In 2012, CCRI’s Dr Damian Maye was part of a collaborative research team, contracted by Defra and the Animal Health and Veterinary Laboratories Agency, to undertake an exploration of factors that influence the expansion of the area affected by endemic bTB. The other partners involved were Cardiff University, Exeter University, UWE and the Royal Agricultural University.
Alhough pre-movement testing for bTB had had a significant impact on the long distance spread of the disease, especially on transmission to areas with relatively low incidence, the role of local spread in the expansion of bTB-affected areas was not well understood. Despite the net annual benefit of pre-movement testing for bTB being predicted to reach tens of millions of pounds by 2015, illustrating the benefits achievable by controlling risk factors, the predicted long term trend is for bTB to continue to increase its geographical extent in England and Wales (Defra 2010).
This research aimed to further investigate and quantify known factors that are associated with local bTB spread, and also develop novel theories on other factors. The project, through an integrated multidisciplinary approach, used a mixture of existing comprehensive datasets, such as Cattle Tracing System, VetNet, VeBus and land-use maps, and also gathered new data and information from industry representatives through workshops and surveys.
To establish how far and fast areas of endemic bTB are spreading, the primary step was to develop a robust measure of exactly what is meant by endemic status. Endemic not only denotes a high prevalence of disease but also requires the disease to persist in cattle populations (and the associated wildlife). An operational mathematical measure of endemicity based on surveillance results was established, taking into account changes in bTB surveillance activities, and applied to data from the last ten years. Knowing the genotype of the bacterium causing bTB will help distinguish overlapping endemic areas. The areas affected by endemic bTB at regular time points was mapped and measured for speed of expansion.
Once the locations of endemic bTB areas and their rates of expansion were defined, the risk factors aiding spread (including geographical features and farm management practices where the expansion is occurring) were investigated. There is a substantial body of literature on risk factors for bTB herd breakdown and spread. To maximise the use of this previous work we are looking at the literature for factors that have been demonstrated to have a significant impact on bTB spread (e.g. cattle movements) and for other potential factors, and investigating the influence of these factors on the speed of bTB spread. Hypothesising that different risk factors will operate in areas depending on local infection pressure and farming contexts; we are exploring risk factors for TB in the context of disease endemicity.
As part of the project, an interdisciplinary social research component identified relevant farm practices that may act as risk factors in the spread of endemic bTB. It involved intensive social research with farmers in areas vulnerable to the spread of endemic bTB leading to the identification of social risk factors that will be incorporated within a subsequent survey. The social work package drew on observation as well as traditional oral forms of research (e.g. interviews and focus groups) to identify relevant farm practices. It also involved farmers and other participants (e.g. vets) in meaningful ways, for example through the identification and agreement of risk factors.