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Bovine TB: a lack of shared understanding

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01 June 2015, at 12:00am

RICHARD GARD reports on a debate held by the Badger Trust on the role of badgers in the spread of bovine TB and finds there was little common ground on the best way forward in controlling the disease

THE Badger Trust held a debate entitled Bovine TB – the role of badgers in the spread of the disease from a current and historical perspective, following its AGM in April.

The president of the BVA, John Blackwell, Professor John Bourne and Roger Blowey were invited to address the audience. Roger made his notes of the meeting available and there has since been clarification of many of the aspects revealed during the meeting.

It is clear that there is no agreed understanding between the speakers about the role of badger culling as a means of controlling bovine TB. Prof. Bourne continues to say that “badger culling can make no meaningful contribution to cattle TB control in Britain”.

This view is accepted totally by the Badger Trust but strongly challenged by Roger Blowey and John Blackwell, who believe that reducing the number of bTB infected badgers would be of benefit to both cattle and badgers.

Roger Blowey commented that the meeting was well worth attending although there was a minority of unpleasant people present. “There were several people who, although not agreeing, wanted to hear alternative views. One of my own reasons for attending was to try to understand why our views were so very different to theirs,” he said.

The main thrust of the Badger Trust argument, heavily promoted by Prof. Bourne, is that bTB was controlled in the 1950s and 60s by frequent implementation of the standard skin test, movement restrictions on infected herds and some whole herd slaughter.

The frequency of herd testing was then reduced to four-year intervals in many areas of the country and this, with the widespread movement of the alleged untested and bTB infected cattle during the FMD restock, is what led to the rapid rise in bTB from 2000 onwards.

If this was the case, says Roger, it does not explain why areas such as Scotland, where extended testing intervals were first introduced, now have the lowest incidence of bTB nationally.

John Bourne continues to insist that improved cattle controls alone, especially risk-based trading (subdividing the UK into high and low risk areas) will control the disease, and that badger controls have no meaningful part to play. He continually quoted the Australian example (limiting cattle movements across the country) and was very much in favour of the caudal fold test as being more accurate.

Others would, of course, dispute this. When challenged, he admitted that in his segregated areas we would still need to do something about badger infection, but he said “eventually”.

It was a surprise, says Mr Blowey, to hear John Bourne quote that RBCT achieved an 80% removal of badgers, and he maintained this view even when challenged. Perhaps he meant that the reduction was achieved only by the end of the five years, not in year one.

After the meeting, Prof. Bourne said that the best way forward would be to take badgers off the protected species list, although he did add that this would then allow farmers to remove as many as they wished, and it would demonstrate that it had no effect on bTB!

Mark Jones quotes the 50% reduction in bTB levels in Wales since 2010 as evidence that improved cattle controls, improved biosecurity measures and badger vaccination will decrease bTB. It should be noted that in 2009 Wales had the highest incidence of cattle TB in the developed world, so starting from any high point one would expect to see a decrease, and DEFRA statistics show that there has been an increase in reactors slaughtered between 2013 and 2014.

John Blackwell gave details of the BVA’s current position, namely supporting the continuation of the cull, but with the evidence currently available, withdrawing its support for free shooting.

As expected, most people, including John Bourne, tried to rubbish the Roger Blowey Gloucestershire cull data showing no increase in bTB on the basis that it was over too short a time period and “not a scientific study”.

The current differences county by county were alleged by the Badger Trust to be the consequence of improved biosecurity and of increased use of gamma interferon in the cull counties (Gloucestershire, Somerset, etc.), but no evidence was produced to confirm that the cull counties had any better cattle control measures than the rest of the south-west where, in most counties, bTB increased between 2013 and 2014.

The meeting ended with a presentation from Martin Hancox on how gamma interferon and the skin test fails to detect large numbers of heavily infected and excreting bTB cattle, and that if the Enferplex test was more widely used these “hidden reservoirs of infection” would be identified and removed.

He said that Enferplex is widely used in Ireland, which is why bTB is falling there. Mr Blowey said there was a lack of evidence that Enferflex is routinely used in Ireland, but there has been a badger cull programme in operation there for many years, and incidence of bTB has been falling year on year; whereas in Northern Ireland bTB has been rapidly rising.

Roger started his talk with the following statement: “I don’t understand why our views are so divergent – we need to tackle the problem together, not fight each other.”

He then posed the questions: “Does the Badger Trust accept that badgers have bTB? If ‘yes’, what is the answer to its control in badgers?” and followed up with: “Does the Badger Trust agree that badger numbers are increasing? If ‘yes’, should there be an upper limit to numbers?”

Unfortunately he did not get an answer to any of these questions. Vets attending said that they felt the meeting had been well worthwhile, however. Said one: “At least we now understand why the Badger Trust has adopted such a firm stance against any form of badger culling. If they are continuing to be told by Prof. Bourne that badger culling has no meaningful part to play in the control of bTB, and that cattle measures alone will control the disease, why should they consider any other view?”

The recent election results might suggest that the general public are less swayed by the argument; even the Labour Party anti-cull policy seems to be wavering. When interviewed on the BBC Radio Four PM programme, Dame Margaret Beckett agreed that a combination of both cattle measures and badger culling was a sensible way forward, so perhaps there is hope yet.

Editor’s note

Roger Blowey presented AVWM data from five trials that achieved 80-100% badger clearance with a 60-100% reduction in herd outbreaks and the RBCT with 30-70% culling success and a 19-23% reduction within the culling area and a 22-29% increase outside (Table 1).

The data from the Gloucester cull area showed a reduction from 29 reactors and 26 IRs to five reactors and two IRs. In Somerset, 34 herds were restricted before the cull and three afterwards. There were five new herd breakdowns associated with bringing in cattle from outside the cull area.

All the badger control studies have been very effective. It was only the RBCT, where cull levels were poor, that did not demonstrate a good effect.

The cost of the pilot culls in Somerset and Gloucester totalled £6.3 million including £3.5 million of policing costs. It is believed that the cost to the farmers was a fraction of the whole (<5%).

Overview: It seems that the time has come to accept that the RBCT has no meaningful guidance to the control of bTB in 2015 and onwards. The planning for the trial was some 20 years ago, the trial ended a decade ago and much has changed in the countryside since then, not least the huge rearrangements of badgers and cattle due to the FMD slaughtering and the mild winters allowing diseased wildlife to survive and multiply. Figures for West Gloucestershire suggest a 16- fold increase in badger numbers since RBCT was carried out.

The modern approach would be to work with farmers immediately after a herd breakdown, to test and cull the cattle to the best technical ability, to identify the wildlife interacting with the herd and to cull the diseased badgers within one week of removing the cattle. Fortunately, the healthy badgers indicate where to look for the diseased badgers. Published research (Weber et al, 2013) shows that, when foraging in the summer, diseased badgers stay away from the main sett. Targeting the unhealthy badgers is more acceptable than random culling of any badger and this approach is practical, improves badger welfare, changes restricted cattle herds to unrestricted and is low cost