Molecular and Biological Investigations of Tritrichomonas foetus from Cattle, Domestic Cats and Pigs

Abstract

Few organisms have the potential to shed light on aspects of parasitism as much as Tritrichomonas foetus. While it is a commensal organism in pigs, T. foetus is a urogenital parasite of cattle and an intestinal parasite of domestic cats. In this thesis, I show that a high prevalence of porcine T. foetus is maintained in domestic pigs on an Australian farm where pigs and T. foetus-free cattle are farmed in close proximity. A novel Australian reference isolate of porcine T. foetus with close association to bovine T. foetus is established. Baseline transcriptomes of T. foetus from cattle, cat and pig hosts are sequenced and compared to confirm that isolates from the three hosts represent the same T. foetus species. In addition, significant differences are identified in the transcription of virulence factors between the bovine and feline isolates. To understand how the environment of the organ niche in individual hosts influence host choice and epidemiology of the two parasitic T. foetus, tolerance to extracelluar pH was investigated in vitro. The feline T. foetus demonstrated an enhanced capacity to maintain viability when exposed to mild acidic pH in contrast to bovine T. foetus, implying that pH is a barrier to cross-infection between the two hosts. An in silico investigation into plausible drug targets for the parasitic bovine and feline T. foetus revealed that drug targets chosen for more focused investigation in T. foetus originating from cattle may not be ideal for T. foetus in domestic cats. Having made large sequences databases available, this thesis attempts to expand the molecular toolbox for parasitologists working on anaerobes by trialling miniSOG, a flavin-based oxygen-independent fluorescent protein (FbFP) tag in T. foetus. As a whole, this body of work has created a platform to advance future T. foetus research in the fields of epidemiology, drug target discovery and recombinant protein tagging.