Stranded dolphins can get lost because they have Alzheimer’s disease

Dolphins may be stranded in Scottish waters because they are suffering from animal Alzheimer’s disease, a study has suggested.

Researchers examined the brains of three different species of stranded dolphins and found that they showed classic markers of human Alzheimer’s disease.

The brains of 22 odontocetes, all of which had been stranded in Scottish coastal waters, were analyzed in research at the universities of Glasgow, St Andrews and Edinburgh and the Moredun Research Institute in the Scottish capital.

The study, published in the European Journal of Neuroscience, included five different species – Risso’s dolphins, long-finned pilot whales, white-beaked dolphins, porpoises and bottlenose dolphins.

It found that four animals from different dolphin species had some of the brain changes associated with human Alzheimer’s disease.

The findings may provide a possible answer to unexplained live-stranding events in some odontocete species.

The group leader may have become confused

Study authors believe it may support the “sick leader” theory, where an otherwise healthy pod of animals finds itself in dangerously shallow water after following a group leader who may have become confused or lost.

Whales, dolphins and porpoises are regularly stranded around the coast of Great Britain. They are often found stranded in groups, or pods, in shallow water and sometimes on beaches.

While some animals can be moved to safer, deeper water by teams of experts, other animals are less fortunate and perish as a result. The underlying causes of live stranding incidents are not always clear, and research is ongoing to gain better insight.

For this study, researchers examined stranded animals for the presence of the brain pathology that is part of the hallmarks of Alzheimer’s disease, including the formation of amyloid-beta plaques, the accumulation of phospho-tau, and gliosis (a change in cell number in response to damage to the central nervous system).

The results reveal that the brains of all the old animals studied had amyloid-beta plaques.

Three animals in particular – each from a different odontocete species – had amyloid-beta plaques as well as a number of other dementia-related pathologies in the brain, showing that some species develop Alzheimer’s-like neuropathology.

However, the study cannot confirm whether any of the animals would have suffered the same cognitive deficits associated with clinical Alzheimer’s disease in humans.

Lead researcher, Dr Mark Dagleish from the University of Glasgow, said: “These are significant findings which show for the first time that the brain pathology in stranded odontocetes is similar to the brains of humans affected by clinical Alzheimer’s disease.

Further research is required

“Although it is tempting at this stage to speculate that the presence of these brain lesions in odontocetes indicates that they may also suffer from the cognitive deficits associated with human Alzheimer’s disease, more research needs to be done to better understand what is happening to these animals. “

Co-author Professor Frank Gunn-Moore of the University of St Andrews said: “I have always been interested in answering the question: do only humans get dementia?

“Our findings answer this question as it shows that potential dementia-associated pathology is actually not only seen in human patients.

“This study is also a good example of both different research institutes, but also different branches of life sciences working together.”

Professor Tara Spires-Jones, of the University of Edinburgh, said: “We were fascinated to see brain changes in old dolphins that are similar to human 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.”

All the animals in this research were studied after a stranding event. Marine Scotland and Defra fund necropsy investigations, via the Scottish Marine Animal Stranding Scheme, of cetaceans (including odontocetes), pinnipeds and marine turtles that strand and die in Scottish coastal waters.

The article, “Alzheimer’s disease-like neuropathology in three species of harbor porpoise” is published in the European Journal of Neuroscience.

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