Variant Creutzfeldt-Jakob disease: update

Two years ago we reported current thinking on the potential for gastrointestinal endoscopy to act as a vector for patient to patient transmission of variant Creutzfeldt-Jakob disease (vCJD).¹ In that article we stressed that the advice would be updated if new evidence became available. Gastroenterologists may be aware of a recently published article in the Lancet² that describes the tissue distribution of abnormal prion protein (PrP^sc) in monkeys that have been inoculated with brain homogenate from first passage animals with bovine spongiform encephalopathy (BSE) via the oral route, which is the route by which the vast majority of patients developing vCJD will have become infected. As the prion protein responsible for vCJD is found in all lymphoid tissue, our advice was to reduce “random” biopsies to an absolute minimum and ensure that re-useable biopsy forceps were meticulously cleaned and decontaminated according to the strict British Society of Gastroenterology (BSG) guidelines. We also advised on the use of disposable biopsy forceps, particularly in the ileum, as it was felt that biopsies from this area posed the greatest risk to both endoscope and forceps becoming contaminated. Other inexpensive accessories such as cleaning brushes and the rubber cap covering the biopsy port were also to be disposed of if a biopsy had been taken.

The paper from Herzog and colleagues² is the first to look specifically at the tissue distribution of PrP^sc after oral and intravenous inoculation in a primate model utilising Cynomolgus macaques. The findings confirm that the highest concentration of PrP^sc is in the tonsil but that it is also abundantly present in the terminal ileum and ileocaecal fold where gut associated lymphoid tissue is present in large amounts. The whole of the gastrointestinal tract was positive for PrP^sc from the duodenum to the rectum. Both gut associated lymphoid tissue and the autonomic nervous system were highly involved, including nerve fibres lying just below the mucosal boundary The authors suggested that the possible risk of transmitting vCJD via endoscopic procedures might be currently underestimated as the detection of PrP^sc is the best marker for infectivity in prion diseases.

This new information should help to inform gastroenterologists that the risk of transmitting vCJD via an endoscopic procedure remains a distinct possibility and the advice of two years ago remains as relevant today as it was then. All patients undergoing gastrointestinal endoscopy should be considered potential carriers of vCJD in the context that the majority of the UK population is likely to have had dietary exposure to the BSE agent during the 1980s. Perhaps the most important aspect of this new information is the increasing realisation that any biopsy from anywhere in the gastrointestinal tract is as “high risk” as a biopsy of the terminal ileum. It is not logical to reserve disposable biopsy forceps for this one area; it seems more appropriate for endoscopy units to move entirely into using disposable forceps for all procedures and phase out the use of re-useable equipment that might be difficult to trace or decontaminate.³ Biopsy should only be performed where this is likely to influence clinical management.

Although one recent case of vCJD has been associated with blood transfusion,⁴ no case of vCJD has so far been attributed to an endoscopic procedure. However, we would urge all staff involved in endoscope decontamination to remain vigilant and adhere strictly to guidelines already issued by the BSG³ in order to minimise this risk.