KHV knowledge base increases with time

[JasPR]

Interesting blip;

Israeli virologists have conducted a study to investigate the antibody response and disease resistance of carp exposed to Koi Herpes Virus and KHV vaccines.

The scientists experimentally infected fish with either the wild-type virus or the attenuated-virus in the KHV vaccines and measured their antibody response and their resistance to the disease.

Both groups of fish developed an immune response which made them resistant to further exposure to the virus, which is now officially known as Cyprinid Herpes Virus 3 (CyHV-3).

Those fish inoculated with the virus and vaccine developed anti-CyHV-3 antibodies, but the number of these gradually decreased, and at 280 days after exposure they contained levels only slightly higher than those seen in naiive fish - the term used to describe fish which haven't been exposed.

The protection against the virus is proportional to the amount of anti-virus antibodies in the fish, with those fish that have experienced recent exposure to the virus or vaccine being better equipped to fight off further infections than those who were exposed long before.

However, the study claims that even immunised fish, with antibodies that are no longer detectable, remain resistant to the virus, an effect the scientists believe to be caused by the rapid response of high affinity anti-virus antibodies.

"The fact that anti-virus antibodies neutralize in vitro the pathogenic effects of the virus emphasizes the central role probably played by the antibodies in anti-CyHV-3 protection in vivo," the authors wrote.

The study, which was undertaken by Ayana Perelberga, Maya Ilouzeb, Moshe Kotlerb and Michael Steinitz from Israel's Ministry of Agriculture and Rural Development and The Hebrew University, has just been reported in the journal Vaccine.


Is the vaccine safe?

The news will add to the confusion and debate regarding the safety of fish vaccinated with the attenuated virus.

Suppliers of Israeli Koi have been vaccinating their fish with attenuated vaccines, which are based on live but less virulent viruses, rather than inactivated or 'dead' viruses, and shipping them around the world with claims of resistance to KHV.

However, it is legal to import vaccinated stock, it is illegal to administer the vaccine in this country, and concerns have been raised over the safety of the fish.

A previous paper by Perelberg, Kotler and co-authors in 2005 claimed that the attenuated virus was safe, however, others have been skeptical.

In 2006, the Institute of Fisheries Management (IFM) released a position statement on KHV advising fisheries against fish that had been vaccinated against the disease.

It said: "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."

Koi Herpes Virus affects Koi and Common carp and has been responsible for a number of mass mortalities around the world.

For more information see the paper: Perelberg A, Ilouze M, Kotler M, Steinitz M (2008) - Antibody response and resistance of Cyprinus carpio immunized with cyprinid herpes virus 3 (CyHV-3). Vaccine. 2008 May 12.

[gcuss]

u n c l e ...

damn virus... damn vaccines.

Grant

[mrbradleybradley]

Hi JR

Thanks for the reference.



BB

[MikeM]

Hmmmmm..... So it might turn out that vaccinating the koi only succeeds to spreading the disease more widely.

[schildkoi]

Here's another consideration as well. Currently, blood serology testing through (VN) is the best way to determine if a koi has had a recent exposure to the virus. Throw that out the window for those koi that have been vacinated...they can test positive as well. So is the koi vacinated or exposed in that scenerio?

Steve

[JasPR]

Well that was the assumption early on Mike ( 2005) and a warning was issued that the virus could revert. But it is now 2008 and that has not happened.
As you know, natural immunity is the goal. Vaccines just 'tease' the immune system into responding and being vigilant. And koi have poor immune memories as a general statement. The 'six month' comment however is in my guesstimation, a booboo. In that this is a immune comment that is taken from vaccines that cover bacteria vaccines in fish.

The Israeli data is often attacked. To me there is science, politics and personal agendas. And both sides sin in all these areas. The pure truth suffers. You have seen how researchers want to own this disease and control the information as if it was copy righted and not meant for the benefit of all. And there are highly influencial individuals that insist that if the information is not from their mouths, it is automatically invalid. On the other hand, you have business agendas and a lot of money at stake. So overly confident statements can and do come from that camp.
And then there are the facts. There are ---- MILLIONS of vaccinated carp in the world as we speak. And more governments considering use of this vaccine. And the sky has not fallen in the food carp industry. The koi business is just one 'quirky' part of a giant industry.
Ultimately the facts will come from the food carp side as other countries push ahead with vaccine programs. It will continue as a slow process. But in another 8-10 years we will be know and there will be no grey areas about the vaccine. IMHO JR

[Brian]

Hi Jim,

So if the level of antibodies decreases are the Israelis mentioning anything about booster shots as you might see with other so-called vaccines? Have they re
challenged vaccinated fish a year or two after the fact with no boosters successfully?

[JasPR]

Not sure of the settled on time intervals Brian. I can ask their biologist to come on and talk about the most resent vaccines done this past spring, if you think it is a good idea?

Steve, yes, the tests pick up vaccinated fish as well as diseased fish and healthy carriers. This is why the Israeli have worked to put a marker in the vaccinated fish. This is the last hurdle to get the fish into the European markets. JR

[MCA]

It is one thing to use a vaccination machine on a farm to shoot fish in the thousands before shipment. But can you see the average hobbist trying to give booster shots every year or so to every koi? And hobbyists will not call in a vet to do it either....try to find a vet who even knows carp.

We had better not be depending on vaccines that need boosting in X years. That ain't gonna happen in the hobbyist world.

[Nancy M.]

Quote: Originally Posted by MCA It is one thing to use a vaccination machine on a farm to shoot fish in the thousands before shipment. But can you see the average hobbist trying to give booster shots every year or so to every koi? And hobbyists will not call in a vet to do it either....try to find a vet who even knows carp. We had better not be depending on vaccines that need boosting in X years. That ain't gonna happen in the hobbyist world.

If giving a booster shot every year or two years to my koi, would save me and my koi from having or getting KHV, I would do it in a heartbeat..

Luckily we have a koi vet, and I would call him.

No different than getting my dogs there shots.