Flavobacterium columnare

If you see fish with big white areas on the body, fungus-like growths, “cotton mouth”, “saddle back”, different sized areas of necrosis, destruction of bone and cartilage tissue especially in the mouth or caudal fin, you could be looking at the result of a Flavobacterial infection. Flavobacteriosis is caused by the Flavobacterium columnare bacteria. These are relatively large (50-100 μm) bacteria, already clearly visible at a 100 fold magnification. Under the microscope you see them moving in a typical gliding fashion. Gram-negative and rod-shaped, these bacteria form colonies resembling “haystacks” on the body of the fish, being whitish to characteristic yellow-orange in color, due to the pigment contained in the cells.

𝘕𝘪𝘤𝘦-𝘵𝘰-𝘬𝘯𝘰𝘸: 𝘵𝘩𝘦 𝘸𝘰𝘳𝘥 𝘍𝘭𝘢𝘷𝘶𝘴, 𝘧𝘳𝘰𝘮 𝘸𝘩𝘪𝘤𝘩 𝘵𝘩𝘦 𝘯𝘢𝘮𝘦 𝘰𝘧 𝘵𝘩𝘦 𝘨𝘦𝘯𝘶𝘴 𝘰𝘧 𝘣𝘢𝘤𝘵𝘦𝘳𝘪𝘢 𝘪𝘴 𝘥𝘦𝘳𝘪𝘷𝘦𝘥, 𝘮𝘦𝘢𝘯𝘴 ‘𝘺𝘦𝘭𝘭𝘰𝘸’ 𝘪𝘯 𝘓𝘢𝘵𝘪𝘯.

These bacteria secrete enzymes and other substances, which are toxic to fish, and lead to the destruction of tissues and cause necrosis. In the video you’ll see a neon tetra with extensive lesions on the back (neon back). Raised scales, accumulation of mucus and colonies of bacteria in between the scales are visible when using a stereo microscope, just like loss of pigment in the affected area. You can notice lesions on your fish, not only developed on the back, but also in the mouth area. You can also see destruction of the epidermis and there is noticeable loss of scales.

Be careful when diagnosing your fish, based only on external signs. Without microscopic examination, the observed symptoms can be confused with diseases caused by other pathogenic agents. In skin scraping samples from the affected area of the fish’s body, at 100 fold magnification, scales beset by a yellow-orange coating are visible. At 400 fold magnification, we see that this plaque is formed by gliding rods – these are colonies of bacteria of which the individual cells are visible. The video shows how seemingly the shape and size of these bacteria change, like waves. Flavobacterium columnare is able to actively move by sliding. Wavy, bending movements of individual cells create a undulating movement – this is the main characteristic of this type of bacteria. Flavobacterium columnare will affect both the skin and the gills of fish and likes temperatures between 25 – 32 °C.

Flavobacteriosis is a deadly disease for fish, slowly decreasing the temperature, into your fishes lower optimum temperature range, is a smart move. the earlier the disease is detected and treatment is started, the greater the chances of success. In this case, we recommend using eSHa 2000.


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