Veterinary Medicine for Fish

  • By Lexi Krock
  • Posted 10.01.05
  • NOVA scienceNOW

In this audio slide show, correspondent Rebecca Skloot describes some of the latest developments in veterinary medicine for fish, including how vets treat infectious diseases, cancer, buoyancy disorders, and even broken spines.

Launch Interactive

Learn how fish are treated for infectious diseases, cancer, buoyancy disorders, and freak accidents.


Rx for Fish

Posted: October 1, 2005

Section 1 - Infectious Disease

REBECCA SKLOOT: Hi, my name's Rebecca Skloot. I'm a freelance writer and a correspondent for NOVA scienceNOW, and I'm going to tell you a bit about fish medicine.

These are Australian rainbow fish. They're a freshwater fish. These all belong to a woman named Diana Walstad in Chapel Hill, North Carolina. It's a gorgeous tank from the outside, and these fish look very healthy and colorful, but you wouldn't want to stick your hand in the water because they all have tuberculosis.

This is the same kind of – mycobacteria is what it's called – that causes TB in people. Some of the most common problems with fish are things like bacterial infections and viruses. They get tuberculosis, they get herpes, they get rubella – all kinds of transmissible diseases that they pass on to other fish and that will kill them, usually. There's often not a treatment for this. The only thing that she can do is try and support their immune systems.

Other infectious diseases you can treat. There's drops of medicine you can add to the water, there's – you can actually give them oral antibiotics when they get bacterial infection by mixing it in with their foods. So there's things you can do to treat a lot of these, but not some of them. Herpes in fish is not treatable, and it's deadly.

Section 2 - Cancer

REBECCA SKLOOT: This fish, his name's Comet, he's a one-pound goldfish, and he has this skin tumor on his back. Fish actually get the same kinds of cancers that people get. They can get pancreatic cancer, liver cancer, skin cancer like this guy has, and he's about to go into surgery to get the tumor removed and to also to have laser surgeries. And they're also going to take a piece of the tumor and send it off for a biopsy to see what kind of cancer it is. Because if it's a really malignant cancer, they might give it chemotherapy after this to make sure it doesn't spread. Anything that you would do for a human who has cancer, they can do for a fish.

This is the anesthesia set-up. They absorb the anesthetic the same way a human would. We breathe anesthesia mixed with air into our lungs, and then we go out, and essentially the same thing happens with fish. It's just they absorb oxygen and anesthesia through water, so eventually they end up belly-up on the top of the tank, completely unconscious. And that's when you take them out of the water and put them on the operating table, and you intubate them with an endo-trachial tube – just like you would a human, except in this case their tubes are usually just a little rubber hose you can get at a garden store.

This is the surgery set-up. This whole set-up is on top of a tank that has fresh water mixed with liquid anesthetic, and then there's a submersible pump that's in the water that's attached to the tubing that goes in the fish's mouth. It works just like a re-circulating fountain.

The surgical instruments – you can see some of them on the table – are human-quality, and since this is a big fish, they're actually standard-sized instruments, but with smaller fish they use tiny surgical instruments that are designed for doing eye surgery on humans.

What you're seeing on the right is a Doppler. It's a sort of heart monitor that uses sound waves to pick up the heart rate and the blood flow through the fish's heart. So you can actually hear in the background, while you're doing the surgery, the fish's heart rate.

[Doppler audio and doctors' conversation.]

This surgery's happening at the University of North Carolina in their vet school. Vet students are learning how to do these sort of surgeries. So this woman is studying to be a veterinarian who will be able to specialize in fish medicine. She's actually removing the bulk of the tumor. She's cutting it from the surface while the surgeon on the opposite side of the table instructs her on how to do this.

The surgeon on the left is stepping in to sort of check the area, and he's a specialist in laser surgeries. He's actually an equine surgeon, a horse surgeon. And just a few hours before this surgery he was doing a surgery on this gigantic horse.

Across the table from him a veterinary technician is doing what they call basting, which is taking a little bit of water out of the tank and squirting it onto the fish to make sure that it stays wet. Their skin has a special slime coat on it that protects them from bacteria and all kinds of infections, and so if they dry out, the slime coat gets damaged, and they can get very sick. So they actually do this basting throughout the surgery, and I've seen surgeons pull out turkey basters – like the kind you would use on Thanksgiving – and baste the fish.

This is like one of my favorite pictures. It just always makes me laugh. So this on the left is the equine surgeon, and he's getting ready to do the laser surgery on the fish, and here he's actually doing the laser surgery, and the laser itself literally just burns away the tissue, and he goes around the edge of the area where the student removed the tumor to make sure that all of the potentially cancerous tissue is gone. It creates this new layer of fresh tissue beneath that will then heal over and hopefully not be cancerous.

At the end of the surgery they fill what is now the hole where the tumor used to be with antibiotic ointment to protect the fish from getting an infection. And then they wake him up by putting him in a bucket full of fresh water with no anesthesia in it. But eventually – it takes about five or ten minutes – he'll wake up, and he'll just be swimming normally. And then he goes back to his aquarium, and he's hopefully all better.

I recently talked to the vet who did this surgery, and he reported that Comet is doing very well, and that it doesn't look like the tumor is going to come back.

Section 3 - Buoyancy Disorder

REBECCA SKLOOT: Cancer is really common in fish, but by far the most common medical problems are buoyancy disorders.

Fish actually have this special organ that's called a swim bladder, and it's located in their abdomen, and it's this sort of thin, flexible pouch that is filled with gas, and the fish use this bladder to regulate their density. So gas actually decreases their density. The more gas they have inside of them, essentially the lighter they are. They have evolved this incredible mechanism to keep themselves at just the right buoyancies.

This is an X-ray of a fish on its back, basically, so you're looking from the stomach down. And those two big black circles are two different compartments of the swim bladder, and they're not supposed to take up that much space in the fish – they're far too big. Now it's laying on its side, and so you can see how most of its body is being taken up by the swim bladder.

Buoyancy disorders aren't really something you can ignore because, you know, not only is it weird for the fish to go through life upside down, but they can actually get serious physical problems because of this. In this picture the big lesion on the fish's side is caused from exposure to the air, and this will eventually kill the fish.

To surgically fix buoyancy disorders, doctors have a few options. The most common is that they actually open the fish up and remove all or part of the swim bladder, and in its place they'll put a small stone. I know one surgeon who uses little tiny amethyst pieces.

The idea is that the stone will weigh it down just enough so that it sinks but not all the way to the bottom, so it just sort of gets to that right level of buoyancy so it can swim normally.

This is Belly Bob who has been swimming upside down and he is about to go into surgery to get his swim bladder removed. This is Belly Bob getting the pre-op Doppler. He's got his intubation tube in his mouth, and he's being checked out thoroughly.

Now he's open, and that's his swim bladder. They're using a pulse-ox, which is the same instrument that's used in humans to measure oxygen and blood flow. And he's now sutured up – you can see the stitches on his abdomen. They're about ready to wake him up. And, as you can see, the surgery was a huge success. Belly Bob is now swimming around right-side up in the proper position in the tank, and he's very happy.

Section 4 - Accidents

REBECCA SKLOOT: So those are the most common medical disorders in fish, but there are also the freak accidents, the sort of fish emergencies.

This is Wendy. She's a koi that belongs to a man named Dave Smothers, and Wendy broke her back when lightning struck a tree in a neighbor's yard and the electrical current traveled through the groundwater into the pond and caused her muscles to sort of contract violently and snap her back.

They did CAT scans, and using this CAT scan they create this 3-D image of her back, and here you can see there's this curve in her back is where it was broken.

No one had ever done surgery on a broken fish back before. So, the surgeons actually went to a seafood store – like where you buy seafood for dinner and bought a carp so they could practice.

They couldn't straighten her back because it was so deformed at that point, but they could stabilize it by pouring a kind of surgical concrete around it and then stabilizing it with pins and screws. She did recover from the surgery and went home with her owner.

He brought in chiropractors to try and adjust the fish's back. He would get in his pond every day and do physical therapy with her, and this picture's actually him doing physical therapy on a different fish because, unfortunately, Wendy died a couple of months after the surgery of a parasitic infection.

So now Dave is actually on his third fish who's broken its back because of being struck by lightning, and this one is the most recent one. This one's Sassy, and Sassy is – they haven't had to do surgery on her yet because her back isn't as badly broken as the others, so they think that physical therapy might just fix her.

So that's a little overview of fish medicine. Thanks for listening.



Produced by
Lexi Krock
Edited by
David Levin


"Infectious disease" section photos

(tuberculosis bacilli)
© Visuals Unlimited
(all others)
© Andrea Cross, © NOVA/WGBH Educational Foundation

"Cancer" section photos

© Andrea Cross, © NOVA/WGBH Educational Foundation

"Buoyancy disorder" section photos

(fish diagram)
© Fish Medicine, by Michael K. Stoskopf, D.V.M., Ph.D., professor and head of Department of Companion Animal and Special Species Medicine, illustrations by Timothy Phelps, M.S., F.A.M.I., and Brent Bauer, M.F.A., F.A.M.I., Department of Arts as Applied to Medicine, Johns Hopkins University, published by W. B. Saunders Company, Harcourt Brace Jovanovich, Inc.
(Belly Bob swimming upside down)
Courtesy Benjamin Brainard, University of Pennsylvania Veterinary School
Courtesy University of Pennsylvania Veterinary School
(all others)
Courtesy Jaleen Briscoe, University of Pennsylvania Veterinary School

"Accidents" section photos

(Dave Smothers)
© Andrea Cross, © NOVA/WGBH Educational Foundation
(all others)
Courtesy North Carolina State University Veterinary School

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