Flavobacterium columnare is the causative agent of  Columnaris disease, "saddleback" or "cotton-wool disease".  Gills of fish can be infected in addition to cotton-like masses or plaques on the head, fins or tail .   Flavobacterium columnare may also be one of the causative agents of "Fin rot" . 

Diagnosis is typically based on clinical signs and microscopic examination of the lesions under the microscope revealing "haystack" protrusions of rod shaped bacteria.  

Bettas and livebearers (Platys, sword tails, mollies) are commonly infected with Flavobacterium columnare .

Treatment options include antibiotic bath treatments (oxytetracycline), and potassium permanganate.  Systemic antibiotic therapy may be needed in more severe infections.  Correcting water quality problems and removing stressors is an integral part of treatment.

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