Bay Area sea lions sick with deadly bacterial disease transmissible to humans, pets

SAUSALITO, Calif, - The patient roster at Sausalito’s Marine Mammal Center ballooned to unheard-of levels in July with 100 sick sea lions suffering from the bacterial disease leptospirosis.

"This definitely has caught us by surprise, and it's an immense challenge," said Giancarlo Rulli, a spokesperson for the center. 

This time last week, the center completed 19 necropsies, all sea lions. 

Dr. Padraig Dugnan, the Marine Mammal Center's director of pathology, says scientists have known about this disease for over 50 years, but that the current outbreak is not following usual patterns.

"Right now, we are seeing an unprecedented outbreak of [the] disease very early in the season," Duignan said. "Typically it would have started late August, run through the fall and maybe finish up in the new year.  This year it started really early and seems to be peaking in July." 

Duignan isn’t sure how long the outbreak will last, but says this year is an unusual case.

KTVU visited with a group of sea lions this week. They are mostly likely on the road to recovery, but others will not be so fortunate. 

Roughly two-thirds will not survive this aggressive disease.

Why are so many sea lions getting sick?

What we know:

While no one knows the answer for sure, there is a lot of focus on a strange event that happened in the ocean over ten years ago.  That event could be a key factor leading up to today.

That event was called the warm blob in the Northern Pacific.  The blob of unusually warm water lasted for several years and peaked in 2015.  

Previous outbreaks of leptospirosis have occurred and were previously predictable, usually with a return rate of three to five years. 

There is growing concern that a new normal is emerging – that the warm water event may have disrupted normal ocean cycles.

"It reversed it from being a cold water system like we see now to being a warm water system," said Duignan. "Completely changed where the fish and the prey were moving, completely changed where the sea lions were traveling up the coast and where they were feeding."

If contracted, the disease can be harmful to humans and animals. While the spread of disease is being controlled at the center with strict measures in place, a sick sea lion interacting with a curious dog at the beach can be fatal.

"I didn’t realize, if your dog interacts with a dead sea lion, they might potentially get sick," said Nathalie Kaemp, who was walking her dog at the beach.

Leptospirosis can be fatal to your pet, according to the Marine Mammal Center.

The center is sounding the alarm for beach-goers and their pets. While vaccines are available from local veterinarians, these simple steps can keep your dog safe.

"Keep your dogs leashed on the beach and maintain a safe distance of 150 feet," said Rulli. "If you think you see a marine mammal in distress, don’t intervene, keep that distance and give the experts a call so we can make an informed evaluation."

The outbreak continues to roar into the month of August and at this point, experts don’t know when this disease will be in the rear-view mirror.   

The new normal in the marine environment could be redefined in the coming years based on what is happening right now.