BSE in calves: another nasty surprise

Cows can pass on bovine spongiform encephalopathy (BSE) to their calves, the Government admitted yesterday, after yielding to requests from scientific advisers to reveal preliminary results from a seven-year study.

The announcement was a "disappointing setback" to hopes of an early end to the European ban on British beef, said the European Union Agriculture Commissioner, Franz Fischler, in a letter to Douglas Hogg, the Agriculture minister. He said that the UK's plans to eradicate BSE may have to be re-examined, which could substantially delay the resumption of beef exports from the UK.

Scientists said, however, that they did not know how the disease is transmitted from the mother to the calf - raising the possibility that there may be an additional risk to humans from tissues currently considered harmless. "It's a problem to explain it," said one member of SEAC, the independent advisory committee on BSE and its human equivalent, Creutzfeldt-Jakob disease.

SEAC suggested that the news that cow-to-calf, or "vertical", transmission has occurred could mean that the culling strategy can be more carefully targeted. "Rather than saying that this is 'shock-horror' news, I think that there's something good to it," said Professor John Pattison, head of SEAC. "It means that the feed ban [to prevent BSE-infected material reaching humans or farm animals] has been more effective than we thought, as some of the current BSE cases must have come from their mothers."

The results came from preliminary examination of a seven-year study of two groups of cattle each containing more than 300 animals. The study was carried out at the Central Veterinary Laboratory, and had not been due to finish until autumn. But SEAC pushed for an interim examination of the animals which had died so far.

This showed that there was up to a 10 per cent chance that a cow with BSE could pass the disease on to her calf. However, the chance of passing it on was much lower for cows which were infected with BSE but were in an earlier stage of the disease. The research showed an average risk of 1 per cent.

The results have thrown up the question of how the disease is passed on in the womb, since there is no contact with the most infective tissues, such as the central nervous system. Milk has been ruled out as a medium, as dairy calves develop the disease without ever suckling their mothers' milk. Kevin Taylor, the Ministry of Agriculture's assistant chief veterinary officer, said there were 28,402 known cases of BSE in animals born after the feed ban. Of these, 1,203 were the offspring of diseased animals. He said: "That rate is 4.2 per cent, but that's misleading because many of them will also have been exposed to the risk of [infected] feed."

Mr Hogg said: "We shall need to take stock of the practical implications, in particular for the proposed selective cull of cattle, and what basis of selection stands to produce the most effective acceleration in the decline of BSE." However, Professor Pattison said that the figures suggest that BSE will die out in the cattle population. "If the infection rate drops below 1 [per cent], then the epidemic dies out," he said.

Britain's chief veterinary officer, Keith Meldrum, said after talks with counterparts from other EU states that the Government would be "re-evaluating" the BSE eradication plan but declined to speculate how. He dismissed suggestions that the plan was "off the rails" and said there was no new risk.

Mr Meldrum underwent intense questioning from the EU committee on the basis for the claim that the risk of infection in herds via maternal transmission is only about 1 per cent - an interpretation that one SEAC member described as a "Maff gloss" on the wide variation in transmission rates between cows of different ages. European vets agreed to refer the findings to a panel of independent scientific advisers.