Conflicting info

[Jennewt]

Refrigeration is not necessarily beneficial to the animal, but harmful to the pathogen, by taking it out of that natural range.

That's the theory. However, I also have a hunch that, even within the animal's normal range, the cooler end of the range is less stressful for the salamander.

But then you have the pathogens that DO thrive at cooler temperatures, such as chytrid fungus.

I just learned that "ordinary" fungus (Saprolegnia, the "white fuzz") also thrives at cooler temperatures (below 68F). This makes me re-think our standard advice of telling people to refrigerate axolotls with fungus. I still have a hunch that refrigeration "works" for fungal infections, but if so, it's working by some mechanism that differs from the theory above (not by discouraging the pathogen). Or maybe 40F is sufficiently below the thermal optimum for Saprolegnia that the theory is still correct. I wish I knew!

 

[Kaysie]

Oh I hear ya. Too bad we don't have pathologists here.

 

[Mark]

With my fairly layman’s understanding - I assume that bacterial infections develop faster in temperatures at the upper end of most caudates thermal limit (which is where most hobbyists keep their animals). This may not be all bad as the animals immune system will be operating more effectively at warmer temperatures and there’s a better chance the infection can be fought. Some bacteria have narrow temperature ranges or minimum temperatures before they can cause problems – cooling to the lower end of the animals thermal range can potentially affect the bacteria.

Development in viral infections is controlled by the animals metabolism. The warmer the animal the faster the metabolism and hence faster replication of the virus. Cooling slows the metabolism and will slow the spread of the virus. It may also make the animals immune system less effective.

Fungal infections will be affected by cooling if the fungus can’t progress at the cooler temperature so it depends on the fungus. If the fungus can survive at fridge temperature you may be doing more harm by slowing down the animals immune system.

It's somewhat of a gamble to cool the animal down. The hope is that you affect the infection, slow the metabolism and leave the animal with sufficient immune system to recover. Anecdotal evidence suggests it works regularly.

 

[Jan]

Jan, I would say that the 37C optimum would be true in humans, but I would think the pathogens that attack poikilothermic animals are more apt to survive at a higher range of temperatures. But they would only be pathogenic in the animal's natural range of temperatures. Refrigeration is not necessarily beneficial to the animal, but harmful to the pathogen, by taking it out of that natural range. So refrigeration of caudates is indeed a nonharmful and effective way of reducing most pathogens. But then you have the pathogens that DO thrive at cooler temperatures, such as chytrid fungus.

Kaysie, we are on the same page and note I was addressing bacteria in specific not pathogens in general. With newts/salamanders, do you know of pathogenic bacteria that would be outside of the classification of mesothelic into thermophilic? Fungus and other parasites such as protozoa are a different animal, so to speak.

 

[Jan]

Oh I hear ya. Too bad we don't have pathologists here.

Microbiologists?

 

[tupinambis]

I think it matters also the functionality of any medications that one is employing as well or the specifics of the offending pathogen. Not all medications work specifically to kill off directly the infesting organism. Some are employed to impede reproduction in said organism, and thereby you would likely want to warm up your host salamander in order to speed up the metabolism of the pathogen and finish it's lifecycle fast. Alternatively, some pathogens may be induced into a state of stasis by the cooler temps, and therefore cooling the host would only prolong the problem.

Bruce, I only know of an early paper that describes cold therapy. Emerson, H., & C. Norris, 1905. "Red-leg" - An infectious disease of frogs. Journal of Experimental Medicine 7:32-58.
If you have access to Web of Science, you could do a citation search and see who has possibly cited it (or any of the other papers listed in this thread) as a means of possibly turning up any other research into cold therapy.

 

[herpvet]

Hi Colin,

Thanks for that - useful paper. I haven't been able to find any others as yet, or any mention in veterinary textbooks, but I'm still researching.

Related to the other comments above, Wright & Whittaker's book recommends elevated temperatures as adjunct therapy for Saprolegniasis.

Cheers,

Bruce.