| Summary: | Published research indicates that Giardia spp. infections in Canidae, both domestic and wildlife species, are caused by several different subtypes. Four different genetic sequences of Giardia spp., termed ‘Assemblages’ infect domestic dogs, two of which also infect humans. Currently, DNA sequencing is the only method for distinguishing between different types of infections and published studies concerning potential transmission remain inconclusive. Nevertheless, it is well established that infections primarily affect juveniles and immuno-compromised individuals whilst the complexity of definitive diagnosis of symptomatic and asymptomatic Giardia spp. infections in dogs is problematic. The focus of this research programme concerns Giardia duodenalis, which infects mammalian species, specifically Giardia spp. infections in Canis lupus familiaris, or domestic dogs. Faecal sampling was conducted from naturally infected populations over a three-year period, from breeding kennels and from the urban dog population in Perth, Western Australia. Sampling strategies used microscopy and commercially available immuno-antigen tests to record enteric parasites infections and to confirm the earliest time of infection in different breeds of puppies. Results indicated that puppies could be infected with Giardia spp. within three weeks after birth and that clinical signs were associated with enteric parasite infections. This additional information detailing the impact of Giardia spp. infections on the canine host is an important factor for accurate diagnosis and understanding pathogenesis. Innovative methods were developed for analysing phenotypic descriptors of Giardia spp. extracted from canine faecal material using proteomic tools. Results from this work identified novel proteins and peptides, not previously published for any parasite protein extracted from mammalian faecal samples. This thesis discusses those peptide sequences identified in the context of canine gastro-intestinal ecosystems in conjunction with host-parasite interactions, and further explores the application and integration of molecular genomic and proteomic data. This work supplements annotation of Giardia spp. genomic data and may prove pivotal in accurate differentiation between host genotypes. Finally, one protein identified during the proteomic analysis, lactoferrin, was further investigated using a commercially available enzyme linked immunosorbent assay (ELISA). Results suggest that elevated levels of faecal lactoferrin occur in dogs with clinical signs of infection. A critical analysis of the challenges facing veterinarians and medical epidemiologists in diagnosis of enteric parasites in humans and canines is discussed and some important implications for the management and health of domestic dogs are presented.
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