Re:Vibrio outbreak?

Pete Giwojna

Dear Elina:

I’m sorry to hear you lost more of your Hippocampus fuscus to this affliction, but that is a very positive development that the veterinary department at the University of Munich is willing to get involved. It is immensely helpful to have an accurate diagnosis to work from and hopefully we can use it to save your remaining fuscus and assure that your H. reidi remain healthy.

Certainly when inbreeding resulting from brother/sister crosses allows undesirable recessive traits to be reinforced and weakens a strain of seahorses, disease resistance and the immune response are among the areas that are most often adversely affected. Inbreeding may well have been a factor as to why the fuscus were hit hard by this infection yet your reidi remain unaffected.

If Munich University found ciliated protozoans during their necroscopic examination of your fuscus, then you are most likely dealing with Uronema, Elina. That’s a nasty bug that’s very difficult to eradicate from your system, but there are several different ways it can be treated effectively. Here’s some information on Uronema from my new book (Complete Guide to the Greater Seahorses) that discusses these parasites in greater detail, including the most useful treatment options:

Uronema marinum

Uronema marinum is the marine equivalent of the Tetrahymena pyriformis parasites that plague freshwater fish (Basleer, 2000). Uronematids are probably the most commonly encountered protozoan parasites of seahorses in the aquarium. They frequently plague wild-caught seahorses and store-bought fish in particular. Unfortunately, they are also one of the deadliest and difficult to eradicate marine parasites.

They live in seawater and normally feed on bacteria and dead tissue, but they are opportunistic invaders that are always on the lookout for food, and are quick to take advantage of weakened fish (Kollman, 2003). It is when conditions favor them and their numbers get out of hand that Uronema becomes a problem. Under those circumstances, they soon begin to attack healthy tissue as well as dead material, invading the gills and muscles, eating red blood cells, and infiltrating the internal organs (Kollman, 2003).

High temperatures and poor water quality are among the environmental factors that favor Uronema. Elevated water temps speed up their life cycle and accelerate the growth rate of Uronematids accordingly (Kollman, 2003).

These ciliated parasites are very common on freshly imported wild fishes suffering from shipping stress (Basleer, 2000). Long-distance shipping is one of the factors that commonly contributes to Uronema problems. The deteriorating water quality in the shipping bags of fish transported for 24-48 hours is very conducive to their growth. Low pH, too much ammonia and organic waste, too little dissolved oxygen, and the presence of weakened fish with compromised immune systems all combine to create ideal conditions for these parasites (Basleer, 2000). They feed on damaged tissue, multiply quickly, and invade healthy tissue as their population explodes (Basleer, 2000).

The initial symptoms are excess mucus production, heavy breathing, and loss of color (Basleer, 2000). As the disease progresses, pale patches or bloody sites appear, which become large ulcer-like wounds as the Uronema parasites multiply rapidly and invade the underlying muscle tissue in the advanced stages (Basleer, 2000). Infected fish often scratch these irritated areas. These open bloody lesions are often mistaken for bacterial infections (e.g., marine ulcer disease or "flesh-eating bacteria"), and the affected fish are doomed if antibiotic therapy is administered on the basis of such a misdiagnosis.

These dreaded parasites also infect the gills, and as with Brooklynella, heavy gill infections may result in dead by suffocation before the characteristic skin lesions develop (Basleer, 2000). When skin lesion do appear, the open wounds invite secondary bacterial infections, which further complicate the clinical picture.

Microscopic examination of skin smears can confirm the diagnosis of Uronema. Under the microscope, Uronema marinum parasites appear as pear-shaped, single-celled ciliates with a single large macronucleus and long hairlike cilia at the rear end (Kollman, 2003). Numerous small (35-50 microns), fast-moving, oval or pear-shaped parasites will appear on skin and fin smears (Basleer, 2000).

Formalin, malachite green, or formaldehyde/malachite green combination drugs are effective treatments (Basleer, 2000). The treatment needs to be maintained for at least 21 days to cover the life cycle of the parasites. Chloroquine phosphate, quinine hydrochloride and quinacrine hydrochloride (antimalarial drugs) also work well but are difficult to obtain, difficult to use, and difficult to dispose of properly (Kollman, 2003).

Freshwater baths, concentrated baths in methylene blue, and hypersaline baths at 45-50 ppt are also very helpful. Even 10-second dips in a 3% hydrogen peroxide solution are known to be effective. The peroxide dipping solution is prepared by taking one gallon of dechlorinated freshwater and then removing 10-oz of the water and replacing it with 10-oz of 35% hydrogen peroxide instead. This formula will produce a 3% solution of hydrogen peroxide for the brief dip (Kollman, 2003).

There are mixed reports on the effectiveness of hyposalinity at eliminating Uronematids. Kollman highly recommends it, but the latest thinking on the subject indicates that hyposalinity is contradicted when treating Uronema (Kollman, 2003). For example, Thom Demas, the Senior Aquarist at the Tennessee Aquarium, finds that low salinity actually seems to encourage Uronema, whereas higher salinity thwarts it. He reports that raising the salinity of the system to 38-40 ppt while gradually lowering the temperature will greatly slow down the growth rate of Uronema and make it much easier to control (Demas, pers. com.). My latest experience treating Uronema with hyposalinity was decidedly negative and I also feel that hypersalinity produces better results for this parasite. It appears that Uronematids are unique among ectoparasites in their tolerance for hyposalinity, so treat accordingly. They cannot withstand freshwater, but hyposalinity seems to be quite another matter.

With all these different treatment options for Uronema, one would think that these parasites would be fairly easy to control. Nothing could be further from the truth! Uronema is a very stubborn pest and terribly difficult to eradicate from your system once and for all. The problem is that formalin, malachite green, and the various dips and baths all do a fine job of killing the Uronema ectoparasites that are on the skin and gills of the fish, but they cannot touch the parasites that have penetrated within the fish’s body. The parasites that are attacking the muscle tissue, internal organs, and red blood cells aren’t touched by such methods and they are the ones that do the irreparable damage. What is needed is therefore a way to get the antiparasitics inside the affected fish where they can kill the ciliates that have invaded the tissue.

Dr. Alistair Dove, the Aquatic Pathologist at the New York Aquarium, has found the solution. He reports that intramuscular injections of metronidazole at a dosage of 50mg/kg repeated every 72 hours for a total of 3 treatments work extremely well for eliminating Uronema in seahorses (Al Dove, pers. com.). The IM injections deliver the drug inside the seahorse’s body, precisely where it’s needed most. Of course, we humble hobbyists cannot manage such injections, but we sure can bioencapsulate metronidazole by gut-loading live shrimp with it and get the medication into our seahorses that way. That will allow us to attack the parasites from the inside and the outside at the same time.

Because Uronema is so difficult to control, Basleer recommends treating it with a combination of treatments. He suggests treating the main tank with formalin/malachite green and then adding daily baths in freshwater and concentrated methylene blue for best results (Basleer, 2000).

Lower the water temperature during the treatment period and stay on top of the water quality in your hospital tank. Make partial water changes as necessary to keep your aquarium parameters perfect. [End quote]

It’s unfortunate that you are unable to get formalin in Germany, Elina, since that is the treatment of choice for Uronema. In your case, I would treat the remaining fuscus with malachite green in your hospital tank along with daily freshwater baths and brief dips in a concentrated solution of methylene blue or 3% hydrogen peroxide. Of course, continue the antibiotic therapy for those secondary infections (did the University culture the bacteria that was present and test their sensitivity to various antibiotics?). If the veterinary department at the University of Munich could possibly provide injections of metronidazole for the remaining fuscus, that would be extremely beneficial.

Here in the United States, we would use formalin combined with copper sulfate to eliminate the Uronema from an infected aquarium. Since that’s not an option in your case, I would suggest that you sterilize the aquarium and everything in it with a good stiff dose of chlorine bleach (Clorox or any equivalent brand) instead.

The appropriate dosage is 1-2 cups of chlorine bleach for every 50 gallons of water in the aquarium. Keep the filters running on the hospital tank while you treat it with the chlorine bleach so that they are thoroughly exposed to the chlorine as well. Be sure to sterilize any nets, dip tubes, hydrometers, basters or any other equipment that was used on the H. fuscus tank with chlorine as well. Give the chlorine about two days to sterilize everything in the aquarium, nets, accessories and all. After 48 hours, you can add chlorine neutralizer to your hospital tank to remove the bleach, change out all the water, and rinse everything very thoroughly with freshwater. And then you can safely set the tank up from scratch and cycle it again. Keep your fish room well-ventilated while you’re treating the aquarium with the chlorine bleach and be careful not to breathe in the chlorine fumes when you’re handling the bleach. When you’re done treating the fuscus, sterilize your hospital tank and everything in it the same way.

Best of luck resolving this problem, Elina! Here’s hoping your remaining fuscus pull through and that your H. reidi remained healthy!

Happy Trails!
Pete Giwojna, Ocean Rider Tech Support

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