12/02/2024
Please please please read I know it’s long but it’s worth it
Columnaris infection?
I’m frequently contacted by people with sick axolotls. Most of the time they are simply dealing with minor infections brought on by stress, injury, or poor water quality, all of which have easy fixes that often require no major medical intervention.
Now and then, though, I see something more serious. Over the last few weeks, I have been contacted by multiple people with very sick axolotls, usually with the following symptoms in order of appearance:
- Reduced appetite over several days (and maybe much longer).
- Reduced activity and attentiveness.
- Reduction of gills, which may include reduction of gill filaments and shortening of the gill stalks (rami).
- White, fuzzy patches on the head and body.
- Short, white stringy material on the lips, gill stalks (rami), and later coming from the white patches on the skin.
- Peeling skin.
- Bleeding from sores on the head and body, especially when touched or after thrashing movement.
- Death.
Note; Bloating is a common sign of late-stage infection, but may not occur in all infected axolotls.
While a lot of different bacterial and fungal infections can cause the first 3-4 symptoms, only one disease causes all 8: Columnaris.
Columnaris is a bacterial disease caused by Flavobacterium columnare (identified in older literature as Bacillus columnaris, Chondrococcus columnaris, Cytophaga columnaris or Flexibacter columnaris). It is a rod-shaped, Gram-negative bacterium that is common and often abundant in warm, freshwater environments. The name is descriptive of the column-like (or thread-like) structures you see under a microscope. It can infect a wide range of freshwater fish and amphibians, including axolotls.
Columnaris is an opportunistic pathogen. This means that it is pretty much always around in natural environments at low levels, but can’t cause illness unless some other illness, injury, or stress weakens the animal’s immune system. It then enters the body through an open wound or damaged skin.
An axolotl can sometimes live for years with a columnaris infection. The bacteria only cause severe disease when the axolotl is weakened or environmental conditions are especially favorable for bacterial growth, allowing the bacteria to overwhelm the axolotl’s immune defenses.
Columnaris primarily infects soft tissues such as the skin, gills, and mouth. The bacteria gain entry through abrasions, ulcers, or other weakened areas of the skin. Once inside, they produce enzymes that break down tissues, leading to visible signs like white skin lesions, oral ulcers, and peeling skin.
Left untreated, a columnaris infection will spread through the body. The bacteria eventually invade internal organs, leading to systemic infections causing severe damage to internal tissues and organs. This usually causes death from organ failure within a few days of obvious symptoms.
The white lesions on the skin also shed huge numbers of new columnaris bacteria (which is what the white, stringy stuff really is) into the surrounding water. At later stages, when the kidneys and intestinal lining are infected, bacteria are also shed in their waste. The high concentration of bacteria in the confined space of the aquarium dramatically increases the probability that otherwise healthy axolotls in the same tank will also get infected.
Edit: Be aware that it can be harder to see infections on lighter animals, particularly hypos with light skin and spots. It is always best to assume that if a dark animal in the tank is infected, they all are.
Once a columnaris infection is detected, immediate steps must be taken to save the axolotls.
Immediately quarantine the infected animal, and any other axolotls in the tank, even if they appear healthy. Columnaris is highly contagious, so it can spread through direct contact with infected individuals, contaminated water, or shared equipment. Also keep in mind that other aquatic organisms in the tank, such as guppies and even snails, will also be infected.
Tub each axolotl in cool water, treated to remove chlorine (as always!). The lower the temperature, the better, ideally about 50 F (15 C). In fact, this is one of the few times I recommend refrigerating an axolotl. Cold water slows the reproductive rate of the columnaris bacterium, allowing time for the axolotl’s immune system to build up a defense. Just make sure the refrigerator is not set below 40 F (5 C). Keeping them very cool also allows more time to obtain proper medication or schedule veterinary care. You don't need to keep them refrigerated after antibiotic treatment begins.
Tub each axolotl individually so that they can be medicated and monitored. Keeping them apart reduces risk of further stress and reinfection. It also allows you to keep track of which ones are eating, and when. Use a tub large enough to keep the axolotl safely submerged and wide enough to allow comfortable movement, since treatment is going to take 5-7 days, if all goes well.
When the tub is not actually in the refrigerator, add a bubbler (airstone) to each tub to increase oxygen levels. Columnaris damages skin and gill filaments, which reduces the axolotls' ability to absorb oxygen from the water.
Now for the treatment:
Whenever possible, get to an exotic veterinarian or aquatic specialist for a precise diagnosis and prescription as soon as a columnaris infection is suspected!
The critical, life-saving treatment is ANTIBIOTIC THERAPY.
The recommended antibiotics are:
Kanamycin. This is available in the USA as Kanaplex.
Oxytetracycline. Available as Aqualife Oxytetracycline.
Nitrofurazone and furazolidone. This used to be available in Furan II, but I don’t think it is sold anymore. An exotics vet or aquatics facility will have this on hand.
Edit: More experienced aquarists have suggested adding metronidazole in combination with kanamycin or nitrofurazone. This approach should be more effective since these meds attack the columnaris (and other Gram negative bacteria) in two different ways, which reduces the probability of resistant strains surviving the treatments. Metronidazole is available in Seachem MetroPlex and Fritz MetroCleanse, among other commercial sources.
Follow the veterinarian’s or package instructions carefully regarding dosage and treatment duration. Continue treatment for 5-7 days EVEN IF SYMPTOMS SEEM TO GO AWAY! Stopping too early may leave the more antibiotic-resistant columnaris bacteria alive. They can then re-infect the animal, which means the next time you try to use the medication it won’t work!
For localized skin ulcers you can apply a dilute antiseptic such as povidone-iodine or methylene blue using a cotton swab. There used to be a product called RidRot that was good for this, and it may still be available in some areas. Don’t be surprised if this causes bleeding. Rinse off any residue before returning the axolotl to its tank.
I do not recommend salt, tea, or methylene blue baths. These can further irritate damaged skin, and can cause serious harm if done too frequently or at too high concentrations. Besides, there is no evidence whatsoever that any of these will stop columnaris, and at least a couple of published studies stating clearly that they do not!
While the animals are being treated, STERILIZE EVERYTHING!
Proper disinfection of equipment is critical when managing an outbreak.
Some aquarists who work with fish may think my approach is overkill, but in my opinion the inconvenience of complete sterilization, including all filter media and substrate, is trivial compared to the potential death of the axolotls and risk of infection of others. And yes, you will have to get the nitrogen cycle established all over again after the cleaning is done. Again, that is a small price to pay to protect your animals.
If you have never seen a columnaris infection, that’s awesome. If you never want to see one, avoiding these conditions dramatically reduces the likelihood of a columnaris outbreak:
1. Warm water (above 70 F):
Columnaris bacteria can survive and reproduce at any water temperature, but grow exceptionally well in warm water, and absolutely thrive between 25–30°C (77–86°F). This is one of many reasons that maintaining a cool environment for axolotls is essential. Axolotls have evolved in relatively cool, snow-melt and spring-fed lakes that naturally had a very low concentration of these (and other) warm-water bacteria, so their immune systems have lost much of their ancestor’s ability to fight off these types of opportunistic pathogens. If they are held in warm water, the high levels of columnaris bacteria can simply overwhelm them.
2. Poor Water Quality. We axolotl people are constantly preaching this:
High levels of ammonia, nitrite, or nitrate stress axolotls and compromise their immune systems. Ammonia and nitrite should never be above ZERO when water is tested between feedings. Nitrate should never be allowed to exceed about 40 ppm. Exceptionally hard water is also favored by columnaris bacteria, so check periodically and keep GH between 7–14° (125-250 ppm).
3. Stress:
Just like humans, axolotls don’t handle constant stress well. Overcrowding, frequent handling, constant noise/activity, and aggressive tank mates cause the release of stress hormones that push the immune system to its limits, making axolotls more susceptible to disease.
4. High bioload/low dissolved oxygen:
It is not so much that the bacteria prefer these conditions; It is that these conditions weaken the axolotls. Always clean up uneaten food and visible p**p before it decays. The bacteria feeding on these organic materials pull oxygen from the water, weakening the axolotls. They also produce ammonia, which among other things will burn skin, leaving the axolotl open to infections.
5. Nutritional Deficiencies:
A lack of a balanced diet - particularly a lack of protein - will impair immune function and healing ability.
6. Introduction of an infected animal:
This is a big one! ANY new animals should be quarantined in isolation for AT LEAST 14 days under observation to watch for any sign of infection or parasites. I actually quarantine for a month or more before I risk introducing any new animal to a community tank.
I wrote this quickly and without much proofreading, so please let me know if anything seems off or needs clarification. Hope it helps.
