For a sea otter, a bad infection with the Toxoplasma parasite may feel a bit like drowning.
“The brain is no longer able to function and tell the body how to swim,” said Dr. Karen Shapiro, a veterinarian and pathologist at the University of California, Davis. The parasite, Toxoplasma gondii, enters the otter orally and makes its way to the brain, where it can cause swelling, weakness, seizures, disorientation and death. If the parasite doesn’t kill the otter directly, it can render it more likely to be hit by a boat or eaten by a shark. Among California sea otters, a protected species whose numbers are closely monitored, Toxoplasma infections contribute to the deaths of 8% of otters that are found dead, and is the primary cause of death in 3%.
Scientists have been working to determine where the Toxoplasma comes from and how to keep it from striking sea otters. They have long viewed one potential culprit with suspicion, and a study published last week identified the offender definitively: house cats.
“This is the ultimate proof that strains that are killing sea otters are coming from domestic cats,” said Shapiro, a lead author of the study.