Hikui has been the despair of many a Koi keeper, and indeed Koi breeder, over the years, yet its real cause is as yet unknown and subject to much hypothesis.
Hikui, which literally translates as ‘red eating’, affects only the red parts of the Koi, initially appearing as a lightening of the skin/pigmentation, and in latter stages ‘eating’ right through the red to leave white patches on the skin.
Historically ‘hikui’ used to be translated as ‘red eating worm’, although there was never any ‘worm’ or parasite evident. Some believe it is hereditary, other believe it down to water conditions. Some research has found evidence of cancer type cells, however there is still no concrete proof that it is a cancerous disease, likewise none that it is a bacterial or viral condition.
Japan Pet Design (JPD) have started a period of research in conjunction with the Department of Applied Aquabiology, National Fisheries University, led by Associate Professor Dr.Shinya Yasumoto to try to identify cause and effective treatment/prevention of the occurrence of hikui in Nishikigoi.