Alzheimer’s disease is caused by a fungus growing in the brain, research suggests.

Yeasts and moulds were found in grey matter and blood vessels of all the dementia patients studied. By contrast, the brains of healthy people were free of fungi.

The Spanish researchers said fungal infection could ‘readily explain’ all the symptoms of Alzheimer’s – and may be the cause of the neurodegenerative disease.

The study, published by the highly respected Nature group of journals, is the second in a matter of weeks to question whether it is possible to catch the devastating condition.

Could Alzheimer's disease be caused by fungus? Traces have been discovered in the brains of sufferers,The reigniting the debate over whether the disease is actually caused by an infectious microbe

Last month, UK research suggested it could be spread through blood transfusions, operations and even dental work.

Before that, it was thought that Alzheimer’s was either caused by faulty genes or a combination of bad luck and ageing.

The latest study will further fuel fears that Alzheimer’s can be caught. But it could also lead to much-needed new treatments for a disease that affects at least 500,000 Britons and robs people of their speech, memory and dignity.

However, much more work is needed to confirm the link.

Researchers from the Autonomous University of Madrid found traces of several different types of fungus in the brains of 11 people who had died with Alzheimer’s disease.

They said the range of fungi might help explain why the disease can vary so much from patient to patient.

And that symptoms of Alzheimer’s disease, including its slow progression and the involvement of the immune system, can be ‘readily explained’ by a fungal infection.

Writing in the journal Scientific Reports, they added that if the condition is caused by a fungus, this could help explain why drug trails until now have had disappointing results.

It also means that existing antifungal drugs may be able powerful weapons in the fight against Alzheimer’s.

The conclusions were drawn after the scientists found cells and other material from 'several fungal species' in the brain tissue and blood vessels of all 11 deceased Alzheimer's patients analysed

Lead researcher Luis Carrasco said: ‘It is evident that clinical trials will be necessary to establish a causal effect of fungal infection in AD.

‘There are a number of highly effective antifungal compounds with little toxicity.

‘A combined effort from the pharmaceutical industry and clinicians is needed to design clinical trials to test the possibility that Alzheimer’s disease is caused by fungal infection.’

VIRUSES AND BACTERIA 'COULD FUEL BREAST CANCER' One of the most deadly types of breast cancer could be fuelled by viruses and bacteria. A study found tissue from triple-negative breast cancer – an especially fast-growing and hard-to-treat form of the disease – to harbour a range of bugs rarely found in healthy tissue. These included bacteria, viruses, fungi and parasites. The University of Pennsylvania study wasn’t able to show if the bugs cause the cancer – or if they just like to live in the diseased tissue. But in either case, a test for the bugs might be help doctors spot the disease. Early detection might even be possible, according to the journal Scientific Reports. Although the idea that bugs might cause cancer is strange, it is not unheard of, with a virus being to blame for most cases of cervical cancer and a bacterium strongly linked to stomach cancer. Katie Goates, of charity Breast Cancer Now, said: ‘Triple negative breast cancer is an aggressive type of the disease which we desperately need to find more effective targeted treatments for. ‘This is an intriguing study but only tells us that viruses, bacteria and fungi might be present in triple negative breast cancer. ‘The results do not show that these factors cause triple negative breast cancer and we don’t know if their presence is unique to this specific type of the disease or could be found in all cancers. ‘However, the results do suggest this is an interesting avenue for further research in larger studies.’ Advertisement

However, he also cautioned that his study does not prove that Alzheimer’s is triggered by a fungus.

It is also possible that the fungal infection may follow Alzheimer’s disease, with yeasts and moulds finding it easy to take hold in brains weakened by dementia.

Sylvain Lehmann, a French researcher on neurodegenerative disease, described the results as ‘very speculative’.

British experts were also cautious.

Dr Laura Phipps, of charity Alzheimer’s Research UK, said: ‘While this very small study suggests that fungal cells may be present in the brains of people with Alzheimer’s, we cannot conclude from this work that such infections cause or increase the risk of the disease.

‘Without a corresponding medical history, we do not know whether the fungal infection occurred before or after the onset of Alzheimer’s disease, or whether this group of people had an increased risk of fungal infection due to other health complications.’

‘The best current evidence suggests that eating a healthy and balanced diet, not smoking, staying physically active and keeping weight and blood pressure in check can all help reduce the risk of dementia.’

However, she added that the charity is funding research into whether infections play a role in Alzheimer’s.

Dr Clare Walton, of the Alzheimer’s Society, said: ‘Traces of fungus in the brains of these few people with Alzheimer’s is not enough to conclude that it plays a role in the development of the disease.

‘Although there has been research in the past to explore whether infectious diseases can raise the risk of developing Alzheimer’s disease, the results have so far been inconclusive.

‘We do know that Alzheimer’s disease weakens the internal barrier that protects the brain and this may make it more open to infections.

‘There is still much research to be done in order to truly understand the causes of dementia.