NoBlood

Jan B. Wade · #1 (**permalink**) 07-04-2005, 08:19 AM

http://www.irishhealth.com/?level=4&id=7791

vCJD-fear of the unknown
By Niall Hunter-Editor

The latest Irish case vCJD is the third reported to date. What makes it different, and potentially more serious on this occasion, is that the person concerned had donated blood, and this blood had been transfused into two patients.

What also makes it worrying is that nobody really knows what the risks are of a patient getting vCJD from blood from someone who has the disease.

The latest vCJD case is the third to date in Ireland. It has not yet been officially confirmed but it is defined as a 'probable' case.

One of the two patients who received blood from this man has since died from an unrelated cause and the second patient has been informed that he received blood donated by a person with suspected vCJD.

Cases of vCJD in Ireland are extremely rate and the chances of infected blood being donated and then given to a patient, who might then contract the disease from the transfusion, are also regarded as extremely low.

However, this latest vCJD case, the third to date, underlines the fact that there is no foolproof method in place to completely rule out the risk of transmission of vCJD by blood transfusion.

While past history has now led to much greater vigilance about protecting the blood supply, any case such as this is bound to cause public unease.

What is almost completely unknown is what the risks are of contracting vCJD if you receive blood from someone who has the disease.

An Irish Blood Transfusion Service (IBTS) spokesperson told irishealth.com that it was extremely difficult to ascertain what the risk was, and it was 'unquantifiable'.

However,it is estimated that the risk to the person who received the transfusion in the latest case may be reduced by the fact that the blood donated had had its white blood cells removed, which lessens the chances of infectivity.

So far in the UK there have been two cases reported of vCJD infection caused by blood transfusion.

The IBTS has in recent times been putting in place precautionary measures to protect the blood supply from vCJD.

The Blood Bank has already imposed a ban on donors who have lived in the UK,which has a relatively high incidence of vCJD, for more than a year.

IBTS National Medical Director Dr William Murphy, in a recent interview with irishhealth.com, said this ban, while helping, doses not completely protect us against vCJD through transfusion.

He said residency in the UK contributes around 33% of the total chance of a donor in Ireland having variant CJD.

However, there is also a potential risk, albeit extremely small, from people who have eaten either UK or Irish infected meat ,he added.

The IBTS has recently been undertaking a three-pronged approach to protect the blood supply further from vCJD.

Firstly, the Blood Bank is ensuring that patients only get transfused if they really need to. A report last year said too many unnecessary transfusions were carried out in hospitals in Ireland. The IBTS says it is working with the Department of Health to ensure that patients only get transfused where there is a genuine risk to the life or health of the patient.

The Blood Bank is also planning to introduce a special filter to remove infective agents from donated blood. The plan is to treat each blood donation with this filter, which would be specific to the prion protein for vCJD ( the infective agent for the disease in the blood).

Initial lab studies on a new filtration system that can potentially remove the vCJD virus from the blood have recently been completed by the IBTS.

The third aspect of the Blood Bank's approach is to look at introducing the testing of people for vCJD when they turn up to donate at blood clinics. The Blood Bank is looking at introducing testing at some stage in the future, although at present there is no actual test available.

However,with such tests, there is always the chance that there will be false positives, which would obviously cause undue alarm. It has also been pointed out that the fact that these tests would be carried out in blood donation clinics could put people off donating, thereby affecting the blood supply.

Dr Murphy said research to date had indicated that the likelihood of vCJD being transmitted by blood transfusion in Ireland is close to zero or very low.

Research carried out by a team at Beaumont Hospital in Dublin recently estimated that we should expect very few, perhaps one to two at a best estimate and 15 at a very worst estimate, future clinical cases of vCJD in Ireland. So the incidence to date, while worrying, is largely in accorance with projections.

However, this report warned that considering the exposed to infected meat, the possibility that there may be a large number of people with 'subclinical' disease cannot be discounted.

People in this category might suffer no adverse effects themselves, but they retain the possibility of possible transmission to others through surgical procedures or blood transfusion.

Using recent data from the UK, it is estimated that the likely detectable prevalence of sub-clincial disease could be 120 cases per million.

This could increase the upper limit on possible future Irish cases from 15 to 46, but the Beaumont researchers said these estimates should be interpreted cautiously.

A recent report commissioned by the IBTS concluded that the exposure to infected beef from the BSE (mad cow disease) epidemic in Ireland was about 0.06% of that in Britain.

Until the latest case, two cases of vCJD had emerged in Ireland, . The first case was of a woman who had lived in Britain and the second case was of a man who had never lived in Britain.

Both people have since died.

NoBlood

Ireland - vCJD-fear of the unknown