A Recent and Interesting Health Management Case

[IntoTheMystic]

Over the last few months, there has been a small surge in the number of sea urchins brought back to my Hospital with suspected Bald Urchin Disease. I saw my first case a year ago last summer. This disease usually begins with some type of insult that penetrates the skin and exposes the test. Opportunistic bacteria, (appears to be mostly Vibrio spp. so far) set up shop and create a lesion that slowly grows in size and also penetrates the test of the animal, adding osmoregulatory stress to the mix and further taxing its immune system.

 

When I first worked this animal up, I found tons of different bacteria and ciliates swarming at the site, Working with Dr. Tim, I implemented a series of 10 medicated baths over that many days to nuke the ciliates and the bacteria and give the critter's immunocompetence a chance to turn the corner on the infection but it still wouldn't eat and the lesion did not respond well.

 

Note the size of the original infection in the middle of the side in this shot:

 

 

I then began treating it with a topical antiseptic and a medicated cream that I have used successfully in combination for years (the whitish looking stuff is the remnants of the cream.) Please bear in mind that invertebrate medicine is still very experimental in a lot of ways and sometimes you get unexpected results. The antiseptic, which was diluted by 50%, caused a reaction on the skin on the animal, causing a type of burn that exposed a lot more of the test. This was most unexpected and appalled me and the vet student I was working with that day.

 

 

Dorsal view. Note the anus, or vent, in the middle.

 

 

Ventral view. Note the animal's Aristotle's lantern, or mouth, in the center there. Everywhere the antiseptic went, there was near-complete loss of epithelial tissue, spines, tube feet and pedicellariae.

 

I worked on this animal for weeks, trying to get some healing at the margins and reduce the osmoregulatory distress but to no avail. It reacted to food and stimuli but would not eat and eventually I determined that euthanasia was the right thing to do. Because this is such an interesting case, I conducted a necropsy after the animal expired and prepared it for submission to an aquatic animal pathology lab here in the NW. I thought you guys might find the post-mortem images interesting.

 

 

You can see the initial infection site on the left there. You can also see that the infection totally penetrated through the test, making it very thin and brittle. Note the shrunken appearance of the organs. The infection and the additional loss of epithelial tissue made it impossible for this animal to osmoregulate, causing these tissues to lose water and basically preventing them from functioning. No wonder the animal did not want to eat.

 

 

Check out the internal structure of the Aristotle's lantern. Notice the delicate musculature. Looks like the muscles are constantly pulling against each other as they control the 5 plates that rasp algae and other food off rocks. The esophagus and stomach are at the 10 o'clock position. Ordinarily, they would point straight up to the vent.

 

This case was difficult, as we are accustomed to routine success with med cases, even when the treatment is experimental. However, this story does have a bit of an upside: I am caring for four more urchins that have/had these lesions. With the lessons learned on this case, I have changed my approach and the lesions on all but one have closed completely. The other, a large Red Urchin, is healing well, with the lesion growing smaller by the day. The treatment was experimental on these animals also and three of them will be ready to go back on exhibit soon. 

[Higher Thinking]

Wow! That is super interesting. Do you have a photo of what a healthy specimen would look like?

 

You say you "changed" your approach. What seems to be working?

[IntoTheMystic]

 

You say you "changed" your approach. What seems to be working?

 

The medicated cream is silver sulfadiazine. They use it on burn patients, as it's a moisturizing cream but also has bacteriostatic sulfa. The problem is, it's quite hydrophobic, so you have to get creative to get the stuff to stick on the animal once it goes back in the water. I applied the SSD to the lesion and put a small piece of saran wrap over it to form a kind of seal over it. The cream stayed in place for days instead of hours (at best), it retarded the infection and also created a seal to help the critter osmoregulate without having to burn extra energy.

[Flashy Fins]

This is fascinating!  I would also like to see a healthy uchin for comparison, but I can certainly understand not cutting up a perfectly good one for a peek.

 

Thanks for sharing this with us!

[IntoTheMystic]

Link to freshly opened healthy urchin anatomy:

 

https://commons.wikimedia.org/wiki/File:Gonadi_Paracentrotus_lividus_riccio_di_mare_adventurediving.it.jpg

 

Sushi lovers likely already know that the lush, orange tissue are the gonads. Enjoy!

[Emerald525]

Interesting thanks for sharing. There is some debate of the benefits of silvasene on preventing infection of burns and also that it may impair healing of the burn but it sounds like it is working well for urchins. Nice job!

[youcallmenny]

Link to freshly opened healthy urchin anatomy:

 

https://commons.wikimedia.org/wiki/File:Gonadi_Paracentrotus_lividus_riccio_di_mare_adventurediving.it.jpg

 

Sushi lovers likely already know that the lush, orange tissue are the gonads. Enjoy!

Having enjoyed Uni more than a few times, that was my first thought upon seeing the meat. Usually it's bright orange but even the meat on that specimen looks dull and unhealthy. Is that just because it has expired or because of the disease?

 

My next thought was that I was unaware I was eating reproductive organs...

 

Thanks for the post, your input on this forum is always frankly amazing to the amateur hobbyist like myself.

Edited January 12, 2017 by youcallmenny