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Meyer and I recently had a chat about the KHV (CyHV3) virus so to the uninitiated what on earth is it and why should we be worried about it?

How many koi keepers, ponders, worry that their koi can be carriers of Latent KHV (CyHV3)?

The KHV (CYHV3) virus, as Meyer was telling me, is an insidious virus and there are dozen's of variants of this disease identified.

Now each one of these variant’s each one with their own mortality rates can lay dormant for years until conditions are right for an outbreak.

Once these conditions are right then the virus comes to life and one by one your koi fall ill and die, with up to an 85% kill rate at its worst 20% at it weakest variant.
Infected fish are surviving but one must not take the survival of a koi after an outbreak as immunity to this virus because it isn’t. From what I’ve learned it only means that the koi’s immune system is healthy enough to keep the virus 'at bay'.

This can very quickly change should the same koi be subjected to enough stress through overcrowding, poor water conditions mating high pond temperatures etc to weaken its already damaged immune response. This can cause the virus to switch on and replicates explosively infecting others with the KHV (CyHV3) virus.

The question is are all our koi infected with the KHV (CyHV3)?
The answer could surprise you as "YES" there is a very good chance your koi do have it but the virus is in a dormant phase waiting until conditions are right .

The KHV (CyHV3) virus can remain dormant, but viable, indefinitely.

As Meyer aptly put to me, they are technically not classified as being a form of life. Viruses do not meet the present criteria to be termed a form of life. they retain their potential toxicity much like a Heavy Metal. “Only they can replicate “!!!!!.......

As such this will continue to be a problem within this hobby and will likely worsen than get better.

Why ? well again as Meyer says its because with the advent of social media, in that more and more people are swapping/selling fish than ever before.

Recently of the GPF we've had cases of koi brought on line then put directly into the pond only to come down with this parasite or that "no names no pack drill" but think what if it was KHV (CyHV3) instead of parasites?

“Warning” because .these are fish with an unknown health history, you have no fall back at all, unlike buying from a koi dealership should they have it.

However even dealerships are not safe but in here in the UK. The dealers have decided to fight back against this dread virus and have banded together to form the – PKDA a group of dealerships dedicated to the irradiation of the KHV (CyHV3) virus before it gets to us the hobbyist

I’m unsure however if the same sort of organization has been put together in the US or Canada or South Africa.

Without these dedicated dealerships the subsequent potential of the virus to spread is enormous.

Because of the nature of the KHV CyHV3, quarantine of koi will not identify a carrier fish.

Heat ramping is one way to see if the koi is infected “ you raise and lower the temperature of the QT Facility to above that of 25c then lower it in rapid succession repeatedly.

In South Africa a Land-rover is used at speed over rough ground in an effort to shock the virus from dormancy.

Otherwise only submitting koi to a PCR [polymerase chain reaction] assay can identify this virus.

Unfortunately, this can only be done as part of what is termed a necropsy. [You have to sacrifice a koi to get the test done] , though I do believe they are working on another less lethal form of testing in the UK's Labs but cant be sure on that fact at this moment in time .

How many hobbyists will sacrifice one of their fish to determine if a potential problem exists?
The answer "not many of us" unless our koi are of great value to us that is.
Then there is the cost involved in having this PCR testing done, just how many people would have it done if you knew that it’s a rather expensive test to have done.

I think the answer to all this is for us to be aware of this dread virus and buy only from reputable dealerships. You might at least get some money back should your koi then come down with KHV (CyHC3).

In our time around koi I’ve heard about and know people who have been visited by this dread virus and from what they were telling me it’s not a nice thing to have happen to ones pond, it is in actual fact devastating.

Once discovered all your remaining koi must be sacrificed**
Your pond disinfected numerous times [every last inch nook and cranny].
Pipework must be totally replaced and then the pond left dry for a number of months prior to disinfecting it again prior to use.
The same can be said about your filters all the media in them must be gotten rid of as well as any pipe-work.
All your equipment must be either thrown away or disinfected.

Even then you can’t really be sure you’ve gotten the virus it’s a risk you’ll have to take.

Note** or you can keep the survivors in a kind of perpetual QT being unable to add other koi least they too come down with the virus , you can't give them away nor ever sell them on.
If you showed these koi prior to the outbreak, forget it they can never be shown again .

Many of the koi keepers I know aren’t prepared to take that risk but that’s purely down to each person.

So where does KHV come from and what other species does it effect
KHV affects all strains of Carp, but not Grass Carp,, Crucian. Carp or Trench, although like Wels Catfish, they can carry the virus.

When did the KHV (CyHV3) virus first make its appearance?
.KHV (CyHV3) was first encountered in Israel in 1998 on Koi rearing farms and the first outbreak at a fishery in England was in 2003.

This virus may cause between 20-100% koi mortality within a pond dependent on strain.

No treatment or licensed vaccines exist to prevent potential infections, although trials with such are underway in Israel, they have not been sanctioned in Europe.

In March 2009 KHV (CyHV3) became a notifiable disease within the UK, prior to this fish infected with the virus were not restricted from importation into the UK, which enabled the virus to spread to fisheries with legally imported stock. The Fisheries Health Inspectorate within CEFAS/DEFRA deals with on establishing the best methods of screening and adapting British controls on the movement of fish into the wild.

The disease typically occurs at water temperatures of between 17c to 23c
Typical symptoms of infected fish have included:
1) lethargic
2.) Erratic swimming behavior
3) increased mucus production.
4) KHV (CyHV3) often leads to the fish’s immune system being suppressed, with secondary infections widely increasing the potential range of symptoms.
5) Koi’s eyes become sunken
6) Mortality follows

This YouTube video will take you through all of the major points about KHV:-

KHV (CyHV3) has become a major problem in many of the UK’s angling lakes. The spread of which has been blamed on koi keepers.
The virus has found its way into many of these lakes through poor bio security on behalf of the anglers, who did not practice bio-security, did not dry out their equipment, nor disinfect them.
The net result of which this virus has spread at break neck speed throughout these lakes

Further information :-

1. Koi Herpes Virus KHV CY-HV1 information from the Fish Helpline
A mass die-off of carp at lake Mohave in Arizona U.S.A. Over 100.000 dead carp.
Also in the States this is getting so common I am dealing with over 30 cases via email at the moment .... I am writing you from Chilliwack, British .... However, two things are absolutely clear: First, that KHV has spread to all Koi ...

2. Koi Herpes Virus (KHV) Disease - EDIS - University of Florida Methods of spreading (transmission) of KHV include direct contact with infected fish, ... The infectious virus primarily enters susceptible fish through the skin, ..... a British organization representing the interests of ornamental fish importers, ...

I hear goldfish owners breathing a sigh of relief but sadly for you there is another Herpes Virus know as GHV (CyHV2).
GHV (CYHV2) is to goldfish what KHV (CyHV3) is to koi and its wild cousin the common carp .
Both viruses are members of the Herpesviridae family and both viruses are highly contagious.

Like KHV, GHV only shows its symptoms when the water temperature is within a critical range, and like KHV, GHV is believed to be highly host-specific.
The virus can affect all varieties of the goldfish, but it is not yet known whether the disease has the potential to spread to the UK’s native Crucian carp, Carassius.

When was GHV (CyHV2) first reported?
GHV (CyHC2) was first described from Japan in 1995 following outbreaks in 1992 and 1993, when at the time it was known as Herpesviral Haematopoietic Necrosis Virus (HVHN). The virus has subsequently been reclassified as CyHV-2 and has since been reported from the USA, Taiwan, Australia and the UK

The symptoms of GHV (CyHV2) are as follows

In the case of GHV (CyHV2) you will find that like koi, goldfish infected will become:
Lethargic, stop eating and develop pale, patchy-looking gill necrosis.
Some specimens may also develop small white blister-like pustules on the skin.

If doing an autopsy you will find the following:
Internally, the spleen and kidneys may become pale and swollen and granular lumps and nodules may appear in the spleen.

So as you see it’s a question of which came first GHV (CyHV2) or KHV (CyHV3) sadly we will never know.

So it looks like both sides of the hobby will have to live with this shadow hanging over them
However it’s a which came first the chicken or the egg
This scientific articl may just answer the question for us :-

This article ties in importantly with Maria's/ bettasngoldfish's Article:-

Also it ties in with my latest article :-

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