Organic Farmer Charles Mann challenges The Ecologist's anti badger cull stance.

Organic farmer Charles Mann, aroused by The Ecologist's anti-cull stance, makes an evidence-based case for culling badgers in areas of high TB incidence - together with other measures including enhanced testing in apparently 'low risk' areas that present a high risk of disease spread.

No one has ever said badger culling alone will solve the problem of bTB. But the scientific evidence shows that culling badgers in areas where the disease is endemic can help reduce bTB levels in cattle in those areas.

As a farmer who has had to deal with bovine TB on my farm on a number of occasions I'm sick of being told there is no scientific evidence to support culling badgers to control the disease in cattle - because it isn't true.

I'm an organic beef cattle farmer in one of the most beautiful parts of England - the Cotswolds.

Like many farmers I face an ongoing battle to keep my herd free of bTB.

And like many farmers I'm fighting this battle with one arm tied behind my back because action is only being taken to tackle one reservoir of the disease, despite the scientific evidence.

Steps are constantly being taken to deal with the disease in cattle - movement controls are being tightened on a regular basis:

• all cattle in areas where the disease is rife are tested at least annually (the same testing frequency as Wales);
• any cattle moved from areas deemed as high risk for bTB are tested before they are allowed to move;
• any cattle that test positive for the disease are immediately isolated and slaughtered to minimise the risk of further infection;
• and any herd that has a positive bTB test is then tested every 60 days until it has two clear tests before animals can be moved anywhere, except for slaughter.

But we also need to take action against the reservoir of disease in badgers - and the science shows that doing so can have a beneficial effect on bTB in cattle.

Scientific evidence? We have plenty

It is a proven fact that badgers carry bTB and spread it to cattle. Scientific research has estimated that badgers contribute to up to 50% of all cattle TB breakdowns in areas where the disease is endemic.

So, surely, if you're taking action to tackle the disease in one species (cattle) the only way to stop reinfection occurring is to deal with it in the other main reservoir of disease as well?

Is there any scientific evidence that culling badgers can help to reduce bTB in cattle? Yes, there is. And this evidence is based on research carried out on the results of the Randomised Badger Culling Trials (RBCT), a ten-year Government trial carried out in the late 1990s and early 2000s.

Both the Independent Scientific Group's (ISG) final report into the RBCT in 2007, and the then Government Chief Scientific Adviser Sir David King's review of that report carried out later in 2007, said that badger culling would have an overall beneficial effect on cattle TB in England.

Where they differed was in how significant the benefit would be and the economic and practical feasibility of carrying out culling on a scale necessary to gain these beneficial effects.

'An overall beneficial effect'

Since the ISG report was produced, further analysis of the long-term impact of the cull on bTB incidence has been carried out by Professor Christl Donnelly, a member of the ISG, which showed that a positive reduction in bTB cases within the cull area could still be seen years after culling had finished while the initial negative results around the cull area disappeared within 12 to 18 months.

Professor Sir Bob Watson, who was the government's chief scientific adviser, met with a group of leading experts on bTB in April 2011 to assess the potential benefits of culling in light of the further scientific evidence produced since the ISG report was written.

One of the meeting's conclusions was that: "The scientific base generated from the RBCT shows that proactive badger culling as conducted in the trial resulted in an overall beneficial effect compared with ‘survey only' (no cull) areas on reducing new confirmed cattle herd breakdowns, which is still evident five-and-a-half years after the final proactive cull."

It also concluded that culling over a 150 sq.km area would see an estimated reduction in bTB incidence of 16% in cattle herds in the cull area, and the area surrounding it, over a nine-year period.

Badger culling is an 'evidence-based' policy

Writing in Nature magazine in June 2013, Professor Mark Woolhouse, Professor of Infectious Disease Epidemiology at the University of Edinburgh, and Professor James Wood, Alborada Professor of Equine and Farm Animal Science at the University of Cambridge, argued:

"As epidemiologists, we agree with the Defra chief scientists that badger culling is an 'evidence-based' policy for controlling bovine TB in Britain.

"We disagree with other, less positive interpretations of that evidence. The evidence comes from a large-scale, long-term government project - the Randomised Badger Culling Trial. This roughly halved the incidence of TB in cattle herds in the culling area following four to seven annual badger culls."

The RBCT is the only badger cull that was conducted as a scientific experiment, and therefore it is only the conclusions of this trial that can be scientifically accepted.

But it is worth pointing out that, while the design of the RBCT was exemplary, its implementation was not: to take just one example, all culling was suspended for a year in 2001 because of the foot and mouth epidemic.

And it is also worth noting that other culls, although not conducted as controlled experiments, have shown more dramatic impacts on the disease in cattle.

For example: Thornbury, Gloucestershire, no bTB for 10 years; Steeple Leaze, Dorset, no bTB for seven years; Hartland Point, Devon, 80 to 90% reduction over 10 years; East Offaly, Ireland, 88% reduction for seven years.

The real question: is it worth it?

So, to say there is no scientific evidence to show that culling badgers will have a beneficial effect on reducing bTB in cattle in endemic areas is wrong. There clearly is. The real argument is a subjective one about whether the reduction that can be achieved is enough to justify the method of achieving it. And I believe it is.

No one has ever said that badger culling alone will wipe out bovine TB. Just like no one has ever said badger vaccination alone will wipe out bovine TB. In fact, there is no scientific research data to show what the effect of badger vaccination on the incidence of bTB in cattle would be.

To wipe out bovine TB we need a comprehensive strategy that tackles the disease on all fronts at the same time. Only by doing this will we have the best chance of wiping this disease out and making England TB free.

But maintaining a viable cattle industry has to be a key part of any strategy. Computer-based models that suggest solutions like whole herd culling if one animal tests positive for the disease without taking into account the social or economic impact of such steps offer idealised, but unrealistic, answers.

They do not offer practical solutions. Whole herd culling would condemn thousands of extra cattle to death unnecessarily and would devastate cattle farming in areas of the country that are best suited to it.

Risk-based testing

There are concerns over the sensitivity of the skin test used to test cattle for bTB, and it is important that research into improved diagnostic tools continues. It is effective at picking up the disease in herds and if the disease is found a herd is tested every 60 days until it is free of disease and every animal passes two consecutive tests.

Estimates of how effective the current test is at detecting the disease in individual animals should not be treated as facts. They are estimates and should be treated as such.

The skin test is an internationally recognised test for bTB which is used around the world, including in Wales where much has been made of the success of the country's approach to tackling bTB.

It is worth noting that the number of cattle slaughtered for bTB in Wales actually rose by 4.5% in 2014, compared to 2013, from 6,102 to 6,379. Cattle in the high risk bTB areas in England are tested at least annually (the same testing frequency as in Wales).

The need for annual testing across the whole of England has been looked at by the Bovine TB Eradication Advisory Group, an expert group created to advise Defra ministers, which found it would not be cost-effective, and the EU Commission, which approves the UK's strategy for tackling bTB before it provides funding, does not believe it is necessary.

A more cost-effective approach would be 'risk-based testing' - the annual testing for herds in low-risk areas that may pose a particular disease spread risk because of the amount of trading they do and the number of cattle movements they are involved in.

We must tackle the disease in all reservoirs

No one has ever said badger culling alone will solve the problem of bTB. Just like no one has ever said badger culling needs to be carried out across the whole country. But the scientific evidence shows that culling badgers in areas where the disease is endemic can help reduce bTB levels in cattle in those areas.

Cattle movement controls and cattle testing have an important role to play, badger vaccination could play a role in areas on the edge of the disease spread to stop it spreading further, and cattle vaccination has a role to play once a workable vaccine is available.

But one isn't and we can't wait for ten years until one becomes available. If you have a reservoir of bTB in wildlife in endemic areas and it isn't dealt with reinfection will continue to occur and the disease will continue to spread.

I believe using all options, and tackling the disease in all reservoirs, gives us the best chance of achieving a TB free England.