Q: What is Hole-in-the-head/head and lateral line erosion?

A: Hole-in-the-head (HITH) and Head and Lateral Line Erosion (HLLE) are two terms for the same problem--skin de-pigmentation and the formation of holes, ranging from pin-hole sized to large craters, in the head and along the lateral line of fish. A small 'hole' in the head doesn't always mean HLLE though--the fish most commonly affected have small pores in their face area naturally--if you aren't sure, compare the size and location of the 'hole' to other fish. If it's the same on all fish or on both sides of the fish's head, it's probably nothing to worry about, but even this can be difficult to judge since the holes often appear in the same locations on different affected fish. As such, a good familiarity with your fish and/or a good picture of a healthy fish can be valuable for diagnosis. Freshwater HLLE is most commonly found in the larger South American cichlids, particularly discus, oscars, and Geophagus species.

Q: Is HLLE dangerous to my fish?

A: HLLE is a chronic disease, meaning that it's presence is not fatal in the short term. However, affected fish can eventually become anorexic and lethargic, and the open wounds can easily become the source of secondary bacterial and fungal infections.

(1) E. Noga speculates that these secondary infections may be the ultimate cause of death in fish with HLLE. Although it is not normally immediately fatal, HLLE should be treated as soon as possible, both for the fish's health and to prevent permenant disfigurement of your pet fish. (Small holes at least can heal fairly quickly, but very large holes may take months to heal or never heal completely at all.)

Q: What causes HLLE?

A: Nobody knows. There is not enough research to authoritatively say what causes HLLE, however, there are several theories:

HEXAMITA SPECIES: These flagellates can cause problems in tropical fish, but their association with HLLE is not conclusive. It is suggested that they may spread through the fish's system, causing damage directly (1), or interfere with absorption of nutrients, with the malnutrition of the fish being the actual cause of HLLE. (2) In favor of this theory is the presence of Hexamita in many fish with HLLE, and that treating with anti-hexamita medications is often effective against HLLE. However, cases of HLLE with no Hexamita present indicate that while Hexamita may be one cause of HLLE, it is apparently not the cause in all cases.

THE CALCIUM/PHOSPHORUS DEFICIENCY THEORY: HLLE may be the result of deficiencies in these minerals. This theory is supported by low levels of calcium/phosphorus in affected fish and reports of adding calcium/phosphorus supplements being beneficial to the recovery of fish with HLLE. It is suggested that the deficiency is caused by an infestation of Hexamita interfering with absorption of nutrients. (2) That most flake and pellet foods provide a great deal of both minerals, yet HLLE occurs in fish on such diets suggests that other factors are involved (listed in the other theories) that interfere with the absorption and/or utilization of these minerals.

VITAMIN C DEFICIENCY: It has been noted that adding vitamin C can aid in the recovery of fish suffering from HLLE, leading to speculation that lack of vitamin C is the original cause of the disease. While vitamin C is very important to the immune system and the healing of wounds, fish fed vitamin C deficient diets show no signs of HLLE but do show deformities not found
in HLLE affected fish. (3) Because it is such an important vitamin in the recovery from illness and wounds, adding a vitamin C supplement to the food of fish being treated for HLLE is recommended. Fish fed large doses of vitamin C have still developed HLLE (5), so the mere presence of C in the diet doesn't appear to offer protection from HLLE, although it still has other benefits.

VITAMIN D DEFICIENCY: Insufficient levels of vitamin D have also been proposed as the cause of HLLE. This theory has a certain 'neatness' to it, as vitamin D has been identified as the precursor to a hormone important in maintaining levels of calcium and phosphorus in the blood and bones (3) which explains low levels of both minerals in affected fish. In support of this theory are reports that adding D to the diet of fish with HLLE is beneficial (2), as well as observations that exposure to ultraviolet light (which is used to manufacture D in the fish's skin) may be beneficial. (4) Since little vitamin D is found in most ingredients of fish foods, vitamin D should be added as a supplement in most commercial fish foods. (3) Like vitamin C, however, HLLE has NOT been produced in the laboratory as a result of feeding vitamin D deficient diets.

THE STRESS THEORY: HLLE has also often been associated with poor tank maintenance, and been suggested as a reaction to constant stress. (1) This might occur as a result of higher nutritional needs while under stress not being met, or by simply weakening the fish to the point where they are vulnerable to infections like Hexamita (or other unidentified pathogens.) My
personal experience supports the association with poor water conditions, although anecdotal evidence should always be treated with some skepticism.

THE CARBON THEORIES: There are several theories that the use of activated carbon in tanks may cause HLLE. 

One version of this theory is that the carbon could be causing nutritional deficiencies by adsorbing vitamins or trace minerals either directly from the water, or by adsorbing molecules that the needed nutrients could then bind to. This theory, however, has several problems: There aren't any vitamins in tap water to begin with, and minerals like calcium, phosphorus, and iron should be available in large quantities in most prepared fish foods. Additionally, it is reported that fish rely on food for nutrients, trace and otherwise, making the presence of nutrients in the water irrelevant (4) although fish have been shown to be able to extract various minerals from the water (calcium, iron, zinc, etc.)

A second carbon theory is that some types of carbon may release toxins which cause HLLE. Perhaps a more specific variant of this theory is that some poorly manufactured carbons might release chemicals that cause stress to the fish. (See THE STRESS THEORY.) Another theory is that loose particles of carbon dust in the water have some caustic affect, but there is no support for this that I have been able to find.

All carbon-related theories regarding the cause of HLLE suffer from one other significant shortcoming: HLLE can be found in tanks which have never had carbon of any sort used in them, yet is NOT found in many tanks using carbon. While it remains possible that carbon may be involved in some cases, there is no reason to believe it is a factor in most cases, if any. There is no sound evidence for a link, or even a logical specific theory--at best, the carbon-HLLE theories amount to a handful of individual cases where HLLE was seen in tanks using carbon, but appeared to improve after the carbon was removed. Since there is little to no information on what other steps where taken in the treatment of the HLLE, the association with carbon is rather suspect.

ASSORTED THEORIES: Electrical currents in the tank, a virus, and a few other factors have also been suggested as causes of HLLE. No data available on their likelihood as a cause.

Q: How do I treat HITH/HLLE?

A: Lacking a solid answer as to what causes it in the first place, I would recommend all of the following:

1. Keep the tank as clean as possible. The water should be clear and not smell, and the bottom should be regularly cleaned, with frequent water changes (and I do mean frequent--at least every few days or even daily.) If your tank is anything less than the ideal environment, it's time to get religion. Try to provide as clean and stress-free an environment as possible at all times, not just when your fish actually get sick. (Regardless of the role of water quality in HLLE, I would urge everyone to keep their tanks as clean as they can--there are many problems that are definitely caused by poor water quality and can be prevented simply by doing regular water changes.)

2. Treat for Hexamita. Given the frequent association of Hexamita with HLLE, this seems like a prudent step to take, and if nothing else, it can help with other infections possibly present. Indeed, many (most?) cases of HLLE seem to respond to Metronidazole. (Metronidazole is used in most hole-in-the-head medications or can be readily found in common anti-protazoan
medications like Paragon II.) Also suggested are giving magnesium sulfate (Epsom salts) orally, and raising the tank temperature to 95F (35 C) for seven days. (1) Many commercial products like Hex-a-mit contain Metronidazole, or it is available under the name "Flagyl" to pharmacists and veterinarians.

Thanks to Jeff (mitt@mitre.org) for contributing the following on medications for Hexamita:

"Metronidazole is the preferred medication. It is the same medication found in Hexamit. It is also found as one of the ingredients in Paragon II. Dr. Axelrods Mini Atlas recommends 100mg metronidazole per 10 gallons every other day for 3 treatments (and the dose can be safely doubled). Hexamit recommends 250mg per 10 gallons with the same time schedule. I found that the 100mg was not effective but the 250 was. Some recommend 3 consecutive treaments rather than every other day (have not tried it).

Metronidazole is a commonly available medication at any pharmacy or vet, so contact your vet (if you have one) and get a prescription--it will be a fraction of the price than buying it mail order or from the local aquarium shop. 250 mg Capsules or tablets work fine (Capsules--empty them; tablets--simply dissolve in warm water).

Metronidazole in food. The Axelrod mini atlas recommends 100mg of metronidazole mixed with 1 tablespoon of food. The food could be beefheart (then refrozen in small servings) or a paste of dry food and water (then frozen into small servings). 

Treatment should include both food (if they are eating) and in the water. I feed them the food for 7 days.

Paragon II is also effective and expensive. Follow the directions on the package--it recommends the "every other day for 3 treatments" method. I found that it disturbed the biological balance in the tank (even though it claims it won't) resulting in elevated ammonia levels and sluggishnish in the fish. It does work quite effectively against HLLE, but be careful with this medication- reduce feeding and check ammonia levels daily.

There are also dips to treat HLLE--never tried it but they are supposed to be very effective if you can get our fish out of the tank and into another container for a while. (I'd like to hear more in this area, too.)"

3. Add vitamin supplements to the food. Since calcium and potassium should already be well supplied by most dry foods, adding vitamin C and D is probably a higher priority. (And don't go overboard with it! Overdosing fish with vitamins isn't good for them either.)

Odds and ends: Giving the fish a tank that receives direct sunlight or has full spectrum/actinic lights for synthesis of vitamin D MAY help, though I haven't seen much on this. Carbon should be removed from filters if medication is being used so it does not adsorb the medication. Given the lack of support for the proposed carbon-HLLE link, I don't see any sound reason to stop
using carbon as a routine practice.
 
 

Sources:

1. "Fish Disease--Diagnosis and Treatment", Edward Noga, published by
Mosby-Year Book, Inc., 1996.

2. "Discus Health", Untergasser, TFH Publications, 1991.

3. "Nutrition and Feeding of Fish", Tom Lovell, published by Van
Nostrand Reinhold, 1989

4. Leo Morin (Seachem), personal communications. (10/96)

5. Nathanael Henderson, unpublished data.