By John Shawn Prescott

In this article we will deal with an all too common infection, which goes by various names

Most typically it is called Tail rot, or Tail and Fin rot. A typical characteristic of the disease is a rotting of the tail and very often the fins, which if unchecked will lead quickly to death of the infected fishes. This is a virulent pathogen, which can infect the vast majority of fresh water fishes, and has been found to occur in almost all parts of the world.

Formation of columns by Columnaris Bacteria, on side of Platy fish

The causative organism is a bacteria usually called today Cytophaga but previously was called Flexibacter and also Myxobacteria . The disease this family of bacteria causes is most often referred to as Columnaris , which describes the easily observed charateristic of the ‘piles’ of haystack like organisms which congregate on an infected part of the fish.

Columnaris Bacteria building columns on scale x160

Scientifically speaking there are several variants of this group of bacteria, but as they all manifest similar pathology, as well as respond for the most part, to identical remedial or prophylactic techniques, it is not necessary for the reader to concern themselves with the minutiae of determinative technology, which is of course of interest to those engaged in scientific research.

The disease is brought on in many cases by fish that have been badly handled , and often have been subjected to undue stress. Among predisposing factors often noted, is a sudden rise in temperature. And the disease most frequently appears, when water temperature is above 64 degrees F.

Black Molly showing typical external signs of Columnaris infection

There are some interesting relationships between the quality of the water, and the virulence of the disease, and by being aware of these factors, it may be possible to use such information in some cases at least, as part of the remedial process.

In waters of a total hardness of 33 ppm as CaCO₃, ( details of the breakdown chemically of this finding can be found in the quoted reference below ) the pathogen was found to be at its most virulent, whilst in distilled water with zero minerals it was determined to be non pathogenic. This would indicate some form of obligate need for certain minerals in order for the bacteria to reproduce and further re-infect fish. However hobbyists should be aware, that no fish I am aware of will survive for a long period of time in pure distilled water, so any experiments along these lines, which could be helpful, must proceed in the direction, of studying the findings of the quoted researchers, and modifying suitably the waters accordingly, where this is practical.

Decaying Gill tissue, turning black, sometimes an indication of Columnaris

When fish are infected with this pathogen, the following signs can be anticipated:

Skin

There will be necrotic lesions on the skin, which often are white/grey coloured with an edging of red. These will quickly in one to two days, transform into ulcers with have an orange/yellow colour, caused by the bacteria decaying the underlying tissue.

Gills

Similar effects very typically occur on the gills, but may for the average hobbyist be somewhat harder to observe at least in the early stages. The progression of these ulcers, causes the fish to have great trouble with its respiration, and thus can quickly lead to fatalities. If the gills are examined, excessive amounts of mucous, are to be expected.

Behaviour

The fish will become very listless and lethargic, often will hang at the surface, trying to breath there, although on occasion, the fish will rest on the bottom of the tank. Reluctance to feed is very typical and the fish will become anorexic. Respiration is often rapid, as the fish fights to overcome the damage done by the infection to its gills.

Body

In some cases, the lips of the fish, will become swollen and macerated, and a milky slime like film can be observed with the naked eye on parts of the body.

Fins

Large milky patches can be seen quite easily on the fins of the fish, and this is usually an indication that the disease has progressed to a degree that cure will become much more difficult. One typical sign is the appearance of a ’saddle’ shaped lesion usually around the area of the dorsal fin, and this occurs so often, that the name ’saddle back disease’ is often used in aquaculture to describe this infection.

Water

Temperature is often elevated beyond what is normal, or the fish have been exposed to a sudden rise in temperature. Furthermore, the quality of the water, is a vital component, in getting this disease under control. Excessive detritus and less than ideal filtration, will ensure the spread of the infection. Hard water seems to make the spread of the bacteria easier than soft.

Histo-pathology

Spread of bacteria in the blood stream are a frequent occurrence, and these are referred to as ‘bacteremias’. When this occurs often other bacteria such as Aeromonads will invade as well as the Flaxibacter species, and these ‘bacteremias’ can lead to a rapid demise of many fish.

Description of the organism

The bacteria are thin rods, ( 0.5- 1.0 microns in diameter, and some 4-10 microns long). Their most noticeable feature is a unusual ‘gliding’ motion, which is not observed in other species. In wet mounted specimens they can be seen piled up into large columns which have given one of the common names to this infection.

Culture of the organism is best done at normal room temperature , and there is a culture media available called Cytophaga media), which is used for this purpose.

Transmission of infection

Once established the infection will spread through the water column, and potentially can and will infect most fish, with which it comes into contact. Heavy losses must be anticipated unless rapid identification and treatment are instituted immediately. The infection can be expected to spread most rapidly if water conditions are less than ideal, and factors that have been observed to enhance the pathogenicity are low oxygen values, hard alkaline waters, excessive nitrite levels, and even the presence of certain trace elements such as arsenic. (see refs).

The bacteria have been observed to thrive on uneaten food, and there is little doubt that they exist without being a problem in most aquaria. When however the fish are stressed, by less than ideal conditions, or when some new fish are introduced without quarantine procedures being observed, and the water in the aquarium is not ideal, then the chances of an outbreak are greatly increased.

Discus fish with acute signs of Columnaris infection

I would stress to the reader, that this disease, can be horrific should it break out, but certainly this is one infection, that can almost totally avoided, just by following good husbandry practices in your aquarium. The avoidance of stress by the routine maintenance as detailed below, should avoid any occurrence of this infection.

Such practices should employ the following techniques.

1. Ensure that you have an adequate and suitable filter for your aquarium, and keep it serviced at all times.
2. Quarantine, for a period of about 10 days, all new fish before introducing them to the aquarium.
3. Do regular water changes of around 10-15% of the water volume weekly.
4. Ensure that no uneaten food, or detrital matter is allowed to accumulate on the gravel bed of your aquarium.
5. Do weekly water quality tests, to ensure that no build up of unwanted nitrites or other undesirable measurements occur without you having time to take suitable remedial action.

Should despite all your best efforts, the infection breaks out, and you have identified the pathogen, as meeting the criteria as shown above, then the following types of treatment can be employed, and if used in good time, should minimize losses.

Treatment

The most popular drugs used in mild cases of infection are a quaternary ammonium dip, for a short period, or a more prolonged bath in potassium permanganate solution. Some persons advocate using copper sulphate, but in this writers experience, the risk of further damage to the gills of the fish, is too great, and I do not recommend this drug for this disease.

Typical patch on back of young trout due to Columnaris i.e. “Saddle back.

I will not try here to give any dosage levels, as your dealer will probably carry many variants of treatments using the above as the active ingredient. As the concentrations will vary from manufacturer to manufacturer, it is better to follow their dosages, but do make allowances for the quality of your water, as well as how far the diseases has progressed, when this is appropriate.

In severely advanced cases, when the disease has already progressed to the point that fatalities, have either already occurred or it is evident that they happen momentarily, there is as I pointed out earlier , a high possibility that further bacterial systemic infection will take place. In such cases, only the use of powerful antibiotics have any real chance of saving the fish, and the one which is most commonly used in this condition with good effect is oxytetracycline. This however needs in all European countries a Veterinary prescription.

“Yellow/brown mouth sign typical of Columnaris infection“

I would stress here, that there are very good reasons, why the hobbyist should NOT RUSH to use antibiotics as a first tool, when faced with such an infection. Also such drugs are NOT available in your aquarium dealer, and there are many down sides to trying this antibiotic first, including the fact that this drug, as well as many others, are becoming less potent, due to resistant strains of bacteria now occurring everywhere on this planet, ans well as for an ever increasing number of drugs. Furthermore, for the use antibiotics, one should be used getting good professional advice, as the tendency of the average untrained person to quit using the such, at the first sign of a cure, leads to exactly the kind of resistant strain, as well as too often a reoccurrence of the outbreak. You may be able to get your local veterinarian to assist you in how to treat your tank, should such be necessary.

John Shawn Prescott john@aquarium-gardening.com

Refs.

Chen C.R. et al (1982). Studies on the pathogenicity of Flexibacter columnaris-1. Effect of dissolved oxygen and ammonia on the pathogenicity of Flexibacter columnaris to eel ( Anguilla japonica) . CAPD Fisheries series No. 8 Rep. Fish Dis. Res. 4: 57-61

Fijan N. (1968). The survival of Chondrococcus columnaris in waters of different quality. Bull. l’Office Inter des Epizooties 69: 1159-1166.

Hanson L.A. and Grizzle J.M. (1985). Nitrite-induced predisposition of channel catfish to to bacterial diseases. Progressive Fish Culturist 47: 98-101.

Stoskopf M.K. Fish Medicine Publ. W.B. Suanders 1993. pp 271-272.

Gratzek J.B. Aquariology. Publ. Tetra Press. 1992. Pp. 261-262

by John Shawn Prescott

This article will be a start in examining the many bacterial infections to which are Aquarium fish are prone.

Tuberculosis with raised Tumour development

Before dealing with the specifics, I would like to reiterate what I stated at the outset of this series, as it is most important for all of you, who wish to prevent or cure any of these potential hazards.

Bacteria including the non pathogenic as well as pathogenic forms are usually present in small numbers on most fish. They in normal situations seldom cause any problems, as the fish’s own quite adequate immune system is more than capable of fending off any infection which may become chronic.

However if parasitic infestations become severe, so that major necrotic damage is done, to the skin, fins, gills etc of the fish, then the opportunistic bacteria will often invade the eroded area, leading quickly to a major infection, which too often can be fatal.

This situation can arise in another way, without the presence of parasites . That is when for any number of reasons the fish become stressed. This lowers their resistance, so that latent bacteria, can then quite quickly manifest themselves, causing a problem for you the Aquarist. Such infections can in some cases, then spread to other fish, though this is not inevitable.

Tuberculosis granuloma in the Liver x 76

The reasons for stress are worth remembering. Among them are poor handling in the many steps of the way, from the farm or capture, to the Importer, then to the store, and finally to you the Hobbyist. Coupled with rough handling, often comes poor water quality. Also the placing together of incompatible species. Any or all of these, will cause trauma, stress, & a lowering of the fish’s natural immune system, with the consequent breaking out of a disease, that in other circumstances may never occur. Thus it only sensible, if you wish to minimize your risks, that you try to ensure that none of these factors will apply to your specimens. It may take a little more trouble, but your reward will be fine healthy fish, and none of the heartbreak of seeing a prized specimen, succumbing and even dying to a problem, that might with a little foresight have been prevented.

Unfortunately with all the best intentions, many of you will still encounter from time to time, such problems, and we will need therefore to have an idea of the various bacterial diseases, which we may encounter, and what signs we should use to identify them , as well as remedial techniques, to be used where such exist.

Eye destroyed by TB Granuloma

It should be noted that for the purposes of identification that bacterial diseases are divided into two broad categories. These are Gram-negative and Gram-positive. This means that prior to the specific tests that determine the particular pathogen we divide them according to a simple Gram stain. This Gram’s stain is a complex formula used today throughout the world as a first determinant to identify the major bacterial group.

When swabs containing the bacteria are stained with this formula if the tissue colonies of bacteria stain Purple or Blue, then Gram positive bacteria are present, if Pink or Red is the result then Gram negative are present.

The majority of bacteria we will meet in Aquaria, are of the Gram negative type. The importance of this to the Aquarist is that the treatment is usually different for the two forms , and obviously to have any success we must know what disease we are dealing with before selecting any treatment.

It is also a fact, that in many cases of opportunistic infections, that mixed colonies of bacteria will be found, as they in many cases, will enter the wound, created as I already stated, by a parasite the ideal place for an invasion. Thus we often will opt for a broad spectrum treatment, if we suspect that this may be the case.

A practical problem, that you as Hobbyists will encounter, is that in the first instance, it is not easy to find Veterinarians who have the specialized knowledge of fish pathogens to identify the precise infectious agent. Secondly the economic value of any given fish, for the most part, will never be worth the cost in pure economic terms the fees a Laboratory or a Veterinarian, would charge for such work. This work requires much specialized equipment, and knowledge, as well as some expensive consumables.

Furthermore assuming that you find such a qualified person, or laboratory, and are willing to pay the asked for fees, the time element may render the answer academic. Most tests will take a few days to get the absolute answers, during this time, in some instances at least your fish may have passed on to another world, or at a minimum, will be more sick, than when you began.

Thus we need to be aware to the extent that is possible of the indications of the bacterial infections that we may encounter, and take such steps as are prudent, to try in most cases to remedy the problem. You should be aware, that those labs or Veterinarians who can do such work, are typically working with large Aquaculture farms, or river boards, where there is a considerable economic value involved, often running into a million pouns or more, of fish, which can be endangered. Thus these specialists do exist, but for the most part they are far removed from the problems which the Aquarist may encounter, even though in a great many instances the disease can be the same bacterial form which they encounter in their daily work.

I now propose to select certain quite commonly encountered diseases, and give the reader the most encountered signs, so that hopefully with this information, along with the aid of their trusted local dealer, some extra good literature, or a professional advisor, they can possibly both identify and apply suitable treatments.

The first pathogen we will deal with is Mycobacteria .

This Pathogen has a couple of forms viz. Mycobacterium marinum , and Mycobacterium fortuitum .

Both of these are in fact Gram positive and they give rise to a form of piscine Tuberculosis.

Miliary lesions (abscesses)on internal organs due to Mycobacterium fortuitum in adult chinook salmon

Although this disease can in fact infect almost all fish, certain species seem more susceptible than others. Among these are Black Mollies, all Gouramis, labyrinth air breathers, Neons & other Tetras, as well as most species of the Carp family.

The observable signs are : Lethargic movements, major wasting, Loss of scales & Fin tissue, ‘Popeye’ skin ulcers often with small haemorrhages, also edema.

Open TB with necrosis ( Gourami)

Most species of fresh water as well as salt water fish are susceptible, and it is very important for the Hobbyist to be aware, that this is one of the few forms of fish disease, that is communicable to humans . This transmission, when it takes place, usually manifests itself with large melanomas on the arms of the fish-keeper. They can spread, and are very difficult if not impossible to eradicate. Any Hobbyist suspecting therefore that they may have encountered this disease, is strongly advised to were surgical type gloves, when handling any fish, to sterilize all nets & other items that may come in contact with the fish, and notwithstanding all these precautions, to ’scrub up’ after handling them. These melanomas usually take some 3-4 weeks after exposure before manifesting themselves, so it is essential that the Hobbyist be aware of the danger, and take precautions, as the writer is aware of a few cases, in which the unfortunate Hobbyist has become infected and has these disfigurements for life.

Histologically in doing a postmortem we may expect to see, a number of white to gray nodules on the liver, kidney or spleen. One often finds necrotic black tissue eating away at the internal organs.

Prognosis In severe cases it is seldom possible to make an effective treatment.

Typical nodules growth on internal organs on TB infected fish

The disease is a slowly progressive one, and can take quite a long period of time, before it becomes fatal. It does not seem to spread from one fish to another, though there are cases recorded where this would appear to have occurred.

Treatment, as recommended by Stopskopf, is a combination of doxycycline & rifampin. These will not however be available from your local store and would have to be obtained from your Veterinarian with a prescription.

Loss of caudal peduncle (”tail rot”) due to myxobacteria

To try and ensure that the problem does not spread to other fish, you must take steps to ensure that your water quality is of the highest standard. Although I am against the continuous use of UV sterilizers, in this case I would approve their use. Furthermore any obviously far gone fish should be removed from the main tank at least, or even humanely ‘put down’. Normally if such methodology is carefully adopted then the problem can be brought under control.

Most observers believe that the causative organism is ubiquitously present, so that it is very difficult to eliminate it entirely. However if effective husbandry is employed, with cleaning of the gravel, along with good filtration as well as regular water changes , coupled with a varied diet which should include some live food, and the addition of a good vitamin mix, the problem can be eliminated as a cause of mortality. This will not apply of course to any fish that have developed the infection to such an extent that they have wasted away , and in such cases as I have said it is better to put them kindly to sleep, this can be done, by placing the fish in a small container with water and adding an Alka Selzer tablet. Do not dispose of the carcass by ‘flushing’ it down the toilet, as this is a prime way to spread the disease. Place the fish in some foil and dispose of it with the solid waste of the household. Also do not feed the dying fish to larger carnivorous fish, as this an excellent way to spread the infection.

John Shawn Prescott john@aquarium-gardening.com

Refs .

Aquariology Master volume Tetra Press. Pages 255-256.

Fish Medicine Ed. Dr. M. Stopskopf pp 559-560.