- 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
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
"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
"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.