Toxin Triggers Epilepsy In Sea Lions And Humans

Just one exposure to the algal toxin domoic acid can trigger epilepsy in sea lions and humans. NOAA scientist John Ramsdell discusses the one known human case of epilepsy from domoic acid poisoning, and what scientists can learn from similar cases of epilepsy in sea lions.

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IRA FLATOW, host:

You're listening to TALK OF THE NATION SCIENCE FRIDAY from NPR. I'm Ira Flatow.

You know, it's not unusual to hear that people can get sick by eating shellfish. Maybe you've done that yourself, but there are a couple of famous incidents, and one in particular in Canada in 1987, when over 100 people got sick eating some bad mussels harvested off the coast of Prince Edward Island.

Their symptoms were by and large what you'd imagine seafood poisoning to be. You know, it's got that abdominal cramping stuff and all the stuff that goes along with it. But in this case, some symptoms were not what you might expect, like short-term memory loss, seizures, and one elderly man recovered from the poisoning was diagnosed a year later with temporal lobe epilepsy.

Now fast-forward a decade. In the late 1990s, wildlife biologists started spotting sea lions on the coast having seizures also. And then later it started to look like some had developed epilepsy themselves, the sea lions.

So was it something in the water? Did the sea lions have something in common with those seafood swallowers?

Well, my next guest has been one of the detectives, so to speak, trying to figure out this mystery of epilepsy from the ocean. John Ramsdell is chief of the Harmful Algal Bloom and Analytical Response branch Of NOAA's National Ocean Service in Charleston, South Carolina, and he's with here today in the program. Thank you for being with us today.

Mr.�JOHN RAMSDELL (National Oceanic and Atmospheric Administration): Thank you, Ira.

FLATOW: This is weird-sounding. Was it unusual, that unusual to you, John, about what happened?

Mr.�RAMSDELL: Yes, indeed. You know, harmful algal blooms and the toxins they produce have always been seen largely as causing poisoning. You know, either a person or animal gets very sick, as you described, or in terrible situations they die, but then it's pretty much gone. And the fact that actually poisoning can translate into a disease, which is a long-term process, is indeed surprising.

FLATOW: And how did you give us the you're the detective working on this. Tell us how you tracked down what was going on here. How did you discover what the cause was?

Mr. RAMSDELL: Well, actually the tracking actually was done by wildlife biologists out of the Marine Mammal Center in Sausalito, and what they had done is, you know, over the last decade there have been probably about eight major events that had led to poisoning of sea lions. Sea lions are a great sentinel for many other animals that are affected as well, we believe.

And what they found was about, you know, three-quarters of the animals that strand corresponded to harmful algal bloom events.

FLATOW: What is a harmful algal bloom event?

Mr.�RAMSDELL: Okay, harmful algal bloom is a microscopic algae that, you know, grows and it concentrates, and they're harmful because, you know, they can, as you mentioned, poison seafood. They can poison animals, and they cause a mess of our environment. So that's why we call them harmful.

FLATOW: And so sea lions - sicknesses was associated when one of these algal blooms would happen.

Mr.�RAMSDELL: Yeah, absolutely, and what the wildlife biologists noted, that over time that about, you know, 20 percent of these animals that were stranding were stranding when there's no bloom present.

That was kind of odd, and you know, we would measure the urine or the fecal matter from the animals and show, hey, wait a minute, there's no domoic acid there. That's kind of strange.

The other thing they noticed was that these animals that were stranding when there were not blooms, the number that was stranding was increasing over time. And so what they did is they looked more carefully at the symptoms, and they saw the symptoms differed a little bit too.

They found that the animals that, you know, were associated with the blooms sort of had an acute poisoning. They showed seizures and they had damage to the brain that was kind of limited to a region called the hippocampus, whereas the animals that were stranding outside the blooms showed recurrent, spontaneous seizures, meaning that the seizures would happen spontaneously well after the poisoning event.

These animals also showed a lot of unusual behaviors. They would strand in atypical places, and they many times were much more aggressive, and they had more extensive brain damage.

And so they proposed that there are two effects here. One is an acute poisoning, and one is a chronic, neurologic disease, and knowing that single human case study that you mentioned, Ira, it suggested that maybe this was, indeed, epilepsy.

FLATOW: So the sea lions were getting epilepsy.

Mr.�RAMSDELL: Well, that was the thought, but of course, you know, it was because it was so long after the bloom event, we couldn't show that the animals actually were poisoned, and so scientists for some time had tried to see whether or not domoic acid, the toxin, would actually, you know, lead to...

FLATOW: And that's what's produced by the algal blooms, domoic acid?

Mr.�RAMSDELL: Yes, absolutely. Domoic acid is the toxin, is a modified form of glutamate, which is an amino-acid building block and also a neurotransmitter, it excites brain cells.

FLATOW: And so they found that the domoic acid would cause the epilepsy, even though the bloom was gone? It would retain the nerve damage for, what, months, days, years later?

Mr.�RAMSDELL: Well, you know, the epilepsy would appear, you know, months later, and it was interesting in that regard. It wasn't clear that it was necessarily domoic acid. The evidence sort of suggests that, but the issue was that previous research had tried to determine that domoic acid in experimental animals would lead to epilepsy, and it found that it did not.

And the case was pretty much forgotten until the sea lions starting beaching again and seemed to have epilepsy, and that's why we tried to revisit it with a different model to study it.

FLATOW: So do you actually know now that it was domoic acid that was causing...

Mr.�RAMSDELL: Yes.

FLATOW: Yes. And does that mean that anything that's in the ocean where these algal blooms are happening, that swimming in a sea of domoic acid - could it be dolphins, whales, other things that suck up the water besides the sea lions?

Mr.�RAMSDELL: Well, yes, in a sense, but it's not swimming with the domoic acid in the water. The domoic acid needs to be concentrated, and that's the real key.

You know, in the case of the human poisoning, the shellfish were concentrated, but out on the California coast there is another (unintelligible) that concentrates it even more, and these are small fish. These are anchovies, and these anchovies act like little vacuum cleaners out there. They just, you know, vacuum up all the toxic algae.

And the other thing of interest is that these anchovies have very, very dense schools of fish, and so it's not like a fish, you know, a sea lion or a dolphin or whale going up and chewing on one or more of these. This is a feeding frenzy, and you know, NOAA observers out there will note that, you know, there might be, you know, several whales, and there might be 100 sea lions, and there might be 100 dolphins of different varieties, there might be 1,000 sea birds out there.

And so they're getting this just concentrated amount of toxin that's being accumulated by these anchovies.

FLATOW: So just to make sure, if people are swimming in the ocean, they're not eating the anchovies and getting the domoic acid?

Mr.�RAMSDELL: Right, and so the risk to swimming in the ocean is really quite minimal.

FLATOW: But if you're eating the seafood that has the domoic acid in it, that's another story.

Mr.�RAMSDELL: That's another story.

FLATOW: And that's the connection between the human, this one case can we say just because it's just one case that it really could apply to other people?

Mr.�RAMSDELL: Well, again, it's a little difference between, you know, the risk for human versus the risk for dolphin, whale or sea lion. The mussels can accumulate the toxin, but they don't accumulate the toxin quite like the anchovies. The anchovies are much more efficient.

And also, you know, a human can eat a plate of mussels, and you know, that's nothing compared to what, you know, one of these magnificent animals is chowing down on in the ocean with these feeding frenzies.

FLATOW: But do we test for it? I mean, do people test the domoic acid in seafood?

Mr.�RAMSDELL: Absolutely, and you know, ever since that incident in Montreal, in Canada, there's been very extensive testing, and the testing in California is phenomenal, in Washington it's phenomenal, and many areas throughout the U.S.

FLATOW: And there's a strange twist to all this, is there not, about domoic acid was actually used as a medicine in Japan at one point.

Mr.�RAMSDELL: Yes, that's an interesting story. Actually, the Ryukyu Islands, which is a chain of islands that goes south of Japan, goes all the way to Taiwan, the native folks there for a long time had known about the use of domoic acid, not knowing it's domoic acid, but there it's found in a seaweed.

And one of the northerly islands noted that when the seaweed died on the beach and flies landed on it, the flies died almost immediately on contact. Domoic acid is a very strong insecticide, stronger than DDT, for that matter.

FLATOW: Wow, no kidding.

Mr.�RAMSDELL: And then a group down on another island down, called Tokashikijima(ph), actually used this as a tea to treat their children for intestinal worms, and it's been used for a long time that way, all the way past World War II, for that matter.

FLATOW: So how can you further the study, the connection, learning more about epilepsy then, from studying these cases?

Mr.�RAMSDELL: Oh, there's a tremendous amount to know. One is learning about the behavior of the animals. You know, so much attention in disease oftentimes is given to the end point of the disease, you know, and but there's much more to it, the progression of the disease and what's happening. And these are important both for human health as well for understanding animal health.

You know, the sea lions, for example, we know have very unusual behaviors. You know, the strand in atypical places. They have been found 100 miles upland in an artichoke fields. They've been found in a car dealership. They're found on highways.

FLATOW: Well, you know, I'm just getting this thought. We see whales beaching themselves all over the place for strange reasons. Could this be part of the reason why they're doing this?

Mr.�RAMSDELL: Well, it could be, but it's I don't think the data really points to that quite yet. Whales and dolphins are a little bit of a different story because wildlife biologists are really not sure that they actually will survive the domoic acid seizures out in the ocean to really become epileptic.

The sea lions are maybe a little more of a special case because, you know, they're just as happy on land as they are in the ocean. They get up on the beach, and they go to the clinical facilities, and they can be helped out.

FLATOW: So there are sea lions - are out there now, could be hundreds of thousands of them with epilepsy?

Mr.�RAMSDELL: Well, there could be. I think the numbers are you know, at least from what the clinicians have found, are in the hundreds right now. For example, in the study where they examined 715 animals that were clinically diagnosed as being poisoned by domoic acid, I saw about 20 percent, or about 155. So maybe tens of thousands might be a high number.

FLATOW: Yeah, but can you look at a sea lion and say that it's been poisoned, or it's suffered from epilepsy?

Mr.�RAMSDELL: Yeah, the clinicians definitely can.

FLATOW: But you can't if I'm going out to the harbor someplace, I can't, myself as a layperson, tell?

Mr.�RAMSDELL: Well...

FLATOW: Maybe I can, you're saying?

Mr.�RAMSDELL: Maybe if it's chasing you up the beach, you might. I don't know.

(Soundbite of laughter)

FLATOW: That's a symptom? In other words, an erratic behavior that you're not expecting of a sea lion. You know, I'm thinking, like, you can tell a rabid animal it's doing things it shouldn't be doing at that point because of the brain damage there. So it's the same thing that's happening with a sea lion.

And is there anything is there any cure for them, or are they just going to live out their lives with this?

Mr.�RAMSDELL: You know, unfortunately, there's not a cure, and I think that's one of the difficult things in human epilepsy as well. You know, the type of epilepsy that's in the sea lions probably translates a little more closely to what happens in early childhood with fevers, and these (unintelligible) seizures and then, you know, later on it develops into temporal lobe epilepsy.

And I think the research there has shown that, you know, even though many of the drugs are, you know, can stop the acute-term seizures, they don't work so great in terms of stopping the prognosis to the disease. And so I think the prognosis for, you know, stopping the development of epilepsy in a sea lion at this point in time is not so good.

But I think on the other side of the coin, what this does do is it tells wildlife managers more what their options are. For example, before our research, the question was, you know: Are sea lions getting this epilepsy because of repeated poisonings, because now we have more and more harmful algal blooms?

But what we can see in the rats that, you know, 94 percent of the animals will develop epilepsy within six months, you know, if they've had a single bout of seizures.

So at least we can say no, it's not the repeated poisoning. If an animal comes in and...

FLATOW: It could be just one, yeah. I have to (unintelligible) so we have to take a break. I want to thank you for that was really informative. I don't think most of us have ever heard about that.

John Ramsdell, chief of Harmful Algal Bloom and Analytical Response branch of NOAA National Ocean Service in Charleston. Thanks for being with us today.

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