Defra - Department for Environment, Food and Rural Affairs.

Science Search

Science and Research Projects

Return to Science Search homepage   Return to Project List

A study to explore what factors are influencing the spread of the bTB endemic area - SE3044

By the 1970s, the disease bovine tuberculosis (bTB) was almost eliminated from cattle in Great Britain. However in the 1980s the disease reappeared and has become more common ever since. This is especially so in South West, West and Central England, and in Wales. Over this time the disease has spread steadily into new areas.

In this project, we will be looking at the geographical spreading of bTB: how fast has the disease spread in different areas, and what local conditions affect the speed of the spread. Various ideas have been proposed about why the disease persists in locations and spreads into new ones. One factor that has been the subject of intensive debate and research is the role of wildlife, particularly badgers, as a reservoir of the disease. It is known that badgers can catch bTB from cattle and vice versa. It is argued that even if the disease is eliminated in cattle in some area, the disease can persist in the badger population, and then re-infect cattle. It is also possible that deer populations are involved.

Changes in farming practices are also possible factors in the increasing rates of bTB. Over the relevant time period, cattle herds have become bigger and fewer. Farms have becoming bigger and more fragmented, so a farmer may move a herd to other fields some miles from their original location. These and other such factors will be examined in our research.

The first step in our research will be to gather data on the incidence of the disease over the time between the 1980s and now, across Great Britain. This information will show us where the disease has moved into previously infection-free areas. One way this can happen is by spreading continuously along "fronts", that is, where the border between infected and infection-free areas moves steadily into the latter. The second type of spreading is by "jumps", where the disease suddenly appears in a new area, some distance from current infection. After a jump the disease may become established in a new area, or it may die out there.
As well as data related to the disease, we shall in parallel gather data on the factors likely to affect the speed of spread along fronts and the likelihood that disease becomes established in a new area, following a jump. These will include the numbers of cattle farms, the numbers and sizes of cattle herds, farming practices, wildlife numbers (especially for badgers), what is known about the prevalence of the disease in the wildlife, and general features of the landscape (such as how heavily wooded it is). Where little is known about wildlife numbers, we will look to use information on those features of the landscape known to favour (or not) the presence of a given species.

When we have these data, we shall use visualisation techniques to show the spread of the disease across the country, for example by animation. This will be used to develop insights into what is happening and develop theories about what is affecting spread that we can then test using statistical analysis techniques.

We will use mathematical techniques (such as correlation analysis and regression analysis) to look for relationships between the speed and likelihood of disease spread, and the local conditions. The type of result we will be looking for is: "on average, the disease spreads this much faster - say, in miles per year - in landscape of type A compared to landscape of type B." Finding relationships like this, or indeed not finding them, can provide evidence in favour of, or against, hypotheses put forward about what causes the spread of bTB. The results may also suggest new hypotheses.

The output of this research will be a better understanding of how this important animal disease has spread, and is spreading across the country. This improved knowledge could allow more accurate targeting of bTB control measures, perhaps allowing ‘smart’ zonal control of wildlife populations without the need for excessive culling, to target the expansion of high incidence areas, and eventually to ‘turn back the tide’ of increasing incidence and spatial distribution of bTB. The outputs of this research could have particular relevance to the targeting of other initiatives such as vaccination of both cattle and badgers. In addition, the databases we will construct during the project will be an important resource for other researchers, looking at other aspects of the disease.
The overall aim of this research is to identify the factors that are influencing the spread of the bTB high incidence (endemic) area(s):

Stage 1: To gather all the relevant data on the geographic spread of bTB high incidence areas and on possible explanatory factors
Stage 2: To map this data onto a unified spatio-temporal framework
Stage 3: To use the data to formulate and test causative hypotheses
Project Documents
• FRP - Final Report : SE3044 final report and appendices   (9033k)
Time-Scale and Cost
From: 2011

To: 2012

Cost: £163,755
Contractor / Funded Organisations
University of Reading, Risk Solutions
Animal Diseases              
Animal Health              
Plants and Animals              
Fields of Study
Animal Health