CJD could be spread by blood transfusions by blood trasnsfusion

Could blood transfusions accelerate the spread of CJD in the human population? And if, as some scientists fear, they could, our Environment Correspondent asks what could be done to minimise the risk

Some senior scientists fear that there is a real possibility that the new variant of the lethal brain affliction Creutzfeldt-Jakob disease (CJD) caused by mad cow disease could pass through the population via blood transfusions.

The Government must urgently consider removing white blood cells, a potential source of infectivity, from donated blood, they say. But that would add at least pounds 50m to the costs of blood transfusions.

The Government says the risks of infection is "negligible" but unknown. Research is being commissioned to try to pin it down. "If you don't have proof, then you have to say there is a possibility," the Department of Health said yesterday.

The scientists' fears emerged at a conference this week organised by one of Britain's research councils. It was held under "Chatham House" rules, which means that those attending - including The Independent -cannot disclose the identity of speakers or give details of the meeting.

"The processes we are going through today, such as blood transfusion, could amplify a disaster lurking behind the scenes," said a genetics professor. "One could make the argument that removing white blood cells [from donated blood] should be done in anticipation."

The conference was held as the Department of Health revealed plans to keep track, in secret, of all those who have received blood from four donors who later became ill with new variant CJD (v-CJD), the human version of bovine spongiform encephalopathy (BSE). The department said the recipients of the blood would not be told because it did not want to cause an unnecessary panic. There have been 21 victims of v-CJD, and only one is still alive.

Scientists are worried because, in experiments in which mice have been infected with BSE, it has been shown that the agent which carries the infection becomes established first of all in glands which make and harbour white blood cells, such as the spleen and lymph nodes. Furthermore, the amount of infectivity in these glands builds up at time passes. Later on the agent moves into the brain and spinal cord, where it causes the disease.

Experiments on mice have also indicated that blood can carry the infective agent, a mutant protein. But the infection can only pass from one animal to another when the blood is injected into the brain. Blood-to-blood transfusions have not been witnessed to transmit the disease.

There are grounds to hope the risk from transfusions is extremely low or non-existent. For years, scientists have been searching to find out whether blood donations from people who later went on to contract "classic CJD" had ever passed the disease to those who received transfusions.

Classic CJD has been killing a small number of people each year long before v-CJD came on the scene. So far, studies have not found a single instance when a blood transfusion passed the infection on.

But these findings provide no absolute guarantee of safety. First, v- CJD has some different properties from classic CJD, which may alter its infectivity. Second, there is the sheer scale of blood transfusions, and the fact that an unknown number of perfectly healthy looking people are incubating v-CJD. There is no way of preventing them from donating blood, because there is no test which shows whether the agent is in people in the early stages of the disease, or when they are incubating it.

Concerned scientists point to parallels with the opening years of the Aids pandemic in the early Eighties. At the time, there was no blood test which could demonstrate the presence of the HIV virus in blood The authorities said the risk to haemophiliacs from stopping transfusions of the clotting agent Factor VIII far outweighed the risk of contracting Aids. Yet, subsequently, thousands of haemophiliacs were killed by Aids due to them receiving contaminated Factor VIII.

The Government avoids outright claims that transfusions are completely safe. Chief Medical Officer Sir Kenneth Calman said: "Any negligible risk of new variant CJD transmission is heavily outweighed by the immediate benefit [of blood transfusions]. For many, that will mean saving their life."

There are 2.5 million blood donations a year and about 800,000 patients receive transfusions. The blood is separated into red blood cells, platelets (which help blood to clot), and plasma. Plasma is mixed with plasma from other donors and products derived from the plasma of one donor can be transfused into many patients.