Alzheimer's may be able to spread to organ transplant patients, study suggests - as experts call for dementia screening for all donors

Alzheimer's disease could spread to patients who receive transplants containing potentially toxic genes, a study suggests, according to DailyMail.

Researchers in Canada are now calling for all donors to be screened for the disease in case cases are going undetected.

The new study looked at mice who had stem cells from their bone marrow transplanted from donors with familial Alzheimer's disease.

This type is caused by a single genetic mutation passed down through families and affects nearly 350,000 Americans and 1 percent of Alzheimer's cases in the UK.

But they noted that more research is needed to see if the effect is the same in humans and other species.

Dr Wilfred Jefferies, senior study author and immunologist at the University of British Columbia, said: 'This supports the idea that Alzheimer's is a systemic disease where amyloids that are expressed outside of the brain contribute to central nervous system pathology.'

'As we continue to explore this mechanism, Alzheimer’s disease may be the tip of the iceberg and we need to have far better controls and screening of the donors used in blood, organ and tissue transplants as well as in the transfers of human derived stem cells or blood products.'

It's unclear if any Alzheimer's cases have been linked to organ or bone marrow donations to date.

The new study was published Thursday in the journal Stem Cell Reports.

Researchers transplanted bone marrow - a spongy substance in the center of the bones - with stem cells containing APP into two different groups of mice: those without an APP gene (APP Knockouts) and those with a normally functioning one.

They found that mice with a normally functioning APP gene developed signs of cognitive decline in nine months, and those without the gene experienced hallmarks of Alzheimer's in just six months.

Normally, mice prone to familial Alzheimer's start showing symptoms around 11 to 12 months of age.

For mice, these symptoms usually include loss of short-term and long-term memory and an absence of fear. Signs in the brain include a buildup of amyloid in the brain and leaks in the blood-brain barrier.

Dr Chaahat Singh, lead study author and neuroscientist at the University of British Columbia, said: 'The fact that we could see significant behavioral differences and cognitive decline in the APP-knockouts at six months was surprising but also intriguing because it just showed the appearance of the disease that was being accelerated after being transferred.'

The findings suggest that the mutated APP gene in donor stem cells could the disease in those without the gene and and that those with a normal APP gene are more susceptible to it.

The team also concluded that Alzheimer's disease can form from amyloid proteins found outside of the central nervous system.

The findings come after a UK study found evidence that at least five patients who were injected with growth hormones containing amyloid-beta protein 'seeds' - harvested from the bodies of dead people - 'caught' early-onset Alzheimer's later in life.

More than 1,800 other patients who received the treatment were deemed 'at risk.'

An NIH panel announced in January that it would launch an 'urgent' investigation into the research, as nearly 8,000 US children were injected with the therapy between the 1960s and 1980s.