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Mathematical modeling of ovine footrot in the UK: the effect of Dichelobacter nodosus and Fusobacterium necrophorum on the disease dynamics

Atia, Jolene; Monaghan, Emma; Kaler, Jasmeet; Purdy, Kevin; Green, Laura; Keeling, Matt

Authors

Jolene Atia

Emma Monaghan

JASMEET KALER JASMEET.KALER@NOTTINGHAM.AC.UK
Professor of Epidemiology & Precision Livestock Informatics

Kevin Purdy

Laura Green

Matt Keeling



Abstract

Dichelobacter nodosus is a virulent, invasive, anaerobic bacterium that is believed to be the causative agent of ovine footrot, an infectious bacterial disease of sheep that causes lameness. Another anaerobe, Fusobacterium necrophorum, has been intimately linked with the disease occurrence and severity. Here we examine data from a longitudinal study of footrot on one UK farm, including quantitative PCR (qPCR) estimates of bacterial load of D. nodosus and F. necrophorum. The data is at foot level; all feet were monitored for five weeks assessing disease severity (healthy, interdigital dermatitis (ID), or severe footrot (SFR)) and bacterial load (number of bacteria/swab). We investigate the role of D. nodosus and F. necrophorum in the progress of the disease using a continuous-time Markov model with 12 different states characterising the foot. The transition rates between the adjacent states are the (34) model parameters, these are determined using Metropolis Hasting MCMC. Our aim is to determine the predictive relationship between past and future D. nodosus and F. necrophorum load and disease states. We demonstrate a high level of predictive accuracy at the population level for the D. nodosus model, although the dynamics of individual feet is highly stochastic. However, we note that this predictive accuracy at population level is only high in more diseased states for F. necrophorum model. This supports our hypothesis that D. nodosus load and status of the foot work in combination to give rise to severe footrot and lameness, and that D. nodosus load plays the primary role in the initiation and progression of footrot, while F. necrophorum load rather increases disease severity of SFR.

Journal Article Type Article
Journal Epidemics
Print ISSN 1755-4365
Electronic ISSN 1878-0067
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 21
Pages 13-20
APA6 Citation Atia, J., Monaghan, E., Kaler, J., Purdy, K., Green, L., & Keeling, M. (in press). Mathematical modeling of ovine footrot in the UK: the effect of Dichelobacter nodosus and Fusobacterium necrophorum on the disease dynamics. Epidemics, 21, 13-20. https://doi.org/10.1016/j.epidem.2017.04.001
DOI https://doi.org/10.1016/j.epidem.2017.04.001
Publisher URL http://www.sciencedirect.com/science/article/pii/S1755436517300762
Copyright Statement Copyright information regarding this work can be found at the following address: http://creativecommons.org/licenses/by/4.0

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Copyright Statement
Copyright information regarding this work can be found at the following address: http://creativecommons.org/licenses/by/4.0





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