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Paratuberculosis in the Small Ruminant Dairy Industries of Ontario: Prevalence, Risk Factors, and Test Evaluations

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dc.contributor.advisor Jones Bitton, Andria Bauman, Cathy 2013-08-29T15:18:59Z 2013-08-29T15:18:59Z 2013-07 2013-07-19 2013-08-29
dc.description.abstract This thesis was to determine the prevalence and distribution of paratuberculosis in the Ontario dairy sheep and dairy goat industries, identify potential risk factors for herds which tested positive, evaluate the accuracy of seven commercially available individual and two bulk tank diagnostic tests in these two populations, and determine the circulating strains of Mycobacterium avium ssp. paratuberculosis in faecal isolates obtained. A cross-sectional study was conducted between October 2010 and August 2011 in 29 goat herds and 21 sheep flocks located in Ontario. On each farm, 20 lactating animals over the age of two years were randomly selected and faeces, blood, and milk were sampled from each animal, and a bulk milk sample from each herd. A questionnaire inquiring about herd management and biosecurity behaviours was also completed. The seven individual animal tests evaluated were: faecal culture using the BACTEC® MGIT™ 960 liquid culture system, direct faecal PCR (Tetracore®, Rockville, MD) based on the hspX gene, the Prionics® ELISA on serum and milk, the IDEXX® ELISA on serum and milk, and the agar gel immunodiffusion (AGID) test on serum. The test evaluations used both frequentist (faecal culture - reference test) and Latent Class Analysis/Bayesian (LCA/BM) methods (no reference test). In goat herds, faecal culture demonstrated the highest sensitivity (Se), 81.1% (LCA/BM). In sheep, while faecal culture demonstrated the highest Se, 49.5%, there was a small probability it was higher than faecal PCR Se at 42.4%. The bulk tank tests evaluated were the 'Hyper-ELISA' test and real-time PCR test based on IS900 (AntelBio®). While PCR did not demonstrate sufficiently high Se to be used as a herd-level test, the Hyper-ELISA performed well as a herd-level test identifying farms with high prevalence when the cut-off was reduced to 0.05. Overall herd-level apparent prevalence was 79.3% in goat herds and 57.1% in sheep flocks when faecal culture was the reference standard and true herd-level prevalence (LCA/BM) was 83.0% and 66.8% in each population respectively. This high prevalence reveals a need for the implementation of a small ruminant paratuberculosis control program in Ontario, Canada based on testing, improving youngstock management, and strengthening biosecurity practices. en_US
dc.description.sponsorship AHSI, OMAF en_US
dc.language.iso en en_US
dc.rights Attribution-NoDerivs 2.5 Canada *
dc.rights.uri *
dc.subject paratuberculosis en_US
dc.subject dairy goats en_US
dc.subject dairy sheep en_US
dc.subject test evaluation en_US
dc.subject prevalence en_US
dc.subject Bayesian en_US
dc.subject latent class analysis en_US
dc.title Paratuberculosis in the Small Ruminant Dairy Industries of Ontario: Prevalence, Risk Factors, and Test Evaluations en_US
dc.type Thesis en_US Population Medicine en_US Doctor of Philosophy en_US Department of Population Medicine en_US
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Attribution-NoDerivs 2.5 Canada Except where otherwise noted, this item's license is described as Attribution-NoDerivs 2.5 Canada