Heartbeat Clue to BSE
09 June 2004
The research, published in this week’s Veterinary Record (pages 687-691), involved taking regular electrocardiogram measurements of cattle at the government research station ADAS Drayton in Warwickshire that had been experimentally infected with BSE by feeding them infected brain tissue.
Heart rate is controlled by nerve cells in the brainstem, the region at the base of the brain where the highest concentrations of prion protein are found in advanced cases of BSE examined postmortem. Two particular structures, the dorsal vagal motor nucleus and the nucleus ambiguous are directly connected to the heart via the vagal nerve. But this nerve also serves the gut and it is thought that the brain is infected in BSE by infective prions tracking up this nerve after being absorbed across the intestinal wall.
An ability to make sudden changes in heart rate is important for any organism in responding to danger or strong emotion and signals from the brain along the vagal nerve help to slow the heart back down again. "This function has been described as the vagal brake and has very powerful effects on heart function. In extreme cases it can even stop the heart completely - there is a condition known as voodoo death in which people can literally be scared to death. What we are seeing in cattle with BSE and human vCJD patients is an intermittent action of the vagus, repeatedly cutting in and out in a very abnormal manner," Dr Pomfrett explains.
He says this pattern of activity which affects the regularity of the gaps between beats but may not actually the change the numbers of beats per minute is "absolutely characteristic" of both BSE and vCJD. The only difference between the two is that those changes seen in cattle are more subtle because cows are usually diagnosed with the disease at a much earlier stage than human patients. "But our test detects changes that precede even the most sensitive clinical signs such as an unwillingness to cross a section of grating on the cattle shed floor."
Cattle are usually slaughtered as soon as these behavioural changes appear and on welfare grounds are never allowed to reach the stage of staggering in-coordination seen in the archive footage shown regularly on television.
The University of Manchester has been granted US and European patents on Dr Pomfrett’s discovery and the technology has been licensed to a private company to develop a system for commercial testing.
Notes for Editors:
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For further information please contact Chrissie Nicholls or Helena Cotton in the BVA Press Office on 020 7636 6541 or email chrissien@bva.co.uk.