KHV Transmission

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Duncan
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KHV Transmission

Post by Duncan »

hi
just when you thought it could not get any worst it turns out just about every fish under the sun is capable of carrying and transmitting KHV without getting sick them selves reaffirming horizontal transmission big style , it was found in tench, roach, pike bull head, well you read it for yourself its a good read

you may find it confusing the amount of PCR primers listed, this is because there is not just one form of KHV there are quite a few variations of KHV all of them deadly but kill at different temps and rates and you have to have a different specific primer for each for PCR

http://www.koiquest.co.uk/khv12.pdf
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Re: KHV Transmission

Post by Manky Sanke »

Thanks Duncan,

I finally found the time to read this report and give it the proper attention it deserves and apart from the list of species that can carry KHV, this statement is cause for concern.

Initially, in 2003, it was believed that the optimum temperature for KHV replication and shedding ranged between 22-26°C (Perelberg et al., 2003). However, KHV induced mass mortality in common carp can also take place when the water temperature is as low as 8°C (Bergmann, pers. comm.). In the present experiment, the water temperature was much lower than in the experiments mentioned above, i.e. 14°C on average, and this resulted in a lack of mortality in SPF carp. However, the authors hypothesise that after six years of KHV presence in Poland, the virus has systematically adapted itself to the Polish system of carp breeding (i.e. 3-year cycle at lower water temperatures compared to warm water conditions, e.g. in Israel or Asia). This situation may be due to modifications which have taken place in Polish or European KHV variants modified to lower temperatures.

For anyone who wants that translated; they believe a variant of the virus has systematically adapted to the lower water temperatures in Poland in six years and can now cause mass mortality at 8°C. If it can adapt that quickly, who knows how it will adapt in the future.

In the present study, the experimental cohabitation of SPF carp with 6 fish species (confirmed as KHV carriers prior to the experimental start up) representing two families, Cyprinidae and Percidae, showed that fish to fish horizontal transfer can occur between selected species and SPF carp.

Translating that; SPF carp (specific pathogen free carp) means that they didn't have the particular disease being looked for in a test. In this experiment it means that they initially didn't have KHV.

Horizontal transfer or transmission means that a disease can be passed from one individual to another via direct contact or a “vector”. A vector is a means of transmission that doesn’t involve direct contact between the carrier and the individual that becomes infected.

E.g. the air and minute droplets in it can be a vector for flu if someone breathes what someone else with flu sneezes. We disinfect nets etc after every use at koi shows so they don’t become vectors of a disease in one vat to another vat.

Elsewhere in the report, it refers to vertical transmission. That means transmission from parent to offspring. E.g. HIV transmission from an infected mother genetically to her unborn child. At least KHV can’t (yet!) be transmitted that way.

List of species confirmed to be KHV carriers (Kempter et al 2008)

Common carp
Prussian carp
Tench
European perch
Common roach
Northern pike
Common dace
Gudgeon
Common bream
Ide
Crucian carp
European chub
Common barbell
Vimba bream
European bullhead
Koi carp
Spined loach
Belica
Common nase
Mattybkic
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Re: KHV Transmission

Post by Mattybkic »

Thanks Duncan for the info and thanks Sid for the detail as ever :wink:

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eds
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Re: KHV Transmission

Post by eds »

Syd the virus adapting and changing in the long run is very likely to be a good thing! Just like flu it will mean that some forms Will become commonplace but much less virulent. There is a trade off with viruses. The more easily and widely spread they are the less virulent they tend to be (with a few notable exceptions). From everything I've read on it it seems highly likely that KHV will go the route of other herpes viruses and if it's adapting that quickly to temperature then that might happen sooner rather than later.

However in the short term it won't change the importance of good quarantine protocols and may mean the virus becomes more disastrous to fisheries especially where water temperatures are less likely to get above 20 degrees in one of our wonderful British summers!

I certainly wouldn't want to risk a vaccinated fish in with my stock as we still seem to have so many gaps in our knowledge of the virus.
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Re: KHV Transmission

Post by JohnKitching »

Excuse my ignorance but isn't KHV killing fish at lower temperatures a good thing?
Won't that reduce the number of fish carrying KHV but showing no symptoms?
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Re: KHV Transmission

Post by Duncan »

not really the host still needs stressing to get KHV to break out cold is nota real stressor

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Re: KHV Transmission

Post by JohnKitching »

Duncan wrote:not really the host still needs stressing to get KHV to break out cold is nota real stressor

dunc
That makes sense thank you.
What would you recommend for a QT to have the best chance of getting a new fish to break out with KHV if it has it?
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Duncan
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Re: KHV Transmission

Post by Duncan »

John the chances are the typhoid mary that has it will survive

you need a know naïve fish or fishes for it to react with

in other words you get the new fish to break and the naïve fish are the litmus paper if you like

heat ramping is the only way the hobbyist can see if KHV is present , ramp them to 25-26 and no more then drop them back to ambient as fast as possible do this two or three times to stress any carriers

dunc
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