New Mad Cow Alarm

GDO Report

Researchers are perplexed by a new discovery about the transmission of variant CJD - the human form of mad cow disease - which challenges previous assumptions about the risk of illness.

Until now the only humans to succumb to the illness have had a particular genetic combination, known as homozygous methionine.

But researchers at Edinburgh University have now identified two patients carrying the disease who have a different genetic arrangement, known as homozygous valine or VV.

The two people had not developed vCJD although signs of the disease were discovered in tissue samples.

Researcher Professor James Ironside said one possibility was that the disease was taking longer to incubate in people with VV - suggesting many more people could be at risk from vCJD. Another possibility is that they simply act as carriers, rather than succumbing to illness.

So far just 161 people in Britain are thought to have contracted vCJD despite fears that widespread distribution of contaminated meat might cause a major epidemic.

Writing in the British Medical Journal, Professor Ironside states: "The fear is that individuals with this genotype may be at risk of developing the condition, possibly with longer incubation periods."

A second piece in the same journal calls for caution in drawing conclusions from the new findings.

Kumanan Wilson, of Toronto General Hospital, Canada, writes: "Studies such as this are essential to the continuing effort to control the extent of the epidemic and highlight the urgent need for ongoing surveillance for vCJD. They also pose challenges to health officials who have to formulate policies comprising difficult trade-offs based on uncertain evidence."