Cancer Plagues California Sea Lions, With Implications for Humans

A virus-linked cancer killing California sea lions is sounding a chilling alarm for mankind.

Exposure to environmental toxins significantly boosts risk for the herpes-like cancer, which was discovered in sea lions in 1979.

Since then, between 18% and 23% of adult sea lions admitted to a California animal rescue-and-research center have died of the disease. That’s the highest rate for a single type of cancer in any mammal, including humans, the researchers said.

“The decades of research looking into this deadly disease clearly shows the ocean environment we all share is in trouble, and that we need to find solutions to protect our collective health,” said study co-author Pádraig Duignan, chief pathologist at The Marine Mammal Center in Sausalito, Calif.

The study — based on more than 20 years of research and examination of nearly 400 California sea lions — was recently published in the journal Frontiers in Marine Science.

The researchers said more must be done to stop ecosystem pollution in order to prevent virus-caused cancer in both wildlife and humans.

The study found that the blubber of California sea lions has among the highest levels of some organic pollutants found in any marine mammal.

“Even though some of the pollutants we’re finding in the blubber have been out of use for years, these cancer-causing elements remain in the environment for a very long time and wreak havoc on opportunistic coastal feeders like sea lions,” Duignan said.

He pointed out that people eat similar seafood to that in the sea lions’ diet.

“The ocean is raising a loud and clear alarm in the sick bodies of a sentinel species,” Duignan said. “We need to continue this critical research and collaborate with the human cancer doctors to find patterns to help discover the link between sea lions and ourselves.”

The animals’ own genetic makeup was not a significant factor to developing the cancer, the study authors said.

Lead author Frances Gulland, who worked at the center for 25 years, said there is more to be learned about the complex causes of this cancer.

“What we learn from these animals contributes to research that underpins the threat to human health from pollutants in the ocean,” Gulland said in a center news release.

More information

The U.S. National Cancer Institute has more on cancer-causing substances in the environment.

SOURCE: Marine Mammal Center, news release, Feb. 2, 2021