Published: Fri, 9 Oct 2015 09:06:36
By: Karen LeFever
OK, Don't Panic.
Columnaris is NOT some exotic new koi disease. However, it can show up occasionally and when it does it can cause a lot of damage to your fish in a short amount of time. Unfortunately it is quite often misdiagnosed.
What is it?
It is a bacterial infection caused by the bacteria Flavobacterium Columnare. It's been around since man started culturing fish and is present on practically all fish and in all fish symptoms from home aquaria to 500 acre catfish farms. As with most pathogens, it causes few problems in the absence of stress to the fish. Over crowding, poor water quality, and especially sudden environmental changes can compromise the fish's immune system, leading to a Columnaris out-break. Fish are especially vulnerable to it after experiencing the stress inherent in shipping, so be on the lookout for it for a few days after receiving fish from us or any other breeder.
Microscopically, these bacteria appear as long thin rods, usually clumped together to form dome shaped masses with a "hay stack" appearance. Fish can develop a white film over their body with disintegrating fins and tails. Advanced infections will cause the fish to become emaciated with sunken eyes and necrotic gills. Anytime you see these symptoms along with rapid mortality, especially in warmer water, you should suspect Columnaris. Left untreated it can kill 50% of a population in 2 or 3 days.
Most importantly, realize that Columnaris is not a fungus. (Despite the marketing of "fungus" medications, true fungus infections that cause mortality in koi and goldfish are rare). So medications used to treat fungus, anchor worm , ich and other parasites will be ineffective. Melafix, formalin and malachite, praziquantel, and salt won't work. So look for medications with antibiotics in them. Nitofurazone, Furazolidone, Tetracycline and Oxolinic Acid have been shown to be effective. We've found that Nitrofurazone seems to work best.
While Columnaris is not something you will see very often, especially if your fish supplier properly acclimates and quarantines your fish before shipping, it can show up occasionally. As a fish retailer you should have medications on hand to treat it.