Blood and organ donations could represent a major source of the deadly Creutzfeldt Jakob brain disease because infected donations from carriers cannot be detected, medical experts in Britain have warned.
The warnings have prompted the House of Commons's science and technology committee to open a parliamentary investigation into measures that will improve the quality of screening of blood and organ donors.
Hidden for decades
The CJD variant, which is caused by prions, can stay hidden in an infected person for decades, Prof James Ironside, professor of clinical neuropathology at the National CJD Research and Surveillance Unit, told MPs.
Illustrating this, Prof Ironside said scientists found that some people who died from variant CJD had their appendix removed earlier in their lives. Extraordinarily, they managed to track the removed appendices of two such people. Both were infected with the prion, tests showed.
Another expert, Dr Roland Salmon, told MPs the danger of variant CJD "becoming a self-sustaining epidemic" – because of the ever-increasing number of infected carriers – "has to remain a significant concern".
Variant CJD – originally found among cannibals in Papua New Guinea – is caused by the same prion strain that caused the BSE epidemic in cattle in the mid-1990s in Britain and Ireland.
In some cases in Papua New Guinea, it stayed incubated for 55 years.
Doctors "anticipate incubation periods in BSE transmission to humans extending, at the extremes, up to and probably beyond the normal human lifespan", said Prof John Collinge of University College, London.
The majority will be carriers of the variant CJD, but won't die from it.
“We do not understand why some people are carriers and some people just have a long incubation period. You cannot formally distinguish those things very easily, other than with the passage of time,” said Prof Collinge.
“Regardless of whether these individuals are in the incubation period and will develop the disease in five, 10, 50 years, or whether they will be healthy carriers for the rest of their lives and die of something else, they still pose a potential risk to others via iatrogenic transmission, particularly with blood transfusion. We cannot identify these individuals without a blood test,” he warned.
The chairman of the Commons committee, Andrew Miller said MPs "were extremely concerned to hear evidence that this incurable disease still poses a significant risk to public health".