Hope for sea lion after surgery for epilepsy linked to global warming

Marine mammals are developing epilepsy after exposure to domoic acid, a toxin released by algae and becoming more widespread as oceans warm

Cronutt the seal lion prepares for a CT scan before the procedure
Cronutt the seal lion prepares for a CT scan before the procedure Credit: Dr Shawn Johnson

A sea lion in California has undergone pioneering brain surgery for epilepsy, offering hope for the growing number of marine mammals suffering from the disorder as a result of climate change. 

Cronutt, a 7-year-old sea lion, was treated by a team of 18 specialists from the University of California, San Francisco (UCSF) who have developed a cellular therapy aimed at reversing epilepsy in animals. 

The groundbreaking procedure involved injecting embryonic pig brain cells into the sea lion's hippocampus, the area of the brain responsible for seizures. 

Scientists hope that the injected cells will spread through Cronutt's damaged hippocampus over the next few weeks and repair the area. 

If successful, the treatment could offer a lifeline to the increasing numbers of sea lions and sea otters developing epilepsy due to exposure to domoic acid - a toxin released by algae blooms. 

Algae blooms have become more widespread as the oceans warm, producing toxins that are ingested by small fish, which in turn are eaten by marine mammals Credit: Faba-Photograhpy 

The algae blooms have become more widespread as the oceans warm, producing toxins that are ingested by small fish like sardines and anchovies, which in turn are eaten by sea lions. 

Sea otters have also suffered from brain damage after ingesting toxin-laden shellfish. 

The animals suffering from the condition frequently get stranded on land, lose their appetite and often die. 

The phenomenon was first discovered in 1998, but cases are on the rise as the world's ocean temperatures increase. According to the UCSF, hundreds of sea creatures are affected by domoic acid poisoning on America's west coast each year alone. 

The pioneering procedure is a last-ditch effort to save Cronutt, 7 Credit: Christie Hemm Klok/The New York Times

Cronutt, who was first discovered by researchers after he became stranded in California in November 2017, has experienced a steady decline, culminating in a grand mals seizure last month. 

His carers at the Six Flags Discovery Kingdom in Vallejo, California described his pioneering surgery as a last ditch effort to treat the sea lion before considering euthanasia. 

The procedure performed on Cronutt on October 6 has previously proved effective in curing epilepsy in mice, but this is the first attempt to use the therapy on a larger mammal. 

Dianne Cameron, director of animal care, and veterinarians Claire Simeone and Shawn Johnson are Cronutt's care team at Six Flags Discovery Kingdom Credit: Christie Hemm Klok/The New York Times

The sea lion appeared to be doing well in the days following his surgery, but it will not be known for several weeks whether it has reversed his condition. 

“This method is incredibly reliable in mice, but this is the first time it has been tried in a large mammal as a therapy, so we’ll just have to wait and see,” said Scott Baraban, a professor of neurosurgery at the UCSF. 

“Over the years I’ve come to learn how many marine mammals can’t be released into the wild due to domoic acid poisoning, and it’s our hope that if this procedure is successful it will open the door to helping many more animals.”

The early stages of Cronutt's recovery suggest reasons for optimism - the sea lion was alert and appeared to have regained his appetite in the days following the procedure. 

After a meal of two-pounds of herring, he “followed me all around, was super engaged, and really alert,“ carer Dianne Cameron told the New York Times. ”His eyes look beautiful.

However even if proved successful, it is unlikely that the surgery will help people with epilepsy anytime soon, in part because of the challenges of using pig cells in human brains.