The cold sore virus and other common bugs are major causes of Alzheimer’s disease, it was claimed last night.
The controversial theory will fuel fears that Alzheimer’s is infectious – and raise fresh concerns about whether it could be linked to blood transfusions.
However, it also suggests that antibiotic and antiviral medicines already on pharmacy shelves could be used to treat the memory-robbing disease.
The cold sore virus and other common bugs are major causes of Alzheimer’s disease, it was claimed last night
An international team of researchers, including experts from Cambridge, Edinburgh and Manchester universities, said evidence that bugs are behind Alzheimer’s is ‘incontrovertible’ and can no longer be ignored.
In a powerful editorial in the Journal of Alzheimer’s Research, the 31 doctors and scientists say the idea that microbes cause Alzheimer’s has been long neglected.
Yet there are more than 100 studies linking the cold sore bug – herpes simplex virus 1, or HSV-1 – to it.
Other suspects include a bacterium that causes pneumonia. The researchers argue that after working their way into the brain the microbes lie dormant, only to be awakened by ageing or illness.
They can then kill vital brain cells, triggering the symptoms of Alzheimer’s. The theory also states that beta-amyloid, the toxic protein often thought to be a cause of the disease, is actually made by the brain to fight off the bugs.
Last autumn, UK research raised fears the disease could be spread through blood transfusions, operations and even dental work.
Conventional wisdom states that Alzheimer’s is either caused by faulty genes or a combination of bad luck and ageing.
Evidence for the latest theory includes Manchester University research on human brain cells, which found that infection with the cold sore virus caused a dramatic increase in levels of beta-amyloid.
The controversial theory will fuel fears that Alzheimer’s is infectious – and raise fresh concerns about whether it could be linked to blood transfusions (file photo)
Other research shows that viruses and other bugs are present in the brains of most elderly people – and that the cold sore virus hides in regions key to memory and mood.
Professor Douglas Kell, a Manchester University biologist and one of the report’s authors, said that dormant bacteria have been found in blood. And while he doesn’t want to cause alarm, it is possible they could be passed on through blood transfusions. The editorial concludes that with tests of hundreds of other drugs coming to nothing, the time is ripe to look at alternatives.
It states: ‘Given the failure of 413 trials of other types of therapy carried out between 2002 and 2012, anti-viral or anti-microbial treatment could rectify the “no drug works” impasse.’
Others cautioned that while more research is justified, there no firm evidence that the disease is contagious.
Dr James Pickett, head of research at the Alzheimer’s Society, said: ‘A large number of different microbes including viruses, bacteria and fungi have been found in the brains of older people – but there do appear to be more of them in the brains of people who have died with Alzheimer’s disease.
‘While these observations are interesting and warrant further research, there is currently insufficient evidence to tell us that microbes are responsible for causing Alzheimer’s disease in the vast majority of cases. We would like to reassure people that there remains no convincing evidence that Alzheimer’s is contagious or can be passed from person to person like a virus.’
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