Alzheimer's disease is a common neurodegenerative disorder that primarily affects older people and leads to memory loss, confusion and forgetfulness.
First Signs of Alzheimer's Found in Toothed Whales
A new study published in the European Journal of Neuroscience has, however, found evidence that other animal species can also suffer from this debilitating disease. Through post-mortem examinations of 22 toothed whales (Odontocetes), researchers discovered signs of Alzheimer's disease in the brains of three dolphin species that had stranded along the Scottish coast.
The scientists examined specimens from five species: Risso's dolphins, long-finned pilot whales, white-beaked dolphins, harbour porpoises and bottlenose dolphins. “We examined whole brains to create lesion profiles containing further markers for Alzheimer's disease,” said the study's lead author, Mark P. Dagleish, an expert in anatomical pathology at the University of Glasgow.
Phospho-Tau and Amyloid Beta Plaques in Dolphins
The analysis revealed that three aged dolphins — a long-finned pilot whale, a white-beaked dolphin and a bottlenose dolphin — displayed brain lesions associated with Alzheimer's disease in humans. More specifically, these animals appeared to have accumulated phospho-tau and glial cells and to have formed amyloid beta plaques, i.e. the clumping of a protein found in the brains of people suffering from the disease.
According to Dagleish, these findings are “the first evidence that animals spontaneously develop the lesions associated with Alzheimer's disease,” which science had previously assumed could only develop in humans. While the similar neuropathology of aged dolphins and humans with Alzheimer's disease suggests that these marine mammals are also susceptible to the disease, a definitive diagnosis could only be made if clear cognitive deficits were also identified.
Theory of the «sick leader»
«The simultaneous occurrence of amyloid beta plaques and hyperphosphorylated tau pathology in the brains of odontocetes demonstrates that these three species spontaneously develop AD-like neuropathology. The significance of this pathology for the health and ultimately the death of the animals has not yet been clarified. However, it could contribute to the causes of unexplained stranding in some odontocete species and supports the theory of the ‘sick leader’, according to which healthy conspecifics in a pod strand due to strong social cohesion», the authors conclude.
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