(KHV then and now)
When the first effects of KHV were being felt in this country and before the virus was fully researched and identified, a well respected name in koi keeping introduced three new koi into his pond. Within days, he realised that these fish had brought with them something new and deadly. As the death toll rose, he researched the problem as far as was possible at that time and wrote an article about his experiences. His intention was to spread information as widely as possible with the aim of warning others, and hopefully nip the spread of this new disease in the bud. Controversially, the article included the recommendation that the movement of koi should cease. This is an obvious course of action when a virulent infection breaks out in any population of livestock. Stop all movement, cull those affected, and maintain this strategy until the outbreak has been contained and eradicated. This is standard practice with many other livestock diseases.
He found a great deal of reluctance when he tried to get the article published. Koi dealers would not be happy to stop selling koi for an indefinite period and would not welcome the implication that they might be selling potentially diseased fish. This is not to suggest that they were indifferent or irresponsible or deliberately acting in any way that might make the situation worse. Each was, no doubt, perfectly certain that they, themselves, were absolutely in the clear. The situation was not helped by a general lack of information. Koi dealers contribute greatly to the advertising income of koi magazines, so editors were unwilling to publish anything that would harm the financial interests of their advertisers.
The man’s name is Alan Coogan, and with the benefit of hindsight, we might now think. “If only his article had been published more widely and his warning been heeded”. This is what he wrote.
Trials and Tribulations of a Koi Keeper
It’s a cold December evening, frost bites deep into the rich fen land soil that stretches out in long black fingers towards Ely Cathedral, that stands eerily and ghost-like on the far horizon. Orion stands in all his brilliance above my head amidst a jewel of a starry starry Cambridgeshire night, the county of endless skies that is my home.
I’ve ‘set fair’ [put to bed] all our thoroughbred breeding stock. I lean over the stable door, eyes fixed dreamily on a young colt, could this be the one that sweeps down into Tattenham corner round and into the straight with the roar of half a million people ringing in his ears? Would he handle the camber, would he have the guts to dig even deeper when his lungs were bursting and every fibre of his being was screaming at him to stop. Could he then battle to the line and on to immortality in the ‘English Derby’ the greatest flat race in the world? ‘Hope springs eternal in the human heart,’ dream on son, dream on.
Alas all is not well here in this idyllic spot next to ‘ye old fen’ we have had several months now of watching our beloved koi die a terrible death one after the other on a sort of conveyor belt of demise. The sorry saga started in mid summer when three tategoi were introduced which had been brought earlier in the year and left with the dealer, “an excellent koi keeper”, to quarantine. Within a few hours of their introduction, I knew all was not well. Like most people connected to any form of livestock as man and boy, the slightest behaviour change sends the alarms clanging. Within three days we were in the middle of a full blown viral attack. Two of the tategoi were dead, most of the other koi were lethargic. This was something in twelve years of koi keeping I had not seen before. I won’t bore the reader with the differing view point between myself and the dealer, suffice to say that he believed they had been poisoned, and I knew we were dealing with something far more sinister. Next a phone call to the good offices of the BKKS health consultant, unable to help as he was already acting for the dealer. We are very fortunate in as much as the place is positively knee deep in veterinarians. With two world-renowned practises close by in Newmarket. Many are close friends and we have spend many a balmy summer’s evening after the routine horsey stuff was finished, round the pond, feeding fish, draining cans, strumming guitar and watching the sun go down.
The local boys were fantastic. Tests were carried out in Rossdale’s Laboratories. Anglian Water were called in, MAFF at Bury St Edmunds became involved. Mike Gubbins came up from Weymouth CEFAS to see the problem at first hand and took our beloved Marilyn, who was close to death, back for the greater good. Having chased this thing now over three continents, it is my opinion that this is an unnamed virulent virus. If allowed to get into your pond it will cause massive losses, heartache and tears.
My only concern over the last few months has been to provide the best possible conditions for my koi to die in. I’ve always been very confident in my pond, which is 31,500 gallons with six main drains, feeding an underground filtration unit that is bigger than the pond itself, with settlement chambers, rows of vortexes, UV’s, Hi Blows, micro bubblers, water purifier and a foam fractionater. Seven Sequence pumps return water either directly into the pond, which is seven feet deep or via two watercress beds and three weirs. An industrial straw burner, backed up by a second oil burning system for fine tuning, heated the whole shooting match.
To date, we have lost forty-one of our sixty koi. The heating systems have all been turned off. It is my belief that this virus is temperature related and waits only for warmer water to raise it’s ugly head. Up until this present crisis we had lost one fish in six years and I see the stupid fool who lost that fish every day in the mirror.
Having now been on the case for several months, having spent, many hours talking to people at home and abroad. It is my opinion that this virus has cost the lives of thousands of koi in this country and thousands more internationally. I believe the only responsible course of action is to stop the movement of all koi.
I now have nineteen koi left, all appear in good health, all of which are potential carriers, all of which could go to any open show and be benched. All of which will never leave these premises but will be housed in a new pond and will live out their lives in complete isolation.
I must now thank several people who have supported us and helped us during our darkest koi keeping days. Sidney Ricketts, LVO, BSc, BVSc, DESM, FRCVS. Dave Dugdale, M.A. Vet. M.B. MRCVS. Hugh Neal, M.A. Vet. M.B. MRCVS. Mike Gubbins and Brain Manders from CEFAS. Bob Van Vonderen from Florida. Mike Reilly from Cape Town and a special thanks to Clive Gibbons another “lone voice in the wilderness” in the early days.
If only we had known then what we know now.
The wise words contained in the article did not get the full publicity they deserved and, with hindsight, it is now possible to say that more could have been done at the outset. It is now clear that if the movement of koi had been stopped entirely, at least until the problem was better understood, then the situation today would be entirely different. As a result of ongoing research into this disease, it has been discovered that it is caused by a virulent strain of Herpes virus that affects koi and other varieties of common carp, but not goldfish or grass carp. It has therefore been called koi Herpesvirus (KHV). Maybe if koi dealers had realised the enormity of the problem we were all about to face, the koi they were selling at the time could, at least, have been better quarantined. It is wishful thinking to suppose that the disease would have been eradicated world-wide, but the uncontrolled movement of carriers of the virus has certainly caused innumerable wipe-outs which have been suffered by koi-keepers and dealers alike.
I would not wish to imply that dealers, in general, have deliberately acted in an irresponsible way. Just as it is heartbreaking for the hobbyist to face the deaths of their entire collection, it is equally hard for a conscientious dealer to face the loss of their entire stock and also, possibly, the loss of a reputation that they may have taken years to build. Some dealers have tried to avoid the stigma by attempting to hide the fact that they have suffered an outbreak. Others have taken the more creditable action of being totally honest about their situation and given full information about what has happened and the measures they have taken to ensure that it does not happen again.
What do we know now?
We now know that KHV is a DNA virus that can remain dormant in a carrier for extended periods. We know that some fish will carry the virus for long periods without exhibiting any external signs of disease and that it can be triggered into activity by sudden elevated temperatures. There are reports that the virus will die quickly at temperatures above 29ºC, although there does not appear to be universal agreement that this is the case. There does, however, appear to be unanimous agreement that the virus is inactive outside the range 15ºC to 28ºC. This dependency on temperature, as far as I can tell, is the one weakness in the virus that we can currently exploit in our fight against the spread of the disease. As part of our quarantine regime we can cycle the temperature from about 15ºC up to about 27ºC and down again at least twice. If the virus is present in the fish, this will cause it to emerge from it’s non symptomatic dormancy and cause symptoms to be exhibited. This is not good news for the individual fish but, at least, we will not add that fish to a pond and infect all the others.
KHV was first recorded in Israel in 1998. It is an extremely contagious viral disease that typical kills 80% of the fish that it infects. KHV is an immuno-suppressant. This means that it inhibits the ability of a fish to defend itself against other pathogens, particularly bacteria and parasites. Consequently, koi suffering from a KHV infection will often also show symptoms of other infections caused by bacteria and parasites.
The virus is asymptomatic (does not cause symptoms) at temperatures lower than about 15ºC, and fish seem most susceptible at water temperatures in the range 22ºC to 27ºC. The disputed reports that the virus will die if the water containing fish diagnosed with KHV can be quickly heated to over 29ºC, and then held at that temperature for a week, originate from Israel. It must be remembered that, even if this should prove to be true, it is not without risks. Abruptly raising the water temperature may well cause the koi, with their immune systems weakened by the virus, to succumb to other diseases. But if this is to be done, speed is essential as an infected fish may die from the effects of KHV in as short a time as one or two days after the symptoms first become apparant. The virus is spread by direct contact between fish or by contact with their body fluids or faeces. Parasites may also carry the infection from one fish to another. It may be transferred if water that has contained an infected fish is transferred to another pond, for example on a net or other equipment that has not been properly disinfected. The virus is able to survive in water on equipment for at least 4 hours and possibly as much as 20 hours in favourable conditions. The survivors of an outbreak will be left as carriers of the disease and will be able to infect new fish that they come into contact with.
On the question of whether vaccination of fish can be effective, The Institute of Fisheries Management has stated: "The technology used to develop this vaccine is unproven, and there is a risk that the live viruses in the vaccine will revert back to a full pathogenic koi Herpesvirus. The vaccine is also unlikely to confer protection on the fish longer than six months, making it inadequate long term protection."
At the present time, (March 2007), KHV is not a notifiable disease in the UK or EU. It has recently been added to the list of diseases required to be notified to the World Organisation of Animal Health (OIE) and it is the intention of Defra that KHV will become a notifiable disease in England in the near future, with April 2007 being the target date.
What are the symptoms and can we cure it?
There is currently no cure for this disease, apart from the possible exception of “cooking” it out of an infected koi with raised temperatures, so rigorous quarantining and early detection is the only way to prevent it from spreading. It can be difficult to diagnose, and visual examination is not reliable as the typical symptoms are also seen in a number of other diseases. Symptoms may include bleeding from the gills due to severe gill lesions and gill necrosis. As a result of gill damage, affected koi often remain near the surface showing signs of respiratory distress. They may swim lethargically and erratically. Other symptoms may include sunken eyes, pale patches or blisters on the skin. In some cases, due to weakening of the immune system, secondary bacterial and parasitic infections may be the most obvious symptoms. This may mask the damage caused by the primary infection. Increased mucus production is possible in the early stages, followed by little or no mucous production as the disease nears the final stage. Once the virus begins to cause symptoms to become apparent, deaths are likely to occur quickly, possibly in as little as one or two days, depending on water temperature.
Skin blisters and pale patches
Pictures courtesy of: Centre for Environment, Fisheries & Aquaculture Science (Cefas)
Home autopsies may reveal adhesions in the body cavity, dissolved internal organs or a mottled appearance of internal organs. While there is no evidence that this strain of Herpes can affect humans, it is a sensible precaution with any examination of any diseased fish that full precautions are taken to avoid physical contact with the fish itself or it’s body fluids, bearing in mind that these may spray when an incision is made.
It is difficult to diagnose KHV by examination alone, due to the variable nature of exhibited symptoms and the similarity of these symptoms with other diseases. There are, however, tests that can be performed in properly equipped laboratories that will prove whether or not a koi has been exposed to, or has died from the disease.
ELISA stands for Enzyme Linked Immunosorbent Assay. This is a test for the virus itself or for the antibodies that are produced by the koi immune system as it attempts to fight the virus. It will also detect the antibodies that are produced when the attenuated (weakened) virus is injected into koi as a vaccine against the disease. The test cannot distinguish between a fish that has been exposed to the disease and one that has been vaccinated. There is no need for the koi to be killed; the test is done on a blood sample which can be taken from live koi.
PCR stands for Polymerase Chain Reaction. This test is performed on tissue samples from koi showing signs of KHV. It is an advanced biochemical test that will identify the presence of virus DNA. It may show negative if the disease is not actually in progress at the time. A negative result from this test does not mean that the fish can be guaranteed to be free of the disease. It only indicates that the virus was not active at the time of the test and unfortunately the fish has to be killed for the test to take place.
KHV Screening PCR Test
This version of the PCR test is designed to provide a disease status check for those dealing with large quantities of koi. For example, dealers who wish to confirm that a batch of koi that they have purchased is free of infection. This test can be performed on fish exhibiting no obvious symptoms of KHV and, as with the standard test, the fish have to be killed for the test to take place. A sample of the koi are killed and tested. If the tests prove negative the rest of the fish in that batch may be considered free of the disease.
What can we do to avoid introducing KHV into our ponds?
If you were to buy a used car, at a bargain price, and the following week the engine blew up, there would be the obvious suggestion that the previous owner may have known more than they were prepared to say at the time of sale. Not everyone is as honest as we would like. It is also possible that the previous owner may have been unaware of impending trouble, but it is best to be sure of the integrity of the seller rather than to be the victim of sharp practice. Sensible buyers of used cars either ask searching questions while they walk round kicking the tyres, (why kick tyres?), or they take someone with them who “knows about cars”.
Apply the same common sense when buying koi. Be cautious of the private pond keeper who is “selling up” and offering their collection at a bargain price. It may be a genuine bargain or they may be offloading trouble. Similarly, be cautious of internet sales where you have no idea of the source of the koi or the conditions under which they are kept. You may be dealing with reputable sellers or the unscrupulous. You must use your judgement rather than approach the sale naively. You could choose the safer option of buying from a reputable dealer, but which one?
FUNGUS FRED’S KOI EMPORIUM
Stall 2, The Boot Sale, M25 junction 33 (Sundays only)
IMPORTERS OF HIGH GRADE NIGERIAN KOI
Specialists in Sankey, Koharkoo, Shoosuey
and all other leading makes
Special this month!
Show quality, potential
GRAND CHAMPION GHOST KOI
All fish quarantined for at least 20 minutes
Customers are advised to wash their hands
after leaving the premises
This one, for instance?
If you are inexperienced and not already a member of a club, this is yet another reason to join.
Experienced club members will be able to privately tell you things about establishments like “Fungus Fred’s Koi Emporium” that many of us would like to put into the public domain, but are unable to, due to libel laws. They may offer to go with you to a “proper” dealer and guide you in choosing, not only a healthy fish, but also one that is likely to develop into something you will be proud of.
Wherever you choose to buy, you should ensure, as far as is possible, that you are buying healthy koi in the first place. There are rules you can observe when buying koi.
Observe the general condition of the ponds or display tanks and the koi themselves. Ensure that the water is clean and doesn't smell. A phrase that cannot be repeated too often is; “we don’t keep fish, we keep water”. If the dealer or private seller has not looked after their water, they have clearly not looked after their fish. If any of the koi look unhappy, it could be a sign of a health problem that may affect all of the fish in that pond or tank.
Green water is not necessarily bad water. Some people prefer it that way. This piece began with an article from Alan Coogan and, if you look into his pond, you will not see much below a foot or so. “My koi prefer green water and this is not a pond for people, it is a pond for koi”. He will tell you, and it would take a very brave individual to try to convince him otherwise.
When choosing a koi, spend time watching it. It should swim normally, not erratically nor spending too much time in one place. Unless it has recently been fed, it should give the appearance of actively looking for food. It certainly should not appear to be sulking in a corner. Healthy koi have erect dorsal fins and well displayed pectoral fins. Reject any fish that has it’s fins clamped to it’s body. Observe the gill movements, they should be clearly defined and regular. Occasionally a koi will appear to yawn and open it’s gills wide. It does this to flush out it’s gills and this is quite normal if done very occasionally. Think of this as the equivalent of the way you or I might cough to clear our throat. Once in a while is normal, too often and there may be an underlying health issue. Healthy koi should not appear to be breathing too hard or too shallow. Nor should it breathe too rapidly or too slowly. They should not be gasping at the surface nor staying near to waterfalls, water returns or venturis etc. This may “only” be a sign that there is insufficient aeration which will no longer be a problem when the fish is transferred to well aerated water, (provided it has not already suffered permanent damage due to long term oxygen deprivation), or it may well be an indication of a serious health problem. Remember, respiratory distress is a typical sign of the early stages of KHV.
Avoid koi with obvious sores, holes, raised scales, split fins or fungus. Ask for the koi to be bowled for a closer look. This will not only give you the opportunity to check the skin quality and pattern, but will allow you to examine it for any redness or marks, or large parasites such as fish lice or anchor worms. An experienced koi keeper would not necessarily reject an otherwise perfect fish that has a slight parasite or other health problem that they are confident that they could easily cure. But unless you have the confidence and experience to take on such a challenge you would be well advised to steer clear of buying koi that do not appear to be in top condition.
Remember that used car analogy that I started with? A car with an engine that is about to expire may give no indication that you, or your expert, can see at the time of sale. Similarly, when buying koi, just because you have chosen a fish that has passed all the above criteria does not guarantee that it does not have a hidden problem. So far, you have only eliminated anything that is obvious, and health problems such as KHV may not show external signs at the time of sale. Unless you want your existing koi to be the first to show you that their new companion has brought something nasty with it, you should quarantine it first.
Unless your faith in the seller is absolute, quarantining of new purchases is essential. Even then, it is the best approach to introducing new koi into an existing pond. KHV is not the only reason to quarantine new additions. Koi can become accustomed to the particular water chemistry in their pond. The water in which the new fish may have been previously kept may be very different from the new pond and koi may show signs of distress if they are forced to adapt to their new environment too quickly. The smaller volume of water in a quarantine tank can be adjusted in advance to be similar to the previous water parameters, such as pH, hardness and temperature. A reputable seller will provide these details, and after the new fish has recovered from the stress of being transported, the parameters can be adjusted slowly to match the existing pond parameters. This will give the new koi a chance to adjust to it’s new conditions without the risk that it may succumb to other stress related problems such as White Spot. In the smaller volume of water it will be easier to observe the koi, examine it if need be, and treat it with appropriate remedies without affecting the existing pond. It will also be cheaper and more accurate to treat, for example, “exactly 500 gallons” rather than “about 4,200”. For this reason, a quarantine tank could serve as a hospital tank when it is not in use for quarantine purposes. When a quarantine tank is not in use it should not be left empty of fish. It could be the permanent home of a few small koi that will keep the biological filters alive in between the arrival of new additions. Having companion fish in the quarantine tank will also have a calming effect on new additions as koi are gregarious fish that do not like being isolated in unfamiliar surroundings. It has previously been the general recommendation that goldfish could be used for this purpose but, since they are unaffected by some koi diseases, including KHV, it is preferable that koi are used instead. These koi will also be the first to show signs of KHV or any other disease that new koi may bring with them. This may, at first, sound heartless but if you buy healthy fish in the first place these companions will never suffer.
Mixing koi from various sources carries the risk that, if any one of them is infected, the others will all become infected when they are placed in the same tank. There will also be no way of telling which fish was originally infected and therefore which seller or dealer who was guilty of selling you the diseased fish.
OK, the koi has arrived home, in the bag, now what?
Biosecurity, Biosecurity, Biosecurity.
While the bag is floating on the quarantine tank for the temperature to equalise, remember that you have been handling a wet bag that, despite all the care you have taken, may contain KHV or something else that is nasty. Do not immediately go and feed your existing koi. Use the time to wash your hands, ensure that you have not brought home any splashes or tiny droplets of water from the seller’s pond on your clothes or on your shoes. Over the top? Just ask a koi keeper who has accidentally introduced KHV into their pond due to inadequate precautions, what they would do differently if they had the chance.
When the new fish is in the tank do not transfer even the tiniest amount of water from the tank to the pond. The infective agent that may carry KHV is minute, and can survive for up to 20 hours in the water on nets or other equipment. Make it an unbreakable rule to wash your hands after handling fish in the quarantine tank. Proprietary hand sanitisers are available. Equipment should be thoroughly disinfected after use in the quarantine tank before it is used in the pond. Better still, have two complete sets and ensure that they are clearly identifiable and kept separate.
When visitors view your pond, make sure that they do not dip their hands in the water after they have just touched the water in the quarantine tank. It is becoming impolite to touch other people’s ponds without permission and hand sanitation anyway.
How long should the quarantine period last?
According to Defra, the minimum quarantine period should be two weeks at 23ºC to 28ºC, although they stress that this is the very minimum period and that longer would be better.
A more rigorous quarantine regime adapted from an idea that was originally recommended by Dr. Paula Reynolds, (Aquatic Patho-biologist at Linconshire Fish Health), is as follows:-
It is important that the initial temperature should be at 15ºC or lower and that the koi should be allowed to acclimatise to this temperature.
Raise the temperature by 1ºC per day until the temperature is in the range 23ºC to 28ºC where koi are most susceptible to the virus. Ideally raising it to the higher end of this range. Maintain this temperature for at least 3 weeks.
Reduce the temperature by 1ºC per day until it is back to 15ºC.
After 1 day at this temperature, repeat the process a second time.
At the end of the quarantine period, ensure that the water parameters have been slowly adjusted to those of the new pond.
Temperature cycling from 15ºC up to around 28ºC and back down again is stressful for the koi, but unless the virus crosses the boundary temperature from the inactive range to the active range, (ie around 15ºC), there is a chance that it may not be triggered into activity. This would result in a KHV infected koi mistakenly being given a clean bill of health and transferred to the pond. The virus could then lie dormant until it is triggered into its infective stage by some future circumstance.
It is essential that the fish are closely monitored during the process as other diseases may be triggered. White Spot, for example, is brought on under stressful conditions. Unless treated at the earliest signs, it can cause too much damage to the osmoregulatory system for the koi to survive.
It is generally thought helpful if koi that have never been exposed to the virus, (KHV naive koi), are included in the tank during the quarantine regime since these are likely to show symptoms of the disease even if the new fish initially do not.
Achieving an initial temperature of 15ºC in summer may be difficult. It may be better to restrict buying of new koi until ambient temperatures allow the tank temperature to fall to this value. Or, if you do not want to miss out on the chance to buy something special that may not be available later, you could keep the new purchase in the tank until later in the year and start temperature cycling then.
And in the future?
Many dealers and private koi keepers have learned some bitter lessons about how deadly KHV is and how easily it can be spread. There is an onslaught of research into this virus. Much of this research is dedicated to the eradication of KHV. At the moment, while there are promising results from some programs of research, there is no immediate hope that a cure will be found in the near future, or even the far future. Vaccination may be a strategy that will one day prove effective, but to eradicate the disease this way would be an enormous task that would need to be co-ordinated, possibly world wide, to have anything other than a limited effect in specific areas. Even then, these areas could easily become re-infected if vaccination ceased and carriers were then brought into that area and allowed to mix with unvaccinated fish. And what of the reservoir of the virus that exists in large natural lakes? It is beyond practicality to round up and vaccinate all wild fish, and so it is likely that they will be an ever present source of new infections.
KHV is a DNA virus. This means that it will only infect koi and other carp with similar DNA. It cannot infect frogs, newts or other amphibians that might travel from natural waters where KHV is present to a koi pond. But, any creature that could make this journey carrying traces of water from an infected lake, could carry the infection in the water that they carry with them. Water may be transferred on the feet of birds or in their feathers, for example.
The risk of a private pond “catching” KHV from a local river or lake in this way must be, by all reasonable thinking, very remote indeed. Breeder’s ponds, however, are a bigger target and it must always be considered possible that infected water or mud could be transferred by visiting wild life, despite all the precautions the breeder might take.
Is this worrying too much? I don’t think so. The BKKS Health Standards Committee advise all those closely involved with the care of koi during shows to take stringent precautions. These, not only include hand sanitation, but also walking on disinfectant mats. Are these precautions unnecessary? No, they are avoiding the possibility of cross infection by any means, no matter how remote the risk might be. Therefore, if there is the possibility that infections may be transferred on our shoes, we should also consider the possibility that birds could transfer infection on their feet! And we don’t even wade in the vats at koi shows.
So it seems likely that KHV will be with us for a very long time, a private seller may be offloading trouble without conscience or without knowing, and even the most reputable dealer may unwittingly pass on a fish that has something contagious, even if it is not KHV. It is the responsibility of the recipient of that fish to ensure that any risk to their existing collection is eliminated. Buy carefully and quarantine as if the lives of your existing fish depend on it. They do!