I thank Senator Gallagher for raising this important issue. 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 classic CJD, the cause of which is uncertain, and new variant CJD. New variant CJD has only been identified in the last three years and is associated with a variety of symptoms and signs different to those found in sporadic CJD. There has been no case of 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 Organization 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 to classic CJD and that further studies were warranted in this area.
In that regard, new evidence has suggested 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 lymphoid tissue in the tonsils of patients with new variant CJD indicating the possibility that it may circulate in the white blood cells.
No data are 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 any possible spread of any infectious agent by blood transfusion. The 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 very 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 classic CJD in the past — dura mater grafts and extracts of human pituitary, e.g. human growth hormones.
There is no test available internationally for screening blood donations for CJD at present although it is anticipated that such a test will become available within the next few years. My Department, through its CJD advisory committee, is maintaining close links with researchers in this area and a consultant haematologist at the Blood Transfusion Service Board 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 any infectious agent. In this regard one measure which is currently being considered is leucocyte depletion, that is, the filtering of blood donations to remove the white blood cells. As I have already said, the agent which causes new variant CJD 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, a process 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 as it is not known whether, if new variant CJD does enter the blood system, it will be confined to white cells. Hence the caution being expressed about the benefit of this exercise as far as CJD is concerned.
Arising from recent recommendations from a UK Government advisory committee, the National Blood Authority is to start work towards a possible extension of leucocyte depletion of blood in order 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 to all donations. It should be noted that certain categories of patients already receive leucocyte depleted blood products to prevent immune reactions; these include transplant patients and leukaemia sufferers. A large proportion of platelets used in Irish hospitals are also filtered.
When considering the transmissibility 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. Nevertheless, the Minister for Health and Children has decided that plasma derived Factor VIII, which is currently used to treat haemophiliac patients, should be replaced as soon as practical with a synthetic product called recombinant Factor VIII. The BTSB is currently making arrangements for supply of this product and expect that it will be available next January. A similar synthetic product to replace Factor IX is not currently available but my Department will be instructing the BTSB to replace plasma derived Factor IX as soon as this is feasible. The full year cost of these measures will be in the region of £3 million.
It is important to stress that risks from CJD or new variant CJD are purely theoretical at this stage and any potential risk is far outweighed by the benefits of receiving therapeutic blood transfusions if they are medically indicated.
The Seanad adjourned at 9 p.m. until 10.30 a.m. on Thursday, 20 November 1997.
