Four otters on the California coast were killed by a rare and extraordinarily potent type of a parasite typically found in cat feces, a discovery that researchers described as unprecedented and potentially harmful to people and other animals on Wednesday. 

The rare strain of the parasite, known as Toxoplasma gondii, has never before been found in sea otters or any other aquatic mammal or bird, according to Karen Shapiro, an associate professor of pathology, microbiology, and immunology at the University of California, who called the early findings a “complete surprise.” 

The findings were published on Wednesday in the journal: Frontiers in Marine Science by Shapiro and three co-authors from the University and the California Department of Fish and Wildlife.

According to a press release from the Fish and Wildlife Department’s Melissa Miller-Henson, who has studied toxoplasmosis in sea otters for 25 years, she has never observed such serious lesions or large numbers of parasites. 

“To let people know about this worrying issue, we are disclosing our preliminary findings,” said Miller-Henson. “Because Toxoplasma may infect any warm-blooded animal, it may also potentially infect people or other species that share the same environment or food sources, such as mussels, clams, oysters, and crabs that are eaten raw or undercooked.”

According to the Centers for Disease Control and Prevention (CDC), toxoplasmosis usually goes undiagnosed in healthy people even though it can lead to serious illness in those with weakened immune systems, miscarriages, and other health problems in women who contract the parasite just before or during pregnancy. 

The announcement states that it is unclear how the uncommon type of toxoplasma might impact people. 

According to the report, the four southern sea otters who were the subject of the study were discovered in the counties of San Luis Obispo and Santa Cruz between February 2020 and March 2022. The scientists hypothesize that rainwater runoff may have provided the animals with the parasites.

The COUG strain of toxoplasma, which was found in their bodies, was first identified in Canadian mountain lions in 1995. Although the publication indicates that the parasite is a recent arrival, it is unclear how it got to California.