Flavobacterium columnare

I study the bacteria Flavobacterium columnare. It is a fresh water bacteria found all over the world. It is an opportunistic fish pathogen and is the cause of Columnaris Disease (CD). It infects many commercially important fish species. Outbreaks in aquaculture facilities are common. Costs associated with CD are high and represent a major barrier to the development of commercially viable aquaculture enterprises.

Outbreaks are brought on by stress and can occur suddenly. Mortality rates can reach 100%. The most virulent strains F. columnare kill susceptible fish within 24 to 48 hours, leaving little time for treatment.

CD is common in tropical aquaria where it is called by various names including, fin rot, tail rot and cotton mouth. These are frequently discussed on websites for aquaria hobbyist. The bacteria responsible is often identified as Flexibacter columnaris, an obsolete genus and species name replaced in the mid 1990. The characteristic fuzzy white growth the bacteria cause, often results in hobbyists mistaking it for a fungal infection.

CD also effects wild fish stocks. Outbreaks usually occur in the spring as the water warms. These outbreaks can be quite dramatic with hundreds or even thousands of moribund fish washing ashore covered with lesions. In less populous areas, these outbreaks go unnoticed. When they occur in lakes in populated areas, the fish die-offs make the news.

No one likes to see (or smell) tons of dead fish washing up on their shore.