Badgers not a key source of bovine TB latest released study shows

The Badger Trust has today welcomed the long awaited release of the Badgers Found Dead Study (BFDS), with results that clearly support the Trust’s view that badgers are not a reservoir host for bovine TB, but rather a spillover host. These latest results support those of a previous survey of culled badgers in 2016, which found less than 5% of culled badgers tested positive for bovine TB*.

The BFDS, commissioned by DEFRA in 2016, investigated the prevalence of bTB in ‘found dead’ badgers in Edge Areas** of England, covering the northern counties of Cheshire, Derbyshire, Warwickshire, Nottinghamshire, Leicestershire and Northamptonshire; and in the southern counties of Oxfordshire, Hampshire, East Sussex, Buckinghamshire and Berkshire. It was carried out by the Universities of Nottingham and Surrey for the northern and southern areas respectively. The results of the study were presented in two separate reports.

A total of 372 badger carcasses underwent post mortem examination and sampling. In all five southern counties only three M. tuberculosis complex bovis (MTCB) positive cases were identified, all from Oxfordshire, giving a prevalence for Oxfordshire of 3.8% (3 out of 79), and an overall prevalence for these counties of 1.0%.

In the northern counties approximately 100 carcasses were tested from each county, and overall 8.3% were culture-positive (confirmed by PCR) for M. tuberculosis complex (MTC). Cheshire (13.5%), Leicestershire (12.4%) and Warwickshire (9.8%) had the highest infection rates, with Derbyshire (4%), Nottinghamshire (4.9%) and Northamptonshire (4.1%) showing the lowest.

Almost all badgers in the northern study showed no clear signs of tuberculosis lesions at post mortem examination. Of those confirmed culture positive only two had widespread tuberculous lesions, and a further two had limited bTB lesions. The University of Nottingham Final Report states therefore that ‘the majority (92%) of MTC positive badgers might be described as ‘latently’ infected – i.e. not showing symptoms and non-infectious.

No lesions typical of M. bovis infection were observed in any of the badgers examined in the southern counties.

Jo Bates-Keegan, Chair of the Badger Trust, stated:

‘The BFDS data supports our view that badgers are not in fact a reservoir host for bovine TB, but instead simply a spillover host. The government’s justification for culling in Edge areas such as Derbyshire is based on highly inaccurate estimates of the number of new herd breakdowns (where a herd loses its officially TB free status due to bovine TB being suspected or confirmed) to have been caused by badgers.’