Witcomb, Luci, Green, Laura E., Kaler, Jasmeet, Ul-Hassan, Atiya, Calvo-Bado, Leo A., Medley, Graham, Grogono-Thomas, Rosemary and Wellington, E. M. H. (2014) A longitudinal study of the role of Dichelobacter nodosus and Fusobacterium necrophorum load in initiation and severity of footrot in sheep. Preventive Veterinary Medicine, Volume 115 (Number 1-2). pp. 48-55. doi:10.1016/j.prevetmed.2014.03.004 ISSN 0167-5877.

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Abstract

Footrot is an infectious bacterial disease of sheep that causes lameness. The causal agent is Dichelobacter nodosus. There is debate regarding the role of Fusobacterium necrophorum in disease initiation. This research used an observational longitudinal study of footrot, together with quantitative PCR (qPCR) of bacterial load of D. nodosus and F. necrophorum, to elucidate the roles of each species in the development of disease. All feet of 18 a priori selected sheep were monitored for five weeks assessing disease severity (healthy, interdigital dermatitis (ID) and severe footrot (SFR)) and bacterial load. A multinomial model was used to analyse these data.

Key results were that D. nodosus was detected more frequently on feet with ID, whereas F. necrophorum was detected more frequently on feet with SFR. In the multinomial model, ID was associated with increasing log10 load of D. nodosus the week of observation (OR = 1.28 (95% CI = 1.08-1.53)) and the week prior to development of ID (OR = 1.20 (95% CI = 1.01-1.42). There was no association between log10 load^2 of F. necrophorum and presence of ID (OR = 0.99 (95% CI = 0.96-1.02))). SFR was associated with increasing log10 load of D. nodosus the week before disease onset (OR = 1.42 (95% CI = 1.02-1.96)) but not once SFR had occurred. SFR was positively associated with log10 load^2 of F. necrophorum once disease was present (OR = 1.06 (95% CI = 1.01-1.11)). In summary, there was an increased risk of increasing D. nodosus load the week prior to development of ID and SFR and during an episode of ID. In contrast, F. necrophorum load was not associated with ID before or during an episode, and was only associated with SFR once present. These results contribute to our understanding of the epidemiology of footrot and highlight that D. nodosus load plays the primary role in disease initiation and progression, with F. necrophorum load playing a secondary role. Further studies in more flocks and climates would be useful to confirm these findings. This study identifies that D. nodosus load is highest during ID. This supports previous epidemiological findings, which demonstrate that controlling ID is the most effective management strategy to prevent new cases of ID and SFR.

Item Type:	Journal Article
Subjects:	S Agriculture > SF Animal culture
Divisions:	Faculty of Science, Engineering and Medicine > Science > Life Sciences (2010- )
Library of Congress Subject Headings (LCSH):	Footrot in sheep, Bacteroides nodosus, Fusobacterium
Journal or Publication Title:	Preventive Veterinary Medicine
Publisher:	Elsevier
ISSN:	0167-5877
Official Date:	1 July 2014
Dates:	Date Event 1 July 2014 Published 5 March 2014 Accepted 15 May 2013 Submitted
Volume:	Volume 115
Number:	Number 1-2
Page Range:	pp. 48-55
DOI:	10.1016/j.prevetmed.2014.03.004
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Open Access (Creative Commons)
Date of first compliant deposit:	26 December 2015
Date of first compliant Open Access:	26 December 2015
Funder:	Natural Environment Research Council (Great Britain) (NERC), Pfizer Animal Health, Biotechnology and Biological Sciences Research Council (Great Britain) (BBSRC), Great Britain. Meat and Livestock Commission (MLC)
Grant number:	BBE01870X1 (BBSRC)
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