Risk Factors for Bovine Tuberculosis in Great Britain

Large herds and fattening herds are more likely to breakdown with bovine tuberculosis (bTB) in all areas, according to researchers in the UK. In areas with lower perceived risk, the risk of breaking down increased with the number of animals brought in from high incidence areas. On the other hand, in areas where the perceived risk is higher, bTB breakdown is more likely to be related to the history of disease and the probability of the disease in badgers.

27 May 2012

2 minute read

The continuing expansion of high incidence areas of bTB in Great Britain raises a number of questions concerning the determinants of infection at the herd level that are driving spread of the disease. In a paper published recently in BMC Veterinary Research, Paul R. Bessell of the University of Glasgow and co–authors there and at The Roslin Institute, the University of York, and Scottish Agricultural College (SAC) report that they have developed risk factor models to quantify the importance of herd size, cattle imports from Ireland, history of bTB, badgers and cattle restocking in determining bTB incidence. They went on to compare the significance of these different risk factors in high and low incidence areas (as determined by parish testing intervals).

A total of 15,358 bTB breakdowns were confirmed between 2002 and 2008 inclusive, of which 11,599 were not recorded as part of a follow-up and so were considered a new breakdown for the purposes of these analyses. The number of herds in Great Britain is declining, whilst the number of breakdowns is increasing.

Large herds and fattening herds are more likely to breakdown with bTB in all areas. In areas with lower perceived risk (longer testing intervals), the risk of breaking down is largely determined by the number of animals that a herd buys in from high incidence areas. In contrast, in higher perceived risk areas (shorter testing intervals), the risk of breakdown is defined by the history of disease and the probability of badger occurrence.

Despite differences in the management of bTB across different countries of Great Britain (England, Wales and Scotland), the researchers found no significant differences in bTB risk at the national level after these other factors had been taken into account.

Bessell and co-authors conclude their work demonstrates that different types of farm are at risk of breakdown and that the most important risk factors vary according to bTB incidence in an area. The results suggest that significant gains in bTB control could be made by targeting herds in low incidence areas that import the greatest number of cattle from high incidence areas.

Reference

Bessell P.R., R. Orton, P.C.L. White, M.R. Hutchings and R.R. Kao. 2012. Risk factors for bovine tuberculosis at the national level in Great Britain. BMC Veterinary Research, 8:51. doi:10.1186/1746-6148-8-51