Stranded Dolphins Discovered With Signs of Alzheimer’s Disease

Three species of dolphins found stranded in the Scottish coastal waters were identified by researchers with brain issues related to Alzheimer’s disease in humans.

The dolphins were part of a pod, or group, of other twenty-two odontocetes. The brains of this specific dolphin group were studied by researchers from the University of Glasgow.

An accumulation of amyloid-beta plaques—associated with the disease—in their brains was identified in a bottlenose dolphin, a white-beaked dolphin, and two long-finned pilot whales.

Researchers say the dolphins with signs of Alzheimer’s could have accidentally led their otherwise healthy pod into shallow waters after getting confused or lost. This is known as the “sick-leader” theory.

Dr. Mark Dagleish, the lead researcher, 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.”

The findings are part of a new, broader pan-Scotland study of three universities, namely the University of Glasgow, University of St Andrews, and University of Edinburgh, in partnership with the Moredun Research Institute.

Alzheimer’s disease, a condition thought to be exclusive to humans

Alzheimer’s disease is currently thought to be a condition exclusive to humans. Therefore, it is difficult to diagnose in other animals with certainty.

The disease is associated with symptoms such as memory loss, impaired communication, and the inability to perform everyday activities. Neuroscientists link Alzheimer’s symptoms to the accumulation of misfolded proteins called amyloid plaques.

Alzheimer’s patients can also show gliosis, an increase in glial cell numbers, in the central nervous system in response to damage.

According to researchers, similar neurological signs in humans have been observed in all aged odontocetes, hence suggesting these animals may also be prone to degenerative disease.

However, Dr. Dagleish said, “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.”

Study conducted on five different species of dolphins

The specific study involved five different dolphin species, including, Risso’s dolphins, long-finned pilot whales, white-beaked dolphins, harbor porpoises, and bottlenose dolphins.

Along the coasts of the U.K., it is not uncommon for whales, dolphins, and porpoises to get stranded in pods in shallow waters and sometimes even on beaches.

Although some can be transferred to safer, deeper waters by teams of experts, other animals are not as lucky and perish as a result.

As the underlying causes of live-stranding incidents are not always clear in some odontocete species, ongoing research will help in gaining greater insight.

Professor Frank Gunn-Moore, a study co-author from 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 potential dementia-associated pathology is indeed not just seen in human patients,” he announced.

“This study is…a great example of…different research institutes…and branches of the Life Sciences working together,” Gunn-Moore added.

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

Of the five species involved in the study, one of these did not have amyloid plaques but did in fact exhibit neurofibrillary tangles and other neuritic plaques indicative of dementia.