Sick larval Pseudotriton ruber with sloughing and red skin

[Lamb]

Hello,

One of the larval red salamanders (Pseudotriton ruber vioscai) that I'm caring for in our lab has developed alarming symptoms. I fed and checked on everyone in the lab 4 days ago, and there was no indication that this individual wasn't doing well. When I went in to feed earlier this evening, I was shocked (see photos).

The gills are very red, and curled. The best sense that I can make of it is that there has been excess sloughing of the skin on the limbs, especially the front legs. Or maybe the whitish transparent stuff is fungus? Regardless, the skin on the legs is very red. There are also behavioral changes. The individual would hold it's pelvic girdle off the bottom of the tank (pushing down with its front limbs and tail). When I gently scooped it up to place it in a smaller tank, it barely moved (usually they swim like mad), and I could almost flip it on to its back. Then, when I placed it in a salt bath (described later), it moved around a little, but it looked like it took a lot of effort to do so. Another oddity, it has lighter patches of skin on its back, but they don't appear to be fuzzy and aren't white (just a bit lighter than the normal background color).

After searching through the forums, and consulting Axolotl pages, I thought that it might help to try salt baths and refrigeration. I placed this individual in a salt bath (3-4 g Cichlid aquarium salt per L water) for 15 minutes, and then changed the water for water at the salt concentration that we use in the lab. It is now sitting in the refrigerator in the lab, and I'll check on it in the morning. If it survives the night, I'll treat it as is recommended in Kaysie's salt bath post (http://www.caudata.org/forum/f46-be...axolotl/72698-salt-bath-picture-tutorial.html).

So, do I have the right idea in terms of treatment? Have others had animals come back after having reached a point where they weren't responding normally to stimuli (like touch)? Any other information would be appreciated.

 

[Lamb]

The nice dissecting scope with a camera is such a new addition to our lab that I forgot that I we even had one. What I saw when I examined this larval P. ruber was not good.

The larva was covered in worm like parasites, from gills to the tip of its tail. The green arrows in the photos indicate the worm like parasites, and the blue arrows indicate the regular fimbrae of the gills. The whitish stuff around the legs are clusters of fungal hyphae, indicated by red arrows. The parasites weren't visible with the naked eye, nor was there a distinctly off-colored area or sheen where the parasites occurred (they were in both the lightly colored and darkly colored patches, across the entire surface of the larva). I also didn't see them when I zoomed in on my photos taken with the macro of my point-and-shoot Olympus. The parasites are much less than 1 mm in length.

Due to the physical and behavioral state that this Pseudotriton was in, we euthanized the larva. I examined 6 other larvae from the lab, and none had any sign of external parasites nor other visible abnormalities. I'll be keeping a close eye on them for a while, though. We've sent photos to a parasitologist, and he's asked for samples of the parasite. Once I know more, I'll update this thread.

 

[Jan]

Thanks Lamb for sharing this story and the detailed photos.

 

[gar4016]

The larva must have been in pretty rough shape to have euthanized it, I'm sorry for you loss. I've never seen this type of parasitic infection before so thank you for sharing the detailed photos and giving us an opportunity to expand our knowledge.

I'm wondering if the parasite did the majority of damage and the fungus only moved in once the larval salamander's body had succumbed enough.

 

[Lamb]

I'm wondering if the parasite did the majority of damage and the fungus only moved in once the larval salamander's body had succumbed enough.

That's my best guess.

 

[Lamb]

The parasitologist has identified the culprit as a Gyrodactylus sp., a type of monogenean ectoparasite, in the flat worm phylum (Platyhelminthes). After a brief search, I found the following website: Gyrodactylus Biology

Here are some interesting points that I took from that source:

• They are a common parasite on fishes (I also found other sources saying that Gyrodactylus sp. had been identified on ranids, Dicatmptodon, and Ambystoma).
• They are often less than 1 mm in length (Hence why I couldn't see them without use of the scope)
• They feed on mucous and skin cells
• They are "hyperviviparous," which means that as soon as one is born, it already has an embryo growing inside it (the F1); moreover, as the first mother ages, the F1 begins to grow an F2. (I think this likely contributed to the rapid onset of symptoms and the massive infestation)
• Why the host dies isn't fully understood, but it may be due to secondary infection of the punctures made by each Gyrodactylus as it feeds, or due to issues with osmoregulation.

All of the other larvae in the lab still appear to be healthy, so hopefully I wont have any other issues with Gyrodactylus in the future. Apparently, this parasite has cost salmon fisheries in Norway quite a bit of money, and is also an issue in the pet trade. The website also says that even a low level infection by Gyrodactylus can cause mortality.

 

[jewett]

So any ideas on where the larva could have become infected? I'm guessing these larvae are wild caught (do Pseudotritons breed in captivity?) If wild caught do you have any location information on where they are from? How long have they been housed in your lab?
That really is too bad about the infection but at least the parasite id is a positive. How easily can the parasite be transmitted and do you need to be concerned for the other animals housed in the lab? And knowing what the parasite is now can it be treated and are there recommended protecols consisting of any prophylactic treatments for the remaining larvae?
Thanks for humoring my curiosity and for posting this thread. I hate to use the term "interesting" when a life has been lost but this episode has been educational. I always appreciate when gained knowledge through experience is shared. Thanks again.
Heather

 

[Lamb]

Even though I felt really bad for the larval Pseudotriton, I am still intrigued by the pathogen. So feel free to call the situation interesting.

So any ideas on where the larva could have become infected?
Not really. The larvae I keep in the lab are wild caught, so it could have come from its native environment. However, I also occasionally feed them wild caught live prey (e.g., fairy shrimp, mosquito larvae), and although I strain the water from the prey, the parasite could have been introduced that way.


If wild caught do you have any location information on where they are from?
I have locality info for all of the animals I keep in the lab, and I have multiple other individuals from the same stream in which the parasitized individual was found. I did a close inspection of everyone yesterday, and they appeared to be physically and behaviorally normal.

How long have they been housed in your lab?
This particular larva had only been in the lab for about 1 month. I've had other individuals in the lab for coming on a year now.

How easily can the parasite be transmitted and do you need to be concerned for the other animals housed in the lab?
My brief search for information regarding how this parasite spreads inevitably focused on Gyrodactylus salaris, the gyrodactylid parasite that has caused the fishing industry so much trouble. This source (http://www.defra.gov.uk/aahm/files/Guide-GS.pdf) and others indicate that the parasite can be easily spread via improperly sterelized equipment, water exchanges between sites, and released animals. Other sources indicate that Gyrodactylus can survive for a while on wet or moist equipment. It seems like disinfecting your gear with bleach or some other substance will work, or allowing it to completely dry and remain dry for a while will also work.

I was very concerned with the other animals in the lab for a few days after the onset of symptoms in this larva. Although these larvae are housed individually, and although there is minimal water exchange between enclosures (i.e., maybe some spray from bubblers, or water from the tip of the siphon I use to suck out uneaten food), there seemed to be enough of a chance for something to spread. When I noticed the symptoms, I immediately moved this larva to a different environmental chamber, and tried to isolate the other larvae further by having dedicated equipment for each of the environmental chambers. Isolating individuals at a level beyond that, however, may be difficult, but I'm still considering what else I can do, apart from more carefully cleaning lab equipment.

I have considered that perhaps this larva came in with the parasites, and that the new environment, or perhaps foreign bacteria from live prey sources, might have stressed the larva and prompted the infestation. Consequently, I have decided to stop feeding large larvae wild caught live prey, as they can grow and do well on frozen foods. However, I have still been feeding wild caught prey to very small larvae. I recognize that it is a risk, but I don't have the room or the time to culture enough Daphnia, and I already culture fairy shrimp.

As it's been a week since the parasitized larva was euthanized, and no other individuals are presenting with symptoms, I'm hoping (knock on wood) that no one else was contaminated. Still, I check individuals each time I change water and feed (every 3-5 days), and try not to harass them otherwise (to reduce stress).

And knowing what the parasite is now can it be treated and are there recommended protecols consisting of any prophylactic treatments for the remaining larvae?
This site (Flukes Disease Education from FishVet, Inc.) includes treatment details, including prophylactic treatments. However, unless other individuals present with symptoms, we wont use these methods because they would surely stress the remaining individuals.

Thanks for your questions. I wonder if anyone else has had similar symptoms in their individuals, or if they have had experience with similar fluke parasites? Also, it seems like salt baths may not be a viable way to treat individuals with Gyrodactylus. They can apparently survive at a range of salinities, but I haven't thoroughly looked in to this.

 

[jewett]

Thank you for the additional information. It sounds as though you are well prepared should this ever surface again but I certainly hope your new found knowledge on the subject will never need to be put to good use. With the precautions you take it seems as though the risk of a reoccurance will be low.
Best of luck with your remaining larvae and again thanks for responding to my many questions!
Heather

 

[Coastal Groovin]

There is nothing that will kill them? You couldn't bath them in a solution of panacure? Maybe even a stronger salt bath?

 

[Lamb]

There is nothing that will kill them? You couldn't bath them in a solution of panacure? Maybe even a stronger salt bath?

If you click on this link Flukes Disease Education from FishVet, Inc., you'll see that you can use formalin dilutions or Acriflavine to treat for these parasites. A quick Google of panacure seemed to indicate that it is used for internal parasites, not external ones like Gyrodactylus (though Gyrodactylus can sometimes be "internal" by infecting the bladder, I think).

A brief Google search suggests that these parasites could tolerate higher salinities to the point that infected fish moving from fresh to brackish to fresh water could transmit the parasite into new areas (http://faculty.uml.edu/rhochberg/ho...DF Papers/Monogenea/Gyrodactylus salinity.pdf). The same paper indicates that longer periods at stronger salinities can kill populations of the parasites, but that it takes a while (i.e., >50 days at 7.5% salt water). Based on how rapidly this individual developed a severe infestation, I don't think that you could take that amount of time to try and treat the infestation with salt baths.