Parasite killing California sea otters, could pose threat to humans

March 27, 2023

A baby sea otter


A rare strain of a parasite has killed four sea otters in California, and researchers warn it could pose a threat to humans, too. [New York Post]

Scientists from the California Department of Fish and Wildlife (CDFW) and UC Davis conducted a study on four sea otters that were stranded on California’s coast between 2020 and 2022. The study found the sea otters died from toxoplasmosis, resulting from a rare strain of the Toxoplasma gondii parasite.

The toxoplasmosis cases were particularly bad, with there being high numbers of parasites all over the otters’ bodies, except for their brains. 

UC Davis researchers say the Toxoplasma gondii strain can infect humans, but there have yet to be any reported cases. Researchers are concerned about the strain contaminating the marine ecosystem, which could pose a public health risk. 

Melissa Miller, of CDFW, said she has studied Toxoplasma infections in sea otters for 25 years, but had never before observed such high parasite numbers or severe legions.

“Since Toxoplasma can infect any warm-blooded animal, it could also potentially cause disease in animals and humans that share the same environment or food resources, including mussels, clams, oysters, and crabs that are consumed raw or undercooked,” Miller said.

More than 40 million Americans carry the Toxoplasma parasite, but their immune systems typically prevent the parasite from causing illness or adverse symptoms, according to the Centers for Disease Control and Prevention.