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WSWS : News & Analysis : Medicine & Health : BSE/CJD

"Mad cow disease" could have spread to Britain's sheep

By Barry Mason
16 September 1998

The September 3 issue of the scientific journal Nature claims that "mad cow disease" or Bovine Spongiform Encephalopathy (BSE), could have infected sheep in Britain. Scientists studying BSE consider this a real possibility. It is widely considered that the practice of using rendered down cattle remains to produce cattle feed led either to the outbreak of BSE or at least its epidemic spread in the national herd. Until the feed ban in July 1988, sheep had been fed with the same feed as cattle.

Sheep in Britain have been subject to an endemic form of a spongiform encephalopathy known as scrapie for about 200 years that could not be passed to humans. Consumption of BSE-infected beef, in contrast, has been shown to be responsible for the 27 deaths to date from new variant Creutzfeldt Jacobs Disease (nvCJD), also known as human BSE.

Because of the similarity of symptoms of scrapie and BSE, there is a danger that sheep carrying BSE might have been overlooked. The government is aware of this danger. It has established a sheep subcommittee of its Spongiform Encephalopathy Advisory Committee (SEAC). This is to be chaired by Professor Jeffrey Almond, professor of microbiology at Reading University. Since July 1996 there has been a ban on sheep brains going into the human food chain and from May 1997 the ban was widened to include the spinal cord, spleen and mechanically recovered sheep meat. This year the Ministry of Agriculture Fisheries and Food (MAFF) is also spending a fifth of its albeit minuscule BSE research budget of £12.7 million on sheep spongiform encephalopathies.

The Nature article points out that if BSE has entered the sheep population it is likely to show the same properties as scrapie of being passed from animal to animal. The official position of SEAC is that BSE cannot be transmitted from cow to cow, though experts such as professor Richard Lacey dispute this. SEAC do believe, however, that in sheep BSE would be transmissable like scrapie and become endemic in the national herd. The infectivity of sheep BSE would also be similar to scrapie, affecting a wider range of organs than is thought to be the case in cattle.

SEAC is concerned that insufficient measures have been taken to detect possible BSE in the sheep population. So far only 9 sheep out of an adult population of 20 million have been tested. It is claimed that the testing is difficult to carry out because it involves injecting material into different strains of mice and can take up to two years for the results to be become apparent. John Collinge, head of the Prion Disease Group at the Imperial College of Medicine in London, claims to have developed a faster and cheaper test, but the government has not provided the resources to carry out the technique on a wide scale.

Commercial interests are again being put before possible risk to human health. Resistance to using Collinge's technique is explained by Nature by quoting the European Commission's independent Scientific Steering Committee. They warn, "The consequences of identifying a first case of BSE in sheep would be catastrophic so we need to be really sure (about the reliability of the identification)."

The Nature article warns that the New Labour government is repeating the "mistakes" of the previous Conservative government which denied the danger posed by BSE in cattle. Jack Cunningham, until recently Labour's Agriculture minister, interpreted the absence of any sign of BSE in the nine sheep scrapie cases investigated so far to say there is no evidence of the possibility of sheep BSE. Professor Almond points out, "absence of evidence is often confused with evidence of absence."

An article in the Independent newspaper of September 8 explains that when the Blair government was made aware of the Nature article they set up a damage limitation operation. A restricted memorandum was sent to Whitehall departments. This outlined 16 questions and answers that could be used to fend off inquiries from the media. Shelia McKechnie, head of the Consumers' Association, has raised concern over feeding lamb to small children. One of the standard answers reads, "The age range of new variant CJD does not suggest that those who were probably exposed to BSE infection, were at any greater risk than those who were young adults ... infants and children were not likely to be more susceptible than adults."

Professor Almond warns of the dangers posed: "I think there is a distinct possibility that BSE is out there in the sheep population ... if we found BSE in sheep it would be a national emergency." He then accepts that "to minimise the risk [of being infected with BSE by eating sheep] you would have to condemn the entire carcass." But Almond goes on say that it would not be justifiable to kill the whole sheep flock, "We had to find a middle ground, which we call a risk reduction strategy as opposed to a risk minimisation strategy." The government chief medical officer, Sir Kenneth Calman, in similar vein said there are "no grounds at this stage for thinking the likelihood of BSE in sheep is any greater now than in the past."

See Also:
Significant breakthrough in diagnosis of human BSE
[3 September 1998]
An exchange of letters on the Mad Cow Disease (BSE) crisis
[23 July 1998]