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Columnaris is know by many different name. Cotton-Wool, Cotton-Mouth, Flavobacterium Columnare, Flexibacter, Mouth Fungus, Mouth-Rot and Saddle Back. Columnaris can be external or internal and may follow a chronic or acute course. Fish with chronic conditions tend to progress slowly, taking many days before eventually ending in fish death. In the more acute cases, the lesions spread quickly and can wipe out entire populations of fish within hours. Warmer water temperatures will accelerate the progression of the disease. Unfortunately,lowering the temperature will not affect the outcome. Most species of fish become susceptible to columnaris following some type of environmental stress.
What to Look For
An early indication of the bacteria infection in fish are frayed and ragged fins. This will be followed by the appearance of ulcerations on the skin. Most Columnaris infections are external, and will show up first as white or grayish spots on or around the head and around the fins or gills. In the beginning the lesions are shallow and may be seen as a paler area that lacks the shiny normal appearance you see on the rest of the fish. As the lesion progress they may become yellowish or brownish in color and the area around it may be tinged toward red. The bacteria also attach to the gill surface, grow in spreading patches, and eventually cover the filaments of the each gill, and the result is cell death. Portions of the gills are then destroyed by protein and cartilage-degrading enzymes produced by the bacteria. Mucus often also accumulates on the gills, head and dorsal regions.
As the bacteria advances, the round or oval lesions develop an open ulcer in the center. A pale white band encircling the body is a characteristic lesion pattern giving rise to the term saddleback condition. A yellowish-brow nulcer can often be found in the center of the “saddle” as the infection progresses. In addition, mucus-like growth of columnaris bacteria the is also yellowish brown will sometimes be found inside the fish’s mouth. The brownish coloration is attributed to mud and detritus particles trapped in the slime produced by the bacteria. Fish will breathe rapidly and laboriously as a sign of gill damage. Anorexia and lethargy are common, as are mortalities, especially in young fish.
Lesions on the back often extend down the sides, giving the appearance of a saddle, leading to the name saddle-back that is often used to describe this symptom. On the mouth the lesions may look moldy or cottony, and the mouth will eventually become eaten away. The fins will erode and have a frayed appearance as the infection progresses. Gills as affected too. As the bacteria invade them the filaments will disintegrate, resulting in the onset of rapid breathing or gasping in the fish due to lack of oxygen. Less commonly, the infection will take an internal course which often displays no external symptoms. In these cases, only anecropsy and cultures will point to the true cause of death.
Why Do You Get It?
Columnaris bacteria are more apt to infect fish that have been stressed by conditions such as poor water quality, inadequate diet, or stress from handling and shipping. The bacteria gain entrance to fish through the gills, mouth, or any small wounds on the skin. Columnaris is highly contagious. It may be spread through nets, tanks, and even food. There are many reasons to use sterile techniques to avoid contamination, and this is one of the big ones. Once discovered in your fish room, treatment of any and all other tanks and paraphanilia is a good precaution, and becomes mandatory if they share a common filtration system.
- White spots on mouth, edges of scales, and fins
- Cottony growth that eats away at the mouth
- Fins disintegrate beginning at the edges
- 'Saddleback' lesion near the dorsal fin
- Fungus often invades the affected skin
- Rapid gilling in cases where gills are infected
The bacteria usually enter fish through gills, mouth, or small wounds, and is prevalent where high bioloads exist, or where conditions may be stressful due to overcrowding or low dissolved oxygen levels in the water column. The bacteria can persist in water for up to 32 days when the hardness is 50 ppm or more.
Columnaris bacteria probably occur in most, if not all, aquaculture environments. The bacteria can cause disease under normal culture conditions, but more likely when fish are stressed. Stressful conditions favoring columnaris disease include low oxygen, high ammonia, high nitrite, high water temperatures,rough handling, mechanical injury, and crowding. Columnaris occurs frequently in fish raised intensively in cages and in closed recirculating systems and is attributed to crowding and cage abrasions. Once established, the infection can spread quickly and cause high mortality rates. While stressful conditions can contribute to columnaris infections, the presence of columnaris may also lead to secondary infection or other diseases. Winter saprolegniosis (also called winter fungus or winter kill) often is preceded by columnaris. In one case
As Flavobacterium columnare is Gram-negative, fish can be treated with a combination of the antibiotics furan-2 and kanamycin administered together. Medicated food containing oxytetracycline is also an effective treatment for internal infections, but resistance is emerging. Potassium permanganate, copper sulfate and hydrogen peroxide can also be applied externally to adult fish and fry, but can be toxic at high concentrations. Vaccines can also be given in the face of an outbreak or to prevent disease occurrence.
- Quarantine new fish for two weeks
- Maintain high water quality
- Provide fish with a nutritionally balanced diet
- Medicate fish prophylactically before moving them
- Disinfect nets and other equipment before using
To avoid spreading the bacterium to other tanks, nets, specimen containers, and other aquarium equipment should be disinfected before each use. Small quantities of aquarium salt can be used regularly as a prophylaxis to prevent disease in livebearer aquariums. When fish are being shipped or moved they are under stress, which leaves them open to contracting disease. To give them a better chance of remaining healthy they may be give prophylactic antibiotic treatment, or fed medicated food
Ulcerations develop within 24 to 48 hours. Fatality occurs between 48 to 72 hours if no treatment is pursued; however, at higher temperatures death may occur within hours. Other symptoms may accompany the disease, including lethargy, color loss, redness around the infection site, loss of appetite and twitching or rubbing the body against objects.