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Studies on swine dysentery in Western Australia

Mhoma, Jumanne R.L. (1992) Studies on swine dysentery in Western Australia. PhD thesis, Murdoch University.

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This work was conducted with the primary aim of determining the prevalence of swine dysentery (SD) amongst piggeries in Western Australia. Accordingly a serological survey to detect evidence of infection with the causative bacterium, Treponema hyodysenteriae, was conducted. The lipopolysaccharide of T. hyodysenteriae of serogroups A, B and E were used as antigen in the enzyme-linked immunosorbent assay (ELISA) tests that were developed. Cut off litres for seropositivity were determined by testing 400 sera from herds known to be free of SD, and sera from immunised or experimentally infected pigs. Forty serum samples from bacon-weight pigs were collected from each of 106 herds at two abattoirs.

To validate the test, 19 herds were re-sampled and retested, and faecal samples from 20 herds were cultured for T. hyodysenteriae. Thirty five of the 106 herds (33%) had serological evidence of infection when only one batch of sera from each herd was tested. The set of ELISA tests using 40 sera was estimated as having a sensitivity of 77.3% and a specificity of 81.8% based on the owners’ opinion of their herds diseases status, although based on the results of retesting actual figures were more likely to be 84.6% and 90.2% respectively. Prevalence of infection within herds ranged from 2.5% to 47.5%, with a mean of 18%.

A questionnaire was also sent to 101 of these piggeries in order to determine which management, husbandry and health factors were associated with the presence or absence of SD in Western Australian piggeries. The owners of 77 herds responded to the survey (76.2% of all herds surveyed). Analysis of the questionnaires revealed that amongst other things the purchase of pigs from saleyards and the presence of frequent visitors to the piggery were significantly correlated with the presence of SD.

Conversely, the provision of overalls and gumboots to visitors and the purchase of replacement stock from one source significantly reduced the risk of introducing SD to a piggery. No individual herd in Western Australia was identified that was disseminating infection to other herds via the movement of pigs. It was concluded that adopting management practices which included the purchase of replacement stock from herds known to be free of SD, a reduction in the number of visitors and the provision of boots and overalls for visitors will assist in preventing SD from entering non-infected herds in Western Australia.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Veterinary Studies
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): Hampson, David and Robertson, Ian
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