There is no way of testing the blood for vCJD, writes Eithne Donnellan, Health Correspondent
There are two forms of the degenerative brain disorder CJD or Creutzfeldt-Jakob disease. These are sporadic CJD, which occurs sporadically in about one in every million of the population every year, and new variant CJD or vCJD, which is otherwise known as the human form of mad cow disease.
Cases of vCJD have been linked almost entirely to the consumption of meat infected with Bovine Spongiform Encephalopathy or BSE. Of the more than 150 cases in Britain to date, only two people have been linked to the blood supply.
The first case in Britain, and in fact the world, where a person picked up vCJD via a blood transfusion, was in December 2003 in a 69-year-old man.
His transfusion came from a blood donor, who was well at the time of donation in 1996 and who died of vCJD in 2000. The incubation period for vCJD can be several years.
The disclosure of this first blood-linked case of vCJD led the Irish Blood Transfusion Service (IBTS) to introduce tighter restrictions on the acceptance of donations from people who have lived in Britain, and later on people who had undergone certain operations in Britain or who had received blood transfusions outside the State.
This is because there is no way of testing blood for vCJD. And in fact, there is no definitive way of diagnosing vCJD in a patient until the brain is examined after death. However, MRI scans and tonsil biopsies give a good indication of the presence of vCJD.
The second case of probable transmission of vCJD through blood was announced in Britain in July 2004. A patient who had received a blood transfusion in 1999 from a donor who later developed vCJD died of causes unrelated to vCJD, but a postmortem revealed the presence of abnormal prion protein (the infective agent which causes vCJD) in the patient's spleen, indicating that the patient had been infected with vCJD.
Experts say nobody knows what the risk is of somebody contracting vCJD if they receive blood from an infected person.
In Britain, some 28 of those who have died of vCJD were blood donors and 50 people have been identified as having received blood or blood products donated by them. Some 17 of the 50 are still alive and they range in age from 30 to 88 years.
While 33 of the 50 are dead, only one of their deaths was linked to vCJD.
In the Republic there have been just two confirmed cases of vCJD to date. The first was in a woman who had lived for a long time in Britain. She died in 1999.
The second, diagnosed late last year, involved a man in his 20s who had never lived in Britain. He died recently and almost certainly contracted the disease, which is invariably fatal, from eating infected meat as he had never received a blood transfusion and never undergone an operation. Neither was he a blood donor.
What is very different about this latest case of vCJD in the State, which is probable but not confirmed, is that the person involved was a blood donor. This could have had major implications for the IBTS were it not for the fact that the man had donated only once and only two people received components from his donation. One of the recipients died shortly afterwards of an unrelated condition. The recipient of the other blood component was informed yesterday. Obviously his family will be worried.
Two years ago, researchers from Dublin's Beaumont Hospital and the Imperial College, London, used statistical modelling to calculate how many cases of vCJD were likely to appear here in the future.
They calculated there was likely to be just one further case of vCJD here, with an upper limit of 15 cases possible.
Prof Bill Hall, chairman of the State's vCJD advisory group, said given this previous analysis this latest suspected case of vCJD in the State was not unexpected. He didn't think anybody knew what the risk was of getting vCJD from blood given by a person who developed vCJD.