This story is original appeared in Watchman which is part of Climate office cooperation.
Scientist Melissa Miller was seeing something in California sea otters she hadn’t seen before: an unusually severe form of toxoplasmosis, which officials confirmed had killed at least four of the animals.
“We wanted to get the word out. We’re seeing something we haven’t seen before, and we want people to know about it and we want people working on marine mammals to be aware of these strange findings,” said Miller, a wildlife veterinarian with the California Department of Fish and Fish. Wildlife (DFW) “Take Extra Precautions.”
In March, a study from DFW and the University of California, Davis, revealed that a rare strain of the parasite, not previously reported in aquatic animals, was linked to the deaths of four sea otters. The subspecies, which was first seen in Canadian mountain lions in 1995, had not previously been detected on the California coast.
“This was a complete surprise,” Karen Shapiro of the University of California, Davis School of Veterinary Medicine said in a statement. “The COUG (toxoplasma strain) genotype has not been previously described in sea otters, nor anywhere in the California coastal environment or in any other mammal or waterfowl.”
The extent of the threat to California sea otters is not yet clear, the study authors said, but the parasite is concerning, due to the effects it could have on populations of threatened species as well as risks to other animals. It can pose a public health risk if it pollutes the environment and the marine food chain, according to an announcement from the University of California, Davis. The parasite can also infect humans.
Miller said scientists are looking at a few other cases that could be linked to the strain, but they won’t know if there is a link until further analysis is completed.
The first case dates back to 2020, she said, and the others appeared in 2022. The otters all seemed to have severe inflammation in the fat all over their bodies, something Miller had never seen before. I noticed large numbers of parasites all over their bodies, except for their brains. Usually, in fatal cases, she would see more of the parasite in the brain.
“It led me to believe that these animals died very quickly,” Miller said. This strain of the parasite, she said, “was behaving in a lot of different ways than we’ve seen before.”
Scientists at the University of California, Davis determined that all four otters are infected with the same strain of the parasite, which the team had previously found in mountain lions.
Toxoplasma is often found in cat feces. Otters, which live along the shoreline, can become exposed to the parasite in rainwater runoff — all four cases the scientists studied came during a heavy rainy season.
Toxoplasmosis infections are common in sea otters — which have about a 60 percent chance of becoming infected in their lifetime, Miller said — and can be fatal, but this strain is of particular concern.
However, Miller cautioned against unfairly demonizing cats.
“I don’t want this to be a war on cats,” she said. “I have two cats. What I try to do is practice what I preach and what I know as a scientist: I keep my cats indoors at all times and make sure they get their waste in something that won’t leak into the environment.”