facial tumour disease and (2) ticks collected from wild devils. To achieve these aims the following objectives were created: (i) assess the species distribution and instar stage of collected ticks, (ii) determine the vectorial potential of these ticks and (iii) conduct phylogenetic analysis of any generated sequences.

Samples were collected from DFTD infected and non-DFTD devils at five sites across mainland Tasmania, for which the DFTD status has been confirmed at different times in the past 20 years. Morphological and molecular techniques were utilised in this study to examine whole tick specimens for species and instar classification. Blood smears created were microscopically examined for inclusions of parasites and blood and tick genomic DNA extracted from all samples, screened by PCR and positives sequenced using Sanger sequencing and phylogenetically analysed.

Samples from DFTD and non-DFTD infected devils successfully amplified on short (~300bp) and long (~1500bp) 18S rRNA assays but no statistical difference was observed between DFTD and non-DFTD devils on either assay. Sequencing and phylogenetic analysis of a subset of samples revealed a Babesia sp. infection consistent with B. lohae on the short amplification, while on the long assay four novel sequences were revealed from one site. Phylogenetic analysis of these novel sequences confirmed their genetic distinctness, as for three of them the closest species match was only 85.7% to 85.9% similar to Stylocephalus giganteus (FJ459761) and the fourth sequence exhibited only 89.2% similarity to Theileria ornithorhynchi (KT937391).

Morphological identifications revealed Tasmanian devils in the present study were infected with all instars of Ixodes sp. ticks and all specimens identified to species level were either I. tasmani or I. fecialis, with I. tasmani the most prevalent. Analysis of genomic DNA extracts of ticks on short (~300bp) and long (~1500bp) assays of the 18S rRNA locus revealed infections of Hepatozoon banethi, Theileria spp. and a sequence 85.8% similar to Stylocephalus giganteus (FJ459761).

The present study documents the first characterisations of haemoprotozoan pathogens in Tasmanian devils, with the discovery of a Babesia spp. sequence and the first observation of Theileria spp. from ticks collected from Tasmanian devils. Molecular screening of both tick and devil genomic DNA also found evidence of novel apicomplexan sequences.

Item Type: Thesis (Honours)
Murdoch Affiliation(s): School of Veterinary and Life Sciences
United Nations SDGs: Goal 15: Life on Land
Supervisor(s): Ryan, Una, Oskam, Charlotte and Duarte Barbosa, Amanda
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