Koi herpes virus incubator at University of Georgia

Koi Herpes Virus: Question and Answers

Written by Dr Erik Johnson
KHV Dialogue – Dr. Conrad and Dr. Johnson – KHV Dialogue

Key to Initials:
: 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.
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?

Koi herpes virus incubator at University of Georgia
Koi herpes virus incubator at University of Georgia

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.

2018: Southeast Asia is “hot” with KHV

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

Thank you.
Doc Johnson