Koi Herpes Virus: A Hobbyist’s Point of View.
By Karl Schoeler
I traveled to Japan last October. It was my second year in a row and something I looked forward to from the moment we came home the previous year. We
had a wonderful time. We visited many koi farms in the Niigata area and of course picked out and purchased choice specimens which would later be
shipped to the states by our dealer.
Our fish arrived in California in November and were held there while our dealer arranged to have them all tested for KHV. This was the first time our dealer
had actively participated in drawing blood for serology so it was as new to him as it was to us. The procedures were finally completed the first week in
December.
Shortly thereafter I was introduced to KHV in a devastating way. When the results came back, three of our fish had tested positive. One of them was mine.
The dealer called and wanted permission to euthanize them. I immediately agreed, but then I started to wonder about the rest of the fish in the group.
Dr. Richard Porter and his wife, Luanne, were two members of our group. We spent the travel time between farms talking koi and then got around to KHV.
He and his wife had been through a terrible KHV outbreak and had learned the hard way about quarantine and testing. I listened to their story and knew
they had suffered deeply. Yet here they were buying koi in Japan. They obviously were very concerned but yet unafraid.
Over the last few months I’ve had a number of conversations with Dr. Porter as well as Luanne. Luanne taught me her method for drawing blood. I will
always be indebted to the Porters as I truly believe were it not for them my collection would have been decimated by KHV. Their insight and information has
always been flawless.
Several months passed. I purchased koi and interacted with dealers around the country. Each one had his/her own story about how to prevent KHV, how
to quarantine, what test to use (if any) and how their fish were quarantined for weeks and were guaranteed. There were so many things that didn’t match
up. The quarantine procedure became the way to be KHV-free. Blood samples were mixed together to defray cost and the results were said to be “just as
accurate”. PCR testing was installed by some as a way to warrant that they were testing for KHV. Serology was performed on a small percentage of fish in
quarantine and the rest were assumed to be safe if the samples tested negative. Assurances were given that the farm where the fish came from was
certified KHV-free; meanwhile the fish in question were knowingly mixed with others from other farms and even other countries.
My search for more and corroborating information led me to Dr. Branson Ritchie, Co-Director of Infectious Diseases Laboratory, College of Veterinary
Medicine, University of Georgia. I had knowledge of Dr. Ritchie some years ago when my wife’s Macaw was suffering from an incurable wasting disease.
Our local veterinarian contacted him because Dr. Ritchie was doing research on the subject. I always thought his insight on that problem was extremely
accurate.
I spent a considerable amount of time relating to Dr. Ritchie the information I had received about KHV from a variety of sources. I already knew that most of
the information I had received on the internet and through other sources was incorrect but I needed to ask someone who was directly involved with testing
blood samples as well as researching a vaccine for KHV.
His answers did not surprise me. Most of the information which I had gathered was as I suspected. It was like the old circle game: “Whisper Around The
World”. One person starts the game by whispering information in the next one’s ear. The process is repeated until the last person states what should be
the same information. Most of the time the information is altered. Sometimes so much so that it bears little resemblance to the original.
So, to the best of my abilities I am going to try to set the record straight in a number of areas. I’ll start with quarantining for KHV testing. This is an area of
some confusion and it is really very simple.
Upon receiving a shipment, whether one or ten fish, they should be quarantined in such a manner that the tank and all associated equipment remain
separate from any other. This is extremely important! Handling, feeding, maintaining these areas must be done with considerable forethought as cross-
contamination can happen so easily. Hand washing, disinfecting of equipment and clothing changes all must be considered.
Hopefully a quarantine tank has been prepared before the shipment arrives and the filter has had time to cycle, whether using dither fish or simply by
adding small amounts of ammonia. During quarantine the koi may be scraped and scoped and treated for parasites if necessary. Simple observation is
one of the best tools in this area.
The tank water should be filtered and the water quality monitored for the standard parameters such as ammonia, Ph, Kh, nitrite, nitrate and any other
parameter which the hobbyist feels necessary.
The water temperature should be kept in the mid-seventies. This is to allow the virus the optimum temperature at which to be active. It does not mean that
the fish will become sick and shed the virus. Contrary to some theories, cycling the temperature up and down over a period of time will not force the fish to
become sick and shed the virus.
Fish that are held at the optimum temperature OR in systems where the temperature is cycled up and down may not show any symptoms but can still be
persistently infected. They may or may not shed the virus but then you’d be able to identify that simply by observation of symptoms.
The objective of serological testing is to detect those fish which are persistently infected, or “carriers”.
After a quarantine period, blood should be drawn for serology. This process is fairly simple. The proper equipment needs to be assembled and the
methods should be studied. Having someone familiar with the process the first time is helpful, but not necessary. I generally hold my fish in quarantine for
at least six weeks, except in the fall or early winter when I hold them for about six months.
Materials needed:
23 gauge 1&1/2” 3cc syringes are most commonly used for drawing blood.
Vacutainers (Green lid) - These must be numbered/labeled for each sample, and are used in the centrifuge for spinning out the blood serum.
Sterile blood sample tubes - These must be numbered/labeled for each sample and these are the vials which are shipped for testing.
Both types of tubes are available through your local veterinarian.
An ice-filled bowl should be available to keep your samples cooled during sampling.
Numbered index cards using a fine point Sharpie. The numbered index card should match the fish being sampled along with the written description. It
should be included in the photograph with the fish.
A legal pad for listing koi to be sampled and descriptions of each.
A “V’ shaped tabletop device, which can be padded with wet terry towels, will hold the fish securely. I use a plastic rectangular window box planter from
Walmart with the end cut out.
I use clove oil for sedation which is readily available at most health food stores.
A small air pump with tubing and airstones.
A sedation tub with aeration and clove oil, I use 10 drops of clove oil per gallon in the sedation tub.
A recovery tub with aeration to allow the koi to quietly recover as well as for measurements and photography.
A catch net/sock
A centrifuge. This is a medical device used for separating blood serum for testing. These are readily available on eBay, or your veterinarian may help you
in this area.
Miscellaneous towels and wipes and a mild bleach solution or other disinfectant.
Bubblewrap packing for the samples with a strong box for overnight delivery.
An extra set of hands for handling makes things go more smoothly.
An extra person to take pictures that document the procedure and the fish completes the group needed for serology sampling.
All details must be discussed with each participant so everyone knows what has to happen and when. Having done this on several occasions I assure you it
is necessary.
The following are pictures of some of those things:
(INSERT PICTURES HERE ACCORDING TO THE ABOVE LIST)
Drawing blood is somewhat tricky the first time or two but it gets remarkably easy once you’ve worked on your own method.
I hold the syringe between my thumb and forefinger on the lowest part of the barrel. I insert the needle with the sharp edge “down” and at a 60* angle. This
reduces the potential for the needle to plug with tissue.
(INSERT AN APPROPRIATE PICTURE HERE)
I insert the needle approximately ½” behind the anal fin and slowly press toward the spine. Once I feel it touch the spine I gently pull the plunger on the
syringe and watch for blood to flow. There is a vein directly under the spine so don’t pull back on the syringe or you’ll miss it entirely. Sometimes I need to
slightly reposition the needle. This can be done without withdrawing it but if no sample is found after two or three tries it is best to withdraw, grab another
syringe and try again. At times the needle will plug with tissue. Don’t worry if you don’t get a sample on the first or second try. Place the fish in the
recovery tank and move on to the next in line. Once the fish has recovered it can be sedated again without concern for any damage and another attempt
can be made.
You’ll need about 1/2cc of blood. I have submitted smaller samples at times and the test can still be done.
Your helper can assist you by keeping the fish upside down and straight in line with your needle position. Your documentation/photography of this
procedure as well as the “after” picture with the numbered index card is important so you are sure which sample goes with which fish; especially when
testing similar fish such as the five gold metallics which I tested August 16th.
(INSERT APPROPRIATE PICTURES)
Once the samples have been drawn and prepared, they should be sent to:
Infectious Diseases Laboratory
College of Veterinary Medicine
University of Georgia
501 DW Brooks Drive
Athens, GA 30602-7300
The form to complete for testing is available on line:
http://wwwkoihealth.org/koiformUG.pdf
The form should be filled out carefully noting the specimen and the number ascribed to each one. A veterinarian’s name and office number as well as fax
should be included. If you have a dog or cat you have a veterinarian and you will find they have a considerable interest in this process. I am fortunate to
have a husband and wife team of veterinarians who take care of my dogs and birds. They are always interested in the koi and stop by periodically for social
visits.
Testing begins each Monday and the results are usually faxed out about eight days later.
It is important to test all koi in the group, regardless of size or cost. Testing a small percentage of the group will reveal their results but obviously will have
no relationship to others in the group. This is dangerous because it gives a false sense of security. In reality unless all fish in the group are tested very
little is learned.
The most dangerous group of fish? A two part answer: Those who have not been tested…..and the small ones. Why the small ones? Because, “they just
aren’t worth it”. I can assure you that small fish can be just as persistently infected as large ones. Yet I hear this frequently. Since the small fish sell for
$25.00 to $75.00 somehow this means they must not have KHV since they’re not very big or not worth much. I don’t understand this logic. It just doesn’t
make sense.
Remember, a persistently infected fish, large or small, within a group does not mean that all others are infected. In fact it has been shown that others within
the same group may never become infected, so finding and removing any “carriers” is paramount. Persistently infected does not mean that the virus is
shedding.
One of my favorite old wive’s tales regards taking blood samples for serology, mixing the samples together and having the result tested. This method is
supposed to reduce cost. It is also said that since the fish are from the same breeder and same quarantine tank that the result will be accurate. However it
is well known that breeders and dealers mix fish in preparation for optimum shipping, in quarantine tanks once they arrive, and in bags when they are
shipped. In addition there is one very important point to remember:
Mixing samples: If four samples are mixed and the results are positive, which fish should you remove? If this same mixed sample is negative, is it accurate?
Far from it. Serology can detect low titers (antibodies) only to a point. A diluted sample could well come in under the radar and not be detected. So each
sample must be tested individually.
The individual cost of serology for each sample is $20.00. This is very cheap when considering the potential for losses to your entire collection, whether
pond or show quality.
PCR (Polymerease Chain Reaction) testing has become a fashionable way to say that the fish have been tested for KHV. However, PCR testing will only
reveal what you may already know or suspect. The fish must be shedding the virus. It probably is sick. The symptoms are probably why a swab was
taken. It is verification, not testing in the true sense of the word. In a nutshell, a sterile (preferably Dacron but it doesn’t really matter) swab is used to
collect samples of the slime coat, gill tissue, anal area and internal organs (dead or dying fish). On a live, apparently healthy fish this is likely to result in a
negative result. Only if the virus is being shed will the test be positive. So yes, a PCR test may be negative while a serology test on the same fish could be
positive.
PCR testing is relatively inexpensive. However current PCR testing is not sensitive enough to detect the very low numbers of virus particles in the
persistently infected (carrier)fish.
PCR is useful to verify the presence of large numbers of virus particles present in an acute KHV disease outbreak. If you suspect something is going on
with your fish, you can obtain a sterile swab at no charge from your veterinarian. Nearly all the labs supply them to the vets at no cost simply to promote
their testing facilities.
There is some question as to how long a koi will continue to produce antibodies to the virus. Some say two to three years but there have been koi with a
history which would indicate exposure more than five years previous to testing. So, what should the hobbyist do?
As hobbyists we can demand that proper quarantine take place, that proper testing be accomplished and by doing so we can control the market. Since
there seems to be an unending supply of koi, we don’t have to buy the one that happens to be offered today if it doesn’t meet our overall expectations.
Or you can take the road I’ve chosen. Yes I will continue to demand that proper quarantine takes place and that testing be done. But I also know the reality
of the situation. If I really want a particular fish I am quite capable of testing it. I may buy the fish regardless. As I observed in Japan with the Porters, I am
concerned but I am educated enough to be unafraid.
My thanks to the following for their editing assistance and general encouragement:
Dr. Richard and Luanne Porter
Dr. Branson Ritchie
Mrs. Karl (Judy) Schoeler