Characterisation of native Trypanosomes and other protozoans in the Australian marsupials the Quokka (Setonix brachyurus) and the Gilbert's Potoroo (Potorus gilbertii)

Trypanosomes are blood-borne parasites that can cause severe disease in both humans and animals, resulting in very large economic losses worldwide. In contrast to the wealth of information on pathogenic species such as Trypanosoma cruzi and Trypanosoma brucei, little is known of the pathogenicity, prevalence and life-cycles of trypanosomes in native Australian mammals. The aim of this thesis was to characterise trypanosomes and other protozoans from the critically endangered Gilbert’s potoroo (Potorous gilbertii) and the quokka (Setonix brachyurus) from Western Australia using morphological and molecular analysis. A novel Trypanosoma species, Trypanosoma copemani was identified in Gilbert’s potoroos and quokkas using molecular and morphological analysis. Further molecular characterisation of T. copemani in quokkas at both the 18S rRNA and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) loci identified multiple T. copemani genotypes revealing that the parasite is genetically variable. Given the phylogenetic grouping of T. copemani as a stercorarian (requiring faecal transmission by vector), the fact that ticks are common ectoparasites of Gilbert’s potoroos and quokkas and the previous identification of trypanosomes in ticks, ticks were examined as potential vectors of T. copemani. Motile trypanosomes were detected in both the haemolymph and midgut sections of Ixodes australiensis ticks removed from quokkas and Gilbert’s potoroos and stained trypanosomes were detected within a faecal smear. Morphologically, the tick trypanosomes resembled in vitro forms of T. copemani, representing epimastigotes and slender trypomastigote stages, with dividing stages detected within the midgut region. Molecular analysis of the tick isolates, showed 100% sequence identity to T. copemani at the 18S rRNA locus, suggesting that the tick is a putative vector for T. copemani. Investigation of the life-cycle stages of native Australian trypanosomes using microscopy and in vitro culture of b