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Koi
Health
This is a very brief guide to some common koi diseases, it is in no way
a substitute for a good book on the subject or professional help.
For a more detailed guide have a look at the koi health sites listed on
our links page. Unless specifically stated most of these problems
can be treated using commercial remedies which state what they are for
on the packaging, or ask for dealer advice if you don't know which one to
buy.
Please click on the various diseases for further information:
Sliminess of the skin
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A greyish white film of
excess mucus on the body. This is a reaction to
protozoan parasites, notably Ichthyobodo (Costia) -
left image, Trichodina - middle image,
and Chilodonella - right image. Other symptoms of infection by these
parasites are scratching and leaping followed by lethargy
and failure to eat. Further risks are secondary
bacterial and fungal infections of wounds caused by
scratching. The parasites are particulary active in
spring when koi are still recovering from winter.
White Spot (Ichthyopthirius)
Caused by Ichthyopthirius multifiliis. The white spots
on the skin, gills and fins are individual protozoan cells
that are under the skin and feed on the body fluids and
cells. They then punch out of the skin and fall to the
bottom of the pond, collect together and begin breeding, the
offspring then re-infest the fish. As well as white
spots symptoms are scratching and swimming into the water
inlet, failure to feed and lethargy. It is fatal if
untreated, fortunately commercial white spot remedies are
widely available.
Anchor Worm (Lernaea)
Crustacean parasite, Lernaea. The juvenile stages in
the gills of kio, when they mature they mate and the male
leaves the koi, the fertilised demale settles on the body of
the koi and continues to grow, becoming the familiar worm
shape. The female buries into the skin and underlying
tissue to hold on. The damage caused can become a
target for bacterial or fungal infection which can spread.
Fish Lice (Argulus)
Argulus another crustacean parasite, round and up to 1cm
wide. They have a sucker to hold on to the koi with
needle-like mouthparts which they stick into the koi and
inject a toxin. This causes intense irritation to the
koi and they scratch and jump and can cause bacterial
infection. If they infect the gills they cause severe
damage and often death. Most antiparasite remedies
will not kill fish lice, a strong chemical is needed which
is not freely on sale. Ask a professional dealer or
vet.
Gill Maggots (Ergasilus)
Are the mature females of the parasitic crustacean Ergasilus.
Heavy infestations can cause severe damage, eroding the gill
filaments and allowing secondary infections to develop.
Skin & Gill Flukes
These are the fish equivalent of fleas. They are two
different types of flukes, but despite of their names both
can be found on the body and the gills, feeding on mucus.
They use hooks to hold onto the koi, this causes irritation
and in a weak, sick or stressed koi can become a problem.
Carp Pox
A cirus that produces solid waxy lumps on koi. It will
not kill koi and is generally harmless, but can look
unsightly. It is most often present in small koi and
in cold weather, clearing up disappearing when koi grow and
in the spring when water temperatures rise.
Finrot & Ulcers
A number of bacteria are associated with finrot, lesions and
internal haemorrhaging, notably Aeromonas and Pseudomonas.
Ulcers usually start at the site of an injury, the bacteria
then infect it causing further damage, and fungal infection
can also occur. Such holes result in osmoregulatory
problems, leading to damaged kidneys and death if not
treated. It is worth adding a weak salt solution to
the pond as well as anti bacterial remedy, a concentration
of 3gm per litre will help to restore the osmotic balance
and reduce strain on the kidneys (make sure that the salt is
fully dissolved before you add it to the pond). Finrot
is easily noticeable, the fins and or tail look chewed and
are red at the edges. Secondary bacterial and fungal
infections can develop.
Cotton Wool Disease
Another bacterial infections. The common name comes
from the white tufts that develop around the mouth and
spread to the body and fins, often leading to ulcers and a
thin appearance. Flexibacter is the bacterium which
causes this disease. Treatment with anti bacterial
medicine is usually effective.
Dropsy
Raised scales (rather like a pine cone)
and eyes standing out from the head. A sign of a number of
conditions, may be congenital heart or kidney failure or an
internal bacterial infection. Bacterial dropsy is
infectious so treat with an anti bacterial remedy and if
possible isolate affected koi.
Saprolegnia Fungus
One of the most common fungal infections of koi. The
fungal spores will grow anywhere on the koi, including the
gills, initally germinating on dead
tissue. Their threadlike hyphae release digestive
juiceswhich break down the tissue so the fungus can absorb
it, as the fungus grows these juices start breaking down
living tissue. Fungus on the body appears as cotton
woll like growths, it is hard to tell if a koi has it in the
gills, but if it hangs at the surface gulping for air it is
likely.
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