Lernea (Anchor Worm).
This koi parasite is most commonly found on newly imported koi, and should be dealt with by your koi dealer, it is rarely a problem for the koi hobbyist. It is visible to the naked eye and the adult parasite may reach 12mm in length, with anchor like appendages at the head. It attaches to the koi and the anchor penetrates under the scale and into the muscle of the fish, where it feeds. This parasite reproduces by laying eggs, two egg sacs are produced at the end of the females body, the larvae hatch from these egg sacs and swim freely until they come into contact with a koi, they then commence the cycle again.
Crustacean parasite, Lernaea - Anchor worm is a common parasite on our Koi which is clearly visible to the naked eye. The parasite burrows its head into the Koi's tissue, under a scale and only the body and tail are normally visible.
The juvenile stages settle in the gills of Koi, when they mature they mate and the male leaves the Koi, the fertilized female 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.
Lernaea lay eggs which can lay undetected in the pond and can hatch when conditions and water temperatures are right.
The parasite can cause serious damage to the koi where it penetrates the tissue. These wounds sometimes heal very slowly and if untreated become infected with bacteria and fungus, it is these secondary infections that cause the most risk to the koi.
To treat Anchor Worm you must treat the pond to sterilize the adults, this treatment should be repeated after seven days to ensure any eggs that were unhatched at the first treatment are now sterilized after hatching. Now all reproduction has been stopped. The treatment used is Dimilin.
Now the adults must all be removed from the koi. To do this you will need to sedate each koi individually and carefully remove the parasite with tweezers, making sure you remove the entire thing including the anchor part. Each entry wound should then topically treated. Check every koi in the pond to ensure none are missed.
Treatment is by manual removal of the parasite with tweezers under anesthetic, ensuring that the whole parasite is removed. To be sure of complete removal, dip a cotton bud in strong potassium permanganate solution and dab the worm with this solution whereupon it will release its grip immediately. Pond treatments include Dimilin or Paradex.
See More Koi Parasites
Identification of Koi parasites. Most koi parasites are not visible to the naked eye. In order to correctly identify any koi parasites you will need a microscope with built in light and a magnification of 400... (click on image for more details)
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Gill and Skin flukes are two of the family of monogenetic trematode genera, all of which are characterised by the large grappling hooks which are used to attach themselves to their victims.
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Ichthyobodo necator (Costia) This koi parasite is extreamly small (10-20 microns long) and a magnification of 100 times is the absolute minimum required to identify costia, 400 times is ideal. When taking a skin... (click on image for more details)
Chilodonella cyprini. Chilodonella is another protozoan parasite which effects the skin and gills of koi.This koi parasite is typically between 40 and 70 microns in length and is oval in shape. Again,... (click on image for more details)
Argulus another crustacean parasite, round and up to 1cm wide. They have a sucker to hold on to the Koi with needle-like mouth parts which they stick into the Koi and inject a toxin. This causes intense... (click on image for more details)
Raised scales (rather like a pine cone) and eyes standing out from the head.
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Gill maggots are the mature females of the parasitic crustacean Ergasilus.
Ergasilus (gill maggots) will appear as grayish black and white parasites several millimeters long infesting the gills.
Heavy... (click on image for more details)
One of the most common fungal infections of Koi. The fungal spores will grow anywhere on the Koi, including the gills, initially germinating on dead tissue. Their threadlike hyphae release digestive juices which... (click on image for more details)