BSE - Preventing Creutzfeldt-Jakob disease

Although the condition is very rare, it can be difficult to prevent Creutzfeldt-Jakob disease (CJD).

This is because most cases occur spontaneously for an unknown reason (sporadic CJD) and some are caused by an inherited genetic fault (familial CJD).

Sterilisation methods used to help prevent bacteria and viruses spreading are also not completely effective against the infectious protein (prion) that causes CJD, although tightened guidelines on the reuse of surgical equipment mean that cases of CJD spread through medical treatment (iatrogenic CJD) are now extremely rare.

There are also measures in place to prevent variant CJD spreading through the food supply or via the supply of blood used for blood transfusions. These are described below.

Protecting the food supply

Since the link between bovine spongiform encephalopathy (BSE or 'mad cow disease') and variant CJD was confirmed, strict controls have been in place to stop BSE entering the human food chain.

These controls include:

• a ban on feeding meat-and-bone mix to farm animals
• the removal and destruction of all parts of an animal's carcass that could be infected with BSE
• a ban on mechanically recovered meat (meat residue left on the carcass that is pressure-blasted off the bones)
• testing on all cattle more than 30 months old (experience has shown that infection in cattle under 30 months of age is rare, and even cattle that are infected have not yet developed dangerous levels of infection)

Blood transfusions

In the UK, there have been four cases where variant CJD has been transmitted by blood transfusion. In each case, the person received a blood transfusion from a donor who later developed variant CJD.

Three of the four recipients went on to develop variant CJD, while the fourth recipient died before developing variant CJD, but was found to be infected following a post-mortem examination.

It is not certain whether the blood transfusion was the cause of the infection, as those involved could have contracted variant CJD through dietary sources.

Nevertheless, steps were taken to minimise the risk of the blood supply becoming contaminated.

These steps include:

• not allowing people potentially at risk from CJD to donate blood, tissue or organs (including eggs and sperm for fertility treatments)
• not accepting donations from people who have received a blood transfusion in the UK since 1980
• removing white blood cells, which may carry the greatest risk of transmitting CJD, from all blood used for transfusions