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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Spatial and spatio-temporal analysis of Salmonella infection in dairy herds in England and Wales
AU - Fenton, S. E.
AU - Clough, H. E.
AU - Diggle, P. J.
AU - Evans, S. J.
AU - Davison, H. C.
AU - Vink, W. D.
AU - French, N. P.
N1 - http://journals.cambridge.org/action/displayJournal?jid=HYG The final, definitive version of this article has been published in the Journal, Epidemiology and Infection, 137 (6), pp 847-857 2009, © 2009 Cambridge University Press.
PY - 2009/6
Y1 - 2009/6
N2 - Using data from a cohort study conducted by the Veterinary Laboratories Agency (VLA), evidence of spatial clustering at distances up to 30 kin was found for S. Agama and S. Dublin (P values of 0001) and borderline evidence was found for spatial clustering of S. Typhimurium (P = 0.077). The evolution of infection status of study farms over time was modelled using a Markov Chain model with transition probabilities describing changes in Status at each of four visits, allowing for the effect of sampling visit. The degree of geographical clustering of infection, having allowed for temporal effects, was assessed by comparing the residual deviance from a model including a measure of recent neighbourhood infection levels with one excluding this variable. The number of cases arising within a defined distance and time period of an index case was higher than expected. This provides evidence for spatial and Spatio-temporal clustering, which suggests either a contagious process (e.g. through direct or indirect farm-to-farm transmission) or geographically localized environmental and/or farm factors which increase the risk of infection. The results emphasize the different epidemiology of the three Salmonella serovars investigated.
AB - Using data from a cohort study conducted by the Veterinary Laboratories Agency (VLA), evidence of spatial clustering at distances up to 30 kin was found for S. Agama and S. Dublin (P values of 0001) and borderline evidence was found for spatial clustering of S. Typhimurium (P = 0.077). The evolution of infection status of study farms over time was modelled using a Markov Chain model with transition probabilities describing changes in Status at each of four visits, allowing for the effect of sampling visit. The degree of geographical clustering of infection, having allowed for temporal effects, was assessed by comparing the residual deviance from a model including a measure of recent neighbourhood infection levels with one excluding this variable. The number of cases arising within a defined distance and time period of an index case was higher than expected. This provides evidence for spatial and Spatio-temporal clustering, which suggests either a contagious process (e.g. through direct or indirect farm-to-farm transmission) or geographically localized environmental and/or farm factors which increase the risk of infection. The results emphasize the different epidemiology of the three Salmonella serovars investigated.
KW - Epidemiology
KW - K-function analysis
KW - Markov chain
KW - Salmonella
KW - spatial clustering
KW - RISK-FACTORS
KW - 2ND-ORDER ANALYSIS
KW - CATTLE
KW - CONTAMINATION
KW - TRANSMISSION
KW - SEROTYPES
KW - ENTERICA
KW - BADGERS
KW - USA
U2 - 10.1017/S0950268808001349
DO - 10.1017/S0950268808001349
M3 - Journal article
VL - 137
SP - 847
EP - 857
JO - Epidemiology and Infection
JF - Epidemiology and Infection
SN - 0950-2688
IS - 6
ER -