A deadly bacteria is threatening marine animals along Santa Cruz County’s coast

A deadly bacterial infection is increasingly threatening marine mammals along California’s Central Coast, including Santa Cruz County, scientists and wildlife experts say.

At least three dead sea lions have washed up near Seascape and Beer Can beaches in Aptos in recent weeks. The advanced state of decay of the sea lions prevented experts from doing tests that could determine the cause of death. However, researchers have been seeing a recent uptick in cases of leptospirosis in other live marine mammals – particularly sea lions, said Giancarlo Rulli, spokesperson for the Marine Mammal Center in Sausalito. The center responds to reports of sea life in distress along a 600-mile stretch of the California coast, including Santa Cruz County. 

Leptospirosis is a type of bacterial blood infection that causes a range of illnesses in animals and humans, from flu-like symptoms to organ failure. Without treatment, it can lead to death in animals.

Finding dead marine mammals washed ashore during this season isn’t unusual, according to the Ornithology and Mammalogy Department at the California Academy of Sciences. Often, strong winds cary animal carcasses from all across Monterey Bay onto local beaches. 

Deaths typically peak during summer months, with July recording some of the highest mortality rates, said Juli Limon, stranding coordinator and lab manager with the UC Santa Cruz Long Marine Lab’s Marine Mammal Stranding Network. The network is part of a nationally established group of volunteers who respond when dead seals, sea lions, whales, dolphins and porpoises wash up along beaches.

But the spread and proliferation of diseases among marine mammals have become increasingly difficult to predict. Previously, the California coast would see a rise in leptospirosis cases every three to five years. But now researchers are seeing them every year as climate change and rising ocean acidity levels have changed the ocean landscape, Rulli said.

Santa Cruz and Monterey counties historically account for 40 to 45% of the center’s responses to cases within its 600-mile authorized rescue area along the California coastline. This is not unexpected, Rulli said, since Monterey Bay and the Central Coast are home to a diverse and large number of marine wildlife.

It’s become a challenge to treat these animals, Rulli said, as many arrive at the shore already severely ill. The center transports very sick animals to its hospital in Sausalito, where researchers collaborate with other scientists, including teams from UCLA, to understand how these diseases spread and to identify early warning signs.

Beachgoers can spot possible signs of infected animals by watching for specific behaviors, such as sea lions with their front or back flippers tightly tucked up around their abdomen, or seeking out drinking water.

It’s incredibly important to exercise caution when encountering sick or dead marine life on the beach, Rulli said, as leptospirosis can be transmitted to humans and pets through contact with the urine of an infected animal. The disease can be deadly for dogs, so humans and pets should always maintain a safe distance of 150 feet from wildlife. Dog owners can also protect their pets through vaccination, available through local veterinarians.

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What happens when dead marine animals wash up on Santa Cruz County beaches?

The process of responding to a dead animal begins with a report from the person on the beach, typically via email, phone call or text, Limon said.

A stranding coordinator will then attempt to gather as much information as possible about the case, including the size of the animal, its location and the name of the beach, and if possible pictures to help identify the species.

After gathering this information, a lab technician or volunteer will respond to the stranding. Limon said response teams vary in size depending on the animal and the individuals available, but at least one person will respond to every case.

Response teams examine the marine mammal carcasses on the beach. If the animal is recently deceased and the resources are available, it is usually brought in for an animal autopsy, otherwise known as a necropsy.

If a necropsy isn’t necessary, response teams will alert the authorities who manage a particular beach. The procedures vary from beach to beach, Limon said. The Long Marine Labs Stranding Network will also mark the dead animal with a biodegradable twine bow on a flipper. In general, a sea lion will be marked on one of the front flippers and a seal on a back flipper, though it can vary case by case depending on the level of decay of the carcass.

Smaller dolphins and porpoises are treated in the same way as seals or sea lions. The network will attempt to collect these animals and bring them in for necropsy because it’s much less common for these types of animals to wash up dead on beaches, Limon said. 

Response teams collect a wide array of data, such as species, sex, age and whether there was a possible human cause or interference with the death. All their findings are then recorded and are available to the public through the National Oceanic and Atmospheric Administration (NOAA) regional stranding coordinator. NOAA personnel are also working on changing the website to make data more publicly available.

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