CJD is an exceptionally rare disorder of the brain which causes rapidly progressive dementia and eventually death. Research has shown that CJD is caused by a unique prion protein which exists in a non-infectious form in all humans. The mechanism whereby this non-infectious prion protein becomes infectious and causes CJD has been under intense study for many years. Four types of CJD have been identified to date, including sporadic or classical CJD, the cause of which is uncertain, and new variant CJD. New variant CJD has only been identified in the past three years and is associated with a variety of symptoms and signs different from those found in sporadic CJD. There have been no cases of the new variant CJD identified in the country to date.
Scientific evidence from the UK has been reported which indicates that the prion protein in the new variant CJD cases shares similarities with the prion protein that causes BSE in bovines, thereby providing convincing evidence that these new variant cases of CJD, which occurred in the UK, were linked to BSE and almost certainly occurred because of the ingestion of BSE contaminated tissue.
Earlier this year the World Health Organisation held an international meeting which considered the risk of transmission of CJD by blood and blood products. The meeting concluded that "there is no proven or even probable instance of transmission of CJD by blood, blood components and blood products". It was, however, acknowledged that clinical and neuropathological observations suggest that new variant CJD may behave differently from classical CJD and that further studies were warranted in this area. In that regard, new evidence suggests that the agent which causes new variant CJD may be present in the lymph glands of patients with the disease. In particular, the agent has been demonstrated in the tonsils of patients with new variant CJD.
No data is available in relation to the transmissibility of new variant CJD by blood transfusion and early clarification of the potential for such transmission appears unlikely. Notwithstanding the lack of concrete evidence in this regard, precautions are currently in place at the Blood Transfusion Service Board against possible spread of any infectious agent by blood transfusion. These precautions, which are in line with international practice, include the exclusion from donation of the following groups: persons with a family history of CJD — this is because on rare occasions the occurrence of CJD may be more common in persons with relatives who have been affected by the disease; donors who have had treatment with material known to have spread classical CJD in the past — dura mater grafts and extracts of human pituitary, for example, human growth hormones.
There is no test available internationally for screening blood donations for CJD at present. It is anticipated that a test will become available within two to four years. My Department, through its CJD advisory committee, is maintaining close links with researchers in this area and a consultant haematologist at the BTSB is a member of this committee. I am committed to introducing effective measures as they are developed to maintain the safety of the blood supply and minimise the risk of transmission of any infectious agent.
The Deputy referred to a process of filtering blood donations in order to eliminate the risk of new variant CJD being transmitted through blood transfusions. There has been recent confirmation that the agent which causes new variant CJD is the same as that which causes BSE. This agent has been detected in lymphoid tissue indicating the possibility that it may circulate in white blood cells. White cells can be removed from blood donations using special filters. This process is called leucocyte depletion. However, I am advised that there is currently no direct evidence that leucocyte depletion will improve the safety of individual blood components.
Arising from recent recommendations from a UK Government advisory committee, the National Blood Authority is to start work towards the possible extension of leucodepletion of blood so that they are prepared in the event that the risk assessment indicates that this would be a sensible precautionary measure. The practicability and feasibility of this process are currently being assessed by the BTSB to allow for immediate implementation should it emerge that this would be a useful precautionary step. The BTSB is also examining the practical requirements of extending leucocyte depletion for all donations. Currently certain categories of patients already receive leucocyte depleted blood products to prevent immune reactions. In addition, a large proportion of platelets used in Irish hospitals are filtered.
In any examination of the transmission of blood-borne infections, special consideration must be given to frequent users of blood products, particularly pooled products. It is important to note that there has never been a reported case of CJD in haemophiliacs, despite many years of treatment with plasma-derived products. Notwithstanding this, I have decided that plasma-derived Factor 8, which is currently used to treat haemophiliac patients, should be replaced as soon as practical with a synthetic product, recombinant factor 8. The BTSB is at present finalising product supply arrangements with a major pharmaceutical company and supplies of recombinant product will be available from next January. Recombinant factor 9 is not currently available, but my Department will be instructing the BTSB to replace plasma-derived factor 9 as soon as this is feasible. The full year cost of these measures will be in the region of £3 million.
The BTSB, as part of its overall development plan, has drawn up a report on consultant manpower requirements. While the overall proposals are being progressed in ongoing discussions with Comhairle na nOspidéal and the special committee of Comhairle na nOspidéal on haematology services, a post of consultant virologist is being examined separately as a matter of priority. Funding will be available to allow the post to be filled as soon as it is approved by Comhairle na nOspidéal. In addition, a post of consultant in infectious diseases is currently under review in the context of the consultant manpower plan. It is important to note, however, that existing consultant staff in the BTSB have extensive experience in infectious diseases linked to transfusion of blood and blood products. In addition, a formal link exists with the microbiology department in St. James's Hospital.
It is important to stress that the risks from CJD or new variant CJD are purely theoretical at this stage and any potential risk of contracting new variant CJD through blood transfusions is far outweighed by the real risks of compromising health through not accepting a transfusion.
