Bacterial Diseases Of Corals: Perspectives and "Cures"
It has recently become apparent that most of the losses of Acropora and other small-polyped stony corals in captivity are due to bacterial diseases. In this lecture, I hope to introduce you to the problem, show you how to recognize the problems, and instruct you on how you may correct them.
How do I know if my corals have a problem?
The brief answer is that they die. There are a number of ways that can happen, however.
- Rapid Tissue Necrosis
- Bacterial-Induced Tissue Necrosis
Both of these describe syndromes where acropora and other SPS corals rapidly (or not so rapidly) slough tissue from thier skeletons. Similar syndromes have been described in the wild. There are several patterns of tissue loss. In the first case, the coral rapidly loses tissue from the skeleotn. When the coral is subjected to current, many times large clouds of coral tissue will be seen sloughing from the skeleton.
I've had the organism that causes this disease cultured. It appears to be one type of Vibrio vulnificus. What is Vibrio? Well, Vibrio bacteria are actually the most common class of marine bacteria. Most of the bacteria in the ocean are one kind of Vibrio or another. Many of them are good citizens. Some of them are luminescent, and help deepwater fish and squid be bioluminescent. This is a symbiotic relationship between the larger host organism and the bacteria. Moreover, the symbiosis is often intracellular. So Vibrio can get inside cells of higher organisms.
Not all Vibrio are good characters, however. Several of them arepathogenic. For example, Vibrio cholerae causes cholera in humans. Vibrio vulnificus is the leading cause of seafood-related deaths in theUnited States, and is a major source of infections in open wounds exposedto seawater in warm regions of the world's oceans.
The organims which seems to cause rapid tissue necrosis in corals has the biochemical signature of Vibrio vulnificus. I've had it cultured, others have as well. I'm in the process of fulfilling Koch's postulate with the organism, and showing that it causes disease in corals by placing clean corals in contact with the organism.Vibrio vulnificus is a tough customer. It secretes powerful proteases into its environment. It can liquefy wounds in humans. In corals, it seems to break the bonds between cells and between the coral and the skeleton, which leads to sloughing of tissue.
There is also some evidence the some type of Vibrio is responsible for the expulsion of zooxanthellae from corals under some conditions. Most people think of bleaching as being caused by various environmental factors, like high temperature or atypically strong light (esp. UV light.) However, there are reports that bacteria can cause bleaching.
There is also some room for confusion here. There is a difference between explusion of zooxanthellae, which can leave a white coral organism, through which you can see the skeleton, and a bare coral skeleton. In one case, you are looking through the organism, which is still alive, although perhaps not for long. In the other case, you are looking at the skeleton, and the coral is gone. It can be difficult to distinguish these two outcomes underwater.
So, there are some accounts of "bleaching" in the wild that might actually be RTN. It is also possible that we have mistakenly ascribed temperature as the dominant factor in zooxanthellae expulsion, when bacterial harrasment also might be as important.
V. vulnificus is found mainly in tropical waters. The hotter the water gets, the more V. vulnificus likes it. It also likes lower than natural seawater salinities. Summer heat brings rain in some parts of the world, and the conbination of high temperature and reduced salinity in shallow water might be enough to give bacteria a foothold on a reef.
NOW THAT WE KNOW WHAT IT IS, WHAT CAN WE DO ABOUT IT?
There are several remidies prescribed for RTN and other bacterial diseases of corals. They are:
- Lugol's dips
- UV sterilizers
- Antibiotic therapy
- Improved efforts to simulate the reef environment, e.g. more waterflow.
I'll go through each in order.
OZONE has been show to be effective at decreasing the V. vulnificus burden of oysters. (People can get V. vulnifucus from eating raw oysters, and when they do, it is like a science fiction nightmare.) However, monsterous doses of ozone are required. The seawater is effectively "brominated" or "chlorinated" by the time an effective ozone dose is reached. Ozone may be capable of reducing the quantity of V. vulnificus in the water in the aquarium, but it will do nothing about bacteria that are already inside. Remember that V. vulnificus can become intracellular.
LUGOL'S DIPS Also have some small degree of efficacy. Iodine is a moderately strong disinfectant that can reduce the surface burden of bacteria on a coral. Again, it will do nothing about intracellular bacteria, because by the time you reach a sufficiently high concentration inside the cell to kill the bacteria, the cell will be dead as well.
In conjunction with fragmentation, Lugol's dips can be somewhat effective.
UV STERILIZERSUV has proven to be ineffective at decreasing the Vibrio burden of shellfish. UV will kill bacteria in the water column, but attached bacteria are inaccessible to it. Use of a UV sterilizer might slow the progress of a V. vulnificus infection in the tank, but it will not cure it.
ANTIBIOTIC THERAPY is the only sure-fire way to kill these bacteria. I've used antibiotic therapy in the aquarium and in isolation vessels.
Paletta's recent AFM article again championed the use of tetracycline. Tet has one thing going for it. You can get it at the pet store. However, in collaboration with Beverly Dixon, the pattern of antibiotic sensitivity in the organism that causes RTN has been determined. The bacteria are almost completely insensitive to Tet. Moreover, tetracycline is unstable in seawater. It forms insoluble calcium salts. And because tetracycline is a bacteriostatic agent, it takes time to kill the bacteria. The 8 hour quaranteen mentioned in Paletta's article just isn't long enough.
Other antibiotics in the tetracycline class may be effective. A friend of mine has tried doxycycline hyclate, with reasonably good results. Paletta has also apparently used this antibiotic with good results. The problem? It is a drug used in humans, and is available only by prescription.
The most effective antibiotic against the organism that causes RTN is chloramphenicol (CAM, CMP.) This antibiotic is available through vets. It is presribed for non food producing animals such as dogs and cats. It is the ONLY antibiotic tested which displayed significant inhibition against the organisms cultured from dying corals.
Other compounds that you might be able to find, like sulfa drugs, neomycin, etc are all ineffective.
There is some reason to be careful when handling chloramphenicol. When
administed to humans in theraputic doses, about 1 person in 40,000 develops
a life-threatening and potentially fatal form of anemia. This is the reason
CMP is so rarely prescribed for humans. It can also cause significant
problems in very young infants. So this drug should be kept of of the reach
of children, and you should minimize your exposure to it.
- Perform a Lugol's dip of the coral at 5-10 drops of Lugol's per literfor 15 minutes. If this proves to be too much in your experience, thenback off the dose and/or duration of the therapy.
- Move the coral to the quaranteen vessel, administer 20 mg/L chloramphenicol. Perform a 100% water exchange after 24 hours.Add new antibiotic at this time.
- To the liquid in the quaranteen tank, or in another container, add5-10 drops of Lugol's per liter for 15 minutes. This gives good surfacesanitization of the coral, and kills whatever is resistant to the antibiotic.
- And this is important: After the coral is removed from the quaranteencontainer, bleach the container and the water it holds. You should also bleach the exchange water prior to disposing it. Add 1/4 cup ofbleach per gallon of water. This destroys the antibiotic and anyresistant bacteria prior to disposing the water. It is extremelyirresponsible to just dump antibiotics into the environment.
Dissolve the chloramphenicol in absolute ethanol or "everclear" drinkable alcohol. It is almost insoluble in water, ao you need to pre-dissolve it.It is soluble to >100 mg/mL in absolute alcohol.
This is very dangerous, and I rec' it only for cases where other measures have failed and the aquarist believes that they are going to lose the entire tank of corals.
Use 2.5-5 mg/L chloramphenicol. Turn off the skimmer, remove any activated carbon or other synthetic adsorbants, then add the antibiotic, dissolved as above. This sets in motion a process that can potentially take the tank down.
Within 1-3 days, there will be a tremendous bacterial bloom in the system. A large part of the bacterial population will be nuked. They die, dissolve, and new bacteria grow. When they grow, the oxygen demandof the system increases dramatically. A few grams of growing bacteria can consume as much oxygen as a adult human. The ORP and DO of the tankplummet, and you must intervene to save the system from crashing.When the bacterial bloom hits, you need to immediately restart the skimmer.If the skimmer is flat, you need to add an oxidant to the system to restartthe skimmer. Failure to act in a timely fashion can result in the destruction of youraquarium. In one of the ten cases where whole tank therapy has been tried,the user failed to act in a timely fashion, and about half of the fishin the system perished.Unfortunately, since Paletta took the protocol from me (unacknowledged) in his AFM article, people were not told how to manage the end of this process.I'm somewhat afraid that people will try to use CAM and will crash their tanks.
Q: Could you tell us what oxidant is added to restart the skimmer?
Either use potassium permanganate, in solution, dropwise near the pump driving the skimmer, or add bleach dropwise, again, until the skimmer shows some signs of life. It can get fairly nasty in the tank when the ORP is below 200 mV. I would start the skimmer if the ORP fell below 250 mV, bacterial bloom or no bacterial bloom.
Q: Do the symptoms of this resemble the "Brown Jelly"?
So, the problem isn't "stress" it is anoxia.
Brown Jelly is caused by a protozoan. It looks like brown jelly on the coral.
These bacerial diseases eithr cause the coral to bleach, or to slough tissue.
Q: Could you give a common name of Potassium Permanganate? And the bleach should be just a plain Chlorine Household Bleach (no scented Clorox!)?
Potssium permanganate has no common name, as far as I know.
Q: Is there any way to tell if the orp is below 250mV if you don't have a prob?
Bleach is just plain old non-scented chlorox or whatever brand is cheapest.
Q: Also, can V. Vulnificus develop a resistance to CAM?
Go easy with all of those things. When I say dropwise, I really mean it. There are all powerful oxidants.
It is possible that there will be CAM resistant variants of V. vulnificus at some point in the future.
Q: As far as a coral seeming to "disintegrate", could this be a bacterial disease?
When that happens, we are SOL, because I have not found another antibiotic that puts a serious dent in the bacteria. CAM works like voodoo right now.
Yes, disintegration of a coral may well be a bacterial disease. I'm sure that soft corals get them as well, but we don't know as much about them yet.
Q: Will the commercial oxidant sold by Kent called Poly-Ox work instead of the bleach?
Q: How can you detect if the coral has a virus or something when it's still in the shop and not opened very much?
I don't know anything about Poly-Ox. Sorry.
If a coral is sloughing tissue, I would not take it home under any circumstances. If the coral is receeding at the base, again, that is a big danger sign. If the coral is not opening after a while in the dealer's tank, that can also be a sign tha
Q: Does cam work 100% of the time ?
I wanted to say a few words about improving our reefs. (I'll get back to the cam question in a bit.)Gregg says I have been informed that the ingredients in Poly Ox are mangainc acid salts. Is this similar to P. Permanganate?Water flow is of critical importance in keeping SPS corals happy. manganic acid salts sounds vaguely like permanganate, yes.
Q: When we're back to CAM, another qustion posted was: Can CAM be stored for any length of time? What's the ideal storage procedure, and what's the shelf life under those conditions?
I use a Gemini pump in my 75.
OK, on CAM. It works essentially 100 percent of the time for me.I did the whole tank therapy gig when my tank was going down.As far as I know, I was the first person to do this. It was about a year ago.Essentially every coral in the tank was affected to some degree.After I added the antibiotic, I only lost one coral that was well on its way to disintegration.None of the corals that I've put through CAM isolation have developed RTN later.
Q: Is CAM is a protected chemical and requires a special licence to purchase?
And my tank is free of the disease now, or at least I see no signs of it.CAM can be obtained from a VET. It is not something that you can just order from a chemical supply house if you are a private individual. CAM is not sanctioned by the EPA for aquaculture purposes, because they don't want CAM residue in foods.
Q: When the whole tank treatment is performed, does this cause a whole cycling of the tank? and, when finished with this, how long until water change or activated carbon?
It does not cause the entire tank to cycle. I was barely able to find ammonia in my system, and I suffered zero fish losses. In my estimation, biological filtration in reef tanks isn't that big a deal, especially if you have a big skimmer on the system I think that the corals actually like whatever ammonia is liberated in this process.The water should clear within a few hours after you restart the skimmer. One important caveat!!! So far, this has only been done in tanks that have ETS skimmers. So they are very strong skimmers, and I can't tell you for sure how this is going to go if you have a small skimmer on your tank.
Back to water flow. The best thing that I ever did for my reef was to put a gemini pump on it. It is a water-flow monster.
Q: Do you have ony other sucess stories in tanks other than yours ? For example, any other tank equipment/parameters we should take a close look at?
The other thing that I did after the bacterial problem was to dramatically increase the flow in my reef, first with two Hagen 802 powerheads, than with the Gemini. I have a 1000 gph circulation pump on the system, so when all the pumps are on, we have 1000 + 800 + 1000 = 2,800 gph in a 75 gallon tank. That is much more than most reef aquaria have.
Q: Is this return flow in lieu of in tank power heads or with in tank powerheads?
The other CAM treatments have been moderately successful. I think that in some cases
Umm, around 800-1000 gallons an hour is going from the tank to the sump. The rest is all internal circulation, driven by the powerheads or the gemini.
Other cam treatments. Yes,others have enjoyed success with the protocol. You have to bear in mind that the only time anyone is willing to chuckan antibiotic into their reef is when things are almost completely out of hand, and they have exhausted all other alternatives.Given that most of the corals in these reefs seemed to be badly affected and almost certainly doomed, I'd say that the CAM works remarkably well. Terry S. ran this twice, he had problems after the first time, probably because of a dose and duration issue, probably also because he added new corals without quaranteen.Again, let me note that the only people who have done this so far are people with downdraft skimmers.
Q: Is this bacteria always present in the aquarium, waiting to hit a stressed coral, or is it introduced with new corals?
I think it is on almost all of the corals we put into our tanks. It is ubiquitous in seawater. What the antibiotci therapy does is to buy you some time so that you can correct whatever is wrong with the system. In my case, that something was inadequate water flow.
Q: What temp and SG do you recommend to help discourage Vibro? (And any other tank parameters worth mentioning?)
I guess that is the end of the prepared lecture material.
Q: How many people have doen this CAM treatment ?
Specific gravity should be identical to full strength seawater at that temperature. My tank varies from 75 to 84 degrees, depending on the time of year. It isn't possible to stop the bacterial disease just by dropping the temperature a few degrees.Salinity is important. Given that V. v. likes less than seawater salinity, that makes me seriously question the wisdom of people who say that the tnaks should be run at less than full-strength salinity (35 ppt, sg 1.024-6, depending on temp.)
Q: Will a drop in temperature will at least slow down the infection, or does it have no effect?
I also have a suspicion that maintaining good alkalinity in the system significantly helps the corals. A drop in temperature may slightly slow the infection, but it will not stop it.
Q: What do you think about the mystery formulas we are adding to our tanks to replenish trace elements such as Strontium, Iodine, Molybdenum......?
I don't think that trace element supplements hurt the system. I use combisan at about 1/.10th the rec dosage.There are a lot of trace elements in fish food.
Q: What the reccomended alkalinity levels would be? Some people believe that iodine is important. I am skeptical.
Certainly, one can't stop this disease just by adding iodine to the system. I have an open mind about bringing the tank to FSS values of Bromide ion. I did that several months ago and have only good experiences with it.However, neither adding I- or Br- will save a coral once it is seriously affected.
Q: Is there a way to check for ionic imbalances in aquariums which use calcium chloride to supplement kalkwasser additions?
It is difficult to determine ionic imbalances without using a technique like ICP. Which costs a lot of money. If you are worried about ionic imbalances, then something like C-Balance or B-Ionic can work.Alk targets should be somewhere between 2.5 and 5 meq/L.
Q: What is the amount of BR in Instant Ocean Salt ? How do you get it up to NSW levels ? Why is not there in the salt at NSW concentrations ?
The amount of Br- in instant ocean and every other major brand of salt is zero.
Q: What would that alk level be in dkh? dKH = meq/L * 2.8
Q: What salt/salts do you recommend?
Br- is omitted from salt mixes because of fears of ozone damage.I personally think that is a bunch of eyewash. Br- salts are somewhat expensive, so they wre probably overjoyed to take them out.So I'm done with the prepared lecture.
Last modified 2006-11-26 04:29