Rare Parasite Kills California Otters and Threatens Human Transmission

Rare Parasite Kills California Otters and Threatens Human Transmission

Researchers warn that a rare variant of the parasite Toxoplasma gondii may be dangerous to humans after toxoplasmosis caused the deaths of 4 sea otters in California.

The peculiar Toxoplasma gondii strain that was under study has never been found in California previously.

California Department of Fish and Wildlife and the University of California researchers published their findings in the journal Frontiers in Marine Science.

Between 2020 and 2022, the sea otters used in the study became stranded on the California coast.

According to the study, toxoplasmosis cases were extremely severe, and high numbers of parasites were discovered on the bodies of the otters, with the exception of the brains.

Researchers worry that the strain might contaminate the marine ecology, endangering people’s health.

Although the strain has not yet been linked to people, according to UC Davis researchers, they nonetheless felt the need to alert the public to their discoveries.

Melissa Miller, who works for the California Department of Fish and Wildlife, says that “Because this parasite is able to infect humans and other animals, we want people to be aware of our findings, recognize cases quickly if they encounter them and take precautions to prevent infection. Since Toxoplasmacan infect any warm blooded animal, it may also potentially cause disease in animals and humans sharing the same environment or food resources, including clams, oysters, and crabs consumed raw or undercooked.”

Miller said that in her 25 years of research on toxoplasma infections in sea otters, she had never seen such high parasite densities or severe lesions.

The Toxoplasma parasite is carried by nearly 40 million people in the United States, but their immune systems often stop it from producing disease or any significant symptoms.

To hopefully prevent contracting this dangerous parasite, the CDC has advised cooking meat to the proper internal temperatures as well as washing vegetables thoroughly.


Katherine is just getting her start as a journalist. She attended a technical school while still in high school where she learned a variety of skills, from photography to nutrition. Her enthusiasm for both natural and human sciences is real so she particularly enjoys covering topics on medicine and the environment.

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