The claim

“If you look at what’s happened in the Republic of Ireland, the number of incidents has come down from 45,000 to 15,000.”
Owen Paterson, 7 March 2014

The background

Government ministers have long looked west to justify the policy of culling badgers in England.

The Republic of Ireland has also had a historical problem with TB in cows, and a big population of wild badgers.

We still don’t know for sure if badgers infect cattle (rather than the other way around) and how the disease is spread, but the Irish government is sufficiently convinced there’s a link after carrying out two key culling trials.

Ireland has actually been culling badgers since the 1980s, and the environment secretary, Owen Paterson, is keen to attribute recent falls in rates of bovine TB infection in the country to the decline of the wild badger.

But like much of the science in the great badger debate, the truth is far from black and white.

The analysis

The excellent website bovinetb.info has managed to source statistics from the Irish government going back to the 1960s.

The figures immediately show that Owen Paterson is correct to talk about a drop in incidents of TB in cattle – although the size of the drop depends on the time frame you choose.

In 2013, just 15,612 animals tested positive in Ireland, compared to 45,000 in 1998. But that year was a historic high point, and it has presumably been chosen arbitrarily to make the decline in TB look as big as possible.

Just one year before, in 1997, there were 28,647 cases. And the cattle population is lower now than it was in the late ’90s.

Working out how many cows were infected as a proportion of the whole Irish herd, we might say that the rate of infection has fallen from 0.37 per cent in 1997 to 0.25 per cent in 2013. A less impressive statistic.

Nevertheless, it remains the case that in very recent years the number of infected animals in Ireland has fallen to an all-time low.

A bigger problem is figuring out whether the culling of badgers has had anything to do with this decline.

One issue raised by anti-cull campaigners is that the culling of badgers in Ireland began in the mid-1980s, but there is little evidence of a consistent drop in bovine TB cases until the 2000s.

It is difficult to be sure if this is a valid point, as estimating the population of wild animals is not easy.

This Council of Europe study sets out the best information we have for the effect on badgers in Ireland, but population estimates are not available for the 1980s.

This makes it difficult to track the fall in the badger population alongside cases of TB in cattle and say whether there is evidence of cause and effect.

But it’s clear that while culling began as early as 1984, the numbers of badgers killed is fairly small compared to later years. Fewer than 1,000 badgers were culled in 1984 compared to more than 6,000 in 2002.

A stronger point for cull sceptics is the fact that badger control is just one of many measures introduced by the Irish government from the late 1980s to try to eradicate the disease.

It’s difficult to strip out the effect of the other measures to say exactly how much culling has achieved, and indeed the Irish government only claims that badger control “has contributed” to the drop in TB.

There’s another problem: Northern Ireland. The province has never culled badgers, but it has seen an overall decline in cases of TB over the last decade. The latest figures are here:

This graph from bovinetb.info neatly sets out what the environment secretary is trying to get across. The red line is England (no cull, TB up) and the green one is Ireland, (cull, TB down).

But Northern Ireland spoils the pattern (no cull, TB down) and makes it difficult to draw simple conclusions.

Having said that, we ought to make clear that TB rates are still substantially higher in Northern Ireland than in the Republic of Ireland: in 2013 6.4 per cent of cattle herds tested positive in Northern Ireland compared to 3.8 per cent south of the border.

What is also very clearly visible in the data for both England and Northern Ireland here is the spike in TB cases in 2001, widely attributed to the effects of the foot and mouth crisis in that year.

The British Veterinary Association says: “The outbreak of foot and mouth disease suspended bovine TB testing in 2001 and many culled herds were restocked without knowledge of the bovine TB status of the replacement animals.

“This is also thought to have contributed to the increased geographic spread and incidence of bovine TB in the last few years.”

This is a piece of history government ministers tend not to mention when they talk about the spread of the disease.

The verdict

It’s true that Ireland has culled badgers, and that it has experienced a decline in bovine TB since the late 90s.

Proving that the one caused the other is more difficult, and it may be that Owen Paterson goes too far when he says the Irish experience provides “clear evidence” that culling is the way forward for Britain.

That was the opinion of the BBC Trust when they partially upheld a complaint about an article on this subject on the BBC News website recently.

Having said all that, many people in Ireland including respected academics are convinced that culling does help curb the spread of the disease to some extent.

The view of the Irish government is actually more nuanced than you might think. It says culling “has contributed” to the TB success story, but it doesn’t make any attempt to quantify the contribution and admits “the difficulty in attributing trends to a single factor and the cyclical nature of the disease”.

It’s also interesting to note that the Irish government’s intention is to replace badger culling with badger vaccination when that becomes a practical option, and Irish scientists are leading the way on researching an oral vaccine.