Scientists have developed a test that can pinpoint a BSE victim from the beat of his or her heart.
The technique - which can also diagnose the condition in animals - offers doctors a way to protect blood banks from infected donations and could also provide farmers with a method for eradicating sick animals from their herds long before symptoms of mad cow disease develop.
At present, the disease can only be diagnosed by studying tissue removed from the brains of animals or humans who begin to show outward signs of illness, such as an uncertain gait.
'This is the first rapid, non-invasive test for spotting animals and humans affected by diseases caused by prions [the infectious agents that cause BSE and CJD] before symptoms develop,' said Chris Pomfrett, a neurophysiologist at Manchester Royal Infirmary. 'It works on a very simple idea - variability in heartbeat.'
The heartbeat of any mammal is controlled by the brain stem, which sits at the base of the cranium and acts like a junction box between the brain and spinal cord. Pomfrett had originally worked on this area of the cortex while investigating heart-rate variations in patients anaesthetised during surgery. He discovered a critical heartbeat pattern in patients at risk of waking during surgery. This was developed into a technique called Fathom, which is now used to prevent patients becoming conscious on the operating table.
'The brain stem is also a major focus of infection by prions once an animal or human becomes infected with BSE tissue,' Pomfrett added. 'So we decided to take our work further and see what effect an infected brain stem has on heartbeat.'
Using simple monitors fitted to animals and humans, Pomfrett and his colleagues studied infected cows and patients suffering from variant CJD, the human form of BSE. The results are pub lished in the current issue of Veterinary Record . They tested the heartbeats of 48 cows unaffected by BSE and 85 deliberately fed with infected tissue. The scientists could tell which animals had contracted mad cow disease even though they still had not begun to display symptoms. In one case, they were able to pinpoint an infected animal 18 months before its symptoms began to be displayed.
'When an animal is infected with prions, its heart rate becomes more variable. All you have to do is take five minutes' worth of electrocardiograms and feed these into a laptop computer fitted with special software. Within seconds, it can tell you if you are dealing with an infected animal or not.'
Since carrying out the research on cattle, Pomfrett has also used the technique to see if it could spot heartbeat variations in humans infected with BSE prions. 'It was just as easy,' he said.
The technique could allow farmers to eradicate animals long before they get a chance to infect pens or soil. It could also be the basis of a test for monitoring blood donors to prevent infected individuals passing on the disease - and help scientists work towards a cure.The Observer:
