California sea lions face 'unprecedented rate of cancer'



When a female adult sea lion came ashore in San Luis Obispo County in central California recently, responders immediately knew something wasn’t right.

She was thin and underweight, swayed her head back and forth, and did not flee as people approached, said Dr. Cara Field, medical director at the Marine Mammal Center in Sausalito.

Once the sea lion was sedated and intubated in a quarantine cell on the center’s grounds for an ultrasound, more worrying signs appeared.

The sea lion inspected on this day was euthanized, a common ending for California sea lions brought here for what has become a frequent and untreatable diagnosis - urogenital carcinoma.

It has wreaked havoc on these marine mammals.

According to a study published in December in Frontiers in Marine Science, almost 25% of adult California sea lions end up with this cancer, the highest prevalence of cancer in any mammal, including humans.

The study found two leading culprits behind the high cancer rates - long-banned chemical pesticides such as DDTs and polychlorinated biphenyls (PCBs) found in the sea lions’ blubber tissue, and the presence of a cancer-causing herpes virus known as Otarine herpes virus (OtHV-1).

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