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Domoic Acid Toxicity on the California Coast

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.

The Center’s veterinary team is also investigating new therapies to try to reduce the amount of inflammation and damage the brain experiences while the animal is recovering, to hopefully minimize permanent brain damage. This year, our researchers are testing the effectiveness of adding alpha lipoic acid to our domoic acid toxicity treatment regimen. This powerful antioxidant may help protect against damage to the brain by preventing the toxin from binding to certain receptors in the tissue. And because it is both water- and fat-soluble, alpha lipoic acid is absorbed into a greater variety of tissue types, which means it can pass easily into the brain tissue as well as help prevent cell damage throughout the whole body.

Read more about the recent outbreak:

San Francisco Chronicle, “Sea lions wash ashore in California amid return of toxic blooms”

CBS News, “Dozens of sea lions sickened with domoic acid poisoning”

KQED Science, “Algae-Poisoned Sea Lions Inundate Marine Mammal Center”

San Luis Obispo Tribune, “This is what’s making sea lions sick — and causing quite a stench in Pismo Beach”

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suffering from domoic acid toxicity and other diseases


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