We used to think only humans suffered from Alzheimer's disease, that debilitating neurological disorder that most often strikes people over the age of 65. But, it turns out, we aren't alone after all. Dolphins have now also been found dead with Alzheimer's-like plaques in their brains, strongly indicating that they likely beached themselves as a result of the disease, reports ScienceAlert.
The discovery is an ominous warning to us all, because it also hints at a potential cause for Alzheimer's: the environmental toxin BMAA.
Each of the dozen or so cases of Alzheimer's identified in dolphins so far has also been associated with BMAA, which is produced by blue-green algal blooms common in dolphin habitats. This neurotoxin is easily caught up in the ocean food web, which the dolphins rely on more directly than we do, but humans also rely on it and may be susceptible to the same concern.
"Dolphins are an excellent sentinel species for toxic exposures in the marine environment," explained co-author Dr. Deborah Mash. "With increasing frequency and duration of cyanobacterial blooms in coastal waters, dolphins might provide early warning of toxic exposures that could impact human health."
The research was published in the journal PLOS One.
The connection to toxin exposure
The connection with BMAA isn't a total surprise. Previous experiments have shown that chronic BMAA dietary exposure can trigger neurodegenerative changes in both humans and non-human primates. Now we can add dolphins to that list.
While researchers aren't sure whether BMAA causes Alzheimer's-related amyloid plaques to develop in humans like it does in dolphins, we know this is a nasty substance associated with brain disease, and it's something that needs to be thoroughly investigated.
While blue-green algal blooms occur naturally, they can grow dramatically in warm water conditions. So as our oceans warm due to climate change, BMAA exposure will only increase.
"People should take simple steps to avoid cyanobacterial exposure," said co-author Paul Alan Cox.
That involves avoiding eating creatures that are at the top of the ocean food chain where BMAA can bioaccumulate. For instance, sharks have been shown to be high in BMAA, and those that consume shark fin soup or take cartilage pills are likely exposing themselves to this neurotoxin.