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NOAA Oceans and Human Health Initiative

National Centers for Coastal Ocean Science

NOAA Harmful Algal Blooms and Analytical Response Branch

NOAA Marine Mammal Health and Stranding Response Network

NOAA Scientists Reveal ‘The Secret Pathologies of Dolphins’”

podcast iconDecoding the Secret Patholigies of Dolphins (Making Waves podcast)

podcast iconWhat are Harmful Algal Blooms? (Diving Deeper podcast)

This study was presented at a NOAA Oceans and Human Health Initiative- sponsored symposium at the annual American Association for the Advancement of Science (AAAS) meeting held in San Diego from Feb. 18-22, 2010.

external linkAAAS symposium overview: Decoding the Secret Pathologies of Dolphins

The symposium featured six new studies by NOAA and several external partners. NOAA’s Oceans and Human Health Initiative seeks to address the challenges that decision-makers face in the areas of public health, ocean-related human health impacts, and natural resource management.

Harmful Algal Blooms and Human Epilepsy

How resolving the riddle of seizures in sea lions led to new insights for human health

sea lion on a crash cart

Staff members at the Marine Mammal Center in Sausalito, California, care for a sea lion that stranded on a California beach after succumbing to seizures.

NOAA researchers have found that exposing laboratory animals to a toxin produced by blooms of microscopic ocean algae can induce seizures and eventually lead to epilepsy. Working with the Marine Mammal Center in Sausalito, California, and other partners, the scientists initially suspected that something amiss in the marine environment could be causing epilepsy in marine mammals and other wildlife with seizures that washed up on California beaches over the past decade.

They discovered that the animals’ seizures were being caused by exposure to domoic acid, a neurotoxin produced by the Pseudo-nitzschia australis alga. After realizing that certain sea lions had stranded with seizures at times and in areas where no harmful algal blooms (HABs) were present, the researchers started to believe that domoic acid poisoning may have progressed to chronic epileptic disease.

It was then that Dr. John Ramsdell, chief of Harmful Algal Blooms and Analytical Response at NOAA’s National Centers for Coastal Ocean Science, undertook laboratory experiments to validate the field observations seen in sea lions. His research team at the Center for Coastal Environmental Health & Biomolecular Research in Charleston, South Carolina, exposed laboratory rats to domoic acid at levels similar to those that a sea lion or dolphin might ingest when eating contaminated fish in the wild.
 “Within six months of the initial exposure, 92 percent of laboratory rats tested developed epileptic disease that worsened over their lifetimes,” says Ramsdell. “The domoic acid itself is not directly causing the epilepsy, but triggers a brief period of seizures that leads to changes in the brain, resulting in spontaneous and recurring seizures -- the hallmark of epilepsy.”

microscopic alga

The microscopic alga Pseudo-nitzschia australis produces domoic acid, a neurotoxin which, according to new NOAA research, can induce seizures and eventually lead to epilepsy.

The type of epilepsy that Ramsdell found in the laboratory rats resembles human temporal lobe epilepsy. This seems to have been confirmed by at least one human case that can be traced back to the consumption of mussels contaminated with the domoic acid toxin.

Dr. Ramsdell’s research provides new information about both marine mammals’ and peoples’ response to domoic acid poisoning and an example of NOAA’s “One Health” approach to connect ecosystem and wildlife health to public health and well-being. Continued study into HABs and their effects on the marine environment will not only guide future efforts aimed at marine creatures in distress, but is likely to help human beings suffering from disease processes, as well.