Yume Koi Has Been Hit With Khv

[KoiCop]

Thanks, Scotty. That would be appreciated.

Any idea whether Duncan is going to respond to Mike's post? (Haven't seen one on KQ)

[B.Scott]

He most likely hasn't seen it yet. I'm sure he will respond soon as well.

B.Scott

[dick benbow]

I'm relieved to see this information has become public. I think it's important for people to have a full disclosure of what about this situation is actually known.I have been keeping up with this thru my friends in europe and because technology is still in the process of making inroads has been hard to comment on in a professional manner that is fair for all sides on the issue. But atleast for now, koi keepers will know what has learned and can act accordingly to their own convictions.

[dick benbow]

Mike by the way is working on an article oranizing all his activity and knowledge he has aquired over this time period. It will definetely help us to understand where we have come from and where yet we'll have to go.

[Spike Cover]

All,

KHV carriers are a tricky subject. We know (scientifically and from the school of hard knocks) that they exist.

Here is some information and some thoughts on carriers:
Fish that show a positive PCR for KHV and have symptoms, virtually always have KHV.
We don’t know if all koi that survive a KHV outbreak become carriers – we suspect that at least some will but have little or no data on just how many.
We don’t know if all koi that survive a KHV outbreak develop antibodies (a/b) – we suspect they all won't but that many will.
We don’t know if koi that develop a/b will become carriers – we suspect some will but don’t have a clue as to how many.
We don’t know if koi that are carriers will test positive for a/b – we suspect some, or maybe even most, will but again don't have a good feel for what percentage.


More info and thoughts:
KHV is almost certainly a herpesvirus. The folks who rule on the taxonomy (put bugs in “families”) of these things haven’t made a decision yet but the U.C. Davis folks have done a credible study (genome comparisons), published that work and applied to have KHV classified as CHV-3 (the third cyprinid Herpesviridae). Most of those who are interested in the scientific world, except some of the Israelis, believe that it’s a herpesvirus.
If it is a herpesvirus, then it probably behaves like it’s relatives and has a latent or carrier state (in the fish). A group out of CEFAS did some experiments to prove that carriers exist and published back in 2005 (S. St. Hilaire was first author).
Fish that survive an infection, will usually test positive for a/b. This said, some groups have had as few at 10% become a/b positive post infection. Others have seen most survivors become a/b positive.
We do not have a good handle on how many (what percentage) survivors will become a/b positive.
I think it’s safe to conclude that fish cannot become carriers w/o being exposed to KHV
Therefore, it is safe to also conclude that fish that test a/b positive, have been exposed to KHV.
Therefore, we can also logically conclude that fish that test positive for a/b MAY be KHV carriers and fish that do not test positive for a/b, are less likely to be carriers than fish that do test positive.


The bottom line here is that a/b testing is probably the best test for prior exposure to KHV that we have. It also indicates that the fish MAY be a carrier and is the best test we have for that to date.


If this all seems confusing, it's because it kindda is. Lots of folks with good intentions are trying to be proactive and help stop this disease. That's a good thing. Whether or not an a/b test identifies a KHV carrier or not is currently scientifically unproven. But again, it's probably our best shot at a test for it.


Best regards,
Spike

[JasPR]

" I think it’s safe to conclude that fish cannot become carriers w/o being exposed to KHV
Therefore, it is safe to also conclude that fish that test a/b positive, have been exposed to KHV.
Therefore, we can also logically conclude that fish that test positive for a/b MAY be KHV carriers and fish that do not test positive for a/b, are less likely to be carriers than fish that do test positive." - SC


I don't know about that Spike? There are always going to be a percentage of fish that are immune to a virus. In the case of THIS virus we know the pathogen must get into a cell to begin the infection and replication process. No one has done a study on the naturally immune fish's ability to block entry to the living cell- a common explanation for immunity. This does not mean that an immune response will not be launched or that an ELISA test will not show antibody response to the presence of virus particles. It does mean however that in theory, a percentage or strain of koi will have natural immunity to the critical dynamic of pathogen invasion of the living cell.
The reason KHV, or any virus, infects a specific species ( in this case, koi and not goldfish) is because 1) the cell does not have the needed composition for pathogen replication and 2) more importantly, the virus has difficulty invading that species' cells.
The immune koi could be an animal that has the ability to block the invasion- and as I just mentioned, those koi would not be a carrier yet it might test positive on a ELISA test as an 'exposed' animal.
If this theory is true, then we are killing the 'cure' for KHV. These animals instead should be used in a breeding program to pass on this genetic antivirus trait.

So as I have posted for a while now we could have:

1) the naive fish ( never sick, never exposed)
2) the disease fish ( two outcomes- death or recovery)
3) the naturally immune fish ( resistant to infection)
4) the survivor - a carrier ( periodically sheds infecteous virus)
5) the survivor - a non carrier ( possible surviving two outbreaks?)
6) the vaccinated fish ( a 'survivor' of sorts and not a carrier)

- JR

[KoiCop]

Thanks to you both of you this should prove to be a very informative discussion. Don

[MikeM]

But, JR, who is going to use the immune fish as a breeder? First, we have to figure out a way to identify such koi (if they exist)... which presumably means exposure to KHV at some stage of selection. Second, we have to convince a breeder taught KHV is an incurable evil (and appropriately so), that they can trust a determination of immunity and use such a fish in their breeding program with at least one of their best oyagoi, and place the offspring in their mudponds. And, third, we have to convince the public that despite all they've been taught, it is OK (even good!) to buy these koi bred from KHV-exposed fish and mix with their pet fish... and even their choice show fish. Whew, not many koikeepers have the level of sophistication to understand this. And, which breeder will be willing to take a risk of error? And, what happens when koi bred from an immune parent show some degree of resistance, but many still die. From a scientific perspective, it could be a tremendous success if 65% of offspring had immunity or even survivable resistance... but would the industry survive a 35% risk of mortality on a regularly recurring basis? ...at least until virus proliferation wiped out non-immune koi at fry stage as a regular course in breeding programs?

In theory, I think you are right. And, I think it extremely likely there are immune carp... there are immune individuals as to most viruses. But, from a practical perspective, I don't see it happening on a planned basis. Maybe over the course of decades it will occur by default thru only immune carp being left to breed, but there won't be much of a hobby left if it occurs that way.

...depressing topic. I'm going to go visit some of those smiley face threads.

[jnorth]

Quote: Originally Posted by MikeM But, JR, who is going to use the immune fish as a breeder? First, we have to figure out a way to identify such koi (if they exist)... which presumably means exposure to KHV at some stage of selection. Second, we have to convince a breeder taught KHV is an incurable evil (and appropriately so), that they can trust a determination of immunity and use such a fish in their breeding program with at least one of their best oyagoi, and place the offspring in their mudponds. And, third, we have to convince the public that despite all they've been taught, it is OK (even good!) to buy these koi bred from KHV-exposed fish and mix with their pet fish... and even their choice show fish. Whew, not many koikeepers have the level of sophistication to understand this. And, which breeder will be willing to take a risk of error? And, what happens when koi bred from an immune parent show some degree of resistance, but many still die. From a scientific perspective, it could be a tremendous success if 65% of offspring had immunity or even survivable resistance... but would the industry survive a 35% risk of mortality on a regularly recurring basis? ...at least until virus proliferation wiped out non-immune koi at fry stage as a regular course in breeding programs? In theory, I think you are right. And, I think it extremely likely there are immune carp... there are immune individuals as to most viruses. But, from a practical perspective, I don't see it happening on a planned basis. Maybe over the course of decades it will occur by default thru only immune carp being left to breed, but there won't be much of a hobby left if it occurs that way. ...depressing topic. I'm going to go visit some of those smiley face threads.

I suppose the simplest thing to do would be to find a male and female immune koi and breed them. Then throw a khv infected fish in with the offspring and see what happens.

[JasPR]

Hi Mike, long time no talk!

In response to your concerns:

But, JR, who is going to use the immune fish as a breeder? First, we have to figure out a way to identify such koi (if they exist)... which presumably means exposure to KHV at some stage of selection. _ Mike M

No Mike, I think we CAN tell. A koi needs to be checked via nested PCR to see if the disease is active within the fish's cells ( This is a recently or currently diseased fish) and then if negative we need to do an ELISA to see if the fish has produced any antibodies in response to being exposed in anyway to the virus.


Second, we have to convince a breeder taught KHV is an incurable evil (and appropriately so), that they can trust a determination of immunity and use such a fish in their breeding program with at least one of their best oyagoi, and place the offspring in their mudponds. _ Mike M

You need to be around some Japanese breeders. Some of these guys are very sophisticated individuals and very resourceful. Not all of them are passive country people. Guys like Momo and Sakai are very successful businessmen and read and question all of the time.
It was the Japanese who did the outcrosses to bring vigor and health back into the exhausted inbred gene pool in the 1970s and again in the 1980s. They get these things and understand about introducing traits of all types, not just color traits.


And, third, we have to convince the public that despite all they've been taught, it is OK (even good!) to buy these koi bred from KHV-exposed fish and mix with their pet fish... and even their choice show fish. - Mike M

That is easiest of all. The public has a very short term memory about these things. Both a blessing and a curse.

JR