The impact of respiratory disease on production in the pig industry in Great Britain
Evans, Charlotte Marie (2010) The impact of respiratory disease on production in the pig industry in Great Britain. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b2338639~S15
This thesis presents research on the epidemiology of respiratory diseases in pig herds in GB and their impact on pig morbidity and mortality. The role of management, characteristics of the herd, presence of multiple pathogens and control and elimination strategies were considered. Questionnaires were completed by veterinarians that attended 116 pig herds in GB. Pathogens were clustered on individual farms, suggesting similar risk factors for infection / persistence. Management factors were investigated for their association with the within and between-herd variability in pig antibodies to porcine reproductive and respiratory syndrome virus (PRRSV) in 103 pig herds. Factors that were important included close proximity to other pig herds, having >250 sows and not isolating purchased stock or not isolating for long enough. Considering the possible fade out of PRRSV, the within-herd transmission dynamics were investigated using a mathematical model. There was a high frequency of fade out in breeding pigs before virus reached young stock and increased persistence in young stock, in large herds, herds with increased contact between age groups and herds that had frequent re-introduction of virus. Results provided evidence for apparent erratic behaviour of PRRSV within and between herds. Mathematical models were also used to investigate the range of impacts of PRRSV on disease in a herd and to test strategies for control and elimination. PRRSV was difficult to eliminate without targeting both rearing pigs and sows. Rapid vaccination of sows once there was an increase in preweaning still births reduced the spread of virus to rearing pigs. Results highlighted that in areas of GB where the density of pigs is low it might be possible to control PRRSV through elimination. In larger herds in pig dense regions elimination might be difficult and control might give more stability. The long-term benefits of elimination will depend on (re)-introduction of virus from within and outside the herd but significant improvements in production might not be observed unless several respiratory pathogens are eliminated from a herd.
|Item Type:||Thesis or Dissertation (PhD)|
|Subjects:||Q Science > QL Zoology|
|Library of Congress Subject Headings (LCSH):||Respiratory organs -- Diseases -- Epidemiology, Porcine reproductive and respiratory syndrome, Swine -- Diseases -- Epidemiology, Swine -- Diseases -- Mathematical models, Swine -- Productivity|
|Institution:||University of Warwick|
|Theses Department:||Department of Biological Sciences|
|Supervisor(s)/Advisor:||Green, Laura E. ; Medley, Graham|
|Sponsors:||Great Britain. Dept. for Environment, Food & Rural Affairs (DEFRA) ; Biotechnology and Biological Sciences Research Council (Great Britain) (BBSRC) ; British Pig Executive (BPEX)|
|Extent:||xvii, 162 leaves : ill., charts|
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