Parasite is killing sea otters
Unusual strain of Toxoplasma gondii could infect humans, scientists warn.
Four sea otters that washed ashore on the California coast died from an unusual parasite that scientists warn could possibly infect other marine wildlife and humans.
There are currently no known infections of the Toxoplasma gondii strain among humans, according to a study published Wednesday from the California Department of Fish and Wildlife and UC Davis.
But the microscopic parasite could infect any warmblooded animal or find its way into the food chain, the study said. That includes marine animals such as mussels, clams, oysters and crabs that are consumed raw or undercooked, corresponding study author Melissa Miller with the Department of Fish and Wildlife said in a statement.
“I have studied Toxoplasma infections in sea otters for 25 years, and I have never seen such severe lesions or high parasite numbers,” Miller said of the dead otters.
Otters are especially susceptible to Toxoplasma infection, researchers said, because they find food along the shoreline and could be exposed to the parasite’s eggs in rainwater runoff as they feed on marine invertebrates.
Typically, the parasite is found in wild and domestic cats and shed through their feces, according to the study authors.
The first otter washed ashore in San Simeon in San Luis Obispo County in February 2020, according to the study. The adult female otter was still alive but thin and unresponsive. The other three otters washed ashore already dead from February through March 2022 in Cayucos in San Luis Obispo County and in Natural Bridges State Beach in Santa Cruz County, researchers said.
All four otters showed obvious signs of inflammation in their body fat, Miller said, and under the microscope, their tissue was flush with parasites, including fastergrowing and actively multiplying invasive cells.
Otherwise the otters were healthy adults that had no other severe disease, according to the study.
Study author Dr. Karen Shapiro with the UC Davis School of Veterinary Medicine said it was surprising to find the parasite in otters because it’d never been recorded in their species.
“So, finding this type [of Toxoplasma] in the marine environment was very unexpected, and particularly concerning,” Shapiro said in an email.
In humans, the parasite can cause miscarriages and neurological disease, the study said.
The type of inf lammation of the fat associated with toxoplasmosis has been reported in Hawaiian monk seals, according to Dr. Devinn Sinnott, a PhD student at the UC Davis School of Veterinary Medicine. That strain has not been determined yet and is being researched in the UC Davis lab, Sinnott said in an email.
“We still have much to learn,” Sinnott said in a statement that accompanied the study.