Marine Ich/Cryptocaryon irritans - A Discussion

[ATJ]

Steve,

Great article. We need a lot more of these to counteract the complete rubbish which abounds in the hobby.

I have found a few things which I see as discrepancies between your article and the literature and I hope you don't mind me discussing them.

This disease is usually associated with several environmental triggers. Changes in water temperature, exposure to high levels of ammonia, nitrite, or nitrate, low pH levels, low dissolved oxygen, and overcrowding are all factors contributing to the onset of the disease. You could lump all of these in a general category of stress, but I find it more appropriate to think of all of these as wholly unnatural conditions.

You don't cite any references for these claims. Are you aware of any studies that have shown environmental triggers? All of the aquarium bases studies (such as Burgess and Matthews, 1995; Cheung et al. 1979; Yoshinaga and Dickerson, 1994) that I have read simply involved placing theronts in a tank with fish without utilising any of the factors you list. in fact, some of the researches take pains to avoid environmental issues and still the fish become infected.

At this point, they are called theronts, and they must find a host within twenty-four hours or die.

There is some discrepancy in the literature on this point. Yoshinaga and Dickerson (1994) found that after 8.5 hours, 81% of theronts had dies and only 0.34% survived past 12.5 hours. Colorni (1985) reports survivability of up to 36 hours.

Mature trophonts leave the host and tomites exit the theront/cyst in the dark (Yoshinaga & Dickerson, 1994).

I'm not sure where you read about trophonts leaving the host in the dark, but I don't believe it was in Yoshinaga and Dickerson (1994). I just re-read the article twice and can find no mention of timing of trophont exits. Further, the timing of excystment of theronts (the theronts exit the tomont rather than the tomites exiting the theront) was found to be circadian regardless of light or dark. All the tomonts were kept in the dark and yet excystment occurred consistently between 0200 and 0900.

Also, if you keep the fish in quarantine for one month without infection, you can be sure that any Ich parasites and their eggs have hatched and died without a host.

This is not entirely true. If you were to add a fish to the tank that had just acquired one or two trophonts. These may be too few to be noticeable as they developed. Six days later, the trophonts leave the fish and encyst in the substrate. If the tomonts reproduce for 22 days and then excyst, the fish may have just acquired a whole new batch trophonts at the very time you catch it and place it in the display tank. Of course, at normal reef tank temperatures, most of the theronts will have excysted in under 10 days, but it is always better to err on the side of caution. A six week quarantine period is far safer. Also note that there are no eggs to hatch. These are single celled organisms.

Copper specifically targets the infectious, free-swimming theront stage of this disease, as being buried deep in the skin of the host protects the trophonts; the cyst walls of the tomonts are similarly impervious (Colorni & Burgess, 1997).
...
Formalin can be administered one of two ways; either in short dips with saltwater or used continually in a hospital tank. The dosage for the continuous use is 1 ml of the 37% stock solution for every 25 gallons of quarantine tank water (Bassleer, 1996). I prefer the formalin dip to continuous use because formalin is a fairly toxic compound.

If being buried deep within the skin of the host protects the trophonts. what is the value of a formalin dip? (Or any other dip for that matter?)

On the contrary, keeping fish in low salinity means that they don't "flush" their kidneys sufficiently. After long-term exposure, this can cause kidney failure and kill the fish (Shimek, pers. comm..)

Far be it for me to argue with Dr. Ron, but research by Woo and Chung (1995) found that Pomacanthus imperator was "physiologically euryhaline" and could make the necessary adjustments to salinities down to 7 ppt without any problems. Of course, this does not mean that all reef species will be the same, but suggests that assumptions about tolerance of reef species to low salinities may be inaccurate.

I also note that you list a number of references, but only cite a few of them. I'm surprised Ron and Eric let you get away with that.

Please note these comments are not meant as criticisms of you or your work, but are just to ensure that the information presented is as accurate as possible.

<b>References</b>

Burgess P.J. and Matthews R.A. 1995. <i>Cryptocaryon irritans</i> (Ciliophora): acquired protective immunity in the thick-lipped mullet, <i>Chelon labrosus</i>. <i>Fish & Shellfish Immunology</i>.<b>5(6)</b>:459-468.

Cheung P.J., Nigrelli R.F. and Ruggieri G.D. 1979. Studies on cryptocaryoniasis in marine fish: effect of temperature and salinity on reproductive cycle of <i>Cryptocaryon irritans</i> Brown, 1951. <i>J. Fish Dis.</i>.<b>2</b>:93-97.

Colorni A. 1985. Aspects of the biology of Cryptocaryon irritans, and hyposalinity as a control measure in cultured gilt-head sea bream Sparus aurata. <i>Dis. Aquat. Org.</i>.<b>1</b>:19-22.

Woo N.Y.S. and Chung K.C. 1995. Tolerance of Pomacanthus imperator to hypoosmotic salinities: changes in body composition and hepatic enzyme activities. <i>Journal of Fish Biology</i>.<b>47(1)</b>:70-81.

Yoshinaga, T. and Dickerson H.W. 1994. Laboratory propagation of <i>Cryptocaryon irritans</i> Brown, 1951 on saltwater-adapted black mollies Poecilia latipinna. <i>J. Aquat. Anim. Health</i>.<b>6</b>:197-201.

 

[Skipper]

I also note that you list a number of references, but only cite a few of them. I'm surprised Ron and Eric let you get away with that.

Hey ATJ. Actually, Ron and Eric didn't. I allowed all the personal communication references to stay. Am I in error?

 

[Steven Pro]

I am going to go through these one at a time.

The environmental triggers part is really a compilation of my own experience and references, but I should have probably listed:
Bassleer, 1996
Calfo, pers. comm.
Dixon, pers. comm.
Fenner, pers. comm.
Joshi, 2003

There is differing research on how long theronts last, I believe due to variations in the parasite due to geographic location. Most say less than 24 hours. Colorni was able to find some still kicking until 48 hours, but he was working with either Red Sea or Mediterranean isolates and even he conceded that almost all are dead after 6-8 hours (Colorni & Burgess, 1997). Plus, I think Colorni was only looking for theront movement under a microscope and did not look for actual infection rates after such a long time.

Ok, I just found something when I was looking for excystment in the dark. From colorni & Burgess, 1997, "A low percentage of infectivity is present at 10-12 h post-excystment, but drops to zero at 18h (Burgess, 1992)." So, a couple may still be twitching, but are surely not infectious after 24 hours.

 

[Steven Pro]

Following up with the rest of your questions...

Darkness:
Yoshinaga * Dickerson, 1994 report excystment between 2:00 and 9:00 AM regardless of lighting. They were the ones to originally discover this.
Colorni & Burgess, 1997:
"The theront emergence from the tomonts is influenced by circadian rhythms (at least under a laboratory-controlled photoperiod), usually taking place during the dark phase."
"Laboratory studies have revealed that mature trophonts exit the host and theronts excyst during darkness."

Also, food for thought, photoreceptors have not been found in Cryptocaryon irritans, while they have been found in other ciliates (colorni & Burgess, 1997). So, they possibly cannot see the light and have some sort of internal clock.

Quarantine and Reinfection:
Sorry, but I was not able to follow your scenario. I think the consensus is 28 days max for the life cycle (Colorni, 1987).

 

[Steven Pro]

I just saw Skip chimed in. Originally I wrote this as one long article, so I had all my references listed. I then split it into two parts when I went over 8,000 words. I know I don't have the patience to plow through something of that length in one sitting, so I broke it into two. This also allowed me to further seperate the scientifically proven methods from the ones I am covering in part two; freshwater dips, quinine-based drugs, 5-Nitroimidazoles, UV, ozone, cleaners, natural immunity (proven but I discuss it here to help illustrate how difficult it is to point to a response in a particular fish as proof of a cure versus an immulogical response), medicated foods, garlic, ginger, pepper, tea extract, and assorted other kitchen "remedies". So, I tried to catch all the ones that should be listed in part two and not part one, but a few may have slipped through due to time constraints.

 

[ATJ]

Originally posted by StevenPro

The environmental triggers part is really a compilation of my own experience and references, but I should have probably listed:
Bassleer, 1996
Calfo, pers. comm.
Dixon, pers. comm.
Fenner, pers. comm.
Joshi, 2003

So nothing demonstrated experimentally or written up in peer reviewed journals, just what appears to be hobbyist opinion and anecdotal evidence.

That paragraph is very much out of place with the rest of the article where you demonstrate that it is the presence of the C. irritans that causes the infections, not environmental conditions. Most researchers would agree that if C. irritans isn't present, fish won't get infected regardless of the environmental conditions and conversely, even if environmental conditions are perfect, the presence of C. irritans in the confines of an aquarium will result in the infection of naive fish. Please note I mean confines in the sense of bringing the parasite and fish in closer contact, not necessarily an overcrowded situation.

There is differing research on how long theronts last, I believe due to variations in the parasite due to geographic location. Most say less than 24 hours. Colorni was able to find some still kicking until 48 hours, but he was working with either Red Sea or Mediterranean isolates and even he conceded that almost all are dead after 6-8 hours (Colorni & Burgess, 1997). Plus, I think Colorni was only looking for theront movement under a microscope and did not look for actual infection rates after such a long time.

Ok, I just found something when I was looking for excystment in the dark. From colorni & Burgess, 1997, "A low percentage of infectivity is present at 10-12 h post-excystment, but drops to zero at 18h (Burgess, 1992)." So, a couple may still be twitching, but are surely not infectious after 24 hours.

I agree that there is differing research. That was my point. I just think it was a relevant point that should have been made in the article - especially if it is due to the source of the parasite.

 

[Steven Pro]

Copper, Formalin, and Dips:
I don't currently see the mechanism for how Formalin works in my references, but something makes me think I read it prematurely causes the trophont to leave the fish. I maybe getting confused with Amyloodinium, though. Anyway, a formalin dip is going to be the same thing as using formalin in flush through systems for food fish aquaculture, just on a small scale.

Hyposalinity:
I had not heard about thenkidney failure potentail until Dr. Ron mentioned it on 8/3/03. I did not have time to find my own references, but I do now have a couple on the way through ILL. I do want to read up more on this myself, but I believe Dr. Ron was talking about long-term exposure versus a couple of weeks for treatment. Dr. Ron has both an online discussion and article that mention this occurance,
http://www.seaplace.org/ronstalk.html
http://www.animalnetwork.com/fish2/aqfm/1997/nov/features/1/default.asp

 

[Steven Pro]

ATJ,
I probably should have been clearer. I meant to say the environmental triggers help to promote the onset of the infection, but you do have to have the parasite present in the first place.

 

[ATJ]

Originally posted by StevenPro

Darkness:
Yoshinaga * Dickerson, 1994 report excystment between 2:00 and 9:00 AM regardless of lighting. They were the ones to originally discover this.
Colorni & Burgess, 1997:
"The theront emergence from the tomonts is influenced by circadian rhythms (at least under a laboratory-controlled photoperiod), usually taking place during the dark phase."
"Laboratory studies have revealed that mature trophonts exit the host and theronts excyst during darkness."

Also, food for thought, photoreceptors have not been found in Cryptocaryon irritans, while they have been found in other ciliates (colorni & Burgess, 1997). So, they possibly cannot see the light and have some sort of internal clock.

Which all goes to show that it is not darkness, but time of day (that just happens to coincide with darkness local time).

It would be interesting to understand how their "internal clocks" are set and what happens when you take C. irritans from the Indo-Pacific to the US East Coast (10-18 hours behind) and see if the C. irritans reset their "internal clock".

Quarantine and Reinfection:
Sorry, but I was not able to follow your scenario. I think the consensus is 28 days max for the life cycle (Colorni, 1987).

Both Colorni (1987) and your article state that reproductive stage (tomonts) is 3-28 days long. Add to that 3-7 days on the fish and up to 18 hours from fish to encystment and you have as long as 36.75 days. And that is not including the theronts which could take the total cycle to 37 days.

My scenario was to show that even if the reproductive stage was less than 28 days, you could still be introducing parasites into your display tank if you transfer the fish on the 28th day. You may think it is unlikely but it happened to me just last year.

I transferred a Forcipiger from my quarantine tank to one of my display tanks right on the 28th day after I had caught it. During the period it had shown no signs of "Ich" at all. A week later, most of the fish in the display tank showed signs of "Ich". The "Ich" went through some 7-9 cycles over the course of 3 months until all the fish were either immune or died.

 

[Steven Pro]

"Which all goes to show that it is not darkness, but time of day (that just happens to coincide with darkness local time).

It would be interesting to understand how their "internal clocks" are set and what happens when you take C. irritans from the Indo-Pacific to the US East Coast (10-18 hours behind) and see if the C. irritans reset their "internal clock"."

The hobby/industry does this routinely, unintentionally of course. We import fish from the Indo-Pacific and bring them all the way around the world. To me, they still seem to drop off and reinfect on a different part of the fish at night.

 

[Steven Pro]

"Both Colorni (1987) and your article state that reproductive stage (tomonts) is 3-28 days long. Add to that 3-7 days on the fish and up to 18 hours from fish to encystment and you have as long as 36.75 days. And that is not including the theronts which could take the total cycle to 37 days."

Ok, I follow you now. I am going to ask Skip about inserting a foot note.

"My scenario was to show that even if the reproductive stage was less than 28 days, you could still be introducing parasites into your display tank if you transfer the fish on the 28th day. You may think it is unlikely but it happened to me just last year."

Yeah, unlikely but possible. Better to err on the side of caution.

I am off to work now. Will check in on this discussion later. Nice "chatting" with you.

 

[Steven Pro]

On last thing before I am off.

"Great article."

Thanks a lot!

"We need a lot more of these to counteract the complete rubbish which abounds in the hobby."

Wait until you see Part Two.

 

[ATJ]

Originally posted by StevenPro

Copper, Formalin, and Dips:
I don't currently see the mechanism for how Formalin works in my references, but something makes me think I read it prematurely causes the trophont to leave the fish. I maybe getting confused with Amyloodinium, though. Anyway, a formalin dip is going to be the same thing as using formalin in flush through systems for food fish aquaculture, just on a small scale.

I still have my doubts that a formalin dip will do anything, in the same way a freshwater dip does very little. It is my understanding (although I don't yet have a direct reference) that freshwater dips are somewhat effective for the treatment of Amyloodinium. At least Cobb and Levy (1998) used freshwater dips to remove Amyloodinium trophonts for counting.

Hyposalinity:
I had not heard about thenkidney failure potentail until Dr. Ron mentioned it on 8/3/03. I did not have time to find my own references, but I do now have a couple on the way through ILL. I do want to read up more on this myself, but I believe Dr. Ron was talking about long-term exposure versus a couple of weeks for treatment. Dr. Ron has both an online discussion and article that mention this occurance,
http://www.seaplace.org/ronstalk.html
http://www.animalnetwork.com/fish2/aqfm/1997/nov/features/1/default.asp

I agree in the kidney failure potential for stenohaline fish. I was pointing out that very few reef fish have been studied in detail to determine if they are in fact stenohaline. The only reef fish that I know that has been studied, P. imperator, was found to be "physiologically euryhaline" and so kidney failure is probably unlikely for that species. I wonder how many other reef fish are also "physiologically euryhaline".

Also note, I am not suggesting that fish be kept long term at lower than normal salinity, but just that the kidney failure scenario is based on a unproven assumptions.

 

[ATJ]

ATJ,
I probably should have been clearer. I meant to say the environmental triggers help to promote the onset of the infection, but you do have to have the parasite present in the first place.

In my opinion, even that is going too far. I agree that poor environmental conditions can decrease the fish's ability to survive the infection and develop an immunity, but if parasites are present in sufficient numbers, the environmental conditions are largely irrelevant in determining whether fish will become infected.

 

[ATJ]

Originally posted by StevenPro

The hobby/industry does this routinely, unintentionally of course. We import fish from the Indo-Pacific and bring them all the way around the world.

That is exactly my point.

All the C. irritans used by Yoshinaga and Dickerson (1994) came from a single Amphiprion percula acquired from a local retailer in Athens, Georgia. We have no idea of the source of the C. irritans on that fish. We don't know if the parasites can reset their internal clocks. If the parasites can reset their internal clocks, we don't know how long it takes and what the required stimuli are. The only thing we can say for sure is that the parasites that they guys had, showed a synchronisation in their excystment that appears to be unrelated light/dark phases. Anything beyond that is pure speculation.

Let's look at a few scenarios...

If we assume the A. percula came directly from the GBR, Australia, with the C. irritans already on it; If we also assume that C. irritans cannot reset its internal clock; As the GBR is 15 hours ahead of Athens, Georgia (ignoring Daylight Saving), the 0200 to 0900 that Yoshinaga and Dickerson observed would have been 1700 to 0000 local time on the GBR.

If we assume that the C. irritans came from the eastern Pacific and it can't reset its internal clock, the 0200 to 0900 would have been 2300 to 0600.

What if the parasites can reset their internal clocks? How long does it take? In the Yoshinaga and Dickerson study, they maintained the infection for 2 years, so if the parasites did reset their internal clock, it must have been before the researchers acquired them - or the timing experiments were performed over too short a time.

As I said, all we know is that for the one group of parasites that Yoshinaga and Dickerson maintained (which were all from the same source) there was a common circadian periodicity.

To me, they still seem to drop off and reinfect on a different part of the fish at night.

But that could simply be because you notice the difference more in the morning that you do throughout the day. Further, as the trophonts are usually too small to see when they first infect the fish, the spots are only noticeable a day or so after infection. Without microscope inspection, it would be very difficult to be certain at what time of day the fish were reinfected.

 

[ATJ]

I am going to ask Skip about inserting a foot note.

This was one of my frustations when writing articles for ReefKeeping. In all three articles I discovered errors (or had them pointed out ) after the article was already published and there's no easy way to correct it. Those authors that write the columns can at least make an erratum in the next month's column but for the one off guys... that's it.

 

[ATJ]

Wait until you see Part Two.

I'll just have to... wait that is.

I hope you put the kaibosh on freshwater dips, UV, "reef safe" treatments and cleaners.

 

[ATJ]

I just saw Skip chimed in. Originally I wrote this as one long article, so I had all my references listed. I then split it into two parts when I went over 8,000 words. I know I don't have the patience to plow through something of that length in one sitting, so I broke it into two. This also allowed me to further seperate the scientifically proven methods from the ones I am covering in part two; freshwater dips, quinine-based drugs, 5-Nitroimidazoles, UV, ozone, cleaners, natural immunity (proven but I discuss it here to help illustrate how difficult it is to point to a response in a particular fish as proof of a cure versus an immulogical response), medicated foods, garlic, ginger, pepper, tea extract, and assorted other kitchen "remedies". So, I tried to catch all the ones that should be listed in part two and not part one, but a few may have slipped through due to time constraints.

Ah, OK. That makes sense.

 

[TerryB]

TB: Gheez,
I didnââ"šÂ¬Ã¢"žÂ¢t want to come across as being too critical because I felt that the article was better than most that have appeared in the hobbyists magazines. I encouraged Steve in another post here. However, since the subject has been breached I will join in the conversation.

SP: There is differing research on how long theronts last, I believe due to variations in the parasite due to geographic location. Most say less than 24 hours. Colorni was able to find some still kicking until 48 hours, but he was working with either Red Sea or Mediterranean isolates and even he conceded that almost all are dead after 6-8 hours (Colorni & Burgess, 1997). Plus, I think Colorni was only looking for theront movement under a microscope and did not look for actual infection rates after such a long time.

TB: I believe that Colorni said that some theronts survive up to 36 hours and not 48. I donââ"šÂ¬Ã¢"žÂ¢t think his study considered the actual infectivity of the theronts during that period of time. They survive a lot longer than they actually have the ability to infect fish.


SP: The environmental triggers part is really a compilation of my own experience and references, but I should have probably listed:
Bassleer, 1996
Calfo, pers. comm.
Dixon, pers. comm.
Fenner, pers. comm.
Joshi, 2003

TB: I questioned this also when I read the article. It should be noted that none of these references are published in the scientific journals and reviewed by their peers. I donââ"šÂ¬Ã¢"žÂ¢t disregard the importance of a low stress environment, but these factors are not a prerequisite to infection. I know that they are commonly held as a reason for Crypt infection, but I think this is largely overplayed.

SP: Hyposalinity:
I had not heard about then kidney failure potential until Dr. Ron mentioned it on 8/3/03. I did not have time to find my own references, but I do now have a couple on the way through ILL. I do want to read up more on this myself, but I believe Dr. Ron was talking about long-term exposure versus a couple of weeks for treatment. Dr. Ron has both an online discussion and article that mention this occurrence,

TB: Ron and I discussed this in person several years ago over drinks at a convention in Vancouver Canada. I am surprised that he would still say something like that. If I remember correctly the comment first appeared online in the context of talking about inverts (i.e.crabs) and not fish at all. I would also like to see a reference from the journals on this. Count me very skeptical on this one. It may be pure speculation. Stoskopf pages 48 ââ"šÂ¬Ã¢â‚¬Å“ 50 would seem to refute the idea. It should also be noted that there is some evidence that ancient seawater was only about 35% as salinity as seawater is today. This would mean that saltwater fish evolved in much a much less saline environment making the contention that hyposaline water causes kidney damage all the more remote. BTW, I do not advocate hyposaline conditions on a permanent basis, only as a therapy. Besides that the research so far does not indicate that hyposalinity causes such problems. Chueng, 1979 concluded that bony reef fish can be kept at a salinity of 16ppt ââ"šÂ¬Ã…"œindefinitely.ââ"šÂ¬Ã‚

ATJ: That paragraph is very much out of place with the rest of the article where you demonstrate that it is the presence of the C. irritans that causes the infections, not environmental conditions. Most researchers would agree that if C. irritans isn't present, fish won't get infected regardless of the environmental conditions and conversely, even if environmental conditions are perfect, the presence of C. irritans in the confines of an aquarium will result in the infection of naive fish. Please note I mean confines in the sense of bringing the parasite and fish in closer contact, not necessarily an overcrowded situation.

TB: I agree.

ATJ: My scenario was to show that even if the reproductive stage was less than 28 days, you could still be introducing parasites into your display tank if you transfer the fish on the 28th day. You may think it is unlikely but it happened to me just last year.
I agree in the kidney failure potential for stenohaline fish. I was pointing out that very few reef fish have been studied in detail to determine if they are in fact stenohaline. The only reef fish that I know that has been studied, P. imperator, was found to be "physiologically euryhaline" and so kidney failure is probably unlikely for that species. I wonder how many other reef fish are also "physiologically euryhaline".

TB: I only use the 28 or 30 day period as a time frame in which to keep the display tank without fish in order to starve the parasite out for lack of a host. I can understand why you would feel it is necessary to treat fish for 6 weeks by your thinking. However, when the aquarium is kept at 14ppt the tomonts will be destroyed (literally) so a longer time frame should not be necessary.
Maybe you can enlighten me as to how a salinity of 14-16ppt could cause kidney failure to bony reef fish? A lower salinity in the surrounding ambient water that is closer (still somewhat higher) to that found in the internal fluids of the fish should actually require less effort by the kidneys while still allowing them to function in a normal manner.
I am also a bit concerned about the idea of there being more than one species of Cryptocaryon irritans, this has not been established. It is pretty well agreed upon that there is more than one strain of the parasite, but not enough differences between them to call them distinct species from one another.
You know, all this discussion between three "ich aficionadosââ"šÂ¬Ã‚ such as ourselves could be dangerous. The next thing you know, we will be critiquing all of each others articles. Then we wonââ"šÂ¬Ã¢"žÂ¢t be able to write anything without consulting one another.
Terry B

 

[MiddletonMark]

I don't have much to say, other than Thanks guys!

This discussion here is quite interesting, and I do say it's great to have Steven's article out in such a visible, available place. Can't wait until part 2 .... I'll be reading here, and there; as the info in all your heads is so much better than anything else online on ich.

Very nice to refer people online to. Most people on boards don't seem to be able to read books or non-online sources of info - leading to much mythinformation.

TerryB helped my understanding greatly about QT practice a month ago - Steve now has added a great reference work ... I'm very thankful to have such knowledgeable folks sharing their smarts with us.

Now carry on, please!