Marine Velvet - Myths and Facts

[leebca]

Marine Velvet (Amyloodinium ocellatum)

If our marine fishes pray to a god, then their devil is Marine Velvet.

Marine Velvet (Amyloodinium ocellatum) is very different from Marine Ich (See: Marine Ich - Myths and Facts). What they do have in common is their cost to the fish farm and aquaculture industries!

Unfortunately, their true differences don't prevent them from being confused with one another. It started out by both of them being referred to as the same disease: White Spot. The reader will note that I never refer to either diseases as White Spot, and other than this one paragraph, will never see me writing it.

Another form of confusion was that the classification of this disease was changed. Marine Velvet (MV) was once scientifically called Oodinium. And of course, if that wasn't enough, the aquarist generally doesn't understand that MV is actually a marine one celled alga, a dinoflagellate, and is the member of the same group of organisms that cause the red tides (but not the same). This is in contrast to the fact that Marine Ich is a ciliated protozoan. But what the heck! Spots are spots, right? NOT! :slap:

MV doesn't give much of a chance for diagnosis before it kills. No time to cure the fish. A tankful of marine fishes can perish in a matter of 24 to 48 hours. This disease is the one aquarists should not allow into their aquarium and is the best disease reason, above all others, to practice a quarantine system.

Part of the problem is the proper diagnosis. MV is not as apparent as MI. It is hard to see. By the time is shows up on the aquarist's fish, it is often too late to save that fish, but it may be in time to save other fishes in the aquarium. Daily fish inspection is the best defense. Any fish breathing fast, flashing or with a substantial change in behavior (lethargic when usually active, for instance) is suspect of having this infection.

There aren't as many myths and rumors revolving around MV as there are for MI. Like mentioned above, MV kills so fast that few hobbyists can make the wrong decision because the fish are dead! Still, there are some facts every aquarists should know:


Life and Visuals:

1. The parasite has several stages in its life cycle. A cyst (cyst-1) releases up to 250 free-swimming dinospores (usually 64) that try to find a fish. The dinospore attaches to the fish mucous layer and sends filaments (roots) into the fish to draw nutrients from the fish. When engorged the filaments are withdrawn and the dinospore forms a kind of cyst (cyst-2) on the fish where it internally divides and multiplies. This cyst-2 comes off the fish or hangs on and becomes cyst-1. The cycle continues.

2. The only time a human can be made aware of the sure infection is from two common features (other than 'normal' symptoms noted below). They are the 'sheen' and the 'spots.' For another means of identification, see 14. below. As mentioned above, by the time these two things are seen, the fish is usually too far gone to save.

3. An infected fish can appear to have a certain sheen to its surface. Quite often the sheen is colored to the appearance of gold. This is the origin of the name "velvet." This sheen has a velvet appearance.

4. An infected fish can appear to have very tiny specs on its body. The white specs are likened to the size of a grain of powdered sugar. The fish has an appearance of being powder sugar coated. This is very hard to see, depending on the color of the fish.

5. Dinospores that have just attached themselves are not visible to the human eye. The sharp human eye can see the cyst-1 or cyst-2 stages when they are developed enough AND with proper contrast. This organism is an obligate parasite. It cannot live and cycle without a fish host.

6. Cycle can be completed within 6 days. 12 days are nearer normal. But some of those cysts have been found to hang around for up to 5 weeks before releasing the up to 250 dinospores. Like MI cycle and stage times, times given are averages and ranges. It is best to treat the timing like that of Marine Ich and go with a 60-day base for a 100% success rate for treatment and fish handling.

7. MV is not the same as MI (see top of post). The organisms actually have very little in common.

8. MV is more sensitive to temperature. The cycle time can be decreased by an increase in temperature. But. . .to do so means the fish will die faster. If there is any merit to altering the temperature, it would be to lower the temperature to slow down the spread of the disease.

9. Parasite usually targets the fish’s gills. So much so that this is the main reason that by the time the aquarist sees the specs or sheen, the fish is too heavily infected. The gill tissue has more water passing by so there is an increase in chance the free-swimming parasite will get to the gill. Also, for MV the gill tissue is more easily attached to, and nutrients gathered from, than on the body mucous coating. This is one reason why fast breathing (over 80 swallows in one minute) is one of the first symptoms of possible infection.

10. The parasite sticks to the mucous layer and thus is more on the surface of the fish than under the fish's skin like in MI. Still the mucous layer can afford the MV some protection from the water environment.

11. Parasite is transmitted in water (free-swimming and cyst stages), or by falling off of an infected fish (even one that seems healthy because of 9.). This means that water OR fish from an infected aquarium can carry the disease to another aquarium.

12. The parasite can infect bony fishes, elasmobranchs, and teleosts including eels, sharks, and rays. Even a freshwater fish moved to a brackish water (like mollies) can be infected, harbor or carry the parasite. Invertebrates, snails, crabs, corals, plants, etc. are not affected/infected by MV, but their water can carry them. These parasites can live, infect and reproduce in water from 3ppt to 45ppt in salinity! This is why hyposalinity is not a means to kill this parasite (see 2. below).

13. There is no such thing as a dormant stage for MV. The parasite can’t wait around for another host. It MUST go through its cycle, or die. It doesn't 'wait' for better times. It was recorded that a cyst can exist for up to 5 weeks before releasing its free-swimming dinospores. This is rare but possible.

14. A simple means of quick identification is to put the fish in a freshwater dip (without methylene blue) for up to 20 minutes. Remove the fish and closely inspect the FW dip water sediment. The small cysts (cyst-1) are just visible to the eye if you have enough contrast (black or dark background). But don't be fooled. It is still best to be viewed under magnification (microscope) for proper identification.

15. MV can live and reproduce in temperatures as low as 60F and as high as 86F. This is a slightly narrower range than MI. Still, temperature is not a means to kill it. Raising the temperature would speed up the disease's life cycle but that would just kill the fish all that much sooner.


Treatments:

1. Copper treatment - Follow medication recommendations. Can be effective in 2 to 4 weeks of treatment. After treatment, remove all copper and observe fish for 4 more weeks. See: Copper - Treatment, Use, Problems.

2. Hyposalinity - Doesn't work.

3. Transfer method - Too slow -- OR -- disease spreads too fast.

4. Only the above copper cure works 100% of the time. Other chemicals will kill the MI parasite, but only in special conditions (not good for the fish) or in lab experiments (not using marine fish). Some chemicals will only kill some of the organisms, letting the others escape death to go on to multiply and infect.

5. Formalin has been known to free the fish of the parasites, but the parasites are still alive and can re-infect. Formalin baths have been used, but since the fish has to be in water not infected with the parasite, this treatment isn't feasible.

6. Treatment must be done in a hospital tank or quarantine tank. The copper treatment would kill invertebrates, live rock, and other non-fish marine life. Substrates and carbonates interfere with a copper treatment.

7. No known ‘reef-safe’ remedies work consistently. It’s easy for any manufacturer to have an independent study done on the effectiveness of a ‘reef-safe’ remedy but they don’t because. . .

8. Cleaner wrasses are not known to pick these parasites off of fish. Their gut reveals no parasites. Cleaner shrimp may pick many of these off of the fish, but an infected fish can't be totally cleaned and is usually doomed. These are not effective controls or preventative measures.

9. Like MI, the display aquarium, if infected has to be treated. Let aquarium go fishless (without any water additions, contamination from infected tanks, live rock additions, etc.) for at least 8 weeks and the tank will be free of MV. This 'fallow period' has over a 99.99% chance of success.


Defense and Immunity:

1. The fish’s mucous coating can provide some protection from the parasite. But there is little in the way of immunity or defense. This in part is the reason why so many fish die in the captive environment.

2. When water temperature drops, mucous coating is often reduced or lost in marine fishes, that is why sometimes MV becomes visible on the body of the fish after a sudden drop in temperature. This meant, however, that the disease was present and living in the aquarium, infecting fish without the aquarist having been aware of it.

3. No fish, no matter how good its defense is, can stop being infected. A healthy fish will and can be equally infected as a sick or stressed fish. What happens is the aquarists sees one or more fish with the disease and assumes because none are seen on the other fish in the aquarium that they are 'disease free.' NOT. Aquarists can't always see the parasites. All fish in an infected tank require treatment.

4. A weak, stressed, or sick fish will die sooner than a healthy fish, but is no more likely to get infected than the healthy fish.

5. Vaccination seems to work, but not affordable or likely available to the hobby for many more decades. The vaccine materials are hard to make, expensive, and slow to produce.


Subjective and Non-Subjective Observations, Claims, and Common Myths

1. Tangs seem more susceptible. True. Their mucous coatings are reduced in thickness and composition. They swim up to 25 miles a day in the ocean in search for food so maybe Mother Nature provided them with this as a means of 'escape.' On the other hand, it has been found that fishes with a very thick mucous coating have some resistance to MV infection. Remember, the disease is stuck on the mucous coating and sends roots into the fish to feed off of it. Evidence and studies show that a thick coating gives some protection.

2. It goes away on its own. Untrue. Only visible at one stage IF it is on the body or fin of the fish. It’s the life cycle. If it was once seen, then it hasn't gone away -- it's just not visible to the aquarist.

3. Aquariums always have MV. Untrue. MV can be kept out of an aquarium. Just quarantine all fish and don’t let non-quarantined livestock get into the aquarium. After keeping thousands of marine fishes, my home aquariums have been free of MV since 1970.

4. Fish always have MV. Untrue. In the wild they often show up to 3% infected (or more). It's not that common in the wild, fortunately, so the wild-caught fishes usually don't have it. In the captive aquarium environment the parasite can 'bloom' and overcome the fishes very quickly. In capture and transportation the fish can share the disease but since few had it to begin with, this is usually not an issue.

5. Just feed the fish well and/or feed it garlic and it will be okay. Untrue. I compare this approach to this one: "Granny has pneumonia. Let's keep her home rather than take her to the hospital. We'll feed her well with chicken soup and vitamins -- and lots of garlic." Nutrition, foods, garlic, vitamins don't cure an infected fish. An infected fish is sick and is being tortured by the itching and discomfort. It can't live long with this disease. Don't let this happen to the fish. Cure it!!

6. A new cure has been discovered. Unlikely. If the aquarist thinks they have found a new cure, then have it researched and independently tested. It's easy and cheap. If it is as good as the copper treatment then the professional veterinarians, private and public aquariums, fish farms, and I will use it. The aquarist needs to keep the perspective of how devastating this parasite is not to just the hobby but to the whole fish farming industry. Any new way of 100% treatment will make headlines!

7. UV and/or Ozone kills MV. Ozone doesn't kill all parasites that pass through the unit, nor does the water treated with ozone kill the parasites. UV only kills the parasites that pass through the unit. Not all MV parasites will pass through the unit, so the UV will not rid an aquarium of MV. A UV can help prevent a 'bloom' of the parasites however, and thus help in its control. UV is not a cure nor a preventative measure for MV.

8. My fish are immune to MV. NOT. The fish immune response can't stop the parasite from sticking to the mucous. Once stuck, the 'roots' that burrow into the fish don't seem to be affected by the immune response. Much work is still being done on this aspect, and it seems there can be some vaccines which will help the fish stop the parasite.

9. Fish in the wild have MV, then let them have it in the aquarium. Not a very responsible approach. In the wild, few fish have this disease. The ones that do can die, but most 'get away' from the parasite by 'traveling' away from the cysts that fall off. In the captive environment the fish can't get away from the reproducing disease. The captive life favors the parasite.

[francoisj]

Thanks for this very interesting information on MV.

Few questions regarding MV:

- Since some fish can carry the parasite without showing any symptoms, how can I be sure the parasite is not there after the quarantine period ?

- Is any/all fish will eventually show sign of the MV during the quanrantine process ?

- Is copper treatment Ok to be used as a preventive treatment for all new fish ? Seems not to me...

- Dropping the temperature as I understand could help to spot the parasite but since nobody seems to suggest this, I assume this is not safe ( too stressful for the fish ? ).

- Does it all comes down to correctly identifying the parasite after a FW dip ? I think I have seen MV cyst on the the FW dip of the last dying fish of my tank (...) but I am not quite sure I'll be able to make a correct guess on the next fish I dip...

Having been 'converted' to 'quarantine everything', I just want to be sure I don't miss anything this time...

Thanks in advance.

[leebca]

WELCOME TO REEFLAND!

All good questions.

The principles of quarantine are many fold. Unfortunately, people in the hobby just think that quarantine has a single purpose. They are wrong, of course.

One of the things a quarantine process does is confine the fish in a small space. This also confines the disease, pathogen or hitchhiking organisms into a small space. In the small space, the parasite group of pathogens get two advantages:
1) it has a captive host;
2) it hasn't got far to go to reproduce.

We use both the above to get the pathogen to 'show' itself. Those that contend the ocean is the same as the marine system should note that this is one major difference. Space. In a confined and limited space, diseases can run rampant because, unlike in the ocean or sea, the fish and host can't get away. This is why diseases in the marine system must be erradicated, just like they do in public and private aquariums.

In the case of MV it is best not to wait for it to show itself. The nature of this pathogen when in a confined space with its host is to kill the host quickly. You probably know that the 'goal' of a parasite is to not kill its host -- otherwise the parasite can't spread, reproduce and continue its existence. But that is in the sea/ocean. In the confines of the aquarium, the parasite ends up killing its host by simply overpowering it.

Since I recommend ALL newly acquired fishes be FW dipped (and have provided a step-by-step procedure for this), this forms the basic method to immediately identify if the fish has the MV pathogen. They are just visible to the unaided eye at the bottom of the dip water. The dip water must be clean and free of such debris before using it. Then after the dip: Finding tiny, talc sized 'stuff' at the bottom of the dip bath then proceed to copper treatment.

Copper is a poison. It is stressful on a fish. Treating with copper should not be done without verifying the presence of a pathogen that can be cured using copper. Copper can lengthen or even prevent a fish from becoming truly and completely acclimated. A copper treatment can prevent a new fish from ever eating, but if the fish is known to be diseased, it is better to treat with copper and risk the fish starving, then it is to condemn the fish to death by disease.

MV has been found at many temperature ranges in the seas and oceans. It can live comfortably at very low temperatures. It can live at limited high temperatures. If the water is raised to above 84F the MV will have difficulty living. However, so with the fish. The manipulation of water temperature is not a good way to try and control the MV parasite and it is not a means to cure fish of this disease. More stress will be put on the fish and the pathogen will still live.

If the pathogen was properly diagnosed and the copper treatment properly performed, there should be no concern about there being any pathogen left. However, another dip can confirm this. It is easier however, on the fish to leave the fish in quarantine at least 4 more weeks AFTER the end of the treatment for MV. MV will show itself and the aquarist at that point should have the med and test kit on hand to administer another treatment (and try to figure out what went wrong with the first treatment).

Just because a fish has been treated for one ailment or disease, doesn't mean the fish is free from the other 100+ marine pathogens. The quarantine process must continue for no less than 6 weeks total AND proceed no less than 4 weeks AFTER a treatment, to verify the fish is disease free and eligible (disease-wise) to move into the display.

[baobao]

Lee,
You mentioned, "Formalin has been known to free the fish of the parasites, but the parasites are still alive and can re-infect. Formalin baths have been used, but since the fish has to be in water not infected with the parasite, this treatment isn't feasible."

I believe there are two ways to treat with formalin. a) pull the fish out and do a bath (I think 3.75ML/Gallon for 30 minutes?) b) dose QT with a smaller quantify of formalin for longer duration (1 ML/20 gallons for 24 hours, then I assume redose would be necessary since this stuff breaks down?)

I think you statement refers to a) in which you do the bath, and then return the fish to the QT.

Question - Would b) be an effective against Velvet? I guess the question is does formalin kill the Velvet organism? [I know Copper works, but the question is whether formalin by itself used judiciously can be an effective alternative treatment]

Thanks.

[leebca]

You are correct in assuming my wording was for the Formalin bath.

Unfortunately, the death of the Marine Velvet parasites in low dose Formalin is not good at all. In fact, Formalin doesn't kill the parasite. Thus a prolonged treatment in Formalin has never been prescribed for this parasite.

The thing is, a prolonged Formalin bath (9 hours) will remove most of the parasites from the fish but just as soon as the Formalin is removed, the parasites continue with their life cycle. That is to say, Formalin doesn't kill the parasite. Mostly the Trophont stage is almost totally resistant to Formalin.

The lower level continuous Formalin treatment has even a lesser effect on the parasite on the fish than the 9-hour higher concentration treatment.

[baobao]

Thanks for your insight

[berkdog]

How deadly is MV (you say an entire tank can die within 24-48 hours)? When fish are in the QT, if they're doing well after 4-6 weeks in quarantine, can it be assumed there is no MV in the tank nor are the fish infected? If they can last 5 weeks without any fish, would that be because there are no fish there for them to infest? Or if fish are in the tank, can MV sit and wait 5 weeks before infesting fish nearby?

Thanks! Very interesting (and scary) information.

[leebca]

MV is as deadly as written. That is the point of the QT -- to see if this and other pathogens display. No display, then the fish are free of it. MV goes through cycles, as indicated. There are phases in its cycle that don't require a fish, so the time is to allow the pathogen to go through those phases and get to the phase where a fish is needed to continue living. All that time is part of the waiting time of weeks.