Identifying temporal variation in reported births, deaths and movements of cattle in Britain

Susan E Robinson,Rob M Christley

doi:10.1186/1746-6148-2-11

Abstract

BackgroundThe accuracy of predicting disease occurrence using epidemic models relies on an understanding of the system or population under investigation. At the time of the Foot and Mouth disease (FMD) outbreak of 2001, there were limited reports in the literature as to the cattle population structure in Britain. In this paper we examine the temporal patterns of cattle births, deaths, imports and movements occurring within Britain, reported to the Department for the Environment, Food and Rural Affairs (DEFRA) through the British Cattle Movement service (BCMS) during the period 1st January 2002 to 28th February 2005.ResultsIn Britain, the number of reported cattle births exhibit strong seasonality characterised by a large spring peak followed by a smaller autumn peak. Other event types also exhibit strong seasonal trends; both the reported number of cattle slaughtered and "on-farm" cattle deaths increase during the final part of the year. After allowing for seasonal components by smoothing the data, we illustrate that there is very little remaining non-seasonal trend in the number of cattle births, "on-farm" deaths, slaughterhouse deaths, on- and off-movements. However after allowing for seasonal fluctuations the number of cattle imports has been decreasing since 2002. Reporting of movements, births and deaths was more frequent on certain days of the week. For instance, greater numbers of cattle were slaughtered on Tuesdays, Wednesdays and Thursdays. Evidence for digit preference was found in the reporting of births and "on-farm" deaths with particular bias towards over reporting on the 1st, 10th and 20th of each month.ConclusionThis study provides insight into the population and movement dynamics of the British cattle population. Although the population is in constant flux, seasonal and long term trends can be identified in the number of reported births, deaths and movements of cattle. Incorporating this temporal variation in epidemic disease modelling may result in more accurate model predictions and may usefully inform future surveillance strategies.

Highlights

The accuracy of predicting disease occurrence using epidemic models relies on an understanding of the system or population under investigation
Time series for cattle births reported to British Cattle Movement service (BCMS) over the period 1st Jan 2002 and 28th Feb 2005. (a) Raw data plotted at daily intervals (b) 3-point moving average (c) Residuals after accounting for the 3-point moving average (d) 53-point moving average
In this paper we aim to identify long term trends, as well as seasonality in cattle population dynamics and cattle movements within Britain by analysing data on cattle movements collected by the BCMS and supplied through

Summary

Introduction

The accuracy of predicting disease occurrence using epidemic models relies on an understanding of the system or population under investigation. Mathematical modelling approaches are increasingly being employed to inform disease control strategies Interest in these techniques in this context has been greatly augmented by recent disease outbreaks within the British cattle population. The accuracy of such models relies upon accurate estimates of population structure as temporal trends in the births, deaths and movements of cattle may impact substantially on pathogen transmission dynamics. Figure for cattle births reported to BCMS over the period 1st Jan 2002 and 28th Feb 2005 Time series. Time series for cattle births reported to BCMS over the period 1st Jan 2002 and 28th Feb 2005. Reports of temporal characteristics in cattle movements in Britain already exist in the literature [3], quantification and additional exploratory analysis of the extensive data is required

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Conclusion