I would be willing to bet money that the cause of your chronic wasting disease is cryptobia iubilans and not any of the other causes mentioned. My reasons follow. It can be diagnosed by microscopic analysis of a fresh stool sample. It is easily confused with Spironucleus, a.k.a. 'Hex' even by supposedly knowledgeable researchers, per Dr. Stephen Smith who spoke at the NADA 2018 meeting last month. However, even I have learned to tell the difference.
I am willing to help members with microscopes diagnose parasites in poop. I don’t know if your fish died of this, but I learned to diagnose cryptobia iubilans by examining stool samples and have posted videos of what that looks like. It was confirmed by a vet for me. Cryptobia iubilans parasite is a common cause of chronic wasting disease in discus. My previous post is here:
http://forum.simplydiscus.com/showth...ase&highlight=
At the NADA meeting 2018, Dr. Stephen Smith agreed that cryptobia iubilans is a common, if not the most common, cause of chronic wasting disease in discus. He spoke on the subject for 20-30 minutes. I believe it is one of the most common reasons people give up on discus. It is resistant to the usual treatments including all antibiotics, heat, low pH. It is a single cell flagellated parasite, not a bacteria nor a virus. Metronidazole is ineffective though often recommended. There are published veterinary articles suggesting that dimetridazole (not the same as metronidazole) and 2-amino-5-nitrothiazol may be effective.
http://edis.ifas.ufl.edu/vm077
I was successful at using 2-amino-5-nitrothiazol to stop discus from dying from this infection. I confirmed a resolution of the stringy poop and a reduction but not elimination of the parasite count in the poop. These 2 chemicals are intermittently available in the US. Let me know if you need help with this.
There is much still unknown about this parasite. We should encourage Dr. Stephen Smith and others to continue their research. The problem is there is no money in researching cryptobia in discus and other fish are not affected in the same way by this parasite. If there were sufficient money invested treatments could be easily found. This is a parasite, not cancer! Alternatively, if other scientifically minded people like me, joined together with a generous breeder to supply test fish, we could design and execute studies of the suggested treatment options with very little money invested. I can provide details for those interested.
I would also suggest, for those who can afford it, to spend the $250-300 in a necropsy by a veterinary pathologist to confirm the characteristic granulomas in the stomach and intestines of discus suspected of dying of cryptobia. The only thing that can cause this that is currently known is mycobacterium and the pathologist knows how to tell the difference. The organism will not usually be found in a typical necropsy BTW, but the above findings are strong evidence according to the several pathologists I’ve used. One of the frustrating things about having a fish slowly starve itself to death over weeks and waste away is not knowing the cause. You can prove the cause if it’s cryptobia.
I bought a $200 Amscope microscope from Amazon and that is what I used to examine stool samples and diagnose cryptobia. This is not a huge amount in comparison to the amount many have invested in discus. I am willing help members learn to use it.