One in 2,000 people in the UK carries abnormal proteins linked to variant Creutzfeldt-Jakob disease (vCJD) - the human form of mad cow disease, new research has shown.
Experts said their study has “important implications” for how blood and blood donations are managed and for the handling of surgical instruments.
The findings suggest a “high prevalence of infection with abnormal prion protein, indicating vCJD carrier status in the population”.
But the researchers noted that, despite the higher number of carriers, just 177 vCJD cases have been reported to date in the UK.
VCJD is a fatal, degenerative brain disorder which is the human form of Bovine Spongiform Encephalopathy (BSE).
The disease is believed to have passed from cattle to humans through consumption of meat products contaminated with BSE.
Large numbers of the UK population were exposed to BSE prions in the late 1980s and early 1990s.
The new study, published online in the British Medical Journal (BMJ), involved analysis of more than 32,000 appendix samples from people of all ages who had their appendix removed between 2000 and 2012 at over 41 hospitals in England.
Of these samples, 16 tested positive for abnormal prion protein, indicating that one in 2,000 of all people are likely to be carriers.
The researchers, including a team from Public Health England, found that prion protein in those born between 1941 and 1960 did not differ significantly from those born between 1961 and 1985.
Presence of the protein was also similar in both men and women.
The researchers expressed concern that some of the 16 samples produced information which might suggest people may be susceptible to developing the condition over a longer time than previously thought, or may not show any signs of disease at all.
But they said the number of patients diagnosed with vCJD is still well below the number suggested by the prevalence of abnormal proteins.
Professor Noel Gill, lead investigator at Public Health England, said: “Prevalence studies such as this are important as they enable us to interpret the impact of the BSE epidemic on the population of Britain and strengthen the basis for ongoing risk assessments.
“There are already extensive measures in place to prevent the potential spread of infection.
“Prion diseases can have very long incubation periods, and an understanding of prevalence can help researchers devise measures to prevent further transmission of the disease.
“It is not known whether all infected individuals will develop disease. The peak of the vCJD epidemic in the UK was in 2000, where 27 probable or definite cases were diagnosed that year. Only one case of vCJD has been diagnosed in 2013 in the UK.”
He said further research on samples from the 1970s and earlier - before BSE appeared - were now underway to see whether prion proteins also occurred then, which could reduce the significance of the new findings.
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