THE bovine TB test is a comparative skin test carried out by a vet on the neck of an animal.

The vet injects bovine and avian tuberculin in separate locations and examines the animal some days later, comparing the size of the two sites.

Where the difference in the two injected sites is too large the animal is deemed to be a "reactor" and is taken away and slaughtered. In years when the national herd has been tested, up to 40,000 reactors have been removed.

This does not always mean that the animal has bovine TB because the test is not totally accurate. Vets and scientists agree that until a proper blood test is developed, the true levels of bovine TB will be impossible to determine.

Farmers are paid compensation by the State when their herds are restricted or totally destroyed because of the disease. But the farmers have been contributing about £30 million per year towards the eradication of bovine TB and brucellosis.

In recent years, nearly 5,000 Irish farms have been "restricted", that is, banned from moving their animals because of outbreaks of bovine TB. This represents 0.5 per cent of the national herd.

No country has yet developed a vaccine to protect bovines from the disease, which causes the animal to lose weight, become listless and develop lesions.

Scientists know very little about the disease and cannot say definitely how it is spread. But they believe that it can be passed on from the animals breath, by contact with wildlife, stress or even from the manure of infected cattle.

Badgers and deer have been blamed for the spread of bovine TB and research has shown that where badgers are removed from an area by snaring or shooting, the level of reactors drops dramatically.

Vets are paid nearly £2 per bovine TB test and in a national round of testing over 10 million tests are carried out.

Mr Yates has promised more scientific research into the disease in his new scheme, quality control testing, a mobile test unit to operate free of charge in problem areas where the disease persists, and a TB forum where the parties involved in the scheme would be able to thrash out their differences.

The scheme has cost an estimated £1.5 billion, which a recent report adjudged good value for money from a trading and public health viewpoint.