Stranded dolphins’ brains show common signs of Alzheimer’s disease – study

The brains of stranded dolphins have some of the changes associated with human Alzheimer’s disease, new research suggests.

Scientists suggest their findings may help to explain why some of the species get stranded.

They say the study could support the sick-leader theory, whereby an otherwise healthy pod of animals find themselves in dangerously shallow waters after following a group leader who may have become confused or lost.

These are significant findings that 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

According to the most extensive study into dementia in odontocetes (toothed whales), the brains of three different species of stranded dolphins show classic markers of human Alzheimer’s.

The collaboration between the University of Glasgow, the Universities of St Andrews and Edinburgh and the Moredun Research Institute, studied the brains of 22 odontocetes which had all been stranded in Scottish coastal waters.

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

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

Whales, dolphins and porpoises are often stranded around the coasts of the UK, found stranded in groups, or pods, in shallow waters and sometimes on beaches.

While some animals can be moved to safer, deeper waters by teams of experts, other animals are less lucky and perish as a result.

The underlying causes of live stranding events are not always clear, and research is ongoing to gain better insights.

For the study, researchers examined the brains of stranded animals for signs of Alzheimer’s disease, including the formation of amyloid-beta plaques.

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

However, the study cannot confirm whether any of the animals would have suffered with 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 that 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.

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

Professor Tara Spires-Jones, University of Edinburgh, said: “We were fascinated to see brain changes in aged dolphins similar to those in human ageing and Alzheimer’s disease. Whether these pathological changes contribute to these animals stranding is an interesting and important question for future work.”