Blood transfusion and CJD

It is now clear that there is a risk from the transmission of vCJD through blood transfusion. The reason for this is not completely clear in that attempts to demonstrate infectivity in blood by inoculation into the brains of animals has show no transfer. However the sheer quantity of blood involved in a blood transfusion from a human must mean that the risk is much greater than can be seen with any animal methods.

For a long period it was unclear if CJD was transferred through blood transfusion or not. Initially attempts were made by comparing the difference between transfusion prevalence between those that developed CJD and those that were controls. Unfortunately the number of CJD cases needed to tell the difference would have needed to be several thousands and hence this study was unhelpful.

Later much greater numbers of cases were compared using international studies and with sCJD there did not indeed seem to be any increased likelyhood of having received a transfusion in the CJD cases. Meantime it was clear that infectivity was present in the blood of scrapie cases in various species (mice, hamsters etc) and in 2003 it was shown that if sheep were bled, before they were symptomatic with scrapie, then their blood would transfer the disease to other sheep by transfusion.

From this it was no longer surprising when a patient that developed vCJD (with exactly the same symptoms as a usual patient with the disease) was found to have received the blood donation from another case of the disease before that person had vCJD symptoms.

It must now be assumed that vCJD is present in blood and that it is infective in transfusions. How to remove it or test for it is now unclear but technologies are being developed currently for this purpose. In March 2004 in UK all blood donation by someone that has already received blood as a transfusion may not be accepted.

Risk from tissue transplantation

The major problems with the use of tissues and blood are not yet solved. The recent (2001) announcement from the USA that the Red Cross there would not accept blood donation from people that had lived in Europe or stayed for specific lengths of time shows that the increase in BSE throughout Europe is causing a potential rise in problems.

The blood regulations are present for Europe and for all other countries separately. For tissues, however only a few sources of regulations are available:

  • A Code of Practice for Tissue Banks providing tissues of human origin for therapeutic purposes
  • Guidance on the Microbiological Safety of Human Organs, Tissues and Cells used in Transplantation Advisory Committee on the Microbiological Safety of Blood and Tissues for Transplantation MSBT
  • One of the useful groups of data is the amount of infectivity that has been found in specific tissues around the body of the animal infected with CJD, BSE, TME or scrapie.
  • The risks from dentistry has also had to take this into account and separate risk discussions from the transfer of tissues from one patient to another as a result of dentistry suggests that the risk may not necessarily be low.

These decisions may not seem very rational in that tissue transplantation is actually likely to transfer disease much easier than blood or plasma transfusion.

The reason why much less action is being taken is that there is probably little that can be done. If the patient is felt to need the transplant then the risk from the CJD that may come with it must seem minimal.

Further statistics are clearly needed. It is unlikley at this moment that any of the drugs that are taken with the transplant will have any effect on the rate of onset of the CJD.