Bloated zebra danio

[Black_Rose]

We've had this particular zebra danio for two years now.

This is the second time this fall it has bloated up.
The previous time it went away over a few weeks.

This time it hasn't gone away, and I have no idea what might be wrong with it, or if it's simply coming to the end of it's life.

The bloat has no affect on it's swimming or eating ability.

Any idea on what might be going on with our striped baloon?

I managed to catch it last night and it's in a small tank with PraziPro and a shelled pea.

[nerdRVT]

She looks like she's got blood in that fluid. There's tons of reasons why a fish might bloat up like that, but when I see our ZF with that much ascites (abdominal fluid), it is often caused by organ damage, or cancer. In fact, a lot of the time, folks misdiagnose things like kidney failure or cystic kidneys as that super fun generalized term 'dropsy'.

I'll see fish act normally like this for some time, but then they'll end up having an acute issue and die quickly- generally in not a nice way. Personally, I'd consider euthanasia sooner rather than later. In the interim, you could try to mitigate the ascites by dosing the water with salt to ~3ppt to mitigate osmotic stress. Might help her get rid of some of that fluid.

Do be careful, however. There are pathogens, like mycobacteria, which can cause symptoms like this in a fish, and some species of mycobacteria can make humans sick. Treatment for this zoonotic disease is not fun in humans, and requires a lot of diagnostics and very long series of antibiotics. So just be mindful when handling.

[Black_Rose]

Thank you very much for the detailed reply.

The one thing that I'm really perplexed about is that with this level of swelling, I can't detect any pineconing.

This is the fourth danio to have issues this fall.

I'm very careful with these ones (nitrile gloves and  washing hands & arms with anti-bacterial soap) because I don't know what's going on with them (age related or something more sinister).

I'll add some salt to the treatment tank to possibly alleviate the swelling, but I don't think this one is going to survive long: I'll likely euthanize it (had to euthanize another one last night that was swimming head up/tail down).

Is this common with zebra danios as they are?

[nerdRVT]

The pinecone thing with scales tends to happen in zebrafish when the fluid is building up in the tissues of the skin, and not in the abdomen.

If you are seeing this in multiple fish as they age, I'd worry about something more sinister than just run of the mill kidney or liver failure. It could be mycobacteria, that's one of the most common ones we see in zebrafish that causes this fluid. It tends to attack the liver and cause disease and liver failure related ascites.

This is super technical but does illustrate symptoms of mycobacterium sp. infection in zebra danios. Mike Kent is a wizard when it comes to zebra danio infectious disease. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2765522/

Of note is the fact that mycobacterium sp. *is* the dreaded fish tuberculosis. It is something I've euthanized and sterilized entire systems over. Now at work, I can determine whether it is a zoonotic species that puts myself and my staff at risk, but for the average keeper, there's no simple way, aside from sending samples out for analysis. TFH had a good article about it some time ago. https://www.practicalfishkeeping.co.uk/blog/articles/should-you-be-worried-about-fish-tb

[Black_Rose]

That was the only one that swelled up and filled with fluid.

Two others were swimming head up/tail down.

Thanks for the links. I've read the tropical fishkeeping one before when researching a different fish.

[Black_Rose]

The salt treatment didn't really help the swelling that I could see, so I euthanized the danio.

There was no way it was going to recover.