There are other diseases
which mimic the symptoms of KHV.
These include:
- Columnaris and
Costia-trichodina-childonella also these infections can
be found in large amounts on KHV positive cases. Mostly though its
trichodina.
- Full blown hexamita can pass as KHV when many
of the fish are affected.
- Gill fluke in high numbers and of long standing will look very similar to
KHV but ...
- The most similar is asymptornatic infection of white spot. See
white spot under health.
Fish die in very similar way to KHV. KHV in simple terms destroys the
fish's liver and kidneys. Asymptornatic over-rides and destroys the fishes
immune system, which in the early stages, shows signs that mimic symptoms of
columnaris - fin rot.Both will show massive gill
damage.
Most ulcers appear when KHV is from the pond stock and no new
fish have been added. Either it's not been warm enough, or a system failure has
stressed the fishes. Why this is so I don't know.
I can only say that
KHV works slower, and the fish that have been carrying this virus over a long
period have infected livers and kidneys. This leads to sepsis and destroys the
fish's immune system, and has more time to destroy the fishes muscle tissues
before over-riding the internal organs than an introduced infection, which the
fish's immune system as had no contact with.
The norm seems to be:
- New fish added, they all dead quite soon afterwards
- No new fish added, the fish die slowly and look like thay are rotting away.
The fish linger at the surface or lay on the bottom and move like zombies. You
can lift them from the pond with ease no need for a net.
But, as with KHV, death in most cases comes quickly. Sometimes however,
but not in all cases, death can come in ones and twos.
As with KHV and
asymptornatic white spot, the carrier fish or fishes remains fine in most
cases.
There's no complete way of just looking at fish and be a 100%
sure that it's KHV, but in 70% of KHV cases, death start within 14 days of a
new fish in pond. However, the same applies to asymptornatic white spot.
All the other infections arrive in much the same time zone, but at a
slower degree of infection.
One problem you have is with quarantine.
KHV or asymptornatic do not always show themselves. Asymptornatic will not show
until its exposed to a fish stock, and KHV will not show unless fishes are
heated, and even then then may show if the stress level is safe.
Quarantine needs to have fish in stock when the new fish are added to
the quarantine pond or tank, to stimulate the infection to show itself in other
words. One fish quarantine is a complete waste of time in 99% of KHV and
asymptornatic cases.
