Koi with skin problems

[saferego]

Hi,
I have three koi with skin problems which I hope someone can shed some light on. The are all sanke line but from different lines as far as I know. I have shown photos of two of them here.
One is a 60cm female "kohaku" (the one with shimmies that you can see) and the other is a 55cm female sanke. I have had both fish in my possession for 5 years plus and both fish are at least 6 years old.
The kohaku skin deterioration has been "in progress" for 4 years but I have never got around to doing anything about it because I figured it was carp pox and I've not had any success dealing with that before. When the problem first started it was evident only in winter (water temp ranging from 10C/50F to 18C/65F) and in summer it would disappear completely (water temp range 22C/72F to 30C/86F), only to return in winter again. Now it improves in summer but never completely disappears, and is getting pretty bad now, as you can see (water temp circa 20C/68F). The problems only appear on the body, not the head. As you can see hopefully the problem areas are "raised" above the rest of the normal skin.
The sanke has only just started having problems and they are barely visible in the photo. The problems only appear on the head, not the body so I'm not sure if they are related to the kohaku's problems. They are below the skin so if you wipe the area with your finger nothing changes. They appear as very slight lightening of the hi to a yellower or whiter tone. The other sanke (a male) (which is not pictured here) also has problems on the head which look similar to this one, having only just started.
The pond is 25,000L in a full sun position but with a shade cloth sail providing some sun protection during summer. In autumn (it's mid autumn now where I live) I remove this shade to keep the water temperature up a bit. The pond has 10 fish average size 50cm in it. Any suggestions/diagnosis would be greatly appreciated.
thanks, Richard

[Russell Peters]

My guess would be Hikui, but I have never seen it in person.

[PapaBear]

It does look a bit like hikui, but that is usually progressive and penetrates the beni causing deterioration through the beni and eventually leaving a window on the ones I've seen. I'll be curious to see what others have to say.

[aquitori]

Looks like Hikkui and looking from the water condition from where the fish was brought up it doesnt look too good. But what do I know, I have seen fish with the early stages of Hikkui and they win GC...

[Brutuscz]

I actually read in the AKCA koi health manual that you can treat hikkui with a hair dryer. It was specific on how to do it...but claims it actually stops hikkui from continuing. Sounded risky...but tested.

[Super Kindai]

I beleive it is Hikkui. they say (in Japan) PROPOLIS cure for it....
In General, Red color beni tends to be Hikkui more often than orange color beni.

[JasPR]

Yes, that is hikkui. The problem is no one really knows what hikkui is. And in all likelihood we are calling the 'symptom; we see hikkui when it is probably a look that is given by several different causes.
In winter you can see several skin conditions from clouds/patches of fish mucous 'lifting' from the body. This will resolve itself on it's own once the fish is in warm water again and producing slime coat and moving ( the act of moving sheds slime coat into the water). If the fish is depressed however, this same white gray patch can be a sign of parasites ( especially if red veining on the white skin is also noticed). The area should be scraped and examined under a microscope ( under low light/high power) for costia or Chilodonella).
If the lesion is white or gray but raised ( as if candle wax was dripped onto the body then you are looking at koi herpes ( carp pox). This is a seasonal thing as the virus gets active and then goes dormant based on the stress ( usually to cold but can be due to poor water conditions) and rebound of the fish's immune system which suppresses the virus. There is no treatment although a few hobbyists are experimenting with injectable virus meds.
Koi also get small tumors, fatty tumors and warts. And these can be red, organ, colorless and tan. Harmless but unsightly, they usually come in single lesions and once in a while in rows or patterns ( again a virus).
Finally we have hikkui. Once thought to be 'hi eating worm', it is now considered a virus, a rickettsia or skin cancer. And in fact different cases may be any one of these suspects. It is a disease but it can be triggered by environmental causes. So I have seen a pond full of hikkui fish and I have seen a hikkui free pond with one fish that develops hikkui and one fish only. It is also age related with older fish showing more lesions that younger fish do. The immune system is definitely involved as well and returning a koi to 'mud' will often suppress the disease but only for a while.
I have removed hikkui and warts with cryosurgery with good success but the fish is disfigured to some degree as a result of the treatment. And some have has early success ( must be early before the disease has destroyed dermis and epidermis) with billion liquid. The hair dryer is used with the liquid after the fish has been removed from the bowl and the area is cleaned and billion liquid applied. This dries out the liquid compound and adheres it to the cells. Another treatment is to place the fish in warm water ( 85 F) and manipulate KH. This is reported to be successful in 90% of early cases. This suggests a virus. But again, I believe that people are diagnosing a complex of diseases as hikkui so some things work for some , based on what it is- skin tumor, virus, rickettsia, skin infection, genetic weakness etc, and not for others.
Here is a shot of an advanced case-

[saferego]

Thanks everyone for all your words of wisdom. Sounds like I have a serious problem because I haven't been able to find anything on the net which claims to be a cure for hikui (ie consistent permanent fix), or even found a definition of what it is. eg if it is a virus (?) does it lie dormant in fish without hi and then can spread to fish with hi? Does this mean I have to get rid of all my fish, including the ones without hi and start again? I now have it breaking out or present in 4 out of 10 fish in my "display" pond. Pretty depressing stuff.

[saferego]

Thanks JasPR. Looks like we posted at the same time.

[JasPR]

No, it's not that kind of disease. And contagion possibility have never been proven as part of this complex of symptoms. It may be viral or from even a tinier beast known as rickettsia. But it is the attraction to red cells ( color cells that stories food) that is most interesting. A virus needs to find a cell that is compatible with it's needs. Not all cells in all species will have the 'back door' for a specific species skills of 'breaking and entering'. Nor , when inside, not all cells will have the needed ingredients for the single invader to take over the helm and steer the cell into making more virus particles. So the red color cells seems to fit the bill of a unique cell that is effected by a mystery invader. On the other hand, we know skin cancer can favor epithelial cells.
And that it is a combination of environment and presence of cancer that causes the synergy that produces growth of cancer. So check your nitrate as that is just one parameter than aggravates the condition.
In addition, some Japanese swear that hikkui is lined to certain lines and strains. And there is no doubt that sanke and kohaku get it far more often than any other breed. At one point in the ‘sky is falling; koi history, some believed that koi would all get hikkui and the hobby would be lost. Many breeders of the day begin not using certain breeders to head that concern off. Whether that really helped I couldn’t say?
I have also noticed that koi that are moved from Japan’s relatively neutral pH and low mineral content ( soft water) and placed in very hard water, will often come down with hikkui at a younger age than the normal age group that this problem inflicts. Meanwhile in Japan, one technique for early cure is to place a koi in warm water and bring the KH way way down.
I think most hobbyists accept that if they collect long enough they will see hikkui in one or two individuals in their care at some point. I have 18 koi and one has hikkui. All the rest are clean as a whistle. It is from a breeder that is know to have fish ‘turn’ hikkui at a certain age. There is that genetic component again.
JR