Prions – morphing agents of disease
Box 1 | Public health issues
Because human BSE is a human prion disease, not a bovine one (by the strange nature of prion transmission), the probability of transmission from person to person is high. There is therefore considerable concern world-wide about the large number of people who may unwittingly be incubating vCJD. Even though they may die of some other cause, during life they represent a risk of secondary transmission of vCJD through blood or contamination of surgical instruments.
Why is there concern about blood transfusions?
Most spongiform encephalopathies, including CJD in its sporadic and familial forms, are confined to the central nervous system. However, one additional complication of human BSE or vCJD is that the infectious prion is present also in lymphoid tissue such as tonsils and the white cells of the blood. Furthermore, it is present there during the incubation period of the disease, which in some cases can be very long.
Already there have been three probable transmissions of vCJD in the UK from blood transfusions given some years before the blood donor came down with variant CJD. Anyone who lived in the UK from 1980 to 1996 is potentially at risk of getting vCJD (human BSE). Such people, as well as those who have had a blood transfusion in the UK, are not acceptable as blood donors.
Human growth hormone injections and CJD
People whose bodies weren't making enough growth hormone were given injections of hormone extracted from the brains of corpses. Tragically, some of the people receiving the hormone developed CJD. It was found that the hormone they received had come from people infected with CJD. Nowadays, human growth hormone is safe to use because it is made using genetic engineering techniques, rather than being extracted from human brains.
Boxes
Box 2. The Australian Quarantine Inspection Service and the need for quarantine
Box 3. Australian researchers looking at prion proteins and CJD
Page updated June 2006.