Mad cow threat greater than first thought as second blood transfusion case is confirmed

Main Category: CJD / vCJD / Mad Cow Disease
Article Date: 07 Aug 2004 - 19:00 PDT

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The threat of more humans getting the human version of mad cow disease could be much greater than first thought as the second blood transfusion case is confirmed in the UK. Blood transfusion is an effective means of transmission, says Professor James Ironside, National CJD Surveillance Unit, Edinburgh, Scotland.

Prof. Ironside said that more people are susceptible to the illness than experts had thought. People with a different genetic makeup from previous patients are also at risk.

Prof. Ironside said, "The patients we have seen so far may just be the first of a series of groups of patients. The idea that vCJD somehow is a disappearing disease -- I think we can't entertain that anymore."

Two patients within the last year have caught the human version of mad cow disease (Creutzfeldt-Jakob disease - vCJD) within the last year as a result of transmission via a blood transfusion. The first was a patient, last December who had received blood several years ago from a person who went on to die of vCJD. Last month another patient caught vCJD as a result of a blood transfusion as well.

The last patient belongs to a common genetic subgroup - half the UK population belongs to this subgroup. Previous cases of vCJD included people who belonged to a much smaller genetic subgroup.

Ironside concluded that vCJD may have quite a long future ahead of it.

A total of 142 people in the UK have died (probably) as a result of having had vCJD. Over the last few years the numbers have been falling. Most people, including medical experts, thought the cases would gradually fizzle out.

Now that the infectious agent has been identified in the most common genetic subgroup, Ironside believes it probably has not started fizzling out yet.

Ironside said "It indicates quite clearly that people can be infected by this agent. They can be asymptomatic but can still carry the agent and at some point in the future may develop the disease….In the meantime they represent a risk to others of transmitting the disease through blood transfusion ... or perhaps through contamination of surgical instruments," Ironside explained.

The patient who died last month did not die of vCJD. However, an autopsy revealed the infectious agent in his spleen. Five years ago, this patient had a blood transfusion, the blood came from a person who later died of vCJD.

The problem here is how long the incubation may be. The indication is that people in the largest genetic subgroup have a much longer incubation period.

What we have been seeing over the last few years could have been the first wave of vCJD cases, from the smaller genetic subgroup whose incubation period is much shorter.

Ironside believes it is possible that the larger genetic subgroup of people, who have a longer incubation period, could have vCJD in years to come.

What the experts do not know, is how long this incubation period could be.

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