Fish Health - Koi Herpes Virus (KHV or CY-HV1)

August 2010 - DEFRA have announced that four fish farms have been infected. The symptoms are sunken eyes, gill damage and sloughing mucus

May 2010 - We have been notified by CEFAS that every region in the British Isles now has K.H.V.

When your koi are suffering and you've been to the garden centre and poured everything in but mother ruin, and still your fish are getting worse, and you suspect K.H.V, the then following:

50% water change
add salt at 3lb or 1/2Kg per 100 gallons = 30lb or 15Kg per 1000 gallon,
Let's say your pond is 2000gal break the dose up into 4 equal doses of 15lb per 8 hours until the whole 60lb is in.

But lets say your fish look like they will not last much longer - they are hanging around the filter outlet or clamped up on the bottom - then add your dose in 2 halves 4 hours apart,

and if they are really ill, then add it all at once - I have done this many times. It does make their eyes meet, but it saves your fish.

However: if after the full dose has been in for 48hrs and your fish are no better then you must think the worst. There are two sides to this coin - poison or K.H.V.

You will have read in the fish mags and on the web about salt. I was salting fish before half these so called fish experts where born, Salt has saved more koi than even Supaverm, which works even better with salt. I was reading a article some time ago in a fish mag which said "do not use salt" - the so-called expert didn't have a koi pond and didn't keep fish! It would be like me going down to Sellafield and telling them what they are doing wrong!

50% of what you read in these mags is garbage - people taking quotes from books which are reprints from the fifties, when malachite green was the golden bullet - (it's still first class for white spot)

Once you have past the 48 hours and there is no improvement whatsoever, then think about having a fish tested for khv and have your water tested for man made contaminates.

This is the picture you need to see. This is just what K.H.V. looks like as the virus starts its gruesome work. This fish has I suspect, been infected for some time and the stress of moving bagging etc brought the virus live. (Tests were positive on this fish and 3 of the original stock) This is a non-quarantined fish added to a system which has been without new stock for 4 years. The best bit is that it was bought from an auction for pennies. The symptoms started to show within 5 days of the new fish being added As I said at the start, this picture says it all.


Summer 2009

A mass die-off of carp at lake Mohave in Arizona U.S.A. Over 100.000 dead carp and still many arriving dying at its shore. Any that survive will be carriers for life.

All tests are positive. And they are still allowing anglers to fish lake! No wonder this virus is spreading! All you hear from the states is that they will find a cure, and are asking for donation for research. Money thrown away, they just don't get it - lake Mohave should have been shut down straight away. They are asking anglers to fish for other species! Do they have a note on the hook "no carp thank you". Mind you, knowing the yanks as I do, I am not surprised. Anglers leave the lake and fish elsewhere with contaminated tackle and clothing.

Here's a story from Canada. Also in the States this is getting so common I am dealing with over 30 cases via email at the moment June 2009 Derby.
Awaiting D.N.A. test results from 30 fish. 11 already dead, 5 more to follow 26" to 8".




May 2009 Southern London.
These are classic pictures e.g. sunken eyes and the fish appears to be rotting away.
Once seen never forgotten.




These are from a heated pond in January 2009.

K.H.V. Outbreaks 2008 Americas suspected total= s.v.c 22000 k.h.v 40000 cases Europe suspected cases. s.v.c 3500. k.h.v 12800. Asia inc Japan, Israel and South Africa - numbers are not available - myself I think it's more than all the above together, but nobody seems to know - put it this way nobody wants to want admit it. UK - no recorded/reported cases of S.V.C Birmingham 2 Cambridge 4 Derby 8 (inc. Press Reservoir, Ashover) East Sussex (Moor Hall Pools, Battle and surrounding water) Essex 3 (Including the RHS garden pond) Herts (Colne River valley) Kent 4 London and Greater London area 3 Newcastle 2 Nottinhghamshire 5 Leicestershire 3 Lincolnshire 4 Solihull (Earls Wood Lake ) Somerset 1; (Pavyotts, Mill farm, Yeoville) South East 10 South West 3 West Midlands (Mereside pools) Yorkshire 7 Wales 6 Ireland 2 Scotland 4 France 14 Holland 6 2007 Berkshire * = 1 (November) Cambridge = 1 (August) Essex = 3 (August) Kent = 2 (September) London = 1 Sussex = 1 W Midlands = 3 (September) Yorkshire = 1 (August) * The water temperature was 15.9oC, the lowest recorded with chronic infection and mass mortalities. The samples were taken on 9/10/2007.

Most of these cases did not need confirming - just watched all the fish die. I feel many tears for the owners. I now only approach new pond in a sterile paper suit and foot wear cover and now use no plastic. All nets are destroyed once used. I do not sterilize them - it's not worth the risk. All microscope tools inc slides are binned after use. My mobile lab is taken to our local hand-wash who are used to me now, and do my under the wheel arches, all my tyres treads, and even the roof. The van looks new most of the time as they keep it so clean for me.

A third of all cases are where there are no new fish added - the virus is just waiting for the right stress level. You must watch what you buy.

K.H.V. Outbreak in November

See the news page

As from 6th April 2007 it is now obligatory to notify suspicion of K.H.V disease.

This is classic K.H.V. A fish rotting away. One of the worst cases I've seen. This fish was still alive when the picture was taken.

I haven't taken a picture of the complete pond full, as the lady owner was too distressed to have a record of this disaster. The pond of 30 fish ranging from 15-30inches. One new fish was added in September - said to have been quarantined using heat. Well, heat or not, it wiped out the whole stock. I felt for this lady, she had done everything by the book (that particular book is now out of date, including having a heated system running at 20c), so she thought she knew her fish were K.H.V. free, as she had not added a new fish for two years.

I first thought it might be an immune syndrome affect with muiltifinnis (white spot), but upon closer inspection my thoughts went to K.H.V. and when the lab results arrived they were positive for K.H.V.

This is a classic case - fishes showing mass infection of trichodina which is often the case when K.H.V. is present

The latest on the KHV vaccine:

Kovax - the KHV vaccine manufacturer's web site can be found at:

www.kovax.co.il/


I hope winter temperatures killed off the virus - we need a cold winter and spring (not in heated systems). If you have one, and you have any suspicions with fish loses and you have turned heat off and the problem has gone away, please do not run the water to waste. Put the waste on the garden where it can be exposed to our winter conditions, as with S.V.C. (which has been a good year - no reported cases) as our spring was too cold. Also new findings - K.H.V. can take up to 7 weeks in quarantine (under heat) to show itself. I wish I had know this 3 years ago - half our outbreaks could have been prevented.

If any thing else comes to light with this infection I will post it here.

Remember: follow up all tests in all ponds where positive.

K.H.V. in The USA


After you have visited a dealer, no matter how good they are, do not go near your pond with the same cloths or shoes you where wearing. Do not allow ANY person, including yourself, to go to your pond without washing their hands and shoe soles in warm water with mild bleach and soap if you have been near other waters or a friends pond.

Change your clothing before going near yours. Do not lend equipment - especially nets, koi socks or plastic bowls. A virus classes plastic and nylon and thus porous. DON'T FORGET THAT. No matter how well you wash them after, or when doing microscope scrape for friends, when they arrive ask them to remove their shoes. Of course if you go to visit them you do the same. Destroy slides and cover glasses and wipe your microscope stage down with good antibacterial wipe and wear gloves. Wrap a bin liner around you to protect contact of water to your clothing. All this sounds mean, but one mistake will cost you your fish collection. I know this - nine sites have gone down with one or all of the above mistakes and when I explain this to the pond owner and they think back, they can all remember their mistakes - but its to late then.

KHV has now been been reclassified as CY-HV1.

The following is reproduced with permission of CEFAS.

What is Koi Herpesvirus?
Koi herpesvirus (KHV) is a viral disease of common carp Cyprinus carpio and its ornamental variants. The virus was first recorded in Israel in 1998, following large-scale mortalities of koi. More recently the virus has been isolated from a number of countries throughout the world and has been associated with an increasing number of koi mortalities in England. In all instances so far recorded, the disease has been restricted to carp and its variants.


What does KHV do?
The disease is believed to be highly contagious, reaching up to 90% prevalence in carp populations. This is higher than other viral carp pathogens such as Spring Viraemia of Carp (SVC). In each case the disease has occurred at water temperatures of between 17^oC and 23^oC. Typical symptoms of infected fish have included lethargy, erratic swimming behaviour and increased mucus production. Internally, gross pathologies such as haemorrhaging within the liver and gill necrosis have also been observed. Acting as an immuno-suppressant, fish infected with KHV can become susceptible to secondary infections, increasing the range of symptoms that develop.

How is KHV detected?
Diagnosis of KHV requires detection of the herpes-type virus. Currently this is only possible by cell tissue culture and molecular biology techniques, namely PCR (Polymerase Chain Reaction). To date the virus has been isolated from gills, kidney and brain tissues of affected fish. Being a herpes virus, KHV can lie dormant for long periods within tissues until triggered by a predisposing factor such as stress. This can make identification of infected fish very difficult, increasing the threat of transfer to other waters. More sensitive diagnostic techniques are required before the virus may be identified in carrier fish or hosts not showing signs of disease.

Why is the Environment Agency concerned about KHV?
Due to the pathogenicity of the virus and difficulties with detection the Environment Agency is very concerned about the potential impact of KHV to carp fisheries within England and Wales. The virus has already been detected from 10 carp fisheries following mortality investigations. There are no treatments for KHV, or licensed vaccines to prevent potential infections. As KHV is currently not a notifiable disease, fish infected with the virus are not restricted from importation into the UK. As such, without further controls it is possible that KHV could be spread to fisheries with fish legally imported. Due to this the Environment Agency is working with CEFAS on the best methods of screening and is adapting our controls on the movement of fish into the wild.

What is the Environment Agency doing about KHV?
In order to protect fisheries and prevent dissemination of the virus the Environment Agency has classed KHV as a novel pathogen. This restricts introductions of fish to fisheries from sites known to be infected with KHV using Section 30 of the Salmon and Freshwater Fisheries Act, 1975. Where a significant risk of infection exists (e.g. introduction of fish from Israel) fish will be tested for KHV using available diagnostic tools, these tests are not a guarantee but an assessment of risk. The Environment Agency are also raising awareness of the virus to fishery owners, promoting extreme caution whenever carp are being imported or stocked into fisheries.