CSC Study Day people in their 20s and 30s).
l In 1996, UK beef was banned, and surveillance expanded, following the identification that ‘mad cow disease’ or BSE had entered the human food chain and was linked to the transmission of vCJD in humans.
l Cadaveric hGH and dura mater grafts caused two epidemics. The Dura Mater cases were mainly in Japan – other nations ceased using such grafts in 1987, but Japan continued until 1997. The hGH cases were mainly in the UK and France, although cases continue to be identified and the longest incubation is 44 years.
l vCJD deaths peaked globally in the early 2000s. However, in 2004 and 2006, there were three cases of vCJD linked to transfusion and one case with preclinical disease.
l In 2010, splenic PrP was identified in haemophiliacs who had received plasma.
l Studies in 2015 indicated the possibility of amyloid transmission.
l In 2016, a chronic wasting disease was discovered in deer herds.
l In 2019, two lab workers died of vCJD.
“We see the emergence of evidence of iatrogenic transmission arising from medical procedures, along with the realisation that there is resistance to degradation through decontamination measures,” he commented. This helped to solidify the theory that transmission was due to a protein rather than a virus. He pointed out that there is no ability to test donors for pre-clinical status for vCJD. No other forms of CJD have been transmitted via blood or organs, and screening questionnaires explore the risk status (family, Hx, exposures). Global restrictions around UK donors are now relaxing
and the UK plasma ban has been lifted. However, in recent years, studies have tested appendix samples to establish if there is sub- clinical carriage of vCJD prion material, in people who are not symptomatic. “Alarmingly, these tests have suggested that there may be individuals who are carrying this material in their appendix tissue – the estimates are around 1 in 2000-4200 people. We don’t know what that means yet – is this just trace detection and they are not infective, or are these people incubating it? If so, do these people pose a risk via blood, surgery or organ transplantation? “Nobody really knows what to make of this,
except that exposure was perhaps widespread in our diet – especially in the UK. However, whether these people will go on to manifest this disease remains to be seen,” commented Neil Watson. In the last few years, there has been a case
of vCJD where the individual was found to be “a longer incubator” and atypical in terms of genotype. This also raises the question of whether there may be individuals with a longer incubation than the ‘first wave’. If so, could a ‘second wave’ be yet to come? He added that there are implications
to consider around surgical and medical procedures (before and after exposures); blood; laboratories; and waste; but CJD is not spread through skin, urine and saliva, and CJD patients do not need to be isolated. Some studies do implicate increased risk in healthcare workers, although the epidemiology is complicated (e.g. reporting biases). In non-variant forms, PrPsc
is not peripherally distributed. Tissues
are categorised by high risk level (brain, spinal cord, and posterior eye = high risk; olfactory epithelium = medium risk; all others = low risk.)
vCJD differs and is found in lymphoreticular tissues (tonsils, appendix, spleen and nodes), so there is separate guidance relating to this. Guidance may refer to patients who have symptomatic disease or have been ‘exposed’ (and are ‘at risk’), via donated blood from a person known to have had the disease, for example. Patients identified as being ‘at risk’ may be treated at the end of a surgical list and they may require single-use, disposable instruments, although this is not always possible. He highlighted the importance of track and trace to ensure patient safety. If the tissues are low risk, there are no special
measures. For medium/high risk, single use/ destroy/quarantine for reuse on the same patient are options. NICE suggests this is not cost-effective, however, and recommends decontamination – the options include NaOH + autoclave.
In summary, prion diseases are transmissible
but not contagious, so a rational stratification of tissue/procedure risk should be used. There are cost-effectiveness and sustainability issues to be considered around single-use instruments. However, there are emerging questions around amyloid (and others) which require caution. There is uncertainty around whether these are truly transmissible and what the implications would be.
Prions and the cleaning of instruments Given the potential risks around prions, removal of proteins on medical devices is an important area of focus – particularly in relation to difficult to clean instruments. The next presentation sought to promote discussion and review of current practices within decontamination departments. Jim Tinsdeall, AE(D), reviewed the difference between guidance, law and standards – highlighting the challenges around varying interpretations. 1) ‘The Law’ includes: the Health Act 2008, MDD, MDR, consumer protection act, HSWA 1974, COSHH etc.
2) ‘Guidance’ includes: l ACDP TSE guidance 2015: Minimise transmission risk of CJD and vCJD in healthcare settings.
l Health & Social Care Act 2008: code of practice on the prevention and control of infections (13 December 2022)
l NICE IPG666 (2020): Reducing risk of transmission of CJD from surgical instruments used for interventional procedures on high-risk tissues.
l HTM 01-01 – decontamination of surgical instruments.
3) ‘Standards’ include: BS EN ISO 13484. April 2024 I
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