Commons Select Committees | 24 July 2014
More action is needed to ensure that variant Creutzfeldt-Jakob disease (vCJD), the human form of bovine spongiform encephalopathy (BSE), is not inadvertently transmitted from person-to-person through medical procedures, the Science and Technology Committee has today warned.
- Report: After the storm? UK blood safety and the risk of variant Creutzfeldt-Jakob Disease
- Report: After the storm? UK blood safety and the risk of variant Creutzfeldt-Jakob Disease (PDF)
- Inquiry: Blood, tissue and organ screening
- Science and Technology Committee
Andrew Miller MP, Chair of the Science and Technology Committee, said:
“Variant CJD is a terrible disease and thankfully cases are now rare. However, research suggests that around one in 2,000 of us could be unknowingly carrying the infectious prions responsible for the condition. This raises the worrying prospect that these prions could be transmitted to others via blood transfusions and other medical procedures.
There remains significant uncertainty about the magnitude of this risk and the Government therefore claims to be taking a precautionary approach. But our inquiry has shown that its attitude towards vCJD today is far less precautionary than it was in the past. Indeed, recent policy seems to have been driven less by precaution than by economic prudence and a hope that the storm has now passed. This optimism is not supported by the available evidence.”
Transmission via surgery
Contaminated surgical instruments are a potential source of ‘prion transmission’—the mechanism by which both CJD and vCJD are spread. However, evidence to the inquiry suggests that Government guidance on preventing prion transmission may not have been fully implemented across the NHS. According to figures published by Public Health England, 43 incidents occurred between January 2010 and March 2013 in which surgical patients may have been exposed to CJD as a result of infection control guidance not being properly followed. In many cases this was because the infected patient was not diagnosed with CJD at the time they underwent surgery and enhanced infection control was therefore not deemed necessary. However, in the light of the long period during which people may be ‘silently’ infected with CJD, the Committee recommends that the Government take a more precautionary approach to mitigating this risk.
The Committee says that Ministers must work with the National Institute of Health and Care Excellence (NICE) and the Advisory Committee on Dangerous Pathogens to assess the extent to which precautions are being taken in hospitals and come up with a plan to improve implementation if preliminary findings prove that compliance is unsatisfactory. The Committee also recommends greater support for technologies potentially capable of more effectively decontaminating surgical instruments.
Andrew Miller MP:
“Prions bind strongly to metal surfaces and the Government acknowledges that standard decontamination treatments are ineffective in removing prions from surgical instruments.
It is known that CJD can be transmitted through the use of contaminated surgical instruments but the Government’s response to this threat has been insufficient. It has failed to support development of a technology capable of eliminating this risk and instead chooses to rely on guidance which it knows is only partially effective. And evidence suggests that this guidance is not even followed in some parts of the NHS.”
Transmission via blood transfusion
Evidence presented to the inquiry suggests that we cannot be confident that prions are not present in the blood supply. To date, there have only been four confirmed cases in which vCJD is known to have been transmitted via blood transfusion. All of the implicated transfusions are thought to have occurred in the 1990s; however, concerns were raised during the inquiry that asymptomatic prion transmission could still be widespread and could potentially lead to further cases of transfusion-transmitted vCJD in the future.
Andrew Miller MP:
“We know that vCJD can be transmitted via blood transfusion because it has happened in the past. And we have reason to believe that prions may still be present in the blood supply, so there is a chance that it could happen again. However, in the absence of a reliable vCJD blood screening test, we are unable to discard those donations that might be dangerous.
In our view, the Government could be doing more to help mitigate this risk of infection. Key steps would be for it to reduce uncertainty by supporting relevant research, for example by using the prototype blood test developed by the MRC prion unit in a large-scale study to better understand the rate of ‘silent infection’ across the UK donor pool. The Minister stressed that a lot of public money had already gone into the development of this test and she appeared reluctant to commit more. But the money already invested is a sunk cost and to cut off support now, when the task appears to be nearing completion, would be a false economy.”
In the vast majority of cases the benefits of receiving a transfusion will far outweigh the risk of acquiring a transfusion-transmitted infection. However, the Committee is warning against complacency and is urging UK Blood Services to remain vigilant to the threat posed by vCJD, as well as other blood-borne pathogens such as emerging viruses. In the past it has often taken multiple cases of infection before threats have been recognised and mitigated.
The report recommends that the Government commission a full assessment of the risks currently faced by the UK blood supply so that knowledge gaps can be filled and additional risk reduction measures and technologies developed as appropriate.
A prion is an infectious agent comprised of protein folded into an abnormal form. Prions are responsible for a family of fatal brain diseases known as transmissible spongiform encephalopathies (TSEs). Examples include livestock diseases such as bovine spongiform encephalopathy (BSE) and scrapie and, in humans, Creutzfeldt-Jakob Disease (CJD).
CJD is a debilitating neurodegenerative disease caused by a build-up of abnormal protein in the brain. Symptoms of CJD are similar to those of dementia and include loss of balance, coordination and mobility, loss of memory, slurred speech, personality change and progressive loss of brain function. CJD is invariably fatal and most people die within a year of first experiencing symptoms.
Prior to the mid-1990s, three types of “classical” CJD had been characterised:
- an inherited form that runs in families (typically 5–10 cases per year in the UK)
- an acquired form, transmitted through contact with human tissue contaminated with prions (2–3 per year)
- a sporadic form of unknown cause, historically responsible for the majority of cases (50–100 per year)
Following the BSE epidemic of the late 1980s and 1990s, the first cases of a new form of CJD were identified. Variant Creutzfeldt-Jakob Disease (vCJD) shared some symptoms with classical CJD but tended to affect younger people and led to a longer period of illness before death. Primary transmission was thought to be caused by exposure to BSE-infected material, such as contaminated meat. Since vCJD was first identified in 1995 it has been attributed to 177 UK deaths, the majority occurring between 1996 and 2003.
To read this feature on the Parliament’s website please click here.
Professor Sheila Bird, Programme Leader at the MRC Biostatistics Unit who gave written and oral evidence to the S&T Committee said:
“The Science and Technology Committee’s has stormed through some heavy weather to produce a highly readable report that makes 23 astute recommendations. Their trenchant recommendations, if accepted by the Government, will put UK’s surveillance of sub-clinical vCJD firmly back-on-track.
“Rightly, the Committee has called for major changes: first, well-informed face-to-face communication – not by letter – with those caught up in vCJD-risk networks; secondly, proper registration of those highly at-risk so that follow-up can be maintained; thirdly, proposals to be brought forward by DH/PHE on how to improve substantially consent-rates by those highly at vCJD-risk – both for postmortem testing and for participation in research-studies to delimit actual risks; fourthly, biostatistician membership of the CJD Resource Centre Oversight Committee so that fair-test designs are adopted.
“Most importantly, the Committee called on the Government to ensure that a large-scale vCJD blood prevalence using the MRC Prion Unit’s prototype vCJD blood test was initiated in the UK within 12 months and – an excellent idea – for those at high-vCJD risk to have the opportunity to contribute to the evaluation and subsequently access personal testing (should they so wish).
“Finally, the Committee has urged close surveillance of, and brain-bank attention to, the possibility that dementia cloaks cases of CJD or vCJD in older birth-cohorts. The 2013 appendix surveillance observed a higher sub-clinical carriage rate in the 1941-60 birth-cohort (6/ 8 181), as anticipated by Cooper and Bird’s analysis of dietary BSE consumption by gender and birth-cohort. Further surveillance is warranted to increase precision on the older-cohort estimate (currently: 270 to 1 600 per 1 million).
“After the Storm? is a stormingly good report.” (Source: Sheila Bird / Science Media Centre)
- House of Commons Science and Technology Committee. After the storm? UK blood safety and the risk of variant Creutzfeldt-Jakob Disease. Second Report
of Session 2014–15 (Report, together with formal minutes relating to the report)
- Transcripts: Oral evidence: Blood, tissue and organ screening, HC990 Wednesday 26 March 2014 (including oral evidence from Professor Sheila M Bird) All transcripts can be viewed on the Committee’s inquiry page at www.parliament.uk/science
- Published written evidence: Written evidence submitted by Professor Sheila M Bird (BTO0011)
- Supplementary written evidence submitted by Professor Sheila M Bird (BTO0051)