Plaques linked to Alzheimer's found in the brains of stranded dolphins
Analysis of the marine mammal brains also revealed the presence of BMAA, a toxin produced by cyanobacterial blooms.
"We found β-amyloid plaques and damaged neurons in brain tissues from dolphins that had died on the beaches of Florida and Massachusetts," Dr. David Davis, a neurologist at the University of Miami, said in a news release.
Davis and his colleagues detailed their discovery in the journal PLOS One.
"Dolphins are an excellent sentinel species for toxic exposures in the marine environment," said 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."
In lab tests, scientists have previously confirmed exposure to BMAA triggers the formation of β-amyloid plaques and neurofibrillary tangles in the brains of animals -- the same abnormalities found in the brains of patients with Alzheimer's.
"We cannot say for sure that chronic exposure to cyanobacterial blooms can trigger Alzheimer's in humans but it is a risk that I personally am unwilling to take," said Larry Brand, oceanographer at the University of Miami.
Similar combinations of BMAA, β-amyloid plaques and neurofibrillary tangles were identified in the brains of the Chamorro people of Guam diagnosed with an Alzheimer's-like neurodegenerative disorder called Lytico-bodig disease.
Still, scientists can't yet say for certain whether the plaques and tangles caused the dolphins to strand themselves on the beach.
"Until further research clarifies this question, people should take simple steps to avoid cyanobacterial exposure," said Paul Alan Cox, ethnobotanist at the Brain Chemistry Labs, a nonprofit researcher group in Jackson Hole, Wyoming.
