Salt Solutions in Treating Salamander Diseases


By Ellen Chernoff, Ph.D.

Indiana University Center for Regenerative Biology and Medicine
Indiana University-Purdue
University of Indianapolis

There are no completely harmless pharmacological agents for the treatment of salamander diseases, but the cautious use of salt solutions is relatively safe.  There are four reasonably well-documented uses for salt solutions:

  1. removing fungus from eggs
  2. removing fungus from skin
  3. removing ectoparasites from skin
  4. treating the symptoms of kidney problems (not a cure)

Salt solutions are most commonly used for external Saprolegnia species infections.  These fungi produce fuzzy white or grey masses. Concentrations of salt used vary from 4-6 grams/Liter to 10-25 grams per liter with exposure times of up to 72 hours for the low concentration and 10-30 minutes for the high concentration. The salt used is always non-iodized salt.  Table salt has a compound added to prevent it from caking up, and it should not be used.  Preferred types of salt are: sea salt, freshwater aquarium salt, or Kosher salt.  In a laboratory setting, concentrated forms of Holtfreter’s solution or Steinberg’s solution are often used.

Eggs

At some times of the year fungal spore counts are very high and fungal growth on amphibian eggs is a real problem.  A filamentous or fuzzy white or grey growth is seen on and in the egg jelly.  If treated early, before the fungus penetrates to the embryo, the spawning can be saved.  I have used this method on axolotl eggs.  When fungus is a general problem, a small increase in the salts in the pondwater may help (e.g., 40% Holtfreter’s Solution).  Higher salt concentrations and longer periods of exposure have also been used.

  1. Prepare a clean container with hypertonic saline.  6 grams sodium chloride (salt) per liter of dechlorinated water is sufficient for axolotl eggs.  (This is approximately one quarter-ounce of salt per quart.  For those in labs: 2X Holtfreter’s has this amount of salt.)
  2. Transfer the infected eggs by forceps (tweezers) to the hypertonic saline solution.  When all the eggs are transferred, gently stir them around for 10 minutes. 
  3. Then transfer them back to regular artificial pondwater.  This can be repeated two or three days in a row. 
  4. Removing the egg jelly after treatment is also helpful if you have a microscope and instruments available.
Skin Mycosis

Skin fungal infections can occur in contaminated wounds, but are usually occur as a result of very poor husbandry conditions and in very stressed, immune suppressed animals.  The skin has tufts of grey or white filaments.  Recommended salt concentrations vary widely.  I have only had one animal with skin fungus, a mutant axolotl that also had other problems.  In addition to treatment, the habitat should be disinfected and remade.  A quarantine habitat should be used until treatment is complete.  This type of treatment is easiest to use for aquatic animals.  Concentrations of salt up to 25 grams/liter have been used for brief treatments.  Use the lowest effective salt concentration.  Getting a terrestrial salamander to submerge in a salt solution voluntarily can be a big problem. 

  1. In a clean bowl mix a hypertonic saline solution.  The key feature is a final amount of 6 gm/Liter NaCl (sodium chloride)
  2. Place animal in the hypertonic saline for not more than 30 minutes.
  3. Wearing examination gloves, gently remove fungus
  4. Place in clean normal artifical pond water.

This can be repeated on several successive days, or every other day, for tenacious infections.

Ectoparasites

Aquatic salamanders can get some of the same skin or gill parasites found on fish, such as Costia and Trichodina.  The same treatment used for skin fungus is effective in detaching these parasites.  A microscope is generally needed to tell the skin irritation from ectoparasites from bacterial infection.  The habitat should be disinfected.

Fluid Retention

This last use of hypertonic saline is used under veterinary advice in combination with antibiotic treatment.  Some very ill salamanders will experience impaired kidney function.  Some of the antibiotics used in salamanders, such as Amikacin, can be toxic to the kidney, but there may be no other choice in treating an infection.  Fluid retention (bloating) can be treated with hypertonic saline.  I have used this method with a very ill terrestrial tiger salamander that was bloated and being treated with Amikacin under veterinary advice.  The animal showed body posture and movement that suggested great discomfort.

The veterinarian’s source was a treatment for frogs.  She suggested a 10-15 minute treatment in a 6 gram/liter salt solution.  This was tried, but when the animal was removed the fluid rapidly re-accumulated.  I finally kept the salamander in the solution for 4 days until there was no sign of bloating, then gradually reduced the salt concentration over a two day period.

Getting a sick, uncomfortable tiger salamander to stay in water was a problem initially.  I finally made an arrangement of disinfected cage furniture such that the salamander could wedge herself against the wall of a deep basin with her belly submerged (a weighted screen lid was used to prevent escape).  With the bloating reduced, the animal seemed to rest comfortably.  The infection was the result of a serious husbandry problem with terrarium substrate drainage.  The terrarium was redesigned.  The animal made a full recovery and the illness did not recur.

For terrestrial animals that do not like to be submerged, an additional method that is less effective, but will help is to maintain or reduce the animals’ bloating, is to keep the caudate on unbleached paper towels that are heavily moistened with the hypertonic salt solution. This will reduce the stress on the animal while allowing it to receive the treatment. Change the toweling daily to keep the solution at an effective concentration and to prevent excess bacterial growth on the towels

References:

Wright, KM and Whitaker BR (2001) Amphibian Medicine and Captive Husbandry.  Krieger Publishing, Malabar, Florida, USA.  Chapter 24 mainly

Duhon, S.T. (1989) Diseases of Axolotls. In: Developmental Biology of the Axolotl. JB Armstrong, GM Malacinski, Editors.  Oxford Univ Press, New York. Chapter 25


© 2002 Ellen Chernoff. Posted September 4, 2002.


 

Appendix: Additional specifics on salt treatments

  • The recipe for Holtfreter's solution is available at:

  • A simple salt solution for treating fungus on aquatic caudates is given in:
    FAQ#43 in the axolotl.org FAQ:
    Give a bath in some salty water for about 10 minutes once or twice a day (2-3 teaspoons aquarium salt or non-iodized table salt per litre or quart). That should kill the fungus within a few days. Don't leave the axolotl in the salt bath for more than 10-15 minutes each time, because the salt will start to damage the axolotl's skin and gills.

 

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