Scientists In Vital BSE Experiment
Tested Wrong Animal Brains
By Steve Connor
Science Editor
The Independent

An inquiry has been launched into how a crucial experiment into whether BSE has infected sheep fell apart in disarray after an astonishing mix up in which scientists discovered that they have been testing the wrong animal brains.

The discovery, leaked on Wednesday night by embarrassed government officials, calls into question the quality of some of the science on which Britain's anti-BSE strategy is based. Scientists at the government-funded Institute for Animal Health in Edinburgh discovered that instead of testing sheep brains for BSE they had inadvertently been testing cattle brains for the past five years, making the entire £217,000 study null and void.

The results of the experiment were about to be made public and it is understood that civil servants were bracing themselves for an announcement that BSE had been found in sheep.

But three days before the results were due to be made public today demonstrating that the cattle disease had jumped the "species barrier" into sheep DNA tests on the material showed that it was composed entirely of cattle brains with no detectable sheep tissue.

"Extraordinary is a fair description of this," said Professor Peter Smith, chairman of the Government's Spongiform Encepthalopathy Advisory Committee. "Everyone who's seen these results has been taken aback. It is amazing."

Professor Chris Bostock, a member of Seac and the director of the Institute for Animal Health, said he was also surprised when he was told on Wednesday that another government laboratory had failed to find any DNA material that could have come from sheep brains in the samples undergoing the tests for BSE.

"I was completely flabbergasted when told yesterday morning of what they had found. I've taken steps to set up our own independent audit into the tissue samples and I'm told that Defra [Department for Environment, Food and Rural Affairs] will establish its own audit," Professor Bostock said.

"We were certainly of the view that the samples were fundamentally of sheep origin. I'm not prepared to discuss the results of the [BSE in sheep] experiment because they are now uninterpretable," he said.

However, Professor Smith said that although the experiment was not simple to interpret, some of the features of the results that he is aware of indicated that a "BSE-like" agent was present in the brain tissue. "But that now goes out of the window," Professor Smith said.

The experiment began in early 1997 and involved testing for the presence of BSE in what was then believed to be a pooled collection of 2,860 brains of sheep that had died of scrapie, a related brain disease to BSE, between 1990 and 1992.

If BSE had spread to sheep during the late 1980s, when sheep were fed the same contaminated feed that infected cattle, there was a strong possibility that the pooled collection of brains would indicate the presence of BSE.

The complicated experiment was carried out by scientists at the Institute for Animal Health's Neuropathogenesis Unit in Edinburgh. It involved injecting the brain material into different strains of laboratory mice which would incubate the disease in a precise pattern if BSE was present.

Professor Bostock said that two tests early on in the experiment indicated that the material was at least predominantly sheep brains as there had always been a concern of cross contamination given that the brains were collected for another experiment at a time when scientists used the same instruments to collect both sheep and cattle brains.

However, early in September samples of the brain material were sent to the Laboratory of the Government Chemist for DNA analysis. It is these results that demonstrated unequivocally that the brain tissue came only from cattle, with no traces of sheep tissue present. intable=1


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