Bay Area sea lions are getting sick at a very high rate this year with a disease that is transmissible to people's pets, and the disease called leptospirosis is currently transmitting among sea lions at "unheard-of" levels.

We have seen some unusual behavior with sea lions this year in the Bay Area, but we did not realize that there is a deadly disease going around among them that might have some impact on this. KTVU reports that there’s a rampant outbreak of a bacterial sea lion disease called leptospirosis this year, and that Marin County’s Marine Mammal Center housed 100 sick lions in July, and had completed a highly unusual 19 necropsies of the animals. KTVU estimates that two-thirds of these sick sea lions will not survive.

Leptospirosis is a disease that scientists have known of for more than 50 years, but they have never seen it transmitted at this level, this early in the year. "This definitely has caught us by surprise, and it's an immense challenge," Marine Mammal Center spokesperson Giancarlo Rull told KTVU.

Scientists aren’t exactly sure why this is happening, but it may all go back to a marine heatwave that happened about ten years ago in the Pacific Ocean that was known as “The Blob.” That heatwave killed off a number of plankton and food sources that many animals in the ocean systems rely on, and the effects are still being felt today.

"It reversed it from being a cold water system like we see now to being a warm water system," Marine Mammal Center's director of pathology Dr. Padraig Dugnan told KTVU. "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."

A new Chronicle piece also details how "The Blob" appears to have impacted the blue whale population in the Pacific, which still appears not to have not recovered.

Be warned that leptospirosis can also spread to dogs, and can potentially be fatal to them. Vaccines for leptospirosis are available from your veterinarian, as dogs that interact with sick or dead sea lions can contract the disease.

Dog owners are being warned this summer in particular to keep their pets leashed on the beach. And if dog owners see a marine mammal in distress, they are advised to keep a distance of at least 150 feet and not go near it.

Related: Nine-Year-Old Girl Attacked and Bitten by Sea Lion at Monterey Peninsula Beach [SFist]

Image: Kieran Wood via Unsplash