vCJD carriers: Estimated numbers double
Researchers estimate 1 in 2,000 people in the UK carry the human form of mad cow disease
16th October 2013 -- Twice as many people in the UK as previously estimated could be carrying variant CJD - the human form of 'mad cow disease' (bovine spongiform encephalopathy or BSE). The figure of 1 in 2,000 comes from studying more than 32,000 samples of human tissue removed during appendix operations.
Variant Creutzfeldt-Jakob disease (vCJD) is a fatal, degenerative, brain disease. It emerged in the 1980s and early 1990s after people ate beef products contaminated with central nervous system tissue, such as brain and spinal cord, from cattle infected with mad cow disease. There are now strict controls in place to prevent BSE entering the human food chain.
There have been 177 clinical cases of vCJD in the UK, as of June 2013, but uncertainty remains about how many people will eventually develop the disease. The concern is that individuals may be susceptible to developing the condition over longer incubation periods, or they may not show any clinical signs of disease.
In an attempt to clarify the issue a team of UK researchers decided to conduct a survey to better understand how many people in the UK may be carriers of vCJD and to identify their genetic make-up (genotype).
They examined 32,441 anonymous appendix samples from people of all ages who had their appendix removed between 2000 and 2012 at over 41 hospitals across the UK.
Sixteen samples were positive for the infectious agent that causes vCJD and from this figure researchers estimate that 1 in 2,000 people are likely to be carriers. They also found the risk was similar for both sexes, whatever their age and was about the same across the country.
Their findings have been published in the BMJ.
An accompanying editorial says that although the disease remains rare, “infection” may be relatively common and doctors need to understand the public health measures that are in place to protect patients.
It's still not clear what risk carriers pose of transmitting the disease through blood transfusion or surgery but UK health agencies have already taken steps to secure the blood supply and reduce any risk of transmission by surgical instruments.
The only way currently to confirm a diagnosis of vCJD is with a brain biopsy or, when the patient is dead, during a post-mortem. A prototype blood test for vCJD has been developed by the prion unit at the Medical Research Council.