A Discus Post Mortem, ?Cancer

[ThievingSix]

Skip to the conclusion for the quick version. I'm trying to figure how my fish died and why it bloated up.

Background: A previously well roughly 3 year old male discus with no history of illness of any kind began losing appetite, over the course of 2 months with the most pronounced change occurring within the last 3 weeks.

There was minimal behaviour change until 3 weeks ago where the fish stopped taking food and tended to "rest" in one spot of the tank, whilst not hidden away, would occasionally come out to swim.

Current: Beginning around a week ago I observed the fish to have an increased amount abdominal bloating. Assuming it to be a case of constipation or intestinal parasites, the fish was treated with epsom salt baths, methylene blue and metronidazole over a period of 3 days. Its respiratory rate was almost double that of it's healthy tank mates. It seemed to gain some benefit from the epsom salt baths, but this was minimal relief for the fish.

It continued to deteriorate in the last 7 days ending with it being "face down" in the vertical plane, when touched it swam away with significant jerking motions and upside down with no sense of direction and eyes fixed. It was at this point that i decided to euthanize the fish.

Post-mortem:

Appearance - there was no evidence of visible parasites, fungus, white spot or any external infections/problems. Several external skin tissue samples examined under microscopy demonstrated the same conclusions. There was mild bulging of the eyes present(perhaps occurring post death). There was no clamping or fusing of the external fins, they were all normal in appearance. There did not appear to be any raising of scales. The abdomen area appeared bloated. There was no external leaking of feculent matter from the GI tract. There was no fungus or growths of any kind around the mouth which appeared normal.

On opening the abdominal cavity a large amount of yellowish thickened fluid was drained, which appeared to be ascitic in nature. The intestines were opened and no evidence of parasites were found, the GI tract was empty. The lungs appeared normal. The swim bladder was normal.

My conclusion: I'm not entirely sure what killed this fish. I have very clean water in my tank that meets all the parameters for discus. The yellow fluid seems to me like it indicates liver failure, whether this was the cause of death or secondary to something else i'm not sure. The fact that there's no parasites, fungus or any kind of change other than abdominal bloating leads me to 2 possible causes of death, an unexplained bacterial infection, or liver cancer of some kind. The "end stage" for the fish appears like it ended up having profound chemical imbalances.

Any ideas would be much appreciated

 

[Delapool]

Would viral work?

Also (and I'm really stretching here as have never done it) but did the size of the liver, etc look normal (apparently that involves killing healthy fish to learn so bit expensive for me). A small liver, etc may suggest something else ongoing was the thought.

 

[ThievingSix]

I was considering viral but there's not much that could be done if it was a viral infection.

Unfortunately its very difficult to get any kind of medications in Australia that's suitable for fish. I had to get the metronidazole on the sly and its in significant shortage around the world at the moment.

I tried looking for other discus dissections but there's really not much on the web. He was quite a large discus so it would cost hundreds of dollars to get a similar specimen and compare, let alone i'm not much of a fish killer. I'm curious to know if anyone has ever dissected their discus. The liver appeared normal in size compared to other organs which is really the only thing i can go off unfortunately.

I dont know any local vet which will even examine a fish, let alone the process involved in achieving that.

 

[Autumnsky]

You seem to have done a very thorough examination. It is hard to know viral. Or bacterial unless it was able to have the tissue samples tested.

Just started trying to keep Discus and I can't be of any help other to say so sorry for your loss. I understand the frustration.

 

[Delapool]

I was considering viral but there's not much that could be done if it was a viral infection.

Unfortunately its very difficult to get any kind of medications in Australia that's suitable for fish. I had to get the metronidazole on the sly and its in significant shortage around the world at the moment.

I tried looking for other discus dissections but there's really not much on the web. He was quite a large discus so it would cost hundreds of dollars to get a similar specimen and compare, let alone i'm not much of a fish killer. I'm curious to know if anyone has ever dissected their discus. The liver appeared normal in size compared to other organs which is really the only thing i can go off unfortunately.

I dont know any local vet which will even examine a fish, let alone the process involved in achieving that.

Yes, it was only as we had a presentation from a discus breeder over here in Perth passing across some tips that I thought of these. I've picked up furan 2 and find that about the most useful to date (including for bloating when usually a lost cause). Tough one, can't think of much else here - I don't know of any that get fish inspected by a vet due to the expense. Fingers crossed that all goes well now.

 

[J.Mcpeak]

Could be herpes disease.
The symptoms sound very similar to koi herpes and channel catfish virus.
So I did some looking about, aquatic birnavirus, look that up.
Infectious pancreatic necrosis virus, (known to affect cichlid sp.)

All of the above, the body cavity is filled with a clear yellow fluid.
Some other symptoms are similar, eg abdominal distension.

Most likely viral in nature. Which one exactly would require further investigation.

It's a shame you lost your fish. But well done for this examination.

 

[ThievingSix]

Delapool may i ask where you picked up the furan 2? I can't seem to find it anywhere.

Interesting you mention herpes, I was reading up on Cyprinid herpesvirus 3 which appears to have been deliberately released into the Murray-Darling basin to control carp populations, It's very possible that this virus could have made its way into my water supply. But does it affect discus?

Looking at IPN/aquabirnavidae its possible too, although there was no darkening of the skin or faeces at all. And i didn't spot any trailing faeces(or any for that matter).

Interesting you both mentioned viral illness, since i didn't really consider it at first, and there's no real treatment. Ascites seems to be common in viral infections.

 

[Autumnsky]

Interesting you mention herpes, I was reading up on Cyprinid herpesvirus 3 which appears to have been deliberately released into the Murray-Darling basin to control carp populations, It's very possible that this virus could have made its way into my water supply. But does it affect discus?

That seems an asinine thing to do.

 

[ThievingSix]

The more I read, the more im thinking its possible. It appears they test released a bunch of the virus around 6 months before my discus started showing symptoms.

They say it will definitely affect ornamental koi(Australian koi keepers beware!) but they don't think it will affect anything else. They say it doesnt affect any native species(yet discus arent native!).

 

[Delapool]

We have been hotly debating this on the Perth forum. I've copied across one link. As far as I know the virus shouldn't jump like that - in all the reading I've done I'm not worried for my fish. Is it possible though? Well, still debating

http://www.pestsmart.org.au/carp-herpes-faq/