Category Archives: Viruses

Koi and Goldfish and KHV Cross Contamination

Dr Johnson,

I got your address from my friend Jason who you recently helped with a pecan nut problem.

I may or may not have a KHV problem. If I can give you the story I hope you can tell me if there is anything I should do.

I dug a pond last fall and have 2, 5 inch koi doing fine in it. I have 5, 4 inch koi inside doing very well.

I have a lotus in a whiskey barrel that I’ve had for sometime and put cheap goldfish in for mosquitoes. They usually die quickly and I never thought much about it until I started reading about KHV and saw pics of Koi with KHV. I remember one of the gold fish having a dark patch on its gill cover that looked like a post mortem shot of a koi with KHV.

I have wintered umbrella palms in the lotus barrel.

So my questions.

1. Should I be concerned

2. Is there a nucleic acid test that can test water

3. Is there a non-invasive nucleic acid test for fish

4. At what point should I bring the outdoor fish to you before I move the indoor fish out.

5. Should I throw out the plants or is it safe to put them in the pond

If there are any products I need to purchase from you, please let me know.

Thank you

My Answer:

Koi Herpes Virus is not a legitimate liability to goldfish owners.
Testing is a mixed bag – – because if you test and it’s positive, you have to (by law) go on record with the Federal Government. It’s a “legally reportable” disease so the testing agency has to ‘tell on you’ and that COULD POTENTIALLY mean that you have to surrender your fish to the Fed and the pond gets drained and closed.

Any Koi that carries KHV in cold water will “break” with it when it’s warmed to 70-78 DF
Any Koi that is infected with KHV will ‘get over it’ when it’s warmed to 84 DF.
They’re not considered ”cured”. By anyone but me, and also everyone in Israel.

The plants (left without fish for a week or two) will bring no diseases with them to a receiving facility. I can say that with even more certainty if the plants are in the seventies DF when you quarantine them.

So if you think the Koi outdoors are harboring KHV all you have to do is bring one up to 75 degrees and give it a week to break.

And if it doesn’t, you’re golden, on the KHV issue.

Besides a few recommendations on about heaters and air pumps, I don’t officially “sell” anything so you’re good there ๐Ÿ™‚


CASE: Carp Pox and Flukes Resolved With Heat



Carp Pox should be differentiated from other viral and non viral eruptions with a microscope. In very cold water, there are strains of Ich which will coalesce into large gel-like globs instead of causing the dusting of white spots. Biopsy is important.

  • Carp Pox and certain cancers cannot be differentiated by pathologists in every case.
  • Carp Pox occurs in warm water [Georgia summers] with regularity, so it could be stated that warm water is a cure in some cases.

This fish came to me with Carp Pox and a horrible case of flukes. Fortunately there were no open sores, fin, tail or mouth rot that is commonly associated with the flukes.

Carp Pox and Flukes Resolved With Heat
Carp Pox and Flukes Resolved With Heat

Note the Carp Pox on the body. It shows as “pinkish” colored spots.

The fish came out of a cold pond that had a temperature of 55 degrees. The method of treatment was to warm the water up to 80 degrees. I have found that in treatment of other fish with Carp Pox that heat alone will cure it very nicely.

The hospital tank was set up and salt added to bring it to 0.3% salinity, which is always, my first step in treating any fish. A heater was added to the 25-gallon tank and set at 80 degrees. I then added 3 fluke tabs (PraziPro nowadays) that were pre-dissolved to the tank.

Carp Pox and Flukes Resolved With Heat
Carp Pox and Flukes Resolved With Heat

The above picture was taken just 4 days later. You can see the difference that just 4 days of heat made. By the end of 7 days the fish was completely healed of Carp Pox and no visible signs were left on the body. Also by the end of 7 days all fluke were gone after 2 treatments.

Carp Pox and Flukes Resolved With Heat
Carp Pox and Flukes Resolved With Heat

The major difference is that this fish had the pox all over its body. You can see how the spots look small and “pinkish” in color.

Carp Pox and Flukes Resolved With Heat and Salt

Also, Koi Salting is discussed in the following video.


Heating Koi With KHV Koi Herpes Virus

When confronted by KHV, you can expect high mortalities. In other words, a realistic expectation would be that more than fifty percent of your fish are going to end up perishing.
Should that scare you? No. It should “aware” you. If there’s something you can do to stop the losses, should you? Would you?

The Israelis want to make fish immune to KHV. It takes about 21-30 degree days to do that. No Koi can live that long with KHV. So they gave them KHV and let them break – then heated them into the low eighties, killing the virus. The re-infected the Koi and did the same thing again. Then they re-infected the Koi a third time and created immune Koi because they had seen the virus long enough to become immune, without dying.

So you’d say: How do you know they killed the virus?

It’s simple but no one gets it…..IF THE VIRUS LIVED THROUGH HEAT THEY WOULD NOT HAVE TO RE INFECT THE KOI. The virus would just reactivate when cooled!!

But what if the Koi had already become immune because of the heat, and the virus DID reactivate? THEN THE KOI WOULD NOT BREAK WITH THE VIRUS SYMPTOMS AGAIN (but they did)…(obviating the need for three “infections”)ย  (See also)

What is so hard to understand? How hard would this be to actually test?

Now, as a result of the increasing incidence of this virus among Japanese import fish, a couple of Koi dealers are preemptively establishing a monthly testing regimen for KHV in their livestock offered for sale. I highly doubt that any more dealers will follow suit because it’s a pain, and it costs more, and they frankly don’t care much if YOUR fish die as long as theirs don’t. Since the virus can hide, I’ve thought it is important that dealers test all fish, even the same fish, each and every month. If the virus rears it’s ugly head, it’s caught quickly and that group of fish can be torched.
I’ve (ELJ) been managing a few cases of KHV this winter. The most notable case used cooling to stall the disease progression, slow the losses, and then whenever possible, used high heat to push the fish up past the virus-optimal temperatures and save the fish. It’s worked in the majority of cases: which lived long enough to go through it.

Heating Koi With KHV Koi Herpes Virus

Feb 8, 2003 – “My kohaku (Matsonosuke) you told me to bring in is in the sun room, and was very sick as you know, before. He is doing great and eating every day …. Also, I brought in a orange gin rin Ogon who got completely better too!!!!!! No torn fins, sores etc.”

So, why do some fish get warmed and die, and others get warmed and live wonderfully?

The answer lies in the virus action, combined with the concurrent presence of infection by bacterial opportunists.

First, the virus is devastating to the structure and integrity of the internal organs. Victims report that the insides of the fish are positively liquefied. Also, damage to the gills can be severe and so, when these fish are warmed, oxygen exchange becomes crucial to a fish which is unable to sufficiently respire.

Secondly, when one tries to “warm a fish past the virus” consideration should be given to the fact that very few of these fish are free of bacterial secondary-invaders. Simply, most of these fish also have Aeromonas or Pseudomonas infections. So, CONTROL of these bacterial secondaries will enhance the success of heating KHV.

If one started the heating regimen with a careful examination, observing severe gill damage could portend a failure (death) during the heating regimen on that particular fish. And, without heating, the chances for that fish are dire anyway. But at least a prediction could be made for a more realistic expectation.

Heating Koi With KHV Koi Herpes Virus

Heating Koi With KHV Koi Herpes Virus
Heating Koi With KHV Koi Herpes Virus

The crucial element is taking it very slowly, employing increased aeration and reduced feeding at least at first. Do NOT pull on Superman’s cape when it comes to dissolved oxygen!

Warming a fish up:

Fish in winter ice water sometimes need to be warmed up for various treatments or to rescue them from genuine cold water illnesses such as “Laying Over”.
To avoid shock, the fish should be put in a very large vat of their own, icy pond water in your garage. I repeat, you’re going to use the icy pond water from your pond, that the fish is used to.
This vat should be at least 75 gallons in size or the temperature will equalize too rapidly and kill the fish. They cannot climb up more than 10 degrees F per 18 hours without serious stress or death.
Let the vat slowly warm to garage temperature using the ambient room air. USE NO HEATER. Do nothing to accelerate the warming process. It’s meant to be slow!

They cannot climb up more than 10 degrees F per 18 hours without serious stress or death.

As the fish warm up, they will become more active. Make sure the vat is covered.
Once they have been in the mid sixties for 24 hours, you can raise the temperature with a commercial aquarium heater or a paint-bucket warmer, by five degrees per day til in the low seventies.


Past that, if heating KHV, simply aerate the dickens out of the water and jack it up five degrees per day until you’re keeping the fish in the low eighties.

Common Questions After KHV Outbreak

Here’s why I’m sure that Heat denatures and eliminates the Koi Herpes Virus. The Israelis wanted an “immune” fish. So they infected the Koi and then when they were symptomatic, they heated them to 83-84 dF to clear them. But that wasn’t long enough to generate antibodies. So they re-infected them. And then when they were symptomatic, they heated them to 83-84 dF to clear them. But THAT wasn’t long enough either. So they did it a third time and then the fish had survived “enough KHV” to have antibodies and be immune.

Look at the above.

The fish were saved at 83-84. So we know that saves the fish. You can take THAT to the bank.

Also, note that they had to re-infect the fish. As if the virus was GONE and the fish weren’t going to relapse in the sub-83 dF ideal range of the virus. They have to re-infect them with live virus.

That says to me, the virus is GONE and has to be replaced to re-infect the fish. Otherwise they’d just lower the temperature to the virus’ happy-range (in the proven absence of antibodies) and they’d just break again.

What Should We Do with Any KHV Surviving Koi?

It is unknown if the KHV (Now called CNGV) is latent in the fish or not, although recent tests have shown that of 100 infected and recovered fish, FOUR percent of the survivors had virus particles in their tissues.

This was not done on heated fish that survived KHV and was a study intended to see how many natural survivors carried the virus. Four percent or less.. This means that there is the chance that your fish “carry” the virus and can infect new fish which you might buy.

2019: So far, people who have actually heated and saved Koi are not reporting any further infections among those fish or infection of new comers unless the newcomers brought it.

Even the fish which are heated – may still carry the virus. We won’t know this until or unless there is: A good test for latent virus, and / or there’s feedback from people with KHV survivors who survive a complete Winter-Summer cycle without dying or infecting other fish in a second round or ‘relapse’

KHV survivor Koi should be considered potentially infective

So, KHV survivor Koi should be considered potentially infective and should be kept with OTHER KHV infected or surviving fish in “closed-contaminated” collections. Since KHV/CNGV has become so rampant, there are A LOT of people in the same “boat” with KHV collections who would want your fish.

How Should We Disinfect the Pond When this is All Over?

The virus is extremely fragile outside the fishes’ bodies. In the water, and in some studies, infectious particles in the water disappear within a day of removal of a fish host. In other studies,
seven days is considered safe exhaustion of the virus in the pond. So, some would say that there is no need for disinfection, simply leaving the pond empty for a few days exhausts the virus.
I do not share this opinion and would rather opt on the side of precaution.
I would recommend that the pond be drained. Refilled with plain chlorinated [or chloraminated] tap water – which is NOT dechlorinated. Then, every other day, double dose potassium permanganate would be applied to the system to denature any latent virus or bacteria.

When Should We Add New Fish?

I would confidently add new fish after the above has been executed. There’s been chlorine, time, and several rounds of potassium permanganate in the pond. The key is the “fishless” condition of the system. Since goldfish can carry KHV, these cannot be tolerated during the cleanup process. Any new fish you add after the disaster can be an infectious KHV carrier from the dealer – so it would be commendable to employ a quarantine before re-contaminating the main pond.

How Should We Disinfect Nets, Tubs, etc?

Disinfection of tubs, nets and such is pretty straightforward. The central ‘concept’ here is the use of a spray disinfectant. You can make a suitable ‘spray-on’ disinfectant with Clorox Bleach, mixing one ounce of Clorox in 29 ounces of water. The final concentration is 1:30 Clorox. This is virucidal, bactericidal and fungicidal on clean surfaces but should NEVER be used in contact with, or on fish.

This spray, will have a fairly strong chlorine smell to it but it will probably (to you) smell weaker than you’d think would still work.
Tanks can be drained, scrubbed with the spray you made, above, and refilled with chlorinated water. Use no dechlorinator. If you’re still not sure, you can use potassium permanganate in the tank when refilled in case you’re worried.

Nets can be sprayed off with the 1:30 spray Clorox, given a few minutes for permeation, and then rinsed in clear water. If you do not rinse the nets or other materials with clear water, the Clorox will fade and weaken nets.

How Long Can The KHV Virus Survive Off the Fish on Nets?

Since the virus is very fragile there would be those who would simply recommend ‘time’ to disinfect the net, or at least exposure to sunlight and complete drying for twenty four hours. Still, I cannot stand to see you do this with a new virus which may still come with surprises, so I would recommend that you would use the dilute 1:30 Clorox solution and a clear water rinse to disinfect ANYTHING that came in contact with the fish.

How Can We Limit The Spread Of KHV?

The only way to limit the spread of KHV is detection BEFORE spread occurs, which would require more sensitive testing than we have currently. The PCR test checks for the DNA of the virus but the virus is not always abundant in every sample you might collect. Homogenized (liquefied) organ tissues are best for detecting the virus, which means those tested fish must die. Swabs and blood testing have yielded good results but not as consistently as homogenized tissues. If I needed to test a LIVE fish without sacrificing it, I would bleed it and send a cc of serum to UGA at koilab.

Quarantine functions as the single best means to limit the spread of KHV.

Quarantine coupled with heat at 83 to 86 degrees Fahrenheit – with an eventual vaccine being developed by the Israelis, and or perhaps even testing and exposure of SPF fish for the final assurance check are all available and should be investigated by the Koi community, especially at the retail level. Unfortunately, only a handful of dealers are even aware that KHV / CNGV exists, and even fewer care to try to prevent selling an infected fish.

Common Questions After KHV Outbreak
Common Questions After KHV Outbreak

Over the last several years, we have shown that hobbyists and retailers and even breeders are reticent to spend very much on the development of research or vaccination of Koi for KHV. I have abandoned all hope or interest in KHV and its control based on people’s preference to buy new fish and hope for the best.
Dr Erik Johnson

Koi Herpes Virus KHV Cured or Treated?

Koi Herpes Virus KHV Cured or Treated

This article is dedicated to my personal friends, Brenda and Charlie Atwell, whose pond contracted KHV and was essentially wiped out, after re-introducing some fish which were returned to them, after a breeding-loan.
The koi hobby has been rocked by a fearsome virus which everyone seems to be getting with their new fish lately. [2003 summer] This virus has been reported in Israel and among Japanese fish, but has so far not been diagnosed in its current form in Japan. There are active cases (and a few dealers) now in California, Ohio, Louisville, Atlanta, Chicago, New York, Indiana, Nevada, Arizona, Texas, Virginia, and Florida.

Koi Herpes Virus KHV Cured or Treated


KHV Controlled! (Playing with Fire) – by Dr. Erik L. Johnson
Koi Herpes Virus

Understanding this virus, and what you can do to save your fish, is the intention of this document. It is EASY to save your fish from this virus with heat, at 87 degrees F – if you are prepared, educated, and act fast!!!

KHV Controlled! (Playing with Fire) - by Dr. Erik L. Johnson Koi Herpes Virus
KHV Controlled! Koi Herpes Virus

Koi Herpes Virus is a virus infecting Koi which selectively penetrates and annihilates the epidermal cells of the koi, stripping the gills and skin and leaving them extremely vulnerable to secondary infection by Aeromonas and other fish bacterial pathogens. Most folks report almost total loss of their fish within 10-14 days, but it doesn’t have to be that way.
At left, a Midori with typical gill lesions of KHV
Because of the way the virus works, the fish appear to be burned on the outside, or excessivly slimey as it’s skin fights the virus. The damage to the gills is usually worse.
Typical Symptoms:

  1. Head down swimming
  2. Lethargy and weakness
  3. Sunken eyes
  5. Sandpaper skin
  6. White stringy slime on the skin
  7. Eventual dark discoloration in certain surviving fish
  8. Body sores

Koi herpes virus doesn’t ALWAYS have to appear as mass-mortality (death) and wide scale infection. A case has recently come about that tipped us off to the fact that under the right circumstances, KHV outbreaks can look like routine Aeromonas ulcer cases with 10-20% morbidity. Losses (mortalities) in the case I am referring to were only 7-8% Additionally, losses in this particular case were completely stopped by heating the groups of fish to 87 degrees F.
Here’s a response from another person whose fish were heated to recovery:
“…I am done with the 3 day @ 87df. The koi that I sent you a picture of responded very well. Her back has kind of crusted over as well as some of the other very sick ones. I also heated up my 1,600 gal. facility. I have not had any more die with the sunken eye and sandpaper scales! (Although I have had some losses in small koi). Have you ever seen the koi change color under these temps ? I have one that lost her tancho, and a Sora-goi that went from a light grey to a very dark blue-grey.”
Gill lesions are the safest clinical symptom to associate with KHV. What you would EXPECT to see are fish with red gills, however, there would be white patches or streaks in the gill tissue. Several recent cases however, had no gill lesions at all.

Diagnosis of Koi Herpes Virus can be undertaken via laboratories which are set up to perform PCR testing. This is “Polymerase Chain Reaction” testing in which tissues are homogenized and then a probe is used to find tiny bits of the virus DNA. This test can “miss” DNA particles which are present and in a good number of cases, there’s not enough DNA to find. So false NEGATIVES may occur. However, when the test is positive, against the proper controls*, it cannot be a false positive.

*Some authorities are not using positive or negative controls and may be less careful about the preparation of the DNA probes. Cross reactions and false positives may occur.

How to get the diagnosis: Using a lab which is capable of performing the PCR test for KHV, you are well-advised to send at least three fish for PCR testing. For best results, these test-specimens would arrive alive at the lab, shipped overnight in good water, under pure oxygen.

I have not seen a suspect-case yet which had sent three fish in which at least one fish was negative. This means that in groups of known-positive KHV infection, you have a one-or-two out of three chance of actually finding it. This is because the virus has a peak in its production during an epidemic (reportedly day #4-9) and when that peak is missed within a particular fish, then the fish is likely to test negative even though the virus is, or has been infecting that host.
Always send more than one fish, because among a group, there will be false negatives.

How Common is KHV?

KHV is extremely common. There are three reasons for this.
Hosts can carry the virus until the fish becomes vulnerable and the virus replicates. Therefore, fish can be sold “appearing healthy”, only to infect itself and other fish when conditions are ‘right’.

Dealers have started to understand that heating the fish to 86-87d F seems to salvage most of the infected fish and have intercepted alot of these cases early, before testing is done. Recovered fish may be sold, and, while we do not know this,ย recovered fish may be a source of infection.

There is a strain of KHV which has a low-mortality clinical appearance, in which most of the fish which are infected seem to resist this strain and can be sold after what appears to be a “garden variety” Aeromonas sores outbreak.

What Can Be Done About KHV Outbreaks?

This depends upon who you are. If you are a regulatory agency or epidemiologist, you might suggest destruction of all the fish affected to limit spread. This, however, would be a shame because you would end up destroying HALF the fish being sold in the USA right now. If a dealer were to destroy his infected livestock, he would be doing so while more than half the dealers in the industry bury the problem and continue to sell. Most of these, because they refuse to test even the fish with symptoms.
For example, Pam Kinkade bought fish from Barstow Koi and another koi retailer, both located in Newberry Springs, California. All her fish summarily broke with KHV and before she was able to heat the fish, she lost most of them.

She contacted the two dealers, and (I think this is VERY honorable) Ken Liu of Barstow Koi immediately sent five fish to University of Georgia for complete necropsy and KHV testing. The fish came back NEGATIVE. No virus. Ken Liu of Barstow deserves commendation.

The other dealer in Newberry Springs California flatly refused to have testing done. Therefore, unless hobbyists are prepared to heat, and to heat quickly, they will buy from this type of dealer, and therefore stand to lose all their fish to KHV.

KHV koi herpes virus can be stopped with a bucket warmer on a thermostat
KHV koi herpes virus can be stopped with a bucket warmer on a thermostat

Since, as I have illustrated, not all dealers exhibit ‘due diligence’ when confronted with this virus, HOBBYISTS are going to have to be ready to handle it when their fish develop this disease.
The best defense against KHV is a lengthy quarantine. In quarantine; heat, salt and Prazipro could be recommended but nothing but extended time can really exclude the virus.
The best defense against KHV is a lengthy quarantine.
In an outbreak – HEAT IS CURATIVE of the symptoms, (not necessarily the virus) but there are numerous difficulties.
Heating Drawbacks

  1. Heat accelerates parasite proliferation
  2. Heat accelerates bacterial pathogens
  3. Heat reduces available oxygen for the fish
  4. Heating large facilities is not ‘easy’ or quickly accomplished.
  5. After heating, these healthy looking survivors may still carry the virus.

For the hobbyist – when beloved fish matter:

I have saved just about every KHV fish I have been shipped by employing high heat and medicated food. Sometimes a person really loves a particular fish, or particular group of fish, so letting them all die is not a pleasant option. By heating, a person can save most of their affected fish, and continue to enjoy the collection as a closed “KHV Positive” collection. One advantage is that you can get all the free fish you want from the hundreds of cases across the USA – if you simply offer to give the survivors a home.
Heating fish has its drawbacks.
You must understand that if you heat a bacterial infection, the bacterial pathogen gets a metabolic advantage and accelerates its destructive path. The same is true for parasites. When you heat certain (if not most) parasites, they get a metabolic boost and proliferate explosively. So, if you blindly heat groups of fish to curb the obvious or latent KHV infection, you risk heating up another problem. But there are solutions to this quandary. Simply treating bacterial infections in the Qtank as you heat tends to limit the problem of accelerating a bacterial issue. Also, developing superior “shotgun” parasite regimens in heated facilities, or better still, using a microscope in these facilities, will prevent you from boosting a parasitic outbreak.
If you can diagnose or create a scenario without parasitic or bacterial threats, you are in a good position to “heat out” the KHV which may be carried by a group of fish, but there are two other variables.
Heating lots of water isn’t easy.

When you heat thousands of gallons of water like I do, you should consider using a powerful gas water boiler. I use propane in my indoor-outdoor water heater, and pass the super heated water through an exchanger which gives the heat to the pond water, without risking discharge of hazardous metals into the water. When your water heater circulates directly with your pond, the risk of pipe burst and discharge of contaminated water is great. So heat exchangers are recommended.

KHV koi herpes virus can be stopped with a bucket warmer on a thermostat
KHV koi herpes virus can be stopped with a bucket warmer on a thermostat

If you’re heating a little water, Qtanks (collapsible show tanks) and tubs work well. Never heat a fish in less than a hundred gallons unless the fish or fishes are truly tiny. In some cases, if not many cases, a person is faced with the spectacle of being unable to heat all their fish, so they bring several beloved specimens to safety in a hospital tank, heat them to 87 degrees Fahrenheit, and watch as the rest die outside, unheated.
The bucketwarmers shown above are forty dollars ar most tool rentals, painting supply places, or Lowe’s. They can be variable in their power. The ones shown are 1500 Watts each. They occur in wattages up to 2000 Watts. As a rule of thumb, against a low outdoor temperature in a semi-insulated tub or vat, you would need one thousand Watts per two hundred gallons in order to achieve and maintain sufficient heat.
The thermostat is a Ranco Nema 4X Indoor Outdoor thermostat and is available from Amazon.
Wiring the paint bucket warmers to the thermostat is as easy as the diagram, but if you want to preserve the relative safety of having a “ground” (reduces chances of being electrocuted, which is a good thing), you will probably need an electrician to help you bypass the thermostat with the ground lead and let the thermostat just have the hot wires.
The second variable is the fact that warm water carries less oxygen, so while the fish are being pounded in the gills by this virus, they have less luck with breathing. Then, you get brilliant and start heating them up, further depriving them of oxygen for exchange. I respond thusly: If you don’t heat them, they’re goners. If you do heat them, expect some mortalities as the ones with the worst gills, and worst bacterial infections simply die.
Aeration in the heating facilities is SO VERY important! I prefer to use a water pump, set on it’s side on the tank bottom. The discharge is aiming upward at the water surface. Done correctly, the surface of the tank will show a swell or slight floom as the water meets the surface and glides outward towards the tank sides and back down again. If you have the pump so powerful that the water ‘geysers’ upward, that’s great – but it’s your butt when the house mildews or the splattering geyser tips out of the tank onto the floor. [This happens the instant you head out to the store]
Here are the basic steps to rapid heating fish:
As much as possible, determine if the fish have KHV by sending one or more to a lab for testing.
As much as possible, prevent parasitic acceleration with salt at 0.3 to 0.6 percent
As much as possible, prevent bacterial acceleration by injection of antibiotics, medicated food, Tricide dips* (once the fish are more stable) or some other method.

(*Tricide is off the market I think.)

Fill your intended quarantine or hospital system with water from the main system. If the water is icy cold, you will need it to achieve room temperature under its own power (without agitation or artificial heat sources) before applying any electric or other heat. If the water from the pond is already in the mid fifties or higher, accelerate the heating process at once.
Add pH support (carbonates) to the water as the fish will put a drain on the pH and you don’t want it to crash. (1 tablespoon of baking soda in 100-200 gallons as needed)
Floom, or aggressively-aerate the tank
Begin heating in order to achieve at least ten degrees in 12 hours or twenty degrees in 24 hours. I have warmed fish faster. I have seen fish coming inside from ice water which could not handle that. With the Bergman fish, they arrived at 54d F and were at 87d F within 36 hours. Again, time is of the essence and aeration will help alot with your heating troubles.
Fish should improve when they achieve 83d F but they will be ‘cured at 87d F. They should be held at that temperature for at least four days before cooling them off. I say at LEAST because they seem to do so well when warmed and they need every break they can get.
So, you saved your fish, what do you do with these survivors? Is it worth the pond keeping experience for ‘the remains’ of your former collection? Is it safe to get new fish? Can you show these fish?
When you save your fish from KHV, it raises all these questions.
I think people should save the survivors. How do you know that you’re not going to go out, after killing off the stragglers, and buy new KHV infected fish? In the current climate, you do not know this. So you could kill the fish with names, just to repopulate with fish which could put you through this all over again!
I think keeping a smaller group of survivors has it’s advantages in terms of their eventual growth. Underpopulated ponds are healthier, and the fish grow much larger in less time.
There are at least two ways to get new fish. You can heat the pond, and get all the new fish you want as long as the new fish are prepared for, acclimated to, and mixed at 87d F. I have mixed KHV and non KHV fish in a variety of circumstances and had ZERO transmission:
KHV post-heat survivors seem to be non infectious to other fish. I have mixed healthy non-exposed fish with post-heat KHV survivors at normal pond and tank temperatures without disease. It’s AS IF the post heat KHV survivors are cured. We don’t know this for sure so this might be the most risky way to get new fish.
SAFE: Actively infected fish can be added to healthy populations of fish as long as the pond or tank is maintained (for the minimum four to seven day period) at 87d F. I accidentally did this twice, and have done it intentionally many more times since. It was not until we got the KHV reports back that I discovered I’d added some KHV positive fish to healthy tanks. Since the tanks were at 87d F there was no transmission.
There are quite a few people who have mixed new fish in with their KHV survivors and NONE of them report any losses among the new fish. Now, that might be an issue for this year, and the statistic could change after a long cold winter. It could also be that the KHV survivors are truly negative, by either innate immunity or the heating process which might have saved them, or both. The jury is still out on that one.
I don’t think a person who knows they have KHV survivors or KHV infected fish should take them to shows. The only reason so many people and dealers take KHV infected fish to shows is because they don’t know the fish have KHV. YET.
I have a growing collection of “post-heat KHV survivors” at my home. I think they are great fish and they’ve been nothing less than perfectly healthy. When I want to add new fish, I simply heat the pond to a whopping 87d F and then add the intended new fish*. This is what it ‘is’ to be KHV infected in the aftermath. And I can live with it, happily.
*after a short quarantine and biopsy.

Koi Herpes Virus (KHV) Symptoms in Outbreak Dialogue

What if two smart people got together to clarify some points of public concern regarding Koi Herpes Virus? Well that’s what happened and we got a lot of information out there. Of course new information emerges all the time but here is what we knew back then. It’s an interesting read.

Koi Herpes Virus KHV Symptoms in Outbreak Dialogue
Koi Herpes Virus survivor

KHV Dialogue – Dr. Conrad and Dr. Johnson – KHV Dialogue


Koi Herpes Virus Symptoms in Outbreak Dialogue
1200 W Paint bucket heater on Ranco NEMA 4x thermostat.

Key to Initials:
DRC: Dr. Roddy Conrad
ELJ: Erik L Johnson
DRC: First question. Several folks have reported the virus becoming active at about 65 degrees F.
ELJ: Correct. Verified by Moshe Kotler at essentially 18 degrees Celsius.
DRC: So is the KHV virus active in the 65 to 83 degrees F temperature range?
ELJ: Exactly. In a way that’s very much like a “on and off” switch. Not active below, nor able to live above the range. An oddity of this virus. If the fish have the virus in their tissues and enter that range of temperatures they break with the virus and the disease.
DRC: Second question. To save a collection when KHV is known or suspected, Erik recommends heating the water and koi quickly to over 85F. Perhaps one pond in a million has the heater capacity to do that!
ELJ: Exactly, which is why the Israelis are “keen” to develop some sort of vaccine. In most food carp and other endeavors, rapid, large scale heating is not an option.
DRC: Can someone suggest a practical method to have on hand for this purpose?
ELJ: Look at it practically; my opinion has always been that Koi do better heated over winter. Therefore, perhaps a hobbyist could justify the effort of developing a physical-plant capable of heating their pond as a twofold benefit: Winter heat, and secondly, the ability to “heat-out” a viral pathogen if encountered.
DRC: I assume a bunch of high wattage submersible heaters in a koi show tank inside the house would be the only real option if fish are dying from KHV and you want it stopped?
ELJ: Usually, and most quickly, yes. If you look in various “aquaculture” magazines, you will find cost effective titanium heaters that work well. “Clepco”, might start your search, it’s a company with titanium drop ins at a reasonable price. These wouldn’t be cost effective for long term or overwinter heating of the pond, but in a show tank, for a week they work well.
DRC: The practical aspects of this recommended treatment, meaning how to do it “in time to save the fish” would be useful to many of us. Some of us might even put up such a facility “just in case”, especially those who take fish to shows may want to put returning fish in a tank and heat them to 85-90F for a few days or weeks as a preventative treatment.

Koi Herpes Virus Symptoms in Outbreak Dialogue

ELJ: I had not thought of that. “Show People” might very well be smart to consider it on their return since the virus is “splashable” from tank to tank. Good thought. However, ninety degrees is “way” overkill. Also it should be noted that sometimes, when a Gosanke is super heated, their red goes away. Oops!
DRC: Third question. If the tank was set up as discussed above, it is unlikely to be large enough hold the entire collection all at the same time unless the stocking density is extremely high, then keeping the water quality up and the temperature up through water changes is going to be a significant technical challenge.
ELJ: Aptly noted.
DRC: Do all the fish have to be treated at the same time to kill the virus, or can a few fish be treated and changed out?
ELJ: You couldn’t heat half of them and then allow their mixing before ALL groups were heated. To wit: I know one retailer who serially heats his tanks. Each tank, series of connected tanks, or vat is heated to 86 DF and held there for four to seven days and then the heating “system” is moved to the next one. *Only* after he’s heated all the tanks will he “start” his 21 day waiting game before selling anything.
DRC: It may seem like a dumb question with an obvious answer, but let’s get it straight in this discussion so we have the “fewest misunderstandings”.
DRC: Fourth question. No matter how it is done, heating an entire collection to those temperatures quickly when KHV “usually breaks” in early Spring will be a challenge to maintain the water quality during the treatment. How long do the koi have to be kept that warm (85-90F) water to make sure the KHV is gone?
ELJ: You’ll get two answers.
From the Israelis, they say the fish have to be “hot” for 21 days to show immune response and be virus free. You can restate the question, and they still hang onto this “immunity” thing. When all you want to know is how soon the virus dies out over 83-96 DF.
On closer questioning, it was not *their* work at Hebrew University that showed the virus destabilizes and dies when superheated. (I think it was German or UFLa research) So they were perplexed.
On the worst group of KHV fish I saw, and then again on ONE additional group, a mere four “hot” days was enough to clear it. Now, two groups, even though they contained a pretty good collection of fish, is NOT statistically significant. But to overlook the effect and benefit while waiting on the “big OIE / APHIS study” you could be waiting a long time.
So I will be happy to stick my neck out and say I’d wager it cleared in four days at 86 DF but the smart money would be on superheating and sustaining that heat for seven days.
DRC: Fifth question. The Summer temperature of ponds is obviously highly dependent on the climate and pond construction details.
ELJ: Correct, and also the source water. For example, In Arkansas, KHV survives in its host, all summer in spring-fed naturally occurring ponds that seldom exceed 68-70
DRC: The temperature of the water in our outdoor ponds always gets to the 85F to 95F range in the warmest Summer season.
ELJ: Yes in many temperate climes in North America that are not spring or river-fed or in some way sustained below 65 DF
DRC: So if I introduce no new koi to those ponds after that Summer weather season, and no “live koi carrying bird” visits my ponds, does that define the pond as being KHV virus free?
ELJ: Theoretically, yes. You’re saying that the entire water column and its inhabitants were “through” the 83-86 DF window. So yes, theoretically, the pond and fish population is KHV free simply because the entire limnion was superheated beyond the known survival point of the virus.
ELJ: Never happens in Springs, and even some rivers.
ELJ: I am trying to give people who might otherwise be victims, the ‘earliest’ handles on the problem that I can. I have personally and professionally controlled KHV using the above concepts, and theories. I urge other people to follow suit and report their experiences, and I would be truly delighted if well funded “hard science” came forth with corrections to my anecdotal assertions and recommendations. If it benefits the hobby, I don’t mind having my early “guesses” amended, corrected or plain old debunked.
DRC: Sixth question. If the answer to the fifth question is “yes”, does that mean koi farmers in the quite warm climates of the gulf coast of Texas and in Florida are considerably less likely to have KHV problems?
ELJ: Absolutely, and “case in point” was a lady I saw at my office yesterday, who bought KHV infected fish from Mr. Mason in Atlanta at the same time that Brenda and Charlie Atwell did and were almost cleaned out.
She took her KHV infected fish home and put them in a blistering, full-sun pond. They got a little sick, rapidly recovered, and none of the fish died. So she was amazed and perplexed upon hearing of the Atwell losses, that her fish did not all die, and only after reading about the heat treatment, she put it together that she’d “accidentally” heated out the virus.
Case in point, too, when Galen Hansen was cleaned out with KHV several years ago, there were those hailing from and returning to Arizona, selecting from the same vendors, who took their fish home to blistering ponds, and had no morts, either.
So, a grower who KNOWs his ponds have “hit the hot spot” over summer, can be suspicious, (to the limits of what we know today) that his stocks are “clean” until he goes and screws it up by, (for example), adding new stock in cool water.
Keep in mind, “Mixing cool water and KHV” is like turning the spot lights off in front of a jewelry store. Bad stuff is going to happen.
DRC: If this KHV virus ever hits the Conrad collection, I would like to have these answers at my disposal to know how to best handle the disaster. And I would like to have the facility already set up to handle the problem.
ELJ: If everyone felt like you do, this KHV thing would be halfway to “over” by now. The reason is that if everyone knew to heat, and heat fast, then there would be more testimonials to its effectiveness. Confidence would climb. Compliance would increase. We’d intercept more cases earlier. Retailers “in the know” could “heat out” the virus and not sell it. And then the consumer would have more confidence and import Koi sales would not be sagging so badly. I hear it from several high-end dealers that they can sell fish in the low hundreds all day, but nothing over $500 is moving. This is unnecessary.
DRC: My advice has been to destroy all koi exposed to KHV, which is surely what a dealer, breeder, middleman, shipper still needs to do to maintain their reputation.
ELJ: I think a dealer should NOT sell anything that was confirmed / exposed to KHV. This is because we’re still (in the above) working with “do or die” theories and recommendations. In other words, for the end-consumer, the above is the best thing they’ve got right now. And it works.
But the dealer would be staking *more* than his own personal collection on the real success and viral clearance of the heating method.
ELJ: A dealer with infected fish (and fish he’s saved with heat) would do well to put another year or two on the fish *out* of the consumer path, but NOT killing them.
IF he can safely hold them a year or two, and then use developing technologies that will surely become available, perhaps those post-infected fish could be saved, and eventually, with more accurate information, they could be tested and verified “clean” beyond any “anecdotal” barrier and then sold – with no loss of such beautiful life, or dealer-income. Most koi “appreciate” instead of depreciate over time, so withholding ‘suspect’ fish isn’t as expensive as killing them.
DRC: However, if what Erik says is true, maybe a hobbyist does have other options. If so, we need to be quite specific about how to exercise those options to prevent hobbyists from “doing it wrong”, and then possibly bringing KHV carriers to koi shows.
ELJ: Good point, here again, we THINK and have compelling experience that the heat eliminates the virus and even though study after study supports it, we don’t *even* know for sure if the virus is a herpes-class virus (Simply; we can’t bet our lives on whether the virus is actually DNA incorporated or just hides in nerve sheaths) – so we just cannot confidently suggest that a heated survivor can be put in Shows safely.
ELJ: IMHO I’d leave the heated survivors at home. Here’s the point, I have a whole collection of KHV survivors at my home, and I know a growing list of folks with KHV survivors. In Spring of 2004 we will see more than a dozen ponds full of KHV and non KHV cohabitated fish “going through the warmup” and if all our post-KHV fish break and die, basically all my theories go ‘out the window’.
In the meantime, it’s totally cool, how well early-super-heating works on KHV.
DRC: Maybe those answers are all available and posted, and I just missed it? If so, I can be redirected easily with the right link!
ELJ: Not really. You find the KHV stuff in very different venues and it seems, in some cases, entire nations are unaware of the different advances of other countries. It’s funny (?) how the Israeli research has pertained to their needs (vaccine versus heat) and the stuff some of the Germans are doing is more specific to identification and control, and the Japanese have done it all, too. (Shan’t admit most of it) – but they publicly got a dose of KHV in Indonesia and their experts worked on (studied) this outbreak diligently. Now, with KHV in food carp they can deploy what they have ably learned.
I was communicating with a couple of Japanese researchers (Dr. Shibata in person and Dr. Hatai indirectly) and they all expressed serious concern about the presence of KHV in China and Indonesia. They knew it would only be a matter of time before the virus got back into Japan via a Chinese or Indonesian trade (grow-on) association.
And so it has. And too, how on earth can the Japanese heat tons of water?
What we are talking about here, frankly, is a microcosmic (non-industrial) mode of control available to persons with ornamental collections and capable wallets. Retailers, and wholesalers too, can capitalize on what we know about super-heat, and KHV quarantine.
But probably not certain breeders, again, going back to the ability to super heat “acre-feet” of water.
KHV’s tracks are hidden in too-cool water. Folks who breathe a sigh of relief to have living fish 21 days into quarantine in cool water might be misguided. I think, IMHO that folks should either ignite (activate) the virus in the high to mid seventies, or pass that point and simply ‘burn’ the virus out at 86.
I could be “so very wrong” but the above has helped me out clinically in quite a few KHV outbreaks this 2003 season.
Thank you.
Doc Johnson

KHV and SVC Virus Survival & Stability Outside the Fish

A fomite is an inanimate object. The object, functioning as a fomite spreads a disease. For example, the common cold is spread on doorknobs among other things. The doorknob is a fomite. The question was raised about fomite spreasd of KHV and SVC and I took the question to the highest authority on the viruses I knew. Andrew Goodwin.

Koi Herpes Virus Fomite Survival
Written by Dr Erik Johnson / Andrew Goodwin Correspondence

KHV and SVC Virus Survival & Stability Outside the Fish – by Andrew Goodwin, Ph.D

KHV and SVC Stability, Survival on Fomites

KHV and SVC Virus Survival & Stability Outside the Fish
KHV and SVC Virus Survival & Stability Outside the Fish

“The big problem with talking about the survival of viruses outside of their hosts is that the environmental conditions make a huge difference. Temperature, wet vs dry vs humid, the type of surface, sunlight, competing organisms, pH, and water chemistry are just a few of the variables. I got into this fairly heavily in the early days of SVCV and in answering some recent questions like “what do I have to do to a piece of potentially SVCV-contaminated equipment before I sell it?” Given the variables, and the paucity of research, the best that I can do is give you a general sort of answer. If you are after a particular specific situation or need the most expert opinion for a particular type of virus, I would be happy to put you in touch with folks with specific expertise who can give you more definitive information.
The good news is that KHV and SVCV both have lipid envelopes that make them vulnerable.

The herpes viruses probably die when they are dried, live only a few days in water unless it is very cold and everything is just perfect (then maybe a week?) , and persist in chilled dead fish for only a couple of days. They are easy to kill with mild things like sunlight, high or low pH, detergents or mild heat (50 C). I am not aware of any KHV-specific work in this area.

What does “Domestic” koi mean? Why would you buy that kind? How do you pick good and healthy ones? Who sells them and where do you find the best ones?

SVCV is a rhabdovirus and therefore a bit stouter than KHV, but still definitely on the wimpy end of viruses in general. They might survive drying for a week or two, persist in cool water for up to a month perhaps, and live in chilled dead fish for a few days. They are easy to kill with mild things like sunlight, high or low pH, detergents or mild heat (50 C).

Bottom line, if you keep the viruses cool, moist, and sterile, they will live for much longer than if warm, dry, and mixed up with other organisms.

The other thing to consider is that the virus may be able to get along in organisms other than fish and thus persist in fish-free areas. There is no evidence of this with KHV, but there is a very real chance that SVCV can propagate in invertebrates!

Koi Herpes Virus – Disease Course

It’s not ‘all the time’ that someone documents a KHV outbreak this thoroughly. I’m moticing things like the onset of disease, the source of the fish, the commencement of heating the fish to 82+ DF and the cessation of mass mortality after that.

Koi Herpes Virus – Disease Course

Written by Dr Erik Johnson and

May 24, 2003 โ€“ Purchased beni kumonryu from Bill Jones at Louisville koi show. The fish had been purchased 1 hour before from Ray Abell (And had been in quarantine for 7 weeks.) This fish had been in pond with Bill’s infected fish for that 1 hr. โ€“ then the beni kumonryu was bagged and floated in that pond water for rest of day until 7:00pm when it was introduced directly into my 10,000 gal. Koi pond @ 71-72 degrees.
May 30, 2003 โ€“ Still eating, but not swimming with other fish.
June 1, 2003 โ€“ (8 days later) Kumonryo staying at top of pond โ€“ quit eating.
June 7, 2003 โ€“ Put kumonryo in quarantine.
June 9, 2003 โ€“ Main pond: 4 koi gulping air and forcing out gills.
June 10, 2003 โ€“ Large kohaku (22โ€) had red blotches, a scraping showed costia.

Koi Herpes Virus - Disease Course
Koi Herpes Virus – Disease Course

– Started Proform C treatment
June 11, 2003 โ€“ 30% water change, 2nd Proform C.
June 12, 2003 โ€“ 30% water change, ProformC + Prazi.
June 13, 2003 โ€“ Kumonryu died in quarantine. We had to leave for business trip, returned late Sunday night, June 15.
June 16, 2003 โ€“ First view of fish โ€“ they looked terrible. We thought it was some sort of chemical burn from the Proform C. We did a 40-45% water change. The fish had no slime coat.
June 17, 2003 โ€“ 35% water change. โ€“ Salt at .18%. First of our fish died โ€“ 17โ€ showa. I called Bill Jones and he reluctantly told me that a batch of his fish had been diagnosed with KHV.
June 18, 2003 โ€“ Sent 2nd dead fish to Georgia (KHV Positive), started raising temperature from 71 degrees, reached 75 degrees. (Why?) Added extra aeration.
June 19, 2003 โ€“ Temperature at 82 degrees, salt at .3%, two more fish died.
June 20, 2003 โ€“ Four more fish died.

June 21, 2003 โ€“ Our annual club auction. Thank goodness I knew what I had. Started using KoiZyme twice a week instead of once a week. Ordered antibiotic food from Pond RX. Lost 9th fish.
June 24, 2003 โ€“ Started on antibiotic food for 11 days, but they ate very little, for 3 weeks. Four required further treatment with Baytril, but all remaining fish survived (29 out of 38 + 2 small 6โ€fish & kumonryo) โ€“ Heated to 83 degrees for 11 days, starting the 19th.

Now Aug.12, 2003 โ€“ 9 weeks after outbreak, all are eating well and acting normal. Several lost some color and several still have sunken eyes. No more infections.

I should mention that I did a scraping of two fish 7 or 10 days before introducing the new fish just to be cautious โ€“ I didnโ€™t see any parasites. However, the very first indications I got of the problem was the obvious presence of costia and the scraping showed them to be heavily infested. This was before any โ€œdisease-likeโ€ symptoms, but 16 days after I introduced the KHV fish.
June 17 (24 days after introducing fish and 18 days after it appeared ill) was when a friend called me and told me about three other ponds already wiped out from the same purchases at Louisville. It really appears as if treating for costia, either before or during the heating process might make a big difference in survival rates. My first mortality, other than the initially infected fish was not until this date. And Proform C does seem ideal as it is so quick.
Linda: Something I really want to know and forgot to ask, do the sunken eyes come back to normal?
Doc: Answer: Yes, they do as the fish recover their strength. heat seems to make a big difference in how fast this recovery is.
Linda Kinney

President, Dayton Koi Club

KHV Koi Herpes Virus Versus Spring Viremia of Carp

Koi are generally hardy fish. They’re descended from the common carp and are tough, essentially omnivorous fish with the ability to withstand a range of living conditions.
As an ornamental specimen, the Koi is beautiful, and sought after for it’s highly strained color varieties.
Koi health and disease is essentially a balancing act or “equilibrium” created between stocking density, water-and-environmental conditions, parasites, and the fish itself.
It was once said that “if you take care of the environment, the fish will take care of themselves”. This was true until some of these viruses started showing up with increasing regularity.

Introduction to the Viruses:

There are (at least) two known viruses of importance to Koi. There are other viruses but these are important from the perspective that they can quickly kill the fish and are both highly contagious.

  1. SVC / Spring Viremia of Carp (Rhabdovirus carpio)
  2. KHV / Koi Herpes Virus

These viruses are similar and dissimilar. Some of their differences and similarities are important.

Koi Herpes Virus – Spring Viremia of Carpย – What You Should Know*

Recently Discovered?

No. This virus was described in the literature more than forty years ago.

No. KHV was reported in Japan fully ten years before it’s first outbreak or discovery in Israel. The earliest documentation I can find is from the 1980’s

Kills Fish?

SVC has recently been shown to kill groups of fish when experimentally injected with the virus, earlier researchers maintained that the SVC only allows opportunistic bacterial infections which then can kill the fish. Mortalities may be 20-30% if supportive care is given and the environment is optimized.

KHV kills upwards of 70%-90% of exposed fish which have not been previously exposed to KHV.


SVC Yes – Spring

KHV Yes – Spring and Fall

Endemic (native) to the USA?

Yes and No: The ‘party line’ is that the virus had not formerly been found in North America but there is emerging evidence that the virus was indeed being encountered in fish kills in Wisconsin almost a decade ago.
Reported “absence” of SVC from American waters may have been due to a lack of testing. I personally (ELJ) think that SVC is an endemic, and highly morbid contributor to many of the Springtime die-offs and illnesses we’ve seen every year for the past two decades.
The problem is that testing for SVC can result in quarantine or worse. Retailers are unlikely to “step up to the plate” and endeavor to discover this virus and limit its distribution.

Koi Herpes Virus

This KHV virus seems to be infecting “groups” of exposed fish which go on to infect others, or simply die off en masse. It’s own virulence (aggressiveness) is probably limiting it’s morbidity.
Lesions: Pale white lesions may result due to the co-infection by bacteria. Fish may develop a pink or red color in the skin as infection progresses. Yes. Pale white lesions may appear in the gills of affected fish. Excess slime, especially on the head and nape of the fish seems common. Body-color of the fish may become blotchy and the internal organs may be damaged or even liquefied.

Diagnostic Challenges

People don’t want to submit for, nor do some labs want to test for; SVC because of the maelstrom it causes. SVC is an RNA virus and requires an extra step when using PCR technology to diagnose it. When the virus is not in a vulnerable host or is not in its ideal temperature range for replication, it’s diagnosis is essentially impossible. The PCR test and the other culture and swabbing techniques available are quite accurate for infected fish but false negatives can occur. When the virus is not in a vulnerable host or is not in its ideal temperature range for replication, it’s diagnosis is essentially impossible. Diagnosing “occult” (hidden) carrier-states of KHV may be impossible with current technology.

Immune Carrier States?

Fish usually survive SVC; but their carrier state is unconfirmed.

Survivors of KHV are said to be clear of the virus and cannot be re infected with KHV.
The lack of virus in post-infection specimens is probably due to the difficulty in detecting virus in asymptomatic fish or fish outside the viruses’ ideal range.

Kind of Virus

SVC: RNA virus, rhabdo (bullet) shaped.

KHV: DNA virus. (Herpes virus)


Can be cultured, there is a reverse PCR test for this virus. Can be cultured, can be detected via novel nucleic acid tests (swabs), can be detected by PCR testing.


This morbid SVC virus is reportable by law.

This KHV highly virulent virus is ALSO legally reportable but is as yet unregulated.


SVC Prevent exposure to the virus.

KHV Prevent exposure to the virus.

Control – Treatment

SVC: If fish are supported in ideal environments and secondary infections are controlled through aggressive antimicrobial therapy, including antimicrobial food and injections, 70+ percent survival is possible.

KHV Koi Herpes Virus Versus Spring Viremia of Carp
KHV Koi Herpes Virus Versus Spring Viremia of Carp

KHV: Mortalities may be kept below 70% if the fish are rapidly warmed to above 80 Degrees Fahrenheit.
To put the brakes on a late-summer outbreak, you can let the temperature sail down into the forties instead of heating, and the losses will slow down as the virus is deprived of it’s ideal temperature range. Fish may still die from prior damage done by the virus.
Sooner or later, the fish will have to be warmed up.
During an outbreak; if possible you can move the fish as quickly as possible to temperatures higher than 80 oF, or lower than the seventies (in Fo)

Spring Viremia:

The real issues concerning SVC are it’s status as a reportable virus. It’s very possible that many breeder and wholesale facilities (as well as many residential ponds) have fish which harbor this virus. Testing is currently possible, but is not being undertaken on a widespread basis, because of the cost, the lack of centralized and unified regulation, and a reluctance of civilians, and researchers to open that “can of worms”. Retailers concerned that their stocks could harbor this virus would put themselves out of business by soliciting SVC testing by a laboratory and receiving a positive result *.

Fortunately, SVC isn’t a terribly efficient killer of fish and could be considered ‘mild’ at least compared to KHV. Well-cared-for fish can often survive the virus not unlike the way healthy people survive the Influenza virus, and optimally housed fish may not even break out with signs of infection.
I for one do not spend much time worrying about the SVC condition because I would neither subject my customers to diagnosis (and potential persecution caused by an SVC diagnosis), nor would it change my treatment, which is antimicrobial support “past” the ravages of the virus . I am, as a healthcare provider to fish, almost alone with this opinion *.


KHV Koi Herpes Virus Versus Spring Viremia of Carp
KHV Koi Herpes Virus Versus Spring Viremia of Carp

The real issues concerning KHV is it’s predilection for a narrow temperature range for infection, and it’s ability to hide when it’s outside those temperatures in asymptomatic (not sick) fish. If you grind up a healthy-looking fish which you think might have or be carrying KHV looking for virus, you can easily miss the diagnosis unless the fish is actually viremic. When a fish is symptomatic and sick with a KHV infection, the virus can usually be cultured into certain cell lines, detected by enzyme linked PCR tests, or even detected by unique nucleic acids in it’s structure.

What it boils down to is this:
If you’re considering buying some nice new fish this Spring, how do you know the fish isn’t just sitting there; ready to explode with KHV as soon as it hits seventy degrees Fahrenheit?
You don’t have any security unless the fish has been through the following cycle of cold-then-warm, which are believed to be important triggering events for KHV infections:

  • Stress
  • Cold water,
  • Warming, to the viruses ideal range in the seventies (oF) allowing virus to replicate and damage the fish.

So, a fish which has endured, and survived, a temperate (North American) climate change from winter to summer could be regarded as the safest fish to buy but does not rule out that the fish could be carrying the virus. Some dealers are artificially inducing these cold-then-warm cyclic changes in their recent imports (unnecessarily, all it needs is 74ย oF) to try and bring these cases out of the woodwork before sale by chilling and then warming the fish after importation, creating a “mini” cycle.

Testing for KHV can prove the fish to be without the virus and “not currently infected” but since the carrier state is a relative “unknown” at the present time, there is little security in a negative KHV test in a healthy fish. A negative KHV test in sick fish could be considered much more reliable as most fish with active infections have virus which is capable of detection by available means.

Quarantine will become a necessity, not an ideal, in 2003. This quarantine could arguably be 8-12 months to allow a complete “cold-warm-cold” cycle in order to reveal occult KHV or SVC infections.

An actual case:

KHV Strategy

The following was used on one of several cases of KHV which broke out in the Fall of 2002. The fish were being heated despite the onset of wintertime temperatures outside, to support the fight against what appeared to be a severe bacterial infection. Then an Arkansas laboratory indicated it was KHV. We had stopped the losses initially with Tricide Neo but the losses resumed a week after the Tricide dipping which made us even more suspicious that we were dealing with a virus. (In quotes, my customer communication)

“Your losses have not been on par with the others, most folks lose 70-90% of their fish in a week or two. This is not a cause for optimism. It may be because you used the Tricide-Neo it could also be because temps were falling as they broke….
However, now most of the fish *are* symptomatic and as the Arkansas specialist indicated, you COULD let the heat off and the virus COULD (should?) go dormant.

In the Spring, here’s the possibility: Since most of the fish are showing signs, it’s safe to say they are “viremic”. If they are chilled ***RIGHT NOW*** (today!) – could they not chill down, stop the virus / viremia / replication, and with warming in the Spring, perhaps mount an immune response???

Yes, it’s possible. Researchers I spoke to know that we cannot re infect KHV survivors. Did they survive the KHV with natural immunity or luck?; or do they develop specific immunity afterward, from incomplete (non-terminal) infection???

So, here’s my recommendations for Winter KHV Outbreaks:
1) STOP HEATING NOW if the fish have KHV.
2) STOP the water falls; to prevent the phenomena of “supercooling” from chilling them too fast.
3) Maintain mid-water circulation to maintain aeration and to de-gas the pond.
4) Remove dead as they show up.

5) In the Spring – when the Arkansas specialist , you, and I have talked, we should “accelerate” the heating process. *NOT* letting them warm up slowly, naturally.
We should do a sort of: “On your mark, get set, go!” and move them as quickly and safely as possible through the warming process, for example, when water naturally hits 45-47 oF we could suddenly take them “5-degrees-per-day” to a whopping, most “KHV-unfriendly” eighty oF Six day warm up. Window in the seventies: TWO

Crazy? Maybe. Kill all your fish? Not like the virus probably would if water temperatures were suspended in the seventies..
Finally, you *do* see the problem with complete disinfection, “depop-repop” plans. If you sacrifice all your remaining fish, to get new healthy ones; what on earth will prevent you from restocking with 49 healthy fish and ONE MORE KHV carrier? Nothing.

So I am not really in favor of a wholesale depopulation at this time.

Best regards

Erik Johnson DVM

Outcomes: When the pond was cooled, the losses basically stopped. The fish became lethargic and went to the bottom. A few of the worst fish which were about to die when the water was warmer continued to become sicker and died.
Some other fish were brought inside and rapidly warmed to 80 oF, and made remarkable recoveries. Spring 2003 is not here as of this writing but there is some encouragement that if rapidly warmed, these fish may recover.

Post Script:
It bears mentioning that it is the professional opinion of most researchers and ornamental fish health specialists in this field, that in the interest of the health of our nation’s Koi and carp livestock, all individuals and retailers suspecting that their fish might be infected with SVC or KHV should request testing for these infectious agents.
My (ELJ) position has been to recommend that retailers and wholesalers decline SVC testing and to destroy fish which might be infected. This represents irresponsible behavior on the part of the dealer and puts the hobby at risk because it will hamper attempts to detect and eliminate the SVC virus. However, the position is a result of the following:

Currently, if your fish are diagnosed with SVC you will be summarily bankrupted by the following processes currently in place:

There is (in fact) financial compensation for lost livestock which may be tested and slaughtered. Requests to operate under a new business name with new broodstock and new production ponds will probably be (and have been) denied.

The problem with the financial remuneration policy is that there is NO MONEY allocated in ANY fiscal budget to make the promised payment.

No official process exists to formally determine the length of impound and quarantine. You may be under quarantine for an indefinite period of time.

There are no mechanisms to protect your identity and you may be informed of your SVC infection along with the rest of the industry, simultaneously.

There is no standard format, nor standard interval for testing of your peers or competitors, so you may be the only organization subjected to the penalties associated with reportable SVC infections.

*Errors or omissions in the above are possible but are unintentional. Some of the above is based on hearsay, opinion or verbal exchanges with researchers in the field. Newer information may be available.

APHIS To Indemnify Damages for SVC to Breeders or Sellers

APHIS To Indemnify Damages for SVC to Breeders or Sellers, APHIS has released the following document that identifies the circumstances that they will, although unfunded and unable to pay, remunerate breeders and sellers of Koi and pond fish for livestock destroyed in their SVC eradication program.

Lymphocystis Virus in Koi and Ornamental Fish

Lymphocystis – by Doc Johnson

carp pox is different from lymphocystis

Of all the viruses affecting Koi, the fifth most common is LYMPHOCYSTIS. This is a viral pathogen that is poorly transmissible between your specimens. It strikes fish when some damage has occurred to mouth or fin, and sometimes on the body* (Almost exactly like Carp Pox). The lesions are warty, and rough (Carp Pox are smooth and shiny). They may be singular or numerous. I see this viral infection in fish in immaculate waters, and so I cannot verify that this is a stress related disease. I do know that it is merely disfiguring, not fatal. Lesions may be scraped off, but this could open the skin or fin to bacterial invasion. The only lesions that should be addressed surgically are mouth lesions that interfere with eating. Often, the lesions clear spontaneously, usually, but not always, the SECOND summer after infection, at the peak of the heat.
Curing Lymphocystis
Lymphocystis is a viral disorder which infects cells and causes them to become huge (megaloblastic). Above, a Scatophagus argus (brackish water fish) with Lymphocystis lesions.

It’s important to be *sure* the lesions are Lympho, seen under magnification above.

how to recognize lymphocystisWe tested Neutral Acriflavine according to book doses (theres a chart in there) and found it safe.
Aquarium Products “Lymphocystis Cure” is Neutral Acriflavine. I originally said it does not work, but I did not wait long enough. The studies have been reproduced three times and the Acriflavine was tested on five groups of fish twice. This is insufficient to declare “significant”. However, results have been initially exciting.

Treating in a well aerated hospital vat – Bathe the fish 3-5 hours in a bath made of pond or tank water according to label instructions (Aquarium Products Lymphocystis Cure) and replace the fish in its main tank. Re-bathe again in five days when you will already be seeing a reduction in lesion mass. Regrowth has not been seen after complete clearance.
Key: Must be confirmed Lymphocystis (will not work on other granulomata or cancers.)
As Surface Bactericide
Acriflavine (Neutral) (Click if Still Available)
Kills Surface Bacteria
CAUTION: Kills plants in treated systems, so use as bath.
Daily as needed
lymphocystis in koi and pond fish