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|Title:||Understanding and mitigating the risk of pathogen transmission from wild animals to domestic pigs in Australia|
|Publisher:||University of Sydney.|
Faculty of Veterinary Science
|Abstract:||The pork industry in Australia accounts for 2.1% of all agricultural production with a gross value of AU $865 million. It is comprised of approximately 1,350 pork producers and 2.3 million pigs. Pigs in Australia, similar to most other developed countries, are raised in three different production systems: traditional intensive production, ecoshelters and freerange. Each of these production systems provide opportunities for pathogen introduction and spread by wild animals. Wild animal species, both introduced and native to Australia,pose a disease threat to domestic animals and humans in relation to the introduction, maintenance and spread of emerging, exotic and endemic pathogens. Australia has had few outbreaks of emerging infectious diseases and is well protected from transboundary animal diseases due to stringent quarantine procedures, which protect Australia’s livestock industries. As such, the main threat to domestic pig health in Australia posed by wildlife is transmission of infectious pathogens currently endemic in wild animal populations. Eighty five percent of the pig producing members of Australian Pork Limited that responded to a postal survey experienced wild animal incursions on their piggery. The wild animals presenting the greatest risk to commercial piggeries, determined by the number of pig producers reporting an observation of the species and the frequency of observations, included the European starling (Sturnus vulgarus), rodents (black rat Rattus rattus, brown rat Rattus norvegicus, and the house mouse Mus musculus) and feral cats (Felis catus). The species-specific pathogen transmission potential from feral pigs (Sus scrofa) also presented a high risk. The role of the cat in the transmission of Toxoplasma gondii to domestic pigs in piggeries has been thoroughly studied and consequently has not been examined further in this study. Pig pathogens were detected in European starlings, rats and feral pigs. These pathogens could be transmitted to pigs through direct and indirect pathways, via contaminated food, water and air. The current study detected Escherichia coli, Salmonella spp. and Campylobacter spp. in European starling populations around four large-scale commercial piggeries in South Australia. Escherichia coli was detected in starlings on all four piggeries, while Salmonella spp. and Campylobacter spp. were only detected on one piggery. Salmonella spp. and Lawsonia intracellularis were detected in rats on three large-scale commercial piggeries,two of which were located in Victoria, and one in South Australia. Brachyspira hyodysenteriae and Brachyspira pilosicoli were not detected in rats in the current study. Lawsonia intracellularis, Brucella suis, Leptospira spp. and Mycoplasma hyopneumoniae were all detected in feral pigs within 10 km of two large-scale commercial piggeries in southern Queensland. Results from six collared feral pigs showed that for 5 pigs the majority of their movement was within 5 km of the piggeries. One individual, a large male boar, moved to within 100 m of a free-range piggery. Based on the results of an exposure assessment, rats presented the highest probability of exposure of pathogens to domestic pigs, and Lawsonia intracellularis (median 0.13, 5% and 95% CI 0.05–0.23) and Brachyspira hyodysenteriae (median 0.10, 5% and 95% CI 0.05–0.19; based on the prevalence in rats obtained from literature) were the most likely pathogens to be transmitted. The probability of exposure of domestic pigs to pathogens from European starlings was estimated to be lower than the exposure from rats. However, pathogenic Escherichia coli had a 0.03 (5% and 95% CI 0.02–0.04) median probability of exposure, which was the highest probability among the three pathogens studied in starlings. The probability of pathogen exposure from feral to domestic pigs was found to be lower than rats and starlings for some pathogens. The highest probability of domestic pig exposure to feral pig pathogens was found to be for Mycoplasma hyopneumoniae (median 0.01, 5% and 95% CI 0.004–0.02) and Lawsonia intracellularis (median 0.01, 5% and 95% CI 0.005–0.03) for pigs in free-range piggeries in a region with a high number of feral pigs. The models developed in this thesis identified the presence and number of wild animals around piggeries, their access to piggeries and pig food and water, and their proximity to piggeries, as critical points to mitigate the risk of pathogen exposure. Findings from this thesis indicate that the estimated probability of exposure of domestic pigs to pathogens from wild animals is not negligible. As such, the implementation of mitigation strategies should be further investigated, considering also the magnitude of the impacts of this exposure, the costs involved with the mitigation measures and the practical implications. This would support decision-making to determine the need for and benefits of these mitigation strategies.|
|Description:||Doctor of Philosophy(PhD)|
|Rights and Permissions:||The author retains copyright of this thesis.|
|Type of Work:||PhD Doctorate|
|Appears in Collections:||Sydney Digital Theses (Open Access)|
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