Science Friday - Investigating Animal Deaths At The National Zoo

Episode Date: April 11, 2024

When a critter meets its end at the Smithsonian’s National Zoo, it ends up on a necropsy table—where one of the zoo’s veterinary pathologists will take a very close look at it, in what is the animal version of an autopsy. They’ll poke and prod, searching for clues about the animal’s health. What they do—or don’t—find can be used to improve the care of living animals, both in the zoo and in the wild.On stage in Washington, D.C., Ira talks with Dr. Kali Holder, veterinary pathologist at the Smithsonian’s National Zoo and Conservation Biology Institute, about her work, and they embark on a case of CSI: Zoo.Transcripts for each segment will be available the week after the show airs on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

What happens when an animal at the National Zoo in Washington, D.C. dies? For me, this is a great opportunity to just dig in. It's the last chance we have to get the most information out of these animals about their health status so that we can improve what we're doing, but also affect animals for conservation purposes. It's Thursday, April 11th, and you're listening to Science Friday. I'm SciFri producer, Rasha Iridi. When a critter meets its end at the National Zoo, it gets an animal, autopsy, where one of the zoo's veterinary pathologists will take a very close look at it.

They'll poke and prod and search for clues about the animal's health. What they do, or don't find, can be used to improve the care of living animals, both in the zoo and in the wild. Live from the George Washington University in Washington, D.C., here's Ira Flato. Here to take us on a CSI-style investigation is Callie Holder, Veterinary Pathologist. at Smithsonian's National Zoo and Conservation Biology Institute here in D.C. Welcome to Science Friday. Thank you, Ira.

It's great to be here. Pallie, our theme today is national treasures. Why are dead animals a national treasure? Besides being animals, which are awesome, I love the mystery, the puzzle of dead animals. I also do biopsies, so I do pieces of live things and whole. dead things, but no whole live things. Not that kind of vet. So I'm a veterinarian, and I work on these animals that have regrettably passed on,

but we can learn so much about not only how our care is doing, but how we can improve their care and affect animals that are in other institutions or in the wild even. So for me, this is a great opportunity to just dig in. It's the last chance we have to get the most information. out of these animals about their health status so that we can improve what we're doing, but also affect animals for conservation purposes. How many really cool cases? Can you tell me about some of the coolest cases you've had? So in the last couple of months, I've had been looking into some heart disease issues in some green tree pythons.

Heart disease? Heart disease. Yeah, in a snake. And I've been looking at some battle wounds in naked mulrats. Because cancer doesn't kill naked mole rats, naked mall rats kill naked mall rats. Take home message of this second. Yeah. I mean, we have everything from corals up to elephants in our collection.

We've got bison. We've got animals from all over the world and even aquatic animals as well. Do people send you animals that die that they want to about? So we do everything that dies on property, not just our collection, but also wildlife that dies on property. So I will sometimes get animals that are wildlife that have died on property. And for a while, we had a fishing cat that was just a really good huntress. Her name was juniper.

And so, like, I would get, like, half a bird. And they'd be like, here you go. And we do check that out because you never know why that bird might have been susceptible to being hunted by juniper. I mean, the wrong place, wrong time. But also, we're looking for things like highly pathogenic avian influenza. We survey for that. We look for West Nile, that sort of thing.

So we keep an eye on diseases that may be not just of animal importance, but also human importance. Okay. So when you're doing a necroposy, what do you actually look for? Take me through one. So I friendly, colloquially refer to it as unzipping. So I unzip the animal with a sharp object. And I'm going to be looking at every single organ. I'm going to see, okay, given a...

how long ago this animal died, and usually we know, because we look at our animals quite a lot, how bad is the decomposition? Usually it's pretty good. It's not a particularly bad decomposition. And then I'm going to look at all the different organs. I have done a lot of animals, so I know what the normal colors and textures and sights and smells even are in all of these different organs. And so I'm going to take samples of all of those organs. But if I see anything already with just my naked eye, that's called a gross examination. It's not just like, you, goes, but like, I can see it with my naked eye. I'm going to take a picture, make a note of that, and that's all going to go into my gross report.

And then I'm going to take all of the samples that I took from all of those organs, and I'm going to get them put on microscope slides, and I'm going to look at them under a microscope, and I'm going to see even more things under the microscope. And microscopy is actually beautiful, so I'm really excited that some of the pictures that we have today are photomicrographs that you're going to get to see. And we'll get to see that. First, though, I want you to tell me how you take what you learn and apply it to living animals. Right.

So this is a great story here, where you discover something has gone terribly awry with the animal, and then you figure out what the cause of that is, and it has major impacts for that species. So what has been rolled out on stage is a skull. But does anyone know what this skull? You can just yell what this skull might be from. get from? We're seeing a lot. We got whale, we've got bison coming.

Elephant. Ah, yes. So this is an elephant skull. Good job. Gold star to you. Excellent. Yes, this is an elephant skull. And if you've ever seen an elephant, it looks kind of small.

And that's because this is a baby elephant. So she was about 16 months old. She died in 1995. Her name was Kumari. and Kumari had a terrible disease that caused her to bleed a lot inside, and no one knew why. And the pathologists figured out that by looking under a microscope that they saw characteristic lesions of herpes viruses, and they hadn't recognized that that was a problem in elephants before, but it turns out this is actually what we would call like an index case.

the first recognized death to be associated with specifically a herpes virus. And herpes viruses are endemic. All of the elephants have at least one strain. Many of them have multiple strains. But it turns out that elephant endotheliotropic herpes virus, which is what she had, is the most common cause of death in juvenile Asian elephants in human care. And this was the beginning of figuring out that not only was this a really important cause of death for this species, but this was the beginning of understanding

that we need to be able to detect this. So the National Zoo actually now has the National Elephant Herpes Virus Laboratory. They test samples from all around the country and even other places in the world. We help set up labs in range countries to help elephants in their native habitats because this virus is so important as a cause of death for baby elephants. So Kumari is kind of a celebrity in the veterinary pathology community. And most people and most animals that have herpes virus, it's not usually a big deal. But if you're a baby, it can be a big problem. Sad story. It's a sad story. Now, you see all kinds of critters. I see all kinds of critters. Including this, which is one of my favorites. This is a Sicilian.

From Sicily? No. No. So this one is from Central America. These are legless, blind, amphibians. And so if you're kind of like trying to figure out what's going on here, and you have ever seen the Princess Bride, it looks a little bit like a shrieking eel. Yeah, they're just a tube of mucus covered amphibian there. Very interesting description. Yes, thank you. And when I say a tube, so snakes have a tail. There's a mouth hole and there's anus and then there's tail after that. These guys don't. It's literally one hole at one end and one hole at the other end. They are just a tube. They're great. and they have a lot of really neat adaptations,

and they are a weird subset of amphibians, and I love them. They have teeth that literally do make them look like a shrieking meal, so that's what that looks like. Looks like alien. Yeah, yeah, I love them. So this is an adult. This is great. Why does it need all those teeth?

Because it eats a lot of like invertebrates in the water and stuff, and so it's just going around. But those teeth, they have teeth even when they're in utero, sort of in utero. So this particular type of Sicilian is a live bearer. So they have babies that are in their oviduct, kind of like having a uterus, but they don't run a real uterus because they don't have a placenta. And they're just free swimming. Like you may have heard of sharks doing this.

Cecilian, some of them do this too. So they're just free swimming in the parent, just doing their thing. and they have teeth, and they have big floppy gills. They're really adorable. And how they get their nutrition free swimming in the Overduct is that they graze on the uterine lining. Yeah, mom, nom, nom. They're just eating.

I love that. They're little body horror creatures. I love them. When you get to see this creature, it's no longer grazing. Correct, correct. By the time it comes to me, It's no longer grazing. How did they die? Can you tell?

Well, I could tell. So amphibians are super dependent on their kidneys. And so this gal's kidneys were not doing great. And that's that it was the cause of death there. You want to say a question? Yeah. All right. Let's go to this question right here.

Hi, I'm Leo. And I wanted to ask, is it like something that, like a skill you gain over time? Like when you started the job of doing something. surgery on dead animals. It's a great description. I love it. Like, did it start out as, oh, this animal died? I'm so sad. And it turned

into, oh, I wonder what I could find in this. A little bit? Yeah, no, that's a great question. How did I end up here? I've always been weird. I've always been weird, and I've always wanted to be a vet. So I am a veterinarian, but as I was coming up in the veterinary world,

I found that the puzzles were really the things that got me. So I do nothing but solve puzzles all day. And so how you end up being an anatomic pathologist, you start off kind of weird. You do vet school, and then you do three years of residency in just anatomic pathology. And then if you're extra weird, you're like,

yeah, but what if we got the weirder animals? And then you do conservation pathology, which is how I ended up at the National Zoo. So I did extra schooling and training type programs after my residency to work with the weirdest animals with the weirdest diseases so that I could take apart Sicilians and show y'all. Oh, weirdness. That's our theme today. Let's go on to another case.

Yeah, let's go to another case. This one is of the feline variety. Tell us about who this lion was. So this was Naba. She was a 19-year-old lioness, which is exactly as ancient as it sounds. Like she was very geriatric and had a wonderful long life at the zoo and was getting all kinds of supportive care for, you know, arthritis and renal insufficiency. The things that happen to old cats, right? Anybody who has an old cat, they know.

They know. So she was an old cat. And a year prior to her coming to me, she actually got COVID. And because COVID doesn't just affect humans. It can affect a variety of animals. And a lot of big cats at various different institutions got COVID. and our Big Cat House did have a COVID outbreak, and she was one of the ones affected.

And she came through beautifully. What's the symptoms for an animal? It's respiratory. So they were coughing. And that's a scary sound, by the way, if you've, just as a primate, if you are around a lion when it goes, you're like, oh, Lord, I might die. Yeah, so there was that.

And there's, you know, some snot. They get respiratory disease. Some of them were asymptomatic, just like with humans. So she came through the respiratory disease well, and six months later, she started having problems chewing. So her keepers were like, oh, it might just be dental disease. She was doing okay in terms of being able to eat, but she was eating oddly. Right. So she dies?

She dies six months after that, but also old animals were always concerned about cancer. And in her, I did actually find a tumor in her gastrointestinal tract that was causing an obstruction to bind there. So that invasion is what lets me know it's absolutely cancer. And you were saying that she sort of had a little bit of a funny movement in her face. Yeah, so she had a funny movement in her face. And this explains it? This does not explain it. No. I did not. I was like, hmm, that doesn't explain it. So we took open her skull and this is her brain. So the whole back part of her cerebrum is open. It should not be, and it probably was not that way for most of her life.

This probably happened about six months ago when she started having problems chewing. That area does a lot of the coordination for facial and trigeminal nerves and things like that that are going to help organize how you move your tongue and chew. And so her chewing being abnormal was actually a neurologic sign from this giant hole in her brain. So what happened here is the blood was obstructed and then that center part just died. She sort of had a heart attack in her brain. She had a stroke. Stroke.

This is a stroke. Yeah. So this is a stroke for sure. 100 percent, I can tell you this was a stroke. Why she had a stroke? Well, she's old. She's got kidney disease. Those are two predisposing factors.

But she also had COVID. And COVID does predispose to strokes in humans. And some of the research that has been. and done on it, the stroke size associated with, the stroke lesion size associated with COVID has been shown to be larger. And that was a huge area. That would be like a territorial infarct is how I would describe that. So she had multiple problems. Oh yeah. Oh yeah. Right? She had COVID. She had COVID. And then she had cancer and she also had renal disease. She was still doing okay on that. But the big problem was the cancer. It doesn't take a lot of brain to run a lion.

actually. Really doesn't. Or my cat, honestly, you look at him as just no thoughts-only vibes. There you have it. But yeah, she doesn't have to compete for food. And even if she had visual deficits, cats are really great at navigating places.

We have a blind cat at home, and she does great navigating. So even if she had visual deficits, the fact that she was in a familiar environment, she was doing pretty well with her quality of life. Yeah, yeah. Let's go to the audience. Question here.

So I want to be like something in forensics when I grow up or something in like surgery. And I was just wondering, like, have you ever had that moment when you're doing, I don't know, you're like daily cutting up of animals that you've like opened an animal and you've been like, oh, that should not be there. Oh, yeah, yeah, yeah. I love those. I love when I can open up an animal and it's immediately apparent what happened. This is one of my favorites.

So this is kind of a gross one. opened up a beaver and immediately the smell told me exactly what had happened. Because the beaver smelled like the inside of a horse whose stomach had ruptured. And what had happened was the beaver's stomach had also ruptured and it smelled exactly the same. I was like, oh, I know that smell. That is the smell of gastric rupture in an animal that cannot vomit. So horses and beavers both have very tight sphinxed at the top of their stomach.

So if anything starts producing gas in there, it can cause. burst. And so that beaver not only had gas-producing bacteria, but also had a bacterial infection in the wall that was weakening it, and it busted through. And I could tell by just opening it up and smelling. Yeah, that's when you know you've made it. I think we're ready for a TV show. Yeah. All right. Thank you. Thank you. Kelly Holder, veterinary pathologist at Smithsonian's National Zoo and Conservation Biology Institute here in D.C.

Lots of folks help make this show happen, including Ariel Zich. Santiago Flores. Emma Gomez. Diana Plasker. Join us tomorrow for a roundup of this week's science news.

Catch you then. I'm SciFRI producer Rasha Auredi.