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Domoic Acid Toxicity on the California Coast


The Marine Mammal Center is seeing an uptick in suspected domoic acid cases in California sea lions in San Luis Obispo county. Since mid-July, the Center’s trained volunteers in San Luis Obispo County have rescued a high number of California sea lions exhibiting symptoms of domoic acid toxicity, which primarily attacks the brain, causing lethargy, disorientation, seizures, and if not treated, will eventually lead to death.

Microscopic view of an algal bloom

Produced by a type of algae called Pseudo-nitzschia australis, this toxin accumulates in small fish, like sardines and anchovies, which are then eaten by sea lions in large quantities.

Unfortunately, it’s a diagnosis we know all too well here at the Center. In fact, researchers here were the first to discover the condition in sea lions back in 1998. And we’ve had plenty of opportunities to learn more since then—in 2014, more than one-third of the California sea lions we rescued were affected by the toxin.

Domoic acid will naturally flush from an animal’s system over time, but sea lions repeatedly exposed to the toxin will suffer longer-lasting and more serious effects. If these animals come into our care before significant damage occurs, we are often able to help flush the toxin from their systems by giving them fluids. We also provide them with a fish source that is free of domoic acid. To control any seizures, our veterinarians give these patients anti-seizure medications that are also used in humans.

Although most of the patients we treat for domoic acid toxicity are California sea lions, other marine mammals are susceptible to its effects as well. Domoic acid has been reported in a number of other seal and sea lion species, as well as cetaceans such as blue and humpback whales. In 2014, researchers at the Center were the first to detect domoic acid in Guadalupe fur seals, a threatened species.

Domoic acid can also affect humans who eat contaminated shellfish, causing a life-threatening condition known as amnesiac shellfish poisoning. Because sea lions are often the first to be affected by a toxic algal bloom, we alert the public health department when we see an outbreak, which helps them to better target their surveillance to protect human health.

Your support will help the Center rescue and treat animals
suffering from domoic acid toxicity and other diseases


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