Avian flu devastates elephant seals in Southern Hemisphere, raising concerns for California coast

Avian flu, long associated with birds, continues to surprise scientists as it spreads across species and oceans.

After first jumping to dairy cows two years ago, the virus has now infected elephant seals in the Southern Hemisphere, triggering what researchers describe as an unprecedented wildlife die-off.

A new study led by Dr. Ralph Vanstreels of the University of California, Davis, found catastrophic losses among southern elephant seals. Roughly half of the adult females have disappeared, and an estimated 95% of their pups — about 17,000 animals — died within a single month.

"I've been working with mass mortalities of wildlife for over a decade now, and I have never seen anything like this," Vanstreels said. "I have never read of anything this severe."

The findings have alarmed marine biologists thousands of miles away, as northern elephant seals return to breeding grounds along California's coast.

At San Simeon, near Hearst Castle, about 200 miles south of San Francisco, large colonies of elephant seals are once again gathering, prompting a critical question: Could avian flu spread to the Northern Hemisphere's seal populations?

"That's the million-dollar question," Vanstreels said.

So far, no infections have been confirmed among California's elephant seals. But experts say that may not last.

At The Marine Mammal Center in Sausalito, veterinarian Dr. Dominic Travis has been closely tracking the outbreak's spread through marine mammals.

"We know that the avian influenza in South America came from birds from North America that migrated down there," Travis said. "There's no reason it wouldn't come back. We've not yet seen anything in our elephant seals, but we don't actually know why."

Scientists say the virus's ability to mutate adds to the concern. Vanstreels noted that when the virus reached South America, it had developed new mutations that allowed it to spread efficiently among seals.

"If the same virus now spreads back to the Northern Hemisphere, I would be very concerned for the seal populations there," he said.

In response, The Marine Mammal Center has begun experimental trials using a vaccine originally designed for cows to determine whether it could protect elephant seals.

"We've been asked to help see if it is both safe and efficacious, meaning it does no harm and that it works when administered to elephant seals in California," Travis said.

Avian flu has now been detected in more than 70 species of mammals worldwide. While human infections remain rare, a person infected with the virus died in Louisiana last year.

Researchers emphasize that the full scope of the outbreak among elephant seals may be far greater than current numbers suggest.

"Our sense is that we're only seeing the tip of the iceberg," Vanstreels said. "Many seals live in remote places subantarctic islands and sea ice in Antarctica, where we don't have good ways to measure the impact. But we know they're being affected. It's probably far worse than what we're seeing."