Dolphins show traces of Alzheimer's disease: Study

Researchers have found that three species of dolphin can show traces of Alzheimer's disease. According to new research, the brains of three species of dolphin were found stranded along the Scottish coast with traces of Alzheimer's disease, and provide greater insight into the disease in other species than humans.

This new research might help researchers find possible answers to unexplained strandings of dolphins along the coast.Alzheimer's is a common disease in humans, it is a neurodegenerative disorder that mostly affects older people, with symptoms such as memory loss, forgetfulness and confusion.

Earlier, different types of dementia have been found in other animals but this will be the first time that Alzheimer's disease has been detected in species other than humans.

The study was published on 13 December in the European Journal of Neuroscience by Scottish researchers who conducted postmortem studies on the brains of 22 toothed whales or odontocetes which to prove their findings in a more detailed way.

What do the researchers say?

Mark Dagleish, co-authorand a senior clinician in anatomic pathology from the University of Glasgow said, "It’s more in-depth and breadth as it looks at larger numbers of animals from several different species of cetaceans known to be aged for the species (older in age)".

The study looked at specimens from five species of dolphins- Risso’s dolphins, long-finned pilot whales, white-beaked dolphins, harbour porpoises and bottlenose dolphins. Out ofthe 22 studied specimens, almost 18 were aged.Dagleish further added, "Critically, (it) examined the whole brains to provide lesion (abnormality) profiles using more markers of Alzheimer’s disease"with the same techniques used for human tissues.

Spires-Jones,the personal chair of neurodegeneration at the University of Edinburgh’s Deanery of Biomedical Sciences, said, "Whether these pathological changes contribute to these animals stranding is an interesting and important question for future work".

What does the study say?

Findings showed that three aged dolphins, a long-finned pilot whale, a white-beaked dolphin and a bottlenose dolphin, presented brain changes, or lesions, similar to Alzheimer’s disease in humans. These findings are the closest anyone has been able to show that any animal can develop Alzheimer's disease, which was earlier thought to be developed in humans only.

The odontocetes have been found earlier as well on the UK coasts in groups. Study authors say that this may support the "sick-leader" theory, which is when the group follows an aged leader into shallow waters potentially as a result of the leader's confusion.

The similar neuropathology of aged dolphins and humans with Alzheimer's disease suggests that marine mammals are susceptible to the disease, but Dagleish cautioned that a diagnosis can only be made if cognitive deficits exist. These are typically discovered through cognitive impairment assessments, which are not possible with postmortem studies.

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