A Feline Disease Threatens California's Kelp Keepers

Chris Dixon: Christine, when did the state start noticing that otter populations weren't increasing as they should be?

Christine Kreuder: The United States Geologic Survey was doing abundance data and they noticed in 1995 that the populations weren't increasing as expected.

I was studying wildlife epidemiology and, so I started an otter project with the University of California at Davis to determine what was happening. In the end, there were eight authors and coauthors.

CD: What were the things that you found out?

CK: Well, we know that they're dying of Toxoplasma. That's a major cause. But basically there are three parasites that are responsible for 40 percent of otter mortality. One is called the thorny headed worm. They get exposed to that by eating spiny mole crabs that live in sandy areas. That parasite is found in sea birds and crabs. When otters eat the crabs, they get the parasite.

CD: What does that parasite do to the otters?

CK: It develops in the gut, but then migrates outside of the intestines. It gets into the otter's abdominal cavity and drags all the food particles and bacteria into the body cavity. If that happens, the animals die of an awful infection. That parasite alone is responsible for sixteen percent of animal mortality.

CD: Does it affect all otters?

CK: Well, that worm parasite is typically affecting young otters. Because those crabs are easy food, so the young otters tend to go after these crabs when first learning to forage on their own.

CD: Is that unusual -- to have 16 percent of otter deaths from one cause?

CK: Yeah, 16 percent mortality is a lot to have from any one type of disease.

CD: What about this disease, Toxoplasma?

CK: Toxo kills another 16 percent of otters. It causes terrible brain infections.