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Epidemiological information in sheep health management

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Green, Laura E.. (2010) Epidemiological information in sheep health management. Small Ruminant Research, Vol.92 (No.1-3). pp. 57-66. ISSN 0921-4488

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Official URL: http://dx.doi.org/10.1016/j.smallrumres.2010.04.00...

Abstract

We use epidemiology whenever we consider the management of sheep health. To measure a disease, we need a precise and unique case definition and we often use diagnostic tests to assist in defining a disease. Diagnostic tests are not always accurate. Thus, it is necessary to consider the decisions that will be taken, based on the result of testing, in order to decide the most useful approach to interpret a test based on its test sensitivity and specificity and the prevalence of the disease in a flock. This is particularly important when decisions on culling or selection of sheep to attain, e.g. freedom from disease, are made on the basis of test results. Infectious diseases spread within and between flocks in a variety of ways; brought-in sheep are the most likely source for introduction of a new pathogen or strain of a pathogen. When a pathogen enters a naïve flock, it spreads through susceptible sheep and persists in the flock, whilst there are susceptible sheep that can be infected. Pathogens use a variety of techniques to persist, including changes in the pathogen itself, alterations in infected hosts enabling them to remain infectious for prolonged periods or to be re-infected, persistence in other host species or in the environment. We need to consider these strategies to decide whether elimination or control of a particular pathogen is more likely to be effective. Whatever the flock control strategy, treatment of diseased individuals is essential for their welfare and can also protect the rest of the flock, if treatment reduces the infectious period. Decisions on management of disease are based on our knowledge of the flock and its management and the evidence base for various control strategies. There are now formal techniques for evaluating the evidence base that can assist in evaluating evidence. One area where we need to evaluate evidence is on cause. It is not possible to prove anything, but we can use the weight of evidence to evaluate likely cause. There are nine aspects of association with which we can evaluate a piece of evidence; these are: strength, consistency, specificity, temporality, dose–response, plausibility, coherence, experiment and analogy.

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):	Epidemiology -- Research, Sheep -- Diseases -- Research, Veterinary medicine -- Diagnosis, Evidence-based medicine
Journal or Publication Title:	Small Ruminant Research
Publisher:	Elsevier BV
ISSN:	0921-4488
Official Date:	August 2010
Volume:	Vol.92
Number:	No.1-3
Number of Pages:	10
Page Range:	pp. 57-66
Identification Number:	10.1016/j.smallrumres.2010.04.006
Status:	Peer Reviewed
Access rights to Published version:	Open Access
Funder:	Biotechnology and Biological Sciences Research Council (Great Britain) (BBSRC), Great Britain. Dept. for Environment, Food & Rural Affairs (DEFRA), Rural Economy and Land Use Programme (Great Britain) (RELU), English Beef & Lamb Executive
References:	Abbott and Lewis, 2005 K.A. Abbott and C.J. Lewis, Current approaches to the management of ovine footrot, Vet. J. 169 (2005), pp. 28–41. Anderson and May, 1991 R. Anderson and R. May, Infectious Diseases of Humans, Oxford University Press (1991). Bradford Hill, 1965 A. Bradford Hill, The environment and disease: association or causation?, Proc. R. Soc. Med. 58 (1965), pp. 295–300. Barker et al., 2007 Z.E. Barker, J.R. Amory, J.L. Wright, R.W. Blowey and L.E. Green, Management factors associated with impaired locomotion in dairy cows in England and Wales, J. Dairy Sci. 90 (2007), pp. 3270–3277. Bassett et al., 1995 J.M. Bassett, R.A. Borrett, C. Hanson, R. Parsons and S.E. Wolfensohn, Anaemia in housed newborn lambs, Vet. Rec. 136 (1995), pp. 137–140. Espejo and Endres, 2007 L.A. Espejo and M.I. Endres, Herd-level risk factors for lameness in high-producing Holstein cows housed in freestall barns, J. Dairy Sci. 90 (2007), pp. 306–314. Evans et al., 2008 C.M. Evans, G.F. Medley and L.E. Green, Porcine reproductive and respiratory syndrome virus (PRRSV) in GB pig herds: farm characteristics associated with heterogeneity in seroprevalence, BMC Vet. Res. 28 (2008), p. 48. Evans et al., 2010 C.M. Evans, G.F. Medley, S.J. Creasey and L.E. Green, A stochastic mathematical model of the within-herd transmission dynamics of porcine reproductive and respiratory syndrome virus (PRRSV): fade-out and persistence, Prev. Vet. Med. 93 (2010), pp. 248–257. Green et al., 1993 L.E. Green, E. Berriatua and K.L. Morgan, Anaemia in housed lambs, Res. Vet. Sci. 54 (1993), pp. 306–311. Green et al., 1994 L.E. Green, E. Berriatua and K.L. Morgan, Prevalence, possible aetiologies, control and cost of parasitic lesions in three flocks of housed lambs, Vet. Rec. 134 (1994), pp. 119–120. Green et al., 1997a L.E. Green, E. Berriatua and K.L. Morgan, The relationship between abnormalities detected in live lambs on farms and those detected at post mortem meat inspection, Epidemiol. Infect. 118 (1997), pp. 267–273. Green et al., 1997b L.E. Green, M. Graham and K.L. Morgan, Preliminary study of the effect of iron dextran on a non-regenerative anaemia of housed lambs, Vet. Rec. 140 (1997), pp. 219–222. Green, 1999 L.E. Green, An approach to clinical problems on pig farms, In Pract. 9 (1999), pp. 492–505. Green and Medley, 2002 L.E. Green and G.F. Medley, Mathematical modelling of the foot and mouth disease epidemic of 2001: strengths and weaknesses, Res. Vet. Sci. 73 (2002), pp. 201–205. Green et al., 2007 L.E. Green, G.J. Wassink, R. Grogono-Thomas, L.J. Moore and G.F. Medley, Looking after the individual to reduce disease in the flock: a binomial mixed effects model investigating the impact of individual sheep management of footrot and interdigital dermatitis in a prospective longitudinal study on one farm, Prev. Vet. Med. 78 (2007), pp. 172–178. Jordan et al., 1996 D. Jordan, J.W. Plant, H.I. Nicol, T.M. Jessep and C.J. Scrivener, Factors associated with the effectiveness of antibacterial treatment for ovine virulent footrot, Aust. Vet. J. 73 (1996), pp. 211–215. Kaler and Green, 2008 J. Kaler and L.E. Green, Recognition of lameness and decisions to catch for inspection among sheep farmers and specialists in GB, BMC Vet. Res. 4 (2008), p. 41. Kaler and Green, 2009 J. Kaler and L.E. Green, Farmers’ practices and factors associated with the prevalence of all lameness and lameness attributed to interdigital dermatitis and footrot in sheep flocks in England in 2004, Prev. Vet. Med. 92 (2009), pp. 52–59. Kaler et al., 2010 J. Kaler, S.L.S. Daniels, J.W. Wright and L.E. Green, Randomised factorial design clinical trial to investigate the impact of parenteral long acting oxytetracycline, foot trimming and flunixine meglumine on time to recovery from lameness in sheep with footrot, J. Vet. Int. Med. (2010) 10.1111/j.1939-1676.2009.0450.x. Manske et al., 2002 T. Manske, J. Hultgren and C. Bergsten, The effect of claw trimming on the hoof health of Swedish dairy cattle, Prev. Vet. Med. 54 (2002), pp. 113–129. Mohler and Washburn, 1904 J.R. Mohler and H.J. Washburn, Foot-rot of Sheep: Its Nature Cause and Treatment, U.S. Department of Agriculture, Government Printing Office, Washington (1904). Petrie and Watson, 2008 A. Petrie and P. Watson, Statistics for Veterinary and Animal Science, Blackwell Publishing (2008). O’Reilly et al., 2008 K.M. O’Reilly, L.E. Green, F.E. Malone and G.R. Medley, Parameter estimation and simulations of a mathematical model of Corynebacterium pseudotuberculosis transmission in sheep, Prev. Vet. Med. 83 (2008), pp. 242–259. O’Reilly et al., in press O’Reilly, K.M., Medley, G.F., Green, L.E., in press. 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. Prev. Vet. Med. Sackett et al., 1996 D.L. Sackett, W.M.C. Rosenberg, J.A.M. Gray, R.B. Haynes and W.S. Richardson, Evidence based medicine: what it is and what it isn’t, Br. Med. J. 312 (1996), pp. 71–72. Schalm, 1984 O.W. Schalm, Veterinary Haematology (4th ed.), Lea and Febiger, Philadelphia (1984). Thrusfield, 1995 M. Thrusfield, Veterinary Epidemiology (2nd ed.), Blackwell Science, Oxford (1995). Wassink et al., 2003 G.J. Wassink, R. Grogono-Thomas, L.J. Moore and L.E. Green, Risk factors associated with the prevalence of footrot in sheep from 1999 to 2000, Vet. Rec. 152 (2003), pp. 351–358. Wassink et al., 2004 G.J. Wassink, R. Grogono-Thomas, L.J. Moore and L.E. Green, Risk factors associated with the prevalence of interdigital dermatitis in sheep from 1999 to 2000, Vet. Rec. 154 (2004), pp. 551–552. Wassink et al., in press Wassink, G.J., King, E.M., Grogono-Thomas, R., Brown, J.C., Moore, L.J., Green, L.E., in press. A within farm clinical trial to test the efficacy of prompt antibacterial treatment to sheep lame with footrot. Prev. Vet. Med. Winter, 2004 A.C. Winter, Lameness in sheep. 2. Treatment and control, In Pract. 26 (2004), pp. 130–139. Winter, 2008 A.C. Winter, Lameness in sheep, Small Rumin. Res. 76 (2008), pp. 149–153.
URI:	http://wrap.warwick.ac.uk/id/eprint/3351