Flexibacter columnaris

Sometimes called: Saddle Back Disease, Fin Rot, Mouth Rot
Incorrectly called:  Mouth Fungus, Cotton Wool Disease, Cotton Mouth Disease

Columnaris is a very common disease to afflict guppies. It is one of the first fish diseases to be described by science, in 1922 by Herbert Spencer Davis, although the bacterium causing it was not isolated until 1944.  The bacterium had a number of names over the years, including Bacillus columnaris,  Cytophaga columnaris, and Flavobacterium columnare. Flexibacter columnaris is now the most widely accepted name. Flexibacter columnaris is a type of gram negative rod bacteria bacteria called, Myxobacteria, or "slime bacteria."  Damaging the guppy's slime coat, through rough handling or mechanical injury, provides an opening for the invasion of this bacteria. However, recent evidence shows the gills are the most common point of entry for the disease.

The disease is inaccurately described as a fungus disease in such names as Mouth Fungus or Cotton Mouth Disease. When columnaris affects the mouth it is much coarser, more granular and greyer than a true fungal infection. It also tends to eat the mouth away.

When the bacteria settles on the guppy, it releases protein and cartilage degrading enzymes. This results in lesions or eroded fins or gills. When it affects the mouth, it's most obvious on the lips, which appear to erode away.

The bacterium can affect a wide range of fish, from trout and salmon to warm water fishes. Columnaris may already be in your guppy room, and will make its appearance when the guppy's natural resistance to the disease is lowered by stress.

The disease is usually considered to be external. However, internal infection accompanies it about forty percent of the time. It is often accompanied by other secondary infections or parasitic invasions.
The disease is highly infectious and once it gets started, it will spread quickly to other tank inhabitants. It can also spread quickly to adjacent tanks.

The most thorough study of the disease [Decostere, A.; Haesebrouck, F.; Devriese, L. A.; 1998, 'Characterization of four Flavobacterium columnare (Flexibacter columnaris) strains isolated from tropical fish', Veterinary Microbiology, 62:1; 35 - 45] found that in the four strains studied, the bacteria had an optimum growth rate between 25oC and 30oC (77oF and 86oF). Turning up the temperature of the tank is not a good idea...
They also found significant differences in the strains. They range in the symptoms they produce and their virulence. The most virulent strain can kill a tank overnight. Another strain may take a week to ravage a tank. Although the researchers found four strains, it is possible there are more.

According to an article in the Agricultural Research magazine (http://www.ars.usda.gov/is/AR/archive/oct99/fish1099.htm), fish surviving an outbreak of columnaris show a resistance or are immune to reinfection. Many guppy breeders report that some strains of guppies are more susceptible to columnaris than others. This is in fact something that I have found to be true.

Symptoms and Behavioral Signs
The following symptoms may selectively appear on guppies infected by Flexibacter columnaris:

•    Loss of appetite, slow swimming, hanging at surface.
•    Fish may become lethargic and not resist capture.
•    Yellowish-brown or pale grey sores on gills, skin or fins. The name "saddle-back disease" comes from the appearance of a grayish white ulcer circling the body. The ulcers spread and become deeper.
•    Erosion of gills plates or fins. Sometimes secondary fungus growth on eroded fins or ulcers appears as a brown fuzzy patch. This often leads to erroneously diagnosing the disease as fungal.
•    Inside the mouth a yellowish-brown mucus growth may appear and the mouth may be eaten away
•    Fish may begin to shimmy as it comes close to death
•    Secondary infections and diseases often follow the onset of columnaris.

A trip to the LFS quickly yielded a specimen showing symptoms of columnaris. Notice the eroded caudal. The disease is sometimes
called Fin Rot.

A close-up of the peduncle area shows a whitish band around the peduncle. This is a classic visual clue that the fish has columnaris
disease. Examination under the microscope revealed a significant parasite infestation as well.

The ability to identify the disease is complicated by the fact that it is often accompanied by secondary infections or parasitic diseases. For example, flashing or rubbing, a sign of parasitic infections, is usually not a behavioral sign, unless a parasitic infestation has followed on the heals of the disease. A distended abdomen is not a sign of columnaris, but again may be caused by secondary infections, such as an internal bacterial disease.

In the Decostere, Haesebrouck, Devriese study, the fish exposed to the disease died with in a range of 8 hours and 6 days.

Causative Condition
Columnaris is probably present in most fish rooms and can be found on the slime coating of healthy fish. Stress usually promotes its growth, under such conditions as overcrowding, high ammonia nitrite values (from overfeeding), lots of organic material in the water, inappropriate hardness of the water, low oxygen levels, high water temperatures, the ionic composition of the water, and rough handling. Guppies that have been transported often succumb to it.

Interesting in the Decostere, Haesebrouck, Devriese study is that slow moving water is conducive to the disease because it allows the bacteria to adhere to the guppy's skin. This is a good reason to keep the water flowing vigorously in your tanks. Also using salt in the tanks is a good idea because salt prevents the adhesion of the bacteria to the skin.

Adhesion to the gills is aided by the ionic composition of the water. MG++ and CA++ reduce surface potential and repulsive forces. High levels of nitrites and organic material also aid adhesion. Organic material becomes trapped in the mucus layer of the gills providing a rich nutrient area for the bacteria. Water changes are important in preventing the disease.

Diagnosis
Microscopes that can magnify 200X or more can be used as a tool for verifying the disease. The Flavobacterium columnare appear as a swarm of flexing and gliding rods 7 to 10 millimeters in length, 10 to 20 times longer than wide. (It is the columnar shape of the bacteria that inspired its common name.) The telltale sign is that they spread randomly over an area rather than aggregating into a well-defined round colony.
Examining the gill filaments sometimes reveals extensive erosion. This can be distinguished from parasitic infections where gills are swollen and irritated, rather than decayed There may be a secondary fungal infection, appearing as a fuzzy brown covering.

Signs of internal infection are the presence of excess fluid in the gut or abdomen, pale internal organs with small bloody spots on them.

Loss of appetite and other signs of stress (such as hanging at the back of the tank or on the bottom) usually accompany the disease.

Prevention and Treatment
When introducing new guppies to your fish room, isolate them, even if they do not look sick. Fish that are moved from one fish room to another, even if the distance is only a block away, are at high risk. They are stressed, and stress is the main causative agent in columnaris.

The disease may make its appearance in your fish room even if it has been disease-free for months or years, and you have not recently introduced new fish. Guppies in general are usually raised in relatively crowded conditions and fed so much that the water is high in organic material and various toxins. Culling drops early and finding the optimum feeding regime are the best preventive measures.
As is the case for most diseases, the affected tank should be immediately isolated. Steps should be taken to prevent the spread of the disease.

The most effective treatment occurs when the guppy first shows signs of the disease and before it stops eating. If the guppy has had it for three days, it is extremely difficult to cure.

One of the oldest treatment agents is potassium permanganate (KMnO4). It is the most widely reported treatment that is considered effective against this disease. It is also effective against some of the secondary infections that accompany columnaris, particularly parasites. See the Disease Library entry on Potassium Permanganate for a complete description of the compound and how to use it in a treatment program.
Infections that have an internal component (roughly 40 percent of cases) can be treated with feed medicated with Terramycin, an oxytetracycline compound. Terramycin is fed for 10 days.
Romet*30¨ and Romet B¨ (sometimes marketed as Super Trout Booster) medicated feeds have also been used to treat internal infections. Romet-B contains 85.1 grams of Sulfadimethoxine and 17 grams of Ormetoprin per pound of food.

In the Decostere, Haesebrouck, Devriese study, researchers found that no bacteria could grow in-vitro when immersed in a 1% salt solution. This suggests salt should be part of a complete treatment program. (Some breeders only use salt.) The method for providing a salt dip is described elsewhere on this website.

There was a study subsequent to the Decostere, Haesebrouck, Devriese study: Altinok, I & Grizzle, J M Effects of low salinities on Flavobacterium columnare infection of euryhaline and freshwater stenohaline fish.

Journal of Fish Diseases 24 (6), 361-367. In this study salt was studied as a method for preventing the disease or treating the disease. Channel catfish, goldfish, and striped bass were acclimatized to salinities of 9.0% or less and then exposed to the Flavobacterium columnare. None of them died. In the case of control groups of fish, the mortality rate in fresh water was 97.7%. When fish kept in low salinity (1.0%) were exposed to columnaris, the mortality rate was 61.7%. The authors speculate that salt solutions help prevent the adhesion of Flavobacterium columnare to the gills and skin of the fish. The implication for guppy breeders is that salt in the tanks is a good preventive measure for columnaris.

Formalin is not a recommended treatment for external bacteria. It is better suited to parasitic infestations. Formalin and potassium permanganate should never be used together. Their fumes when mixed are highly explosive.