Significant cancer rates in California sea lions have major human health implications

Significant cancer rates in California sea lions has major human health implications
The Marine Mammal Center's Chief Pathologist Dr. Padráig Duignan (right) and Pathology Fellow Dr. Maggie Martinez (left) make initial surgical cuts during a necropsy, or animal autopsy, on a diseased California sea lion that was humanely euthanized due to untreatable cancer. Credit: Bill Hunnewell/The Marine Mammal Center

Scientists at The Marine Mammal Center—the world's largest marine mammal hospital—have found that viral-caused cancer in adult California sea lions is significantly increased by their exposure to toxins in the environment. The study is the result of over 20 years of research and examination of nearly 400 California sea lion patients by The Marine Mammal Center.

The Marine Mammal Center has been on the forefront of researching and understanding in California sea lions and its connection to both ocean and human health. Since the cancer in sea lions was first discovered in 1979, between 18-23 percent of adult sea lions admitted to the Center's hospital have died of the fatal disease—the highest prevalence for a single type of cancer in any , including humans.

The study, which was published in Frontiers in Marine Science, a peer-reviewed research journal, concluded that efforts to prevent ecosystem contamination with pollutants must improve in order to prevent virally caused cancer development in both wildlife and humans.

"This paper's conclusions mark a significant milestone in piecing together the complicated puzzle of cancer development in California sea lions," said Dr. Pádraig Duignan, Chief Pathologist at The Marine Mammal Center and co-author of the study. "The decades of research looking into this clearly shows the ocean environment we all share is in trouble and that we need to find solutions to protect our collective health."

The findings also show that California sea lions have among the highest levels of certain persistent organic pollutants in the blubber of any marine mammals—a disturbing report that is cause for concern for scientists across the globe.

"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," said Dr. Duignan. "It concerns me knowing that we consume very similar seafood as these cancer victims and that the ocean is raising a loud and clear alarm in the sick bodies of a sentinel species. 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."

Previously, researchers at The Marine Mammal Center determined that these sea lions are infected with a herpesvirus similar to one that causes Kaposi's sarcoma (a viral cancer) in humans. In this newly released study, scientists used complex statistical analysis and modeling to investigate the relative roles of the various factors in the development of fatal metastatic cancer. The results showed that the damage of the DNA in sea lions occurs due to a number of factors, including: the interaction of many environmental factors, including chemical contaminants and pollutants; and infections by tumor-promoting viruses like Otarine herpesvirus-1.

Additionally, their findings found that the animals' own genetic predisposition was not a significant factor to developing the cancer.

"While there is more to be learned about the complex factors that play into the development of this disease, what we learn from these animals contributes to research that underpins the threat to from pollutants in the ocean," said Dr. Frances M. D. Gulland, the lead author of the study who worked at The Marine Mammal Center for 25 years.


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More information: Frances M. D. Gulland et al, Persistent Contaminants and Herpesvirus OtHV1 Are Positively Associated With Cancer in Wild California Sea Lions (Zalophus californianus), Frontiers in Marine Science (2020). DOI: 10.3389/fmars.2020.602565
Provided by The Marine Mammal Center
Citation: Significant cancer rates in California sea lions have major human health implications (2021, February 2) retrieved 21 April 2021 from https://phys.org/news/2021-02-significant-cancer-california-sea-lions.html
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