Dolphins may be suffering from Alzheimer’s disease, say Scottish researchers

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According to a study, three species of cetaceans stranded off the coast of Scotland, including a bottlenose dolphin and a pilot whale, have the classic markers of Alzheimer’s disease.

Although types of dementia have been fairly widely detected in other animals, Alzheimer’s disease has not been shown to occur naturally in species other than humans.

But researchers from the University of Glasgow, the universities of St Andrews and Edinburgh and the Moredun Research Institute in Scotland were surprised to find that post-mortem tests of 22 toothed whales, or odontocetes, detected three changes brain cells associated with human Alzheimer’s disease in three animals. .

Scientists don’t know the cause of this brain degeneration, but it could support a theory as to why some groups or groups of whales and dolphins get stranded in shallow water.

Some mass strandings have been linked to increased anthropogenic noise in the oceans, but Alzheimer’s-like signs in the brain could support a “sick leader” theory, that most healthy cetaceans are stranded because that they follow a group leader who has become confused or lost.

The researchers found signs of Alzheimer’s disease in three of the 22 stranded toothed whales: a white-beaked dolphin, a bottlenose dolphin and a long-finned pilot whale, also a member of the dolphin family.

According to the article published in the European Journal of Neuroscience, the three individuals were old for their species and exhibited three hallmarks of Alzheimer’s disease in humans. Abnormal levels of the beta-amyloid protein had accumulated in plaques that disrupt neurons in the brain, another protein called tau had accumulated in tangles inside the neurons and there was an accumulation of glial cells, that cause inflammation of the brain.

Pathologist and lead researcher Dr Mark Dagleish from the University of Glasgow said it was not possible to confirm whether this damage would lead to the same cognitive deficits associated with Alzheimer’s disease in people. Determining whether dolphins and whales had Alzheimer’s disease would also require studying individual animals when they were alive.

He said: ‘These are important findings which show, for the first time, that the brain pathology of stranded odontocetes is similar to that of the brains of humans affected by clinical Alzheimer’s disease. Although it is tempting at this point to speculate that the presence of these brain lesions in odontocetes indicates that they may also be suffering from the cognitive deficits associated with human Alzheimer’s disease, more research needs to be conducted to better understand this. that happens to these animals.

One possible reason why whales and dolphins have Alzheimer’s-like brain damage is that, like humans but unlike many other animals, they can live for many years after ceasing to reproduce. Another possible cause was suggested by a 2020 study which found that deep-diving beaked whales are more susceptible to Alzheimer’s-like pathologies due to hypoxia – low levels of oxygen in their body tissues – caused by their search for food on the high seas.

Signs of Alzheimer’s disease were also recently discovered in a single 40-year-old captive bottlenose dolphin.

Professor Tara Spires-Jones from the University of Edinburgh, who was part of the research team, said: “We were fascinated to see brain changes in older dolphins similar to those of human aging and disease. of Alzheimer’s. Whether these pathological changes contribute to the stranding of these animals is an interesting and important question for future work.

Dagleish said the research raises further questions for research into Alzheimer’s disease in animals and humans. “If these are the only animals that spontaneously develop these lesions, further study may give us some kind of help and insight into what is happening in the very early stages of these lesion development. If we can determine the triggers likely of this, can we find ways to treat or prevent it?”

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