Dolphins show signs of Alzheimer’s disease, study shows

London
CNN
—

Brains of three kinds dolphin found stranded along the Scottish coast showed the hallmarks Alzheimer’s diseaseaccording to new research, it provides better insight into the disease in species other than humans.

The findings may also provide possible answers to unexplained questions stranding dolphins along the coast, researchers say.

Alzheimer’s disease is a common neurodegenerative disorder which mainly affects older people, with symptoms such as memory loss, forgetfulness and confusion.

According to a study published on December 13 in European Journal of Neuroscienceresearchers in Scotland conducted postmortem studies on the brains of 22 odontocetesor toothed whales, making their discoveries more detailed than others the authors said.

“It is more in depth and breadth because it looks at a larger number of animals from several different cetacean species that are known to be old for the species (older in age),” Mark Dagleish, co-author and senior clinician in anatomic pathology at the University of Glasgow, told CNN on Tuesday.

The study looked at samples from five species: Riss’s dolphins, fin whales, white-beaked dolphins, harbor porpoises and bottlenose dolphins. Of the 22 studied, 18 are old specimens.

“Critically, (it) examined the whole brain to get a profile of lesions (abnormalities) using multiple markers of Alzheimer’s disease,” Dagleish added, using the same techniques used for human tissues.

The findings showed that three old dolphins – the fin whale, the white-beaked dolphin and the bottlenose dolphin – have brain changes or lesions associated with Alzheimer’s disease in humans.

Tara Spiers-Jones, another co-author of the study, said ua statement this week that researchers “were fascinated to see brain changes in old dolphins similar to those in humans (aging) and Alzheimer’s disease.”

“Whether these pathological changes contribute to the stranding of these animals is an interesting and important question for future work,” said Spiers-Jones, personal chair in neurodegeneration at the Deanery of Biomedical Sciences, University of Edinburgh.

The researchers found that the samples accumulated phospho-tau proteins and glial cells and that they amyloid-beta plaques, a protein build-up found in the brains of people with Alzheimer’s disease. The distribution of these lesions was comparable to brain regions in people with Alzheimer’s disease, according to the research paper.

Dagleish said the findings are “the closest anyone has come to showing any animal spontaneously developing Alzheimer’s-related lesions,” which were thought to develop only in humans.

Odontocetes regularly strand on UK shores in groups, which the study authors said could support the “sick leader” theory when a group follows an aging leader into shallow water, potentially as a result of the leader becoming confused.

The similar neuropathology of old dolphins and humans with Alzheimer’s suggests that marine mammals are susceptible to the disease, but Dagleish said the diagnosis can only be made if there are cognitive deficits. These are usually found by assessing cognitive impairment – impossible with postmortem studies.