A Feline Disease Threatens California's Kelp Keepers
CD: Are a lot of otters exposed to that disease?
CK: Yeah, a lot. But most of the mortality from the disease came from the Estero Bay area in Morro Bay. Half the otters in that area died of Toxoplasmosis -- that's the name of the infection caused by Toxoplasma. The cluster of mortality in that area from one cause is really concerning.
CD: And you think the disease is caused by outdoor cats?
CK: Cats are the host of the disease. They're the only animal that excretes Toxoplasma in their feces. But how the disease is actually getting into the ocean environment remains a mystery. A lot of work is being done now to explore the routes of exposure in otters.
Usually, Toxoplasma is a normally a terrestrial animal parasite, but it's in the marine environment that it's killing such a high proportion of otters. We call that pathogen pollution.
It makes us wonder about how it spreads and why it affects otters like it does. Most humans are actually exposed to Toxoplasma, but we don't get sick like otters from it. When Dr. Melissa Miller (one of Dr. Kreuder's colleagues) and Fish and Game examine these dead otters, that come in from people finding them on the beach or from or that Dr. Mike Murray had at the Monterrey Bay Aquarium. If he's got otters who die from seizures, they just have horrible brain inflammations. The animals suffer terribly.
CD: Does Toxoplasma ever affect people?
CK: It affects AIDS patients and women. It can really affect a fetus and cause major birth defects. The people who get Toxopasmosis --the actual disease caused by the parasite -- are usually immune compromised, meaning there is something that has weakened their immune system. If they do get it, the disease just multiplies like crazy.
CD: Why don't more land animals get sick from it?
CK: Well, there are land animals that get sick. Arboreal (tree dwelling) primates, and marsupials -- it's a huge problem in kangaroos. Maybe that's the situation with otters. When they were evolving, they weren't geared up immunologically to deal with this pathogen.
CD: I heard that this disease might come from sewage -- as in cat litter that is dumped into toilets.
RELATED STORIES
|
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.