Lack of Natural Sunlight:
Some hobbyists and scientists hypothesize that exposure to sunlight can help reverse MHLLE. Tom Frakes cited information in his 1993 article that tangs affected with MHLLE at Disney's EPCOT facility were simply transferred from indoor displays to outside holding tanks on the same central system with the same water, and later were noted to have recovered. Hence, the conclusion that sunlight can cure or prevent MHLLE. This makes sense coupled with the complete absence of MHLLE in all wild reef fishes (Blasiola, 1990), which are constantly exposed to sunlight. But it is possible that sunlight could have had only an indirect effect. Perhaps in the outdoor tanks the sunlight encouraged a different, more nutritious growth of algae that was not able to grow under the light of the indoor displays; maybe consuming this improved diet is what actually reversed the MHLLE. Another possible explanation is that this alga (if it existed) removed excess nutrients and dissolved organics from the water. Depending on the flow into and out of these outdoor tanks, it is conceivable that their overall water quality could have been better than in the main indoor tanks, because of the extra algae and the sunlight. Plus, this was not a controlled study. It is possible that the staff and methodologies of caring for the indoor tanks was different than the people/methodologies involved in caring for the outdoor display. Unless great pains were undertaken to eliminate other variables, there is no telling what other changes could have occurred and affected the outcome. Overall, not enough information is given in this brief account to fairly evaluate whether or not sunlight played any direct role in the fishes' recovery.
Tumors:
There is a passing mention of a type of tumor that can cause lesions similar to those seen in Blasiola's 1990 article. He states that some species of damselfish have exhibited raised or eroded areas that resemble MHLLE on their head, and that this was caused by a type of tumor that spread from nerve fibers. Unfortunately, that is the extent of this passage and no reference for further investigation is provided.
Along these same lines, I will add that I have seen some wrasses, most notably the green bird wrasse (Gomphosus varius) and lunar wrasse (Thalassoma lunare), develop tumor-like lumps around their face after being in captivity for extended periods of time. While wrasses are generally thought to be resistant to MHLLE (Hemdal, 2003), I believe it is possible that this is a different manifestation of MHLLE. However, I will freely admit that this could be something else entirely. At the very least, it is another abnormal, mysterious aliment that seems to only afflict fish held in captivity. As such, in my opinion, it warrants further investigation.
Fungal:
This is yet another instance of a potential cause being mentioned briefly but not thoroughly discussed. Fungal infections are mentioned in a list of factors implicated in MHLLE in both Blasiola's 1990 and Frakes' 1988 articles, but without discussion as to why it was thought that fungi may be the cause and without reference to this possibility to follow-up on. Blasiola does state later in the same article that he was unable to find "any evidence of a fungal infection" in the fishes he had examined that had the typical lesions associated with MHLLE, suggesting that fungi do not likely cause MHLLE.
Viral:
The Varner and Lewis paper (1991) centered upon a viral infection as the possible cause of MHLLE. They were able to isolate a reovirus-like agent from what they describe as a moribund Koran angelfish (Pomacanthus semicirculatus). For those readers who don't know what moribund means (I had to look it up), it means dying, declining in health or on its way out. To confirm their suspicions, they exposed an otherwise healthy angelfish to this virus-like agent and were able to elicit lesions similar to MHLLE. There are two problems with this study. First, MHLLE is generally not lethal (Michael, 2003), yet the fish from which they obtained this virus was dying. Second, the study merely exposed healthy fish to this virus, then later noted MHLLE, but did so without a control group. Therefore, their conclusions are more than a little suspect. They didn't, for example, keep a separate but similar group of fish under the same conditions as those in the test group, but without exposure to the virus, to ensure that some other condition(s) that the fish were exposed to, instead of the virus, didn't actually cause the MHLLE outbreak. A control group is an extremely important part of the scientific process, which they chose to omit for some reason that is not clear to me. Because of this, it could be that the virus is what killed the angelfish, but is not what initiated the MHLLE.
Parasitic:
There are some who believe a parasite in the genus Spironucleus causes this condition (Bassleer, 1996). Spironucleus is the correct name of this protozoan, although many still use the name Hexamita when referring to this condition in freshwater fish. So, it seems reasonable that a similarly appearing condition could have a similar causative agent. Additionally, Spironucleus has been found in some marine fish (Blasiola, 1990), although no indication is given that these same infected fish suffered from MHLLE. According to this theory, the parasite infects the intestine and interferes with its uptake of nutrients. This then is alleged to cause stress and the resulting tissue loss characteristic of MHLLE.
Also, in at least one other instance a marine tropical fish was confirmed to be infected with another parasite that causes digestive problems (Hoover et al, 1981). In this paper, a Naso tang (Naso lituratus) was found to be infested with Cryptosporidian parasites which caused the fish to be emaciated from regurgitating its food and passing food with its feces, which appeared to be completely undigested. This fish did not exhibit the characteristic lesions associated with MHLLE, although it did lose muscle tissue. The other thing to note is that Naso tangs are generally thought to not be susceptible to MHLLE (Hemdal, 2003). So it is difficult to say whether or not this fish would have been able to develop MHLLE lesions or if this emaciated appearance is simply another form of this ailment similar to the atypical appearance of Yellow tangs discussed previously.
Dinoflagellate:
I found one reference suggesting that a dinoflagellate in the genus Amyloodinium could be responsible for an outbreak of MHLLE that occurred at the Newport Aquarium in Kentucky (Fry, 2003). The basic premise is that fishes in a large display at that aquarium were developing MHLLE. In this same display, a sponge was found to harbor a dinoflagellate tentatively identified as belonging to the genus Amyloodinium. One of the aquarium's interns began an experiment to establish whether this dinoflagellate caused the MHLLE. Unfortunately, this experiment suffered a series of setbacks, which brings into question whether any results can be drawn from it. For one, most of the fish in the experiment were lost to a Marine Ich (Cryptocaryon irritans) outbreak. Also, one of the other fish died due to a heater malfunction and subsequent electrocution. So, while some of the fish experimentally exposed to the Amyloodinium did exhibit MHLLE, there was no way to determine whether any of the control fish were still alive to verify the dinoflagellate, and not some other variable, as the cause of the MHLLE. As such, there is no way to draw any conclusions from this study.
Bacterial:
One report I found theorized that a bacterial infection might be responsible for a MHLLE outbreak (Hemdal, 1989). In this particular instance, a fish was in quarantine and because of a bad test kit, was exposed to a rather high level of copper, 0.4 ppm, greater than a ten-fold overdose. The error was discovered and water changes and activated carbon were employed to reduce the copper concentration. But the fish was still doing poorly, so it was transferred to a different system. Approximately two months after its exposure to copper, the fish developed a bacterial infection. The fish was treated with antibiotics and recovered, but relapsed shortly thereafter, necessitating a second course of antibiotics. Again, the fish recovered, but soon developed the classic appearance of MHLLE. The characteristic lesions developed rather quickly. It was said that in two weeks the fish showed erosion comparable to other fish that had been suffering with this ailment for six months or more. But, in an unexpected turn of events, as quickly as the condition appeared, it also vanished without any subsequent treatments, or dietary or environmental changes.
Since the release of this report, its author has made a few additional commentaries. For one, he regrets not obtaining a histopathology report to back up his assertion that bacteria were responsible for the MHLLE lesions. Also, he wonders if the activated carbon, used to remove the overdose of copper medications from the quarantine tank, played some role in this outbreak. His current area of interest involves studying the irritant action of activated carbon dust and its possible effects in triggering MHLLE (Hemdal, pers. comm.).
But I am not sure that I am willing to dismiss Jay's original inference. For one, Fish Tuberculosis (Mycobacterium marinum,
http://reefkeeping.com...2003-07/.../index.htm) has been known to cause similar external lesions (Blasiola, 1990). Additionally, Noga briefly mentions in his book "Fish Disease: Diagnosis and Treatment" that he has documented cases of an acid-fast bacterial infection associated with MHLLE. He suggests that this may be evidence that the disease is a symptom of chronic stress in the afflicted fish, which leads me right into the next possible cause.
Chronic Stress and Autoimmune Disease:
This is probably one of this most interesting and novel ideas offered with regard to the causes of MHLLE. The basic premise is that fish held under certain conditions can be subjected to chronic stress and that due to this chronic stress, their immune system does not function properly (Bartelme, 2003a, b, c). This malfunction causes the body's own immune system to seek out and destroy healthy cells that it should otherwise be protecting. The author suggests a variety of ways this might occur, and I encourage all to read his works for further information. It simply would not be fair to try to sum up in a paragraph or two Mr. Bartelme's thoughts on this topic from his entire three part series of articles, so please follow up with my references (Bartelme, 2003a, b, c) below to read the complete and thorough explanation he offers.
What I found most interesting about this theory is that it ties together most all of the other theories of MHLLE's causes (Note: there are at least a dozen other theorized causes. Just about anything and everything has been blamed at one time for causing this affliction.), groups them under the general category of stress, or as an opportunistic infection that thrives under stressful conditions, and then addresses what to do about this "disease complex." The practical application of these articles is in the recommendations Terry gives for combating this ailment. The first part of the treatment would be to eliminate or reduce any and all stress. This is broken down into four broad categories: extreme changes in the physical environment, animal interactions (such as predation, aggression and competition), poor water quality (low pH, high nitrate, heavy metals or dissolved organics) and human interference (such as overcrowding). The second step is to improve the diet as well as to add vitamin supplements and highly unsaturated fatty acids (HUFA's) to the fishes' food. Third, improve water quality via water changes and protein skimming while also limiting the use of activated carbon just in case it plays a role. And finally, he recommends enhancing the fishes' immune function by adding beta glucan and garlic extract to their food as immunostimulants.
POTENTIAL CURES
Miracle Mud:
Some people promote this fishkeeping methodology as an alleged cure of MHLLE (Hildreth and Hildreth & Paletta webpages). As such, it is worth reviewing the theory behind this allegation and comparing its reasoning against the theorized causes of MHLLE to see if there is any correlation. Unfortunately, the online articles don't have much to say about why or exactly how the system works. They merely state that fish held in EcoSystem filtered aquariums don't contract MHLLE, and fish afflicted with the syndrome get better when placed in an EcoSystem filtered tank. While their testimonials are interesting, it is hard to draw much information from them other than that we should all run out and buy EcoSystem's Miracle Mud!
(Disclaimer: The author does use Miracle Mud in his home reef display, but does not work for this company or actively promote this product. Additionally, the author also utilizes a DSB, protein skimming and low stocking levels, as well as regular large water changes, as part of his overall aquarium husbandry.)
Regranex (Becaplermin):
Joe Yaiullo of the Atlantis Aquarium was kind enough to share some information he received on treating MHLLE. Some individuals at the National Aquarium in Baltimore did small-scale testing of a drug commonly used to treat non-healing foot ulcers in human diabetes patients. The drug goes by the trade name Regranex or by its active ingredient, becaplermin. The aquarium staff was having a problem with an Atlantic Ocean surgeonfish (Acanthurus bahianus) that developed MHLLE. They did the standard things: scraping to determine if some pathogen was the cause, changing from their own homemade salt mix to a high-quality commercial blend, providing better full-spectrum lighting on a 12-hour photoperiod and reviewing and improving the diet, all to no avail. After all these changes, the most they had accomplished was to simply stop the disease's progression, with only a very slight improvement in appearance.
It was at this point that they began the drug treatment. The Regranex was applied topically twice per week for four months. By fourteen weeks, the treated area was almost completely healed. The most interesting part of this little experiment was the control. They applied the drug to only one side of the fish and that was the only side that healed.
The downside to this treatment is two-fold. For one, it does not address this ailment's underlying cause(s); it treats only the signs. Second, it is expensive and unavailable to most. At approximately $500 per tube, it would be cost prohibitive to most aquarists. The only people likely to afford this treatment are those aquarists able to justify spending $100 per polyp on Acanthastrea, Dendrophyllia or whatever is the new flavor of the month.
Conclusions:
After all this, I guess I should go out on a limb and give my opinion as to the cause of this syndrome. Well, I am going to go a bit farther than that. I am going to say conclusively, once and for all, what causes this condition. Are you ready? Here goes… captivity. Yes, captivity causes MHLLE. I say that jokingly, but there is also some truth in this statement. As I said previously, MHLLE has not been seen on wild fish on the reefs (Blasiola, 1990). We therefore deduce that it is obviously something we, collectively as hobbyists, are doing or not providing for our aquatic pets that causes this ailment. What exactly that is will require further scientific experimentation to definitively prove. Until then, I agree with the broad recommendations of Terry Bartelme: reduce stress, improve nutritional regime, add vitamins and HUFA supplements to the diet, enhance water quality and also try beta glucan and garlic. Those same things have almost always worked for me when I have had an occurrence of MHLLE in the fish I care for, and hopefully they will work for you.
If you have any questions about this article, please visit my author forum on Reef Central.
References:
Bartelme, Terry. 2003a. "Hypothesis of Head and Lateral Line Erosion in Fish: HLLE, Stress and Immune Function, Part One" Freshwater and Marine Aquarium Magazine, September 2003, pages 100-104.
Bartelme, Terry. 2003b. "Hypothesis of Head and Lateral Line Erosion in Fish: What Really Causes HLLE?, Part Two" Freshwater and Marine Aquarium Magazine, September 2003, pages 88-92.
Bartelme, Terry. 2003c. "Hypothesis of Head and Lateral Line Erosion in Fish: The Role of Nutrition in Enhancing Immune Function, Part Three" Freshwater and Marine Aquarium Magazine, September 2003, pages 84-85.
Bassleer, Gerald. 1996. Diseases in Marine Aquarium Fish. Bassleer Biofish, Westmeerbeek Belgium, pages 47-49.
Blasiola, George. 1990. "A Review of Hole in the Head Disease of Fish" Freshwater and Marine Aquarium Magazine, May 1990, pages 34, 36, 38, 42, & 168.
Borneman, Eric. 2003. "Mything the Point: Part Two" Reefkeeping Online Magazine, December 2003.
Collins, Steve. 1995. "Dietary Control of HLLE in Blue Tangs" SeaScope, Volume 12, Summer 1995, page 3.
Fenner, Robert. 1998. The Conscientious Marine Aquarist. Microcosm Ltd., Shelburne, VT, pages 160-161 & 308.
Frakes, Tom. 1988. "Report on Head and Lateral Line Erosion" SeaScope, Volume 5, Summer 1988, pages 1 & 3.
Frakes, Tom. 1993. "Nitrate Menace?" SeaScope Volume 10, Winter 1993, pages 1-2.
Fry, Michelle Ann. 2003. "Investigating the link between the dinoflagellate Amyloodinium sp.? and marine head and lateral line erosion (MHLLE) on Zebrasoma scopas (brown sailfin tangs)" Norse Scientist, Volume 1, Issue 1, April 2003.
Hemdal, Jay. 1989. "A Reported Case of Head and Lateral Line Erosion (HLLE), Potentially Caused by a Bacterial Infection in a Marine Angelfish, Pomacanthus semicirculatus" Drum & Croaker 22(3):2-3 1989.
Hemdal, Jay. 2003. "Head & Lateral Line Erosion: What we know about HLLE in aquarium fish" Aquarium Fish Magazine, April, 2003.
Hemdal, Jay. pers. comm.
Hildreth, Robert. "Observations of EcoSystem and HLLE"
Hildreth, Robert & Mike Paletta. "HLLE and EcoSystem"
Holmes-Farley, Randy. 2003. "Iodine in Marine Aquaria: Part I" Advanced Aquarist Online Magazine, March 2003.
Hoover, D. M., F. J. Hoerr, W. V. Carlton, E. J. Hinsman, and H. W. Ferguson. 1981. "Enteric cryptosporidioisis in a naso tang, Naso lituratus Bloch and Schneider" Journal of Fish Diseases, 1981, 4: 425-428.
Hovanec, Dr. Timothy. 1998. "Revisiting Activated Carbon" Aquarium Fish Magazine, June 1998.
Kessner, David. 1999. "Stray Voltage" Tropical Fish Hobbyist, April 1999, pages 142-148.
Kessner, David. "Stray Voltages: Explained!"
Michael, Scott. 2003. Saltwater Q&A: Hole-in-the-head disease is also head and lateral line erosion" Aquarium Fish Magazine, September 2003, pages 62-63.
Noga, Ed. 2000. Fish Disease: Diagnosis and Treatment. Iowa State University Press. Ames, Iowa. Pages 245-246 & 282.
Shimek, Dr. Ron. pers. comm.
Varner, Patricia W. & Donald H. Lewis. 1991. "Characterization of a Virus Associated with Head and Lateral Line Erosion Syndrome in Marine Angelfish" Journal of Aquatic Animal Health 3:198-205.
Yaiullo, Joe. pers. comm.
Related Reading:
Pro, Steven. 2003. "Mycobacterium marinum: The Fish Disease You Could Catch" Reefkeeping Online Magazine, July 2003.
here is a link to the actual article with pics of the illness ...
http://www.reefkeeping.com/issues/2005-06/sp/index.php