Ich - self resolving... ?

[tmz]

Clarifications:

Yes, exposed fish do develop partial immunity or better said resistance. According to Burgess and Mathhews 1995, 82% of fish that survive an infestation develop an increased level of resistance. The greater the exposure ;the greater the resistance. They are not ,however, free of crptocartyon irritans . It will likely persist indefinitely with some parasites hosting in the gills, nostrils and mouth unseen. Ther is no guarantee that the resitance is forever. This means it's in the tank to stay unless and until the tank is left fishless for 6 to 11 weeks and the infected fish are effectively treated with copper, hyposalinity or the tank transfer method.

If you have an infected tank and fish are doing ok with low level infections be aware that new additions may not fare nearly as well and may trigger an outbreak as a atress event might.

Ich is not ubiquitous. Confinement gives the parasite a strong advantage with readily available hosts and a lack of natural predation. In the sea most of the parasites would wash away in the current before reinfecting or perhaps be preyed on by some predator absent in our systems. In an aquarium density of ich populations explode with a single parasite multiplying 200to300fold each livfe cycle.

 

[KarlBob]

Ok, so the healthiest fish are fish without ich, but fish who have gotten sick from ich and survived can usually continue surviving with a constantly renewed, low density infestation.

A fish added to a tank with a long-term, chronic infestation will almost certainly contract the parasites, too. If that fish does not fight off the initial infestation, and the parasites get the better of it, then the parasite density in the tank may go way up.

If the parasite density in the tank increases, the parasites may end up overpowering the other fishes, even though they have already survived their own acute, high-density and chronic, low-density infestations.

Adding a new fish also stresses the existing fishes, adding to the chance that the parasites will get out of control, whether the new fish gets sick or not.

Safest bet: Don't let the parasites breed in your system.
Taking the fishes out of the tank for several weeks breaks the parasite's reproductive cycle. Immature parasites without fish to feed on eventually starve.

Treating infected fishes with copper in a separate tank kills the parasites that are already on them, without exposing your reef to lots of copper.

Quarantining new fish kills any parasites they may bring with them.

Result: Your tank stays ich-free, and your fish are healthier because they're not constantly fighting to keep ich infestations manageable (No, I have no idea what that effort actually involves).

 

[wooden_reefer]

I believe different observations for short periods are due the chance factor. The chance factor is due to the lifecycle of the ick organism. Most important is that at one stage the ick organism leaves the host then multiply.

An individual fish has no acquired immunity against ick. It can never get used to it. It has a certain fixed level of defense.

It is a matter of varying chances that yield somewhat different obervations.

Most individual animals do not acquire immunity against higher order parasites (other than bacteria and viruses). Such immunity is attained by natural selection over many many generations.

The implication is that eradication of ick is the only reasonable objective, control is misguided. For ick, there is no control other than eradication.

 

[wooden_reefer]

Actually, in the ocean higher defense against ick may not be rewarded much in terms of natural selection, ie reproductive chances.

Why? It is because the ick organism always leaves the host at one stage of the reproductive cycle. In the ocean, the dilution effect is always quite dominant, except in tidepools. Extra defense against ick in the ocean can be regarded as redundant as is not much rewarded in reproductive chances of the host.

 

[KarlBob]

In terms of individual animals and acquired immunity to parasites, I have no personal knowledge. The posts I was summarizing assumed that fish can develop individual immunity.

I agree re: natural selection. In the ocean a fish get infested, its parasites reproduce, and by the time the next generation of parasites are ready to look for a host, that particular fish is far away. Lots of the immature parasites probably never even find a fish. In the tank, there's not much danger of not finding a fish.

 

[wooden_reefer]

Can an individual human being develop immunity against lice?

Some people may be more susceptible to lice than others, but I think an individual human being has no added immunity against lice infestation.

Not quite the same as ick I know, but I am just trying to make a point.

 

[billsreef]

Something to keep in mind when discussing acquired immunity/resistance to ich, it only applies to the cell line of the outbreak that the fish survives. Hence, when another line gets introduced with a new fish, the acquired immunity of the old fish doesn't count for that new line of ich. The reverse holds true with the new fish, in might be carrying a subclinical infection of a line that it is resitant too, but your existing fish are not.

So it really goes back to what several have said before, prevent it from being introduced right from the start

 

[greenbean36191]

The Burgess and Matthews research did not rely on chance observations. It was a carefully designed, statistically valid experiment.

They intentionally exposed fish to known numbers of theronts and then isolated them in small tanks until all of the trophonts excysted and then counted all of them. They did this to 36 different fish at different exposure levels.

On fish that had previously fought off the parasite there was a significant difference in the number if parasites per fish and the number of fish developing full immunity. That's a clear demonstration of acquired immunity to the parasite. Similar results have been seen with numerous other protozoan parasites.

Google "acquired immunity to protozoan parasites" and you should find dozens of hits giving not only examples of acquired immunity (i.e. immunity that is developed in an individual's lifetime rather than passed on genetically) to protozoans, but also explanations of the mechanisms.

 

[BigJay]

How do fish become "immune" to a strain of ich biologically?

Do they secrete a thicker slime coat?

 

[KarlBob]

Okay. Apparently, a more accurate human comparison would be marine ich vs. toxoplasmosis, rather than marine ich vs. lice. Individual humans can develop immune responses to toxoplasmosis, so it stands to reason that individual fish could develop immune responses to ich. In the paper below, biologists tested a vaccination against marine ich.

From: Science Direct
Immunization of grouper, Epinephelus coioides, confers protection against a protozoan parasite, Cryptocaryon irritans

Apolinario V. Yambot a, c and Yen-Ling Song a, b, ,

a Institute of Zoology, National Taiwan University, Taipei 106, Taiwan, ROC

b Department of Life Science, National Taiwan University, Taipei 106, Taiwan, ROC

c College of Fisheries-Freshwater Aquaculture Center, Central Luzon State University, Nueva Ecija, Philippines

Received 28 January 2006; revised 31 May 2006; accepted 31 May 2006. Available online 6 June 2006.

Abstract
The present study aimed to determine whether protection is conferred by immunization of grouper, Epinephelus coioides, against a protozoan parasite, Cryptocaryon irritans. The immunization of E. coioides was carried out by a low level exposure of fish to live C. irritans theronts from predetermined number of tomonts and by an intraperitoneal injection of a vaccine consisting of formalin-killed C. irritans theronts.

Mucus titers detected by ELISA were significantly higher in fingerling and adult grouper subjected to the low level of exposure to C. irritans theronts at 3-week post-exposure compared to fish that had no previous exposure. In addition, significantly smaller tomonts were produced from adult grouper after three successive exposures than the tomonts produced after a single exposure to the parasite.

In the vaccine-immunization experiment, no mortality was monitored in fish that received high dose vaccine (100 ìg/fish), while 40% cumulative mortality and 100% cumulative mortality were recorded in low dose group (10 ìg/fish) and control group (PBS-injected), respectively. In the succeeding replicate, the vaccine-immunized group (high dose) had 37.5% cumulative mortality and 100% cumulative mortality for the control. In addition, a total of 1830 tomonts were collected at 5-day post-challenge from the control group while none from the vaccine-immunized group. Significantly fewer trophonts and tomonts were enumerated at 5-day and 7-day post-challenge, respectively, in the vaccine-immunized group than the control.

Results suggest that a protective immunity has been conferred on the immunized grouper as indicated by high antibody titers in the mucus of C. irritans-exposed fish and higher survival and fewer parasites in vaccine-immunized fish than the control groups. The conferred immunity played a major role in preventing or limiting the adhesion, invasion, and development of C. irritans theronts on the skin of the immunized grouper.

Keywords: Immunization; Epinephelus coioides; Cryptocaryon irritans; Vaccine; Exposure; ELISA

 

[tmz]

Thanks for the sudy.

 

[KarlBob]

You're welcome. I didn't know there were such studies until greenbean36191 mentioned Burgess and Matthews, so my thanks go to gb.

 

[Eric the half-bee]

My experience in my 1.5 year old reef is that ONLY Tangs have shown signs of ick. I have triggers, wrasses, clownfish, cardinals, gogbies, pipefish and a blenny...Currently, there are no external signs and all the fish look good. When I add another Tang, its bound to arise...

 

[billsreef]

Tangs have virtually no slime coat as compared to the other fish you have. Since the slime coat is the first line of defense, and tangs are lacking in that area, they are more susceptible.

 

[jenglish]

While the experts are around....


I hear that on the opposite end of the spectrum as tangs are things like Dragonettes that have a thicker slimecoat and are "resistent" to crypto. Are they less likely to get and carry ich or only less likely to show visible cysts because they can't get it on their skin. Would they not be just as vulnerable to infections to the gills or mucus membranes?


I don't have these just a question.

 

[tmz]

They are not immune by any means but rarely get ich. I think it relates to mucous coat and maybe the way they move about the tank and settle in for the night. I suppose they could harbor the parasite unseen.
Wrasses although they get it are also relatively resistant in my experience probably due to the mucous web they spin at night. Cryptocaryon cyst usually "hatch" in darkness as I understand it.

 

[illsquaddotcom]

Thanks guys for the great intel. My new powder tang is showing a few ich spots. I'm thinking I'll see how he does for a few days, he's still eating voraciously. If things improve I'll let him heal and maybe when convenient (ie redoing the rock work) I'll pull all my fish and let the tank fallow for a month or so.

 

[wooden_reefer]

Small pathogens like bacteria and virusus are vulnerable to antibodies, but how do immunity against protozoans work? A special substance develops, morphological change of the skin of the fish?

For me this type of discussion is academic. I will never count on any iffy immunity against ick. I am convinced that the only valid strategy against ick is eradication. Control is too iffy or chancy.

Against bacteria and viruses, eradication is both impossible and unnecessary; against ick it is both possible and necessary.

 

[gabbagabbawill]

Does cryptocaryon have a known predator that eats it?

Could LOTS of flow in a tank help in keeping the parasite off of the fish once it becomes water-bourne?

Some people think that crypto may have different strains that could last longer than most people's 6 weeks in a fish and may lie dormant for longer periods, making it through quarantine and into the tank. What do you have to say about that theory?

 

[wooden_reefer]

The ultimate killer of most ick organisms in the ocean is its own lifecycle.

They must leave the host as a part of the lifecycle AND they must find another host within a matter of days at the right moment. This is a very restrictive way to reproduce. This I believe is the absolute crux of it all.

The killer of ick is the dilution effect of the immense ocean, and UV of the sun to some degree.