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The control of Corynebacterium pseudotuberculosis infection in sheep flocks : a mathematical model of the impact of vaccination, serological testing, clinical examination and lancing of abscesses

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O'Reilly, K. M., Medley, Graham and Green, Laura E.. (2010) The control of Corynebacterium pseudotuberculosis infection in sheep flocks : a mathematical model of the impact of vaccination, serological testing, clinical examination and lancing of abscesses. Preventative Veterinary Medicine, Vol.95 (No.1-2). pp. 115-126. ISSN 0167-5877

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Official URL: http://dx.doi.org/10.1016/j.prevetmed.2010.02.012

Abstract

A mathematical model of Corynebacterium pseudotuberculosis infection in sheep flocks was used to evaluate strategies for control and elimination of caseous lymphadenitis (CIA). Control strategies tested were vaccination, serological testing and removal of seropositives, clinical examination and removal of sheep with abscesses, lancing abscesses, and appropriate combinations. Three different infection rates with and without replacement of culled ewes were used to evaluate the control options. Controls were either implemented immediately after infection was detected in a flock or once CIA was at endemic equilibrium, and with different frequencies of examination or testing. Elimination of infection was defined as 99% confidence that no sheep were infected with C. pseudo tuberculosis. The control strategies were evaluated by estimating the reduction in infection or probability of elimination and the number of ewes culled from the flock. Lancing abscesses reduced the prevalence of infection when the initial prevalence was <0.60, but elimination was unlikely. A vaccine efficacy of 0.79 or more led to elimination of infection from the flock, provided that the endemic prevalence of infection was <0.60. A combination of vaccination and clinical examination reduced the prevalence of infection at a faster rate than using clinical examination or vaccination alone where five rounds of clinical examination were done. Serological testing led to elimination of infection after five tests, but was highly dependent upon the diagnostic test sensitivity and specificity and management options used: a test sensitivity of 0.90 always resulted in elimination. A test specificity greater than 0.90 prevented removal of many false positive ewes and consequently prevented a large reduction in lamb production. Elimination was most likely using a serological test with sensitivity and specificity >0.90, but vaccination combined with clinical examination reduced infection rapidly with little impact on lamb productivity. Further research is required to develop a diagnostic test with at least 0.90 specificity and sensitivity under field conditions before any methods of control can be recommended with confidence.

Item Type:	Journal Article
Subjects:	S Agriculture > SF Animal culture
Divisions:	Faculty of Science > Life Sciences (2010- ) > Biological Sciences ( -2010)
Library of Congress Subject Headings (LCSH):	Corynebacterium pseudotuberculosis -- Treatment -- Mathematical models, Sheep -- Infections -- Mathematical models
Journal or Publication Title:	Preventative Veterinary Medicine
Publisher:	Elsevier Science BV
ISSN:	0167-5877
Date:	1 June 2010
Volume:	Vol.95
Number:	No.1-2
Number of Pages:	12
Page Range:	pp. 115-126
Identification Number:	10.1016/j.prevetmed.2010.02.012
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	Biotechnology and Biological Sciences Research Council (Great Britain) (BBSRC)
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URI:	http://wrap.warwick.ac.uk/id/eprint/5756