Stranded dolphins’ brains show common signs of Alzheimer’s disease
A chance conversation in a bar has led to the most extensive study of dementia in dolphins.
The brains of three different species of stranded dolphins show classic markers of human Alzheimer’s disease, according to the most extensive study into dementia in odontocetes (toothed whales), led by a new pan-Scotland research, a collaboration between the University of Glasgow, the Universities of St Andrews and Edinburgh and the Moredun Research Institute,
The new research, published in the European Journal of Neuroscience, (13 December 2022) studied the brains of 22 odontocetes which had all been stranded in Scottish coastal waters. included five different species – Risso’s dolphins, long-finned pilot whales, white-beaked dolphins, harbour porpoises and bottlenose dolphins – and found that four animals from different dolphin species had some of the brain changes associated with Alzheimer’s disease in humans.
A chance encounter by lead research Dr Mark Dagleish from the University of Glasgow and Co-author of the paper Professor Frank Gunn-Moore from the University of St Andrews led to the development of the most extensive study of dementia in dolphins. The researchers, who hadn’t seen each other for nearly 30 years, met at an event in a pub in Edinburgh and the rest, as they say, is history.
Professor Frank Gunn-Moore said: “Mark and my wife trained together as vets in Edinburgh in the 1980s, and I was explaining to Mark, who is a veterinary pathologist, about a paper we had just published reporting on the potential of cetaceans to have similar pathology to humans with Alzheimer’s disease.” Mark was responsible for undertaking the histological examination of dolphins and whales that strand in Scottish coastal waters. Dr Mark Dagleish added: “Due to the specific way we trim, process and examine the brain tissues from these unfortunate animals, that are investigated under the Scottish Marine Animal Standing Scheme (SMASS) funded by Marine Scotland and DEFRA, using large rather than standard blocks of tissue, we were in a position to make direct comparisons with many of the areas in human brains. So, Frank and I hatched an idea for this project which has shown remarkable results’’.
Enlisting the expertise of Professor Tara Spires-Jones from the University of Edinburgh and Professor Ailsa Hall OBE, University of St Andrews, the team of researchers examined stranded animals for the presence of the brain pathology that are 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 numbers in response to central nervous system damage). The results reveal that the brains of all of the aged animals studied had amyloid-beta plaques.
The findings may provide a possible answer to unexplained live-stranding events in some odontocete species. Study authors confirm the results 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.
Whales, dolphins and porpoises are regularly stranded around the coasts of the UK. They are often 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.
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 their brains, showing that some odontocete species develop Alzheimer’s-like neuropathology. 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.
Dr Mark Dagleish 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 Frank Gunn-Moore added: “I have always been interested in answering the question: do only humans get dementia? Our findings answer this question as it shows potential dementia associated pathology is indeed not just seen in human patients. This study is also a great example of both different research institutes, but also different branches of the Life Sciences working together.”
“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,” added Professor Tara Spires-Jones.
The paper, ‘Alzheimer’s disease-like neuropathology in three species of oceanic dolphin’ is published in the European Journal of Neuroscience.
The full study can be found online at: https://onlinelibrary.wiley.com/doi/abs/10.1111/ejn.15900
All animals in this research were studied after a stranding event. Marine Scotland and Defra fund post-mortem examinations, via the Scottish Marine Animal Stranding Scheme (SMASS), of cetaceans (including odontocetes), pinnipeds and marine turtles that strand and die in Scottish coastal waters.
Issued by the University of St Andrews Communications Office.