Chronic Wasting Disease

[LizStreithorst]

I sure hope not. Way back when I had cryptobia I killed all the fish in the fish room and sterilized all my equipment. It was hard on me but I set my mind to do it because I thought that it was the only thing I could do. Nicholson's method of curing it did not work for me.

[shrinkwrap]

Yes it is endemic...but it is a parasite and no doubt treatable if we don't give up.

[Paul Sabucchi]

Yes it is endemic...but it is a parasite and no doubt treatable if we don't give up.

I sincerely hope so but there may be some serious hurdles to overcome. A lot of these protozoa can be really difficult to treat. These flagellates are not too far removed from those that cause sleeping sickness, malaria or leishmaniasis and these diseases can be really difficult to cure even in humans. There is a limited number of drugs, and not easy to get hold of, that have satisfactory effect on these parasites and if criptobias are shielded inside granulomas or if they have an intracellular stage inside macrophages -where medication is unlikely to reach - the chances of being able to eliminate these parasites are probably very thin.
For the short term it may be more effective to establish a reliable screening method to identify "Criptobia free" fish. I think many discus keepers would appreciate the option of purchasing fish with a similar certification. What are your thoughts about it?
A couple of things spring to mind to start with:
Do salmon hatcheries test their breeding stock for Criptobia salmonistica? If so how? Would the same method be reliable to screen discus for C iubilans?
Also does artificial raising prevent vertical transmission? Would be interesting to see if from a pair with positive fecal smares by artificial raising the offspring would grow out negative.
Also is there any evidence at all that the domestic water supply in any developed country could carry Criptobia as it has been suggested (I am skeptical about this).
And lastly, we know Criptobia can affect quite a range of ornamental freshwater fish, West African cichlids, central American ones and discus, do we know if it affects other species, such as other cichlids commonly kept with discus (Apistogramma, Rams, angels?) or even not belonging to this family (carachins, loricarids)

[shrinkwrap]

Paul, you make salient... crucial points.

The most important imho is: "For the short term it may be more effective to establish a reliable screening method to identify "Criptobia free" fish. I think many discus keepers would appreciate the option of purchasing fish with a similar certification?" I hope that your idea catches on, and it could if we keep educating discus-keepers about it's relevance. Market forces can take over.

I don't know if you went to the 2018 NADA meeting but Dr. Stephen Smith made an excellent presentation on the subject.

The 2004 Yanong et al, article on Cryptobia iuibilans infection in juvenile discus addresses many of your other points. It is the best summary article I've seen other than the U Fla Vet schools summary article. Cryptobia is found in rams and other cichlids, but not angel fish. The instability of granulomas containing the Cryptobia does create a challenge in treating the Cryptobia and is one of the reasons that active Tuberculosis granluomas requires long treatments.

I don't yet know the answers to the other questions, but I am interested and will keep looking.

[RogueDiscus]

Hi shrinkwrap,
Thanks for your posts and interest in this topic. I was at NADA too and enjoyed Dr. Smith's presentation. I don't think we've met, but I think you asked a few questions at the presentation, right? I'm actually the guy who's been supplying Dr. Smith with fry. It would be nice to see an effort to tackle this parasite.
Are you trying to do anything in particular to start a research project?
Steve

[Paul Sabucchi]

I read most of those a while back, I have been into African cichlids (mbuna mostly) for far longer than I have been hooked on discus. In those the granulomatous gastroenteritis caused by Criptobia is probably the worst culprit of the dreaded "Malawi bloat". On my wish list would be some sort of snap-test (micro-Elisa?) capable of rapidly telling if a fecal sample is positive or not for the parasite (so it would have to be a direct test aimed at confirming the presence of the parasite itself, not an indirect one for spotting antibodies in a blood sample). This way it could be easy to use by breeders, retailers and fishkeepers even if they are not familiar with using a microscope. The fact that the parasite is not limited to discus might make it a more viable commercial proposition.

[shrinkwrap]

Yes, Steve I remember you. Yes, I asked several questions. I had a page list of questions to ask Dr. Smith but didn't want to take up the group's time. He was generous to let me ask all my questions after the meeting.
Thank you for what you are doing to support the cause. I had dinner with Dr. Smith and he commented that the hardest part of this was getting discus from breeders in order to conduct the research. Keep up your part and we'll get there. I just bought some dimetridazole. I'm not currently dealing with an active infection but I want to be prepared. I would be glad to help with a project design if someone had the fish to contribute to the project.

[smsimcik]

I read most of those a while back, I have been into African cichlids (mbuna mostly) for far longer than I have been hooked on discus. In those the granulomatous gastroenteritis caused by Criptobia is probably the worst culprit of the dreaded "Malawi bloat". On my wish list would be some sort of snap-test (micro-Elisa?) capable of rapidly telling if a fecal sample is positive or not for the parasite (so it would have to be a direct test aimed at confirming the presence of the parasite itself, not an indirect one for spotting antibodies in a blood sample). This way it could be easy to use by breeders, retailers and fishkeepers even if they are not familiar with using a microscope. The fact that the parasite is not limited to discus might make it a more viable commercial proposition.

Hey Paul, I like your idea of a Snap test for fish pathogens like cryptobia, hexamita, herpes virus or intestinal worms. It sure would make diagnosis and treatments easier. I wonder if there would be enough financial incentive for Idexx to ever produce a combination Snap test for multiple fish pathogens similar to their 4Dx Plus heartworm/ricketssial test for dogs?

I'm thinking it would be pretty expensive for Idexx to come up with something like that and it would take a lot of commercial fish people as well as fish hobbyists to make it profitable. But we can always dream.

[brewmaster15]

I wasn't at NADA this year to hear Dr.Smith's talk but was there 2 years ago and have spoken with him about the pathogen abit. I know he has been really looking at this so maybe with his research diagnostics and treatments may improve. I hope so. At his talk this year did he make any specific recommendations on what you should do if your fish have been confirmed by a lab to have Cryptobia? Cull?

al

[DISCUS STU]

A very interesting discussion, I also saw Dr. Smith at NADA 2018, will try to look at necropsy for the next time.

[Paul Sabucchi]

Hey Paul, I like your idea of a Snap test for fish pathogens like cryptobia, hexamita, herpes virus or intestinal worms. It sure would make diagnosis and treatments easier. I wonder if there would be enough financial incentive for Idexx to ever produce a combination Snap test for multiple fish pathogens similar to their 4Dx Plus heartworm/ricketssial test for dogs?

I'm thinking it would be pretty expensive for Idexx to come up with something like that and it would take a lot of commercial fish people as well as fish hobbyists to make it profitable. But we can always dream.

It would be neat but I fear that it would be difficult to manufacture such a test for the aforementioned reason. It would probably be thechnically a lot more easy to highlight the presence of the parasite with some sort of immunofluorescence test but that would have to be run in a lab. It would still be nice to have the possibility of sending a fecal sample to the lab and know for sure if any of these parasites are there, even in very low numbers

[shrinkwrap]

I wasn't at NADA this year to hear Dr.Smith's talk but was there 2 years ago and have spoken with him about the pathogen abit. I know he has been really looking at this so maybe with his research diagnostics and treatments may improve. I hope so. At his talk this year did he make any specific recommendations on what you should do if your fish have been confirmed by a lab to have Cryptobia? Cull?

al

he recommended 3 medication options. Two are mentioned in the Univ of Fla document that I've referenced before:
1. Dimetridazole
2. 2 amino 5-nitrothazole
(unfortunately it is hard to get these chemicals in the US. I don't know if a vet can get them more easily.)
3. metronidazole ( I tried this and it failed at the usual dosage recommendations as a bath).

[brewmaster15]

But did he say that any of these actually have been shown to cure a fish of this pathogen? or that they have just shown some effect? The reason I ask this is because I think its important that hobbyists understand that treating a fish with a medication that is partially effective does 2 things.. Its can create asymptomatic carriers (fish that look fine but are carriers).These carriers can infect any new discus you add to your collection.They can also infect other tanks of healthy discus if you cross contaminate. The other thing that treating fish with medications that are not entirely effective is you create pathogens that are more resistent to that class of medications.

I honestly don't know of any case where cryptobia was cured and documented by pathology after treatment.This is the kind of information that I hope Dr.Smith can one day report.

The University of Florida article is here if anyone wants to read it...

http://edis.ifas.ufl.edu/m/#publication?id=VM077
In this article its states

Treatment for a Cryptobia iubilans infestation is considered more difficult, and current recommendations are based on laboratory experimental trials. Part of the difficulty may be that the parasite seems to have an intracellular stage. Parasites are occasionally seen in phagocytic cells, called macrophages, which are part of the immune system and are supposed to destroy foreign materials by engulfing them. Cryptobia seems to be able to live within these cells rather than being destroyed by them. This can make it difficult to treat Cryptobia because most drugs are not able to penetrate the cell wall of a macrophage. Experiments run at the Tropical Aquaculture Laboratory suggest that these two treatment regimens may decrease the infection load: a) a bath treatment with dimetridazole (80 mg/L for 24 hrs, followed by a 80–100% water change, repeated daily for 3 days); or b) a bath treatment with 2-amino-5-nitrothiazol (10 mg/L for 24 hrs, followed by a 80-100% water change, repeated daily for 3 days).

Decreasing the infection load isn't curing the fish. Its saying these medications arent effective at completely curing the disease. Thats significant.

If you read the article though theres a take home piece of information.

Both Cryptobia and Spironucleus can result in similar disease scenarios on cichlid farms. Both parasites become more serious under conditions of crowding, poor sanitation, high organic load, and handling stress. Diet also may play a role in the development of the disease. It has been demonstrated in laboratory mice that changes in the intestinal bacterial flora, caused by changes in diet, can affect the presence of intestinal flagellates, suggesting greater potential for clinical disease.

It may be the pathogen is in most discus but its not a problem until conditions become favorable for it to overwhelm the host. The note about it being able to survive intracellurely is significant also and probably why its so hard to eradicate.

al

[Paul Sabucchi]

That kind of talies with empirical experience with mbuna, who's diet (depending on the species) is somewhere between omnivorous and vegetarian, if fed on high animal protein diet (either acting directly or more likely by causing intestinal dismicrobism) can lead more easily to the parasite causing granulomas that in turn cause intestinal obstruction commonly referred as Malawi bloat.
Al does highlight very valid points that a treatment that is only partially effective can be a double edged sword and as metronidazole is often used with carefree abandon probably resistance to it and related dimetridazole must be quite high even if it does manage to reach the flagellates.
Besides keeping our fish to the best of our capabilities to minimize stress I think our efforts should be aimed at being able to produce specific pathogen free fish. It would be useful to see if from breeding a pair positive for Criptobia by artificial feeding (and maybe also by treating the eggs with ?acriflavine?) it would be possible to obtain Criptobia free offspring. Should this prove effective, provided future breeding pairs are all from Criptobia free stock, there should be no obstacle to resuming raising naturally

[shrinkwrap]

Thanks for your comments Al and Paul, you raise good points. I agree with Paul that the goal is to raise awareness of Cryptobia to the point that breeders will market their discus as "Cryptobia Free", then we don't have to struggle with treatments that are at this point very preliminary.

The Univ of Fla recommendations to which you refer are derived from an article "Cryptobia iubilans infection in juvenile discus" by Yanong et al, published in Journal of American Veterinary Assn, vol 224, May 15 2004 in which they review, 4 cases I believe, in which they tried several antiparasitic agents against control groups basically out of desperation. The only 2 agents that showed significant benefit were dimetridazole and 2-amino 5-nitrothiazole. They concluded their article stating “additional studies are needed to determine the optimal dose and duration of treatment”. 14 years later that is where we are. No one is researching treatments! We may be able to improve upon their results with tweaks on the dose or duration. FYI, the other agents tried and failed were metronidazole, nitrofurazone, primaquine, and chloroquine.

It is not insignificant that the meds they recommended reduced the number of Cryptobia. For example, gill and skin flukes are common on fish, but only cause disease in excess numbers. It is quite possible that reducing the amount Cryptobia organisms that the discus bears is significant in determining which fish get chronic wasting disease and which don’t. There are other factors for sure, such as innate resistance to infection by some fish. There is more that could be said on this subject but for brevity-sake I’ll stop here.
The bottom line is that at this point, we have a common parasite that causes many discus-keepers to give up on discus because their discus quit eating and gradually starve themselves to death. These folks post every day on the forums asking for help. Even if we can’t cure it today, if we can diagnose it, we need to help them find the truth. We owe them the truth. Some of these people will join the fight for a cure.

(To be clear, I’m not saying all chronic wasting disease is Cryptobia. I have identified and cured Capillaria in a discus with wasting disease. I have a picture I took of the barrel-shaped eggs in the stool.)