A Feline Disease Threatens California's Kelp Keepers
CK: Well, with sewage, they do make an effort to dump it a mile or more offshore. But how much of it comes back is not known.
But an outdoor cat who has this parasite just sheds millions and millions of these Toxo eggs. One cat pooping along a creek bed near the shore could really infect the area. That's why, for example, we want to see what feral and outdoor cats are doing. Feral cats just love to live along the coastline. People feed them.
CD: How is it exactly that sea otters are getting this disease from cat crap?
CK:
There's some work being done at UC Davis on that now -- to figure out
that marine cycle. Are the eggs getting collected somewhere, like in filter
feeding shellfish, and is that allowing otters to ingest them?
CD: Are
there other parasites that otters are contracting?
CK: Well, to complicate things further, there's one called Sarcocystis
neurona. It's a protozoa like Toxoplasma. But this one is found in Virginia
opossums, which like cats, are an introduced species here. They've been
increasing in population, and they shed Sarcocystis, which gets into otters
and also causes a massive brain infection. We found that seven percent
of otter deaths were caused by this. That's a new finding.
So those are two protozoal pathogens that are supposed to be on land, but they've ended up in the ocean somehow. They're definitely killing otters. Work is being done now to see if they may be killing other marine species.
After this female otter lost her pup, she treated this
Rolling Rock bottle like
a youngster, and carried it around with her for several days.
Photo: Stan Foster, Pacific Images (831) 724-8666
And then on top of that, we've been finding otters that have been attacked by sharks. Usually, sharks hang at rookeries and just pick off elephant seal pups. But they're getting otters too. We've been finding otters that have big slashes taken out of them. And the thing is, the otters we've found attacked by sharks are three times as likely to have toxo. What we think is that the parasite alters their behavior enough that maybe they're not able to evade sharks. Or maybe they're drawing attention to themselves because they're having seizures. Or maybe they swim offshore because they don't know what they're doing.
CD: It sounds pretty grim.
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READER COMMENTS
Tue Jan27, 2009, 9:49 AM
What they are not telling you is that over 20% of people are infected with brain-worms (that's what Toxoplasmosis is called); cat feces dumped into sewage remain infective even in the Ocean for a year; and when a surfer ingests seawater (or an otter eats a clam) containing the oocytes (eggs) the brain-worms hatch, migrate through the walls of the intestine, and infest the brain, muscles and eyes. The immune system usually contains them, so they "encyst" and can remain dormant for the rest of the infested person's life. But they do have effects on behaviour; for example, mice infested with brain-worms tend to lose their fear of cats, making them easier to catch and also re-infesting the cat. Cats are the only species in which the brain-worms are excreted in oocyte form; in the encysted form, you can get it from eating uncooked meat. Since all sewage discharges come back to shore (if you don't believe this, imagine if they put dye in the sewage), every swimmer is at risk.