In severe cases the skin may eventually fall away in strips. The gills can be totally destroyed so that only the cartilaginous parts of the gill lamellae remain. Also with it s reproduction temperature between 5 o F and 10 o F, most treatments are inactive. Costia is also a serious contender as one most pathogenic to koi as it reproduces fairly rapidly and in large numbers causes osmoregulatory failure leading to death. White spot is a very important ciliated protozan and it is impossible to remove chemically without killing the host fish.
Treatment is only effective on the life stages outside the dermal tissue of the fish.
Alteration of the protective barrier will also allow opportunistic bacteria or fungi access to underlying tissues and fish may die through secondary infections. Anchor worm leaves largish holes when they die and bacteria etc can penetrate right through to the muscle. Fish lice in sufficient numbers can cause mortalities by sucking out the blood and leaving open wounds for secondary infections to penetrate and as it travels from fish to fish may also be a spreader of viruses. They open up areas where secondary infections and often more serious problems can arise, bacteria and viruses are waiting to invade and take advantage of any situation no matter how small. This article was first published in the May 1995 issue of our club Newsletter.