23 July 2001
Scrapie named as BSE cause
By Alistair Driver
SCRAPIE in sheep has been identified as the probable cause of BSE in a new review, despite being ruled out as the origin of the disease in the BSE inquiry.
An independent review says changes in the rendering process and feeding meat and bonemeal to young calves made UK cattle susceptible to BSE in the 1970s and 1980s.
These changes increased the likelihood that scrapie, a similar disease to BSE, became the agent that introduced it to cattle.
The government commissioned the review into the origin of the outbreak after Lord Phillips BSE inquiry, published last year, failed to identify a cause.
Lord Phillips had concluded that BSE cases identified in the mid-1980s “were not the result of the transmission of scrapie”.
The BSE inquiry also ruled out changes in rendering methods as a factor.
But this is disputed in the latest review of evidence by scientists, led by professor Gabriel Horn, of Cambridge University.
“In the light of recent estimates of the incidence of scrapie in sheep in the UK, it is no longer possible to exclude an unmodified scrapie agent as the agent responsible for BSE,” they say.
This dramatic development coincided with the announcement of a National Scrapie Plan by the government.
Pedigree sheep breeders are being asked to participate in a programme to eradicate scrapie from the national flock.
Prof Horns review tackles the question of why BSE began in Britain in the 1970s and 1980s when sheep are present across the world.
Meat and bonemeal, identified as the vector that spread BSE in cattle, was also used globally at the time.
The review says the UK had the largest sheep population in the EU between 1970 and 1985.
There are between 5000 and 10,000 cases of scrapie in the UK each year, and sheep material in MBM fed to cattle may have contained a BSE agent.
Changes in the rendering process in the 1970s and early 1980s increased the likelihood of infection.
As a result “a 10-fold increase in the amount of infective agent surviving rendering could have contributed significantly to the epidemic”, the review says.
The chance of infection was further increased, the report suggests, by the introduction in 1970 of MBM into feed rations for calves from their first or second week.
There is evidence to suggest most BSE victims were infected as calves.
“The practice was particularly prevalent in Britain, less so in continental Europe and the USA,” the report says.
Secretary of State for Environment, Food and Rural Affairs Margaret Beckett said: “This conclusion will doubtless generate much further scientific debate.
“I shall be interested to hear SEACs views on the findings when they consider the report in September.”
- Scientists link BSE to infected sheep, FWi, 27 April, 2001
- BSE epidemic had little effect on scrapie figures, FWi, 23 March, 2001
- Scrapie link with BSE played down, FWi, 10 June, 1998
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