Since early spring, hundreds of dead and ill marine mammals and seabirds have beached themselves on the shores of Los Angeles, Ventura and Santa Barbara counties. The animals may have become sick by eating schooling fish or shellfish contaminated with domoic acid, a naturally occurring toxin that may also cause human illness.
California sea lions, common dolphins and white-sided dolphins have been hit especially hard, becoming infected with the toxin after eating their typical meals of either anchovies or sardines, said Gregg Langlois, a marine biologist with the California Dept. of Health Services’ Marine Biotoxin Program.
Fish and shellfish feed off toxic algae blooms. The toxin lies dormant in the guts of the fish and shellfish because they lack receptors in the brain that respond to the poison.
Domoic acid is a neurotoxin that affects part of the brain and results in seizures. Other clinical signs of infection include disorientation and ataxia, a kind of behavior where the animal has difficulty finding its center of balance, said Dr. Martin Haulena, a veterinarian at the Marine Mammal Center in Marin County.
With appropriate treatment, sea lions with domoic acid poisoning can recover in one to two weeks. Dolphins tend to die more frequently. The current population of California sea lions is about 200,000 and dolphins number about 300,000 off the California coast.
“We treat it by controlling the seizures. It’s like dealing with people with epilepsy [a neurological disease resulting in seizures],” Haulena said.
Some animals can recover fully from the toxin with rehabilitation. In 1998, three of the sea lions released from the Marine Mammal Center in Marin County received satellite tags to monitor their behavior in the ocean.
“Those three animals went back to areas populated by other sea lions. While the satellite tags were on them they seemed to be moving in patterns that were considered to be normal for them. We do think that some of them can get through it and get back to normal,” Haulena said.
Recent toxin patterns in the waters off Los Angeles, Ventura and Santa Barbara counties remain continually high.
On May 10, the California Dept. of Health Services released a health advisory for consumers of fish and shellfish.
“The health advisory was based on data of rapid increases in toxin levels in areas around the coasts of L.A. County, Santa Barbara and Ventura,” Langlois said.
A Health Dept. advisory warns consumers not to eat sport-harvested species of crab, bivalve (two-shelled) shellfish, sardines and anchovies because of probable contamination with domoic acid.
Although domoic acid poisoning is currently only affecting marine mammals, the toxin is thought to have caused three deaths in people who ate infected shellfish in Canada 13 years ago. No cases of human poisoning from the toxin are known in California.
In addition to cautioning people not to eat specific shellfish and fish, the Health Dept. is now providing a list of domoic acid poisoning indicators.
Symptoms of domoic acid poisoning can occur within 30 minutes to 24 hours after eating toxic seafood. In mild cases, vomiting, diarrhea, abdominal cramps, headache and dizziness can occur. These symptoms usually disappear within several days. In severe cases, the person may experience excessive bronchial secretions, difficulty in breathing, confusion, disorientation, unstable blood pressure, and irregular heartbeat, seizures, permanent loss of short-term memory, coma and even death.
If a person finds a beached animal they should not try to help it, but rather call the Marine Mammal Center hot line at 687-3255. People who believe they are suffering from domoic acid poisoning should call Poison Control at 1-800-876-4766. Poisoning can only occur if a person has ingested infected seafood of the types mentioned by the Health Dept.