How does killing badgers save cows?

Another Life:It is more than 35 years since, as this paper's Environment Correspondent, I first sounded the alarm for the future of the badger in Ireland's cattle counties.

The discovery in the west of England of what was then a strong circumstantial link in the spread of cattle TB carried clear implications of "culls" to come, not to mention freelance persecution of the animal by beef and dairy farmers themselves.

The first Irish badger with bovine TB was found in 1974, an infection gained, perhaps, from rooting for beetles under cowpats. Today, encouraged by the results of intensive clearance trials in Cork, Donegal, Kilkenny and Monaghan, the medium-term culling strategy in the Republic is to eliminate, or virtually eliminate, badgers from 30 per cent of the countryside.

The apparent success of the "Four Areas Trial" in reducing TB outbreaks in cattle has been watched with close interest internationally: many other countries have problems with wildlife reservoirs of mycobacterial infections. In the UK, the Irish strategy increased pressure for similarly wide and pro-active culls. This month, after decades of heated controversy and inconclusive experiment, the final advice arrived for the British government: such culls wouldn't work, might make things worse, and certainly would not pay their way.

Analysing the Irish trials, the UK Independent Scientific Group (ISG) found them dealing with far lower densities of badgers, and clearing areas with good natural barriers - coasts and rivers - to prevent reinvasion. In England, they decided, too many sick badgers would spill out at the edges, and too many would find their way back in. The group was finally mindful of past ministerial advice that "the elimination of badgers from large tracts of the countryside [ is] politically unacceptable."

In the Republic, however, the efforts of Badgerwatch to spread outrage at "Ireland's bloody shame" have met with no greater attention than those of any other conscience-prodding lobby group. Its recent joint report with the UK Badger Trust spoke of 6,000 snares for badgers being laid across Ireland's farmland every night, and charged that badgers are being "systematically strangled countrywide."

Snares may indeed be set in areas meant to be kept free of badgers, as well as in the culling of new "blackspot" areas of high TB infection. They carry stops on the loop intended to prevent injuries, and veterinary checks on hundreds of bodies have shown negligible bruises or cuts. The badgers are "humanely euthanased", as the scientific documents have it - namely, expertly shot with a .22 bullet. In its own Randomised Badger Culling Trial, Britain preferred less efficient, "but perhaps more humane" trapping, but the final bullets were the same. As for numbers, if they mean anything, the badgers killed in the Four Areas Trial were 806 in Cork, 552 in Kilkenny, 208 in Donegal and 660 in Monaghan.

How do I feel about this? Not happy, at all. It takes an effort to accept exterminating Meles meles on such a scale and yet, a river or a mountain away, protecting the badger population as "a valued resource". The strategy, however, was described by the Department of Agriculture and Food's Dr James O'Keeffe, at an international veterinary conference in Dublin last autumn, as "a fair compromise, a triumph for common sense, and a tribute to the generosity of all involved".

Meanwhile, what of the holy grail in this problem: an oral vaccine for badgers to break the stubborn circle of TB infection? A 10-year programme to develop the BCG vaccine began in 2001 with a purpose-built centre near Dublin, called the BROC, for studies on captive badgers. That BCG can protect them satisfactorily is now proved. Long field trials in rural Cork also found the kind of durable bait that badgers love: a bar of mixed peanuts and chocolate.

Now begins a key test - a long field trial of three or four years to see how well the vaccine works in natural conditions. In an undisclosed stretch of countryside of some 700sq km, where perhaps one in three badgers already have TB, half the animals will be tagged, orally dosed with vaccine and revaccinated annually. They will all be live-trapped three times a year to check on their immune status.

At the end of the study, the site will be "depopulated", post-mortems carried out, and tissues cultured. By 2010, or thereabouts, we should be much nearer realising a solution first posited decades ago.

And what of the question that bedevilled the research from the start: how, exactly, do badgers pass TB back to cattle? As UCC's Dr Patrick Sleeman told last autumn's conference, the transmission "is not yet fully understood". But the best belief is that cattle nuzzle at dead or dying badgers appearing on their pastures - and then stick their tongues up their own noses.