Hypothesis of Head and Lateral Line Erosion in Fish

Part - 3

Enhancing Immune Function with Nutrition

By: Terry D. Bartelme

Suppressed Immune Function and Nutrition

The immune system is debilitated by poor nutrition and cannot function to its full capacity without the proper nutrients. For this reason, fish with Head and Lateral Line Erosion will often respond positively to improvements in their diet.

Nutrition

Vitamins and highly unsaturated fatty acids (HUFA) are essential in the treatment of HLLE. Vitamin A, in particular, has been linked with HLLE as beneficial to healing. An important function of vitamin A is to maintain the integrity of the epithelial cells. Frozen broccoli and shredded carrots are a good source of vitamin A. B complex vitamins are helpful for treating stress in humans, but nothing conclusive has been reported relating to feeding fish vitamin B. Vitamin C has shown to increase resistance to bacterial infection and it is also important to tissue repair. Vitamin C is believed to help alleviate the effects of stress in fish. Vitamin E can increase the production of antibodies by the immune system. Vitamins C, A and E are known to enhance immune response in fish. Trace metals, in particular selenium, have proven to help with phagocytosis (the process by which white blood cells consume invaders). The same is true of vitamin E. Fatty acids increase the bactericidal activity produced by macrophages that fight infection (Blazer, 1991). Fatty acid enrichment is also helpful for enhancing stress resistance (Kraul et al., 1993: Ako et al., 1994).

In a study of salmonids in 1994 Waagbo concluded that vitamin E deficiency resulted in immunological malfunction and reduced disease resistance. There has been at least one study indicating that vitamin E reduces stress in mammals (Tengerdy, 1989). Fish fed animal protein appear to have better survivability than those fed vegetable protein (Neji et al., 1993). Spirulina and Euphausia Pacifica krill (plankton) are good sources of carotenoids that are important to fish coloration. Supplement the diet by soaking foods in vitamins and highly unsaturated fatty acids (HUFA). Avoid thawing foods in water because water-soluble vitamins will quickly leach from the food into the water. It is better to thaw frozen foods without water in refrigeration overnight. This will prevent important vitamins from leaching from the food. It is also a safe way to thaw the foods without encouraging the growth of bacteria on the food.

Again, knowledge is always our ally. We should always be familiar with an animal's natural diet before we purchase them. Try to immolate that natural diet as closely as possible. What does the fish eat and what is its eating style? Is the fish a grazer that eats almost continually or a predator that normally only eats a couple of times a week in the wild? Is the fish an herbivore, omnivore or carnivore? Provide a wide variety of appropriate foods for each fish. If it is a marine fish then provide it with foods that are marine in origin. Do not feed saltwater predators freshwater feeder fish.

Enhancing Immune Function

We can support healthy immune function by providing an excellent diet, immolating the natural habitat, with great water quality and reducing or eliminating potential sources of stress. Is there a more aggressive, proactive approach to enhancing immune function in fish? Actually, yes, there are some things that we can do that are most effective when used as a preventive measure.

The health benefits of garlic in our diet are well known. Studies indicate that garlic has properties that are helpful combating viral, bacterial, fungal and parasitic pathogens. Garlic also has some application for fish health management. It appears to be an appetite stimulant when added to foods and garlic has been established as helpful for controlling some types of internal parasites such as nematodes. In his study, Dr. Angelo Colorni found that garlic has some mild antibiotic action for fish (see reference at the end of this article). Many people use garlic as a treatment for combating external parasites such as Cryptocaryon irritans although the evidence for its effectiveness is anecdotal.

I personally believe that garlic is better used in prevention. It can be used to stimulate appetite, combat internal parasites and assist the animal's immune function in preventing potential disease. Garlic can be used occasionally (prior to a stressful event) by soaking the food with it. It can also be used on a daily basis for new arrivals. However, I would caution against feeding garlic on a continuous, daily basis because we do not know the long-term effects. Garlic is better used with a proactive rather than a reactive approach. Feed it to newly acquired specimens during the quarantine period and to fish that have recently been or are going to be exposed to a stressful event.

Beta glucan has proven in numerous scientific studies to be an immodulating agent that can enhance the major host defense mechanisms of the immune system. Beta glucan is a complex carbohydrate. It is safe to use with any drug or chemical and can work synergistically with antibiotics. It is known to enhance macrophage phagocytic function (the consumption of foreign invaders). As with garlic pretreatment with Beta glucan is essential.

Beta Glucan (a B-1, 3 polyglucose) and its effects on the survival of mice infected with E. coli bacteria are profound. "Survival data indicated that an approximate 97% survival in the glucan-treated group in contrast to an approximate 19% survival in the control group." In another study, pretreatment with glucan resulted in 80% survival compared to 80% mortality in control mice infected with Candida. Beta glucan has shown promise in trials against viral, fungal, parasitic and bacterial infection. At least one study used fish as the subjects of the trials.

Pretreatment with Beta glucan means that the host can activate and proliferate defense mechanisms at a faster rate than invading organisms. It can be used to avert infectious or neoplastic disease. Interestingly, it can apparently be used to stimulate host defense against fungal infections in invertebrates as well as viral and fungal infections in plants.

Beta glucan can be found (albeit may take some persistence) at some local health food stores. It is available from Source Naturals. I suggest using the 7.5mg capsules because they are pure B-1, 3 glucan. You can find out more on their website at www.sourcenaturals.com. There are many other product and information sources available on the Internet. Sprinkle some the food just prior to feeding. A little will probably go a long way. A dosage level has not been established, but Beta glucan is a food (complex carbohydrate) and not a drug or chemical. However, use some caution because too much in the way of carbohydrates is not healthy for fish. Feed it periodically to newly acquired specimens during the quarantine period. It should also be administered to fish that are obviously sick (i.e. HLLE). Beta glucan is especially helpful when used in conjunction with other therapies such as antibiotics.

Treating secondary infection

Head and Lateral Line Erosion make fish more susceptible to secondary infection by an assortment of potential pathogens. It is a good idea to examine scrapings from the lesions to look for any secondary invaders including parasites. When an active pathogen is identified the appropriate treatment or course of therapy should be implemented. Such treatments can be enhanced with the addition of Beta glucan to the diet.

Prognosis

Head and Lateral Line Erosion can cause secondary infections and osmoregulation difficulty. It may heal completely, or show no sign of remission at all. Sometimes simply moving the animal to another aquarium seems to give positive results. Moving a fish can potentially improve its environment, diet and stress level. Generally, the progression of symptoms is slow and so is recovery. It can take patience and persistence before seeing visible improvement. The response of fish treated with a variety of methods ranges from fully regaining their natural beauty to no apparent improvement at all. Oftentimes the progression of the disease is halted, but the scaring permanently remains.

Step by step

1. Improve the diet.

2. Add vitamins, Fatty acid and other food supplements to the diet.

3. Improve water quality with water changes, a quality protein skimmer and the limited use of chemical filtration pads and/or activated carbon to remove impurities.

4. Seek out and remove possible sources of stress.

5. Enhance immune function with Beta glucan and/or garlic.

6. Limit the use of activated carbon.

7. Identify and treat secondary invaders.

For further study:

"Chemical Regulation of Immunity in Veterinary Medicine" 1984, pages 443-456, The Role of Glucan in the Prevention and Modification of Microparasitic Diseases by N.R. Di Luzio, PH. D. and David L. Williams, B.S.

Histopathology of sea bass (Dicentrarchus labrax) experimentally infected with Mycobacterium marinum and treated with streptomycin and garlic (Allium sativum) extract. By Colorni A., Avtalion, R., Knibb, W., Berger, E., Colorni, B. and Timan, B. (1998) Aquaculture 160: 1-17.

Hypothesis of Head and Lateral Line Erosion in Fish

Part - 2

What Really Causes HLLE?

By: Terry D. Bartelme

Hypothesis

I believe Head and Lateral Line Erosion is a disease complex and symptomatic of an immune system that is not functioning properly. HLLE may be an autoimmune disease in fish. This could be why HLLE is only seen in captive fish. All of the other so-called causes for HLLE contribute to the stress that causes the immune system to function improperly in the first place, or they are merely secondary infections. If true, this would enlighten us as to why so many different explanations have been given for what causes HLLE. In an immuno-compromised state opportunistic bacterium, virus, etc., can easily become pathogenic.

In human autoimmune disease (we will refer to autoimmune disease as AD), it is common for people to suffer from more that one related disease at a time. It is also possible for multiple aspects of the immune system to be malfunctioning simultaneously. If HLLE is actually caused by an improperly functioning immune system wouldn't the symptoms be more likely to be systemic rather than localized? HLLE lesions are often symmetrical and they usually appear simultaneously on both sides of the fish. The fact that these lesions also are not limited to the lateral line itself indicates a systemic rather than localized infection or condition. This further implicates improper immune response as the cause.

Chemicals treatments for fish disease such as kanamycin, malachite green, tetracycline, formaldehyde and heavy metals inhibit proper immune function. Copper certainly has been established as immunosuppressive. Should it be any surprise that some of the more copper-sensitive species of fish are also some of the most susceptible to HLLE? Is it a coincidence that tangs which are reported to produce less mucus (less protection from pathogens) than other families of fish are also frequently the victims of Head and Lateral Line Erosion?

Could Head and Lateral Line Erosion actually be an autoimmune disease brought about by chronic stress? We have not been able to identify a pathogen that systematically kills the cells in the lateral line system. In autoimmune disease, the body's immune system destroys cells that it should be protecting. Could the fish's own immune system be killing the cells in the lateral line system? I believe that anything that creates undue stress contributes to HLLE.

How Autoimmune Disease Works

There are several ways in which the immune system may function incorrectly causing damage to self-tissues. T cells are immune system cells that coordinate the immune response and help to destroy infected cells. T cells have what is called a T-cell receptor. This receptor combines with major histocompatibility complex (MHC) molecules that help the T cells recognize invading foreign materials (antigens). When T cells and MHC interact they can secrete cytokines and chemokines. Chemokines are cytokine molecules that attract destructive immune system cells such as macrophages, neutrophils and T cells. The overproduction of chemokines in the joints of humans causes rheumatoid arthritis. Is it possible that an overproduction of a protein such as this could cause autoimmune disease in fish?

Macrophages are white blood cells that play a vital role in the body's immune function. When macrophages (means big eater) and neutrophils locate foreign antigens (invaders) they surround or consume these organisms (this process is called phagocytes). These immune system cells then produce toxic molecules such as reactive oxygen intermediate molecules (ROIM) that destroy invading antigens. If ROIM are overproduced they will destroy body tissues surrounding the macrophages and neutrophils along with foreign antigens.

Another agent of the immune system is B cells. In some types of autoimmune disease B cells produce antibodies against self-tissue. These antibodies or auto-antibodies destroy body tissue and interfere with normal cell function. One condition that this causes in humans is a skin disease called pemphigus vulgaristhat produces skin blisters. Could something similar to this occur in fish that causes the loss of the epidermis (skin) in the lateral line region?

When antibodies accumulate in the bloodstream they form a network called an immune complex. A large immune complex can block the blood flow in a small blood vessel that would otherwise nourish tissues. This can cause tissue loss. Another possible explanation for the loss of skin, scale and tissue in HLLE could be Ischemia. Ischemia is a condition that causes localized tissue anemia due to the obstruction of the influx of arterial blood. This leads to hypoxia of body tissue and the death of cells.

We already know that stress in fish can lead to "Frayed Fin Syndrome." This is a loss of tissue between fin rays and is associated with stress and dietary deficiency. One such stressor that is already known to cause anemia in fish is the presence of heavy metals in the water such as copper. Could this same syndrome and consequent tissue loss play a part in HLLE?

How is AD Diagnosed?

Autoimmune disease is difficult to diagnose in humans, especially early in the course of the disease. Diagnosis is based on a physical examination, results of laboratory tests and an individual's symptoms. Laboratory tests are often inadequate or non-conclusive. Needless to say confirming autoimmune disease in fish is something beyond the capabilities of the average aquarist. We cannot ask how the fish feels or what other symptoms that is has, but we can observe them for signs of lethargy, lack of appetite, behavioral changes, etc. In the case of HLLE most fish continue to behave and act normally, at least until the condition has become quite advanced. Even at that point, any changes observed may be the result of secondary infections rather than caused directly by HLLE. That leaves us with just a physical examination or observation of the fish for the obvious signs of HLLE such as eroded tissue and loss of pigmentation along the lateral line sensory system. At this point, we must speculate, use deductive reasoning and hypothesize as to the cause of HLLE.

Treatments

Studies investigating autoimmune diseases in humans are focusing on: 1) the immune system during the progression of an autoimmune disease; 2) the role of infectious agents in autoimmune diseases; 3) studies of animal models of autoimmune diseases; 4) The influence of genetics on autoimmune disease progression and expression; and 5) the effects of therapeutic intervention on the immune system in an autoimmune disease.

The treatment of Head and Lateral Line Erosion is purely empirical. We must rely on eliminating any possible causes. There are medications or therapies that that are used to slow or suppress the immune system response in humans. These immunosuppressive medications include: cyclosporin, methotrexte, cyclophosphamide, azathioprine and corticosteroids. Corticosteroids are released by the body's own immune system in response to stress. These drugs or therapies also suppress the ability of the immune system to fight infection and have other potentially serious side effects making them difficult to use at best. In practical terms, we must rely on eliminating any or all of the purported causes for HLLE. In the process we will enhance the diet, reduce stress and improve the environment of the animal, thereby supporting healthy immune function.

Stress-Nutrition-Immune Function

What can we do to treat HLLE if it is the result of autoimmune disease or suppressed immune function? Treating autoimmune disease in humans is challenging and this is probably true to a greater degree for fish. The link between stress, nutrition and immune function in humans and other animals is well established. The most practical therapies for treating such diseases in fish include reducing stress, improving nutrition and perhaps stimulating or enhancing the animal's immune system. The goal of this effort is to support the animal's own ability to heal itself.

Stress

As stated in the first article in this series, "HLLE, Stress and Immune Function", stress suppresses immune function and can cause it to malfunction in other ways. Phagocytosis is the action of white blood cells (macrophages) when they consume foreign materials in the body. Once the macrophage has surrounded the antigen or invader lysosomes fuse with the foreign antigen and release digestive enzymes. Cortisol hormone that is released as part of the stress response interferes with this process. Cortisol also chemically changes the membrane of lysosomal preventing them from attaching to foreign antigens. Some evidence suggests that vitamin C can prevent this chemical change allowing the lysosomes to fuse with foreign antigens normally. The enzymes can then digest the bacteria or other invading pathogen. Stress also greatly inhibits mucus production limiting the protection that it would normally provide.

Stress Reduction

Before we can reduce or eliminate stress in fish we must first identify any potential sources. Stressors can be loosely placed into four categories. These four categories are: extreme changes in the physical environment, animal interactions, water pollution and human interference. An example of the first category would be large, sudden changes in temperature, or salinity. Animal interactions include predation and competition for space or food. Water pollution includes organic chemicals, heavy metals, nitrogenous waste and low pH. Human interference would include handling, crowding, transport and netting.

Understanding and identifying any sources of stress that your fish may be exposed to will go a long way in helping you prevent problematic circumstances. Stability in the environment is especially imperative to reef fish. Even those changes that improve the water quality should be made slowly.

It is of vital importance that only fish that are compatible be housed in the same aquarium. Study and make yourself familiar with the animal's natural environment, diet and compatibility with tank-mates prior to purchase.

Fish are more intimate and dependant on their environment than terrestrial animals. This makes water quality of paramount importance to their health and well-being. Keep a batch of well-aged and aerated water ready at all times for an emergency water change. Water that has not been aged and aerated prior to use is not chemically stable and it will irritate delicate gill tissues. Test your water parameters regularly to insure that they stay within the optimum range for your animals. A parameter that is tolerated but not optimal places stress upon the animals.

We are responsible for a large portion of the stress imposed upon our aquatic friends in the form of human interference. Many fish (especially wild-caught) suffer from intense, acute stress in the form of handling, transport and netting before they ever reach a retail outlet. Then the abuse (albeit unintentional) can continue at the local fish store and even after arriving into your care. Overcrowding is more than common in home aquariums and netting is a standard practice. Unfortunately overcrowding is detrimental to the health of all the animals that share the aquarium and netting causes more injuries than any other practice.

Knowledge is our best defense against all of these potential stressors. This can help prevent, or reduce the frequency and severity of episodes that cause stress in fish. Read several good books and magazines that can be used later as references.

The third and final installment in this series will continue in the next issue of this magazine. It will include sections on the relationship between nutrition and the immune system, how we can enhance immune function, the treatment of diseases secondary to HLLE and the prognosis for recovery.

Hypothesis of Head and Lateral Line Erosion in Fish

Part - 1

HLLE, Stress and Immune Function

By: Terry D. Bartelme

Controversy

Few diseases or conditions in captive fish inspire as much speculation, controversy, opinion and conversation as Head and Lateral Line Erosion (HLLE). Although the primary etiology of HLLE has not been established, it seems like everyone has a different idea of what causes this syndrome. There is little in the way of conclusive scientific evidence about what actually causes HLLE. However, conflicting anecdotal evidence as to the cause of this condition is plentiful. The disease is not particularly significant to commercial fish enterprise so it does not foster a great deal of scientific research. This places at least a portion of the burden of finding viable treatments and/or a cure to hobbyists and those in the tropical fish industry. Some say HLLE is caused by stray electrical voltage in the aquarium, others suggest that the condition is brought on by dietary deficiency. Pathogens including fungal, bacterial, viral and parasitic have been implicated as causing HLLE. Toxins or heavy metals in the water are other reported causes as well as poor water quality in general. Poor water quality would include a high dissolved organics level, suspended solids, high nitrate level and other impurities. Carbon that is used to remove impurities from the water has also been suggested as suspect.

What is Head and Lateral Line Erosion?

You may be asking yourself; just what is Head and Lateral Line Erosion? This syndrome could be described as a disease or condition that causes skin, scale and tissue loss in the head region and/or along the lateral line sensory system or flanks of fish. The lesions first appear as pinpoint foci that grow in size and numbers. These lesions are non-hemorrhagic ulcers that are devoid of pigmentation and a normal epidermis.

What is the Lateral Line Sensory System?

What is the Head and Lateral Line Sensory System? The lateral line system consists of a row of pores that runs along the flank of fish. Shorter rows of pores can be found in the head region and other areas. The pores contain sensory cells and hair-like projections. Together the subcutaneous pits, sensory cells and hair-like projections make up the lateral line system.

What is the Function of the Lateral Line Sensory System?

The lateral line system gives fish the ability to sense movement and water flow. This helps them to synchronize with their shoal (school of fish), feel the proximity of objects in the water, perceive movement, and orient to the direction of the water flow. It also helps fish with hearing and feeding.

What Happens to Fish with HLLE?

Effected fish generally continue to eat and behave normally, unless the condition becomes greatly advanced. The syndrome itself is usually not fatal, but it is unattractive and makes it difficult for retailers to sell these fish. The loss of tissue and the normal protective barrier along the Head and Lateral Line System causes several complications. It makes maintaining hydro mineral balance between the internal fluids of fish and the surrounding ambient water more difficult. Performing osmoregulation becomes more costly energy-wise. Fish are also more susceptible to opportunistic pathogens, especially those that are bacterial, or viral in nature.

Some Reported Causes for HLLE

A 1991 report written in The Journal of Aquatic Animal Health by P.W. Warner and D.H. Lewis, concludes that a virus is the cause of HLLE (3:198-205). Steve Collins, curator of the Indianapolis Zoo-Aquarium, wrote and article in summer 1995 issue of SeaScope about controlling HLLE with dietary changes. No obvious pathogens were found in the fish studied. Supplementing the diet with vitamin C did not get positive results. However, vitamin A in the form of broccoli and carrots appeared to improve or cure the condition. Head and lateral line erosion has also been associated with an acid-fast bacterial infection (Edward Noga, unpublished data.). Bacteria that cause fish tuberculosis fall into this category.

Like I said previously, everyone seems to have a different idea for what may cause HLLE. I see one common theme that ties all of these various suspected causes together: stress. The importance of stress as the underlying theme cannot be overemphasized.

Stress and Immune Response

Chronic stress can come in many forms. These would include but are not limited to: low pH, toxins in the water, inappropriate water temperature, chemicals, heavy metals, crowding, low dissolved oxygen level, a high dissolved organics level, the presence of pathogens at an intolerable density, a photo period that is either too long or too short and suspended solids. Acute stressors would include photo-shock, aggression from tank-mates, electrical shock, handling, transport and netting. An argument can be made for including an inadequate diet as a stressor or stress factor.

Hormones are released into the blood in response to stressors. Chronic production of cortisol (a stress hormone) does inhibit immune function. These "stress hormones" are adaptive under natural circumstances. However, in captivity, fish are subjected to stressors much more frequently than what would be considered natural circumstances. Under these conditions, the stress response and subsequent release of stress hormones becomes maladaptive in nature. This reduces immune function efficiency and causes other complications. Thermal stress alone can chemically change and reduce mucus production by fifty-percent. This is significant since the mucus layer is the first line of defense against potential pathogens.

Chronic stress causes fish to become more susceptible to infectious diseases caused by bacterial, fungal, parasitic and viral pathogens. I believe stress can also open the way for diseases that are non-infectious in nature such as autoimmune disease.

What is Autoimmune Disease?

A healthy immune system normally defends the body against invading pathogens and disease. Autoimmune disease (we will refer to this as "AD") is when the immune system attacks self, targeting organs, cells and tissues of its own body.

What Causes AD and HLLE?

Viral infections have been known to trigger the onset of autoimmune disease in humans. It is possible that this is also true in fish. Could other pathogens such as bacteria, fungus and parasites also trigger the onset of AD and consequently HLLE in fish? Some other influences that affect the course of autoimmune disease include aging, hormones and stress. Stress does cause the release of "stress hormones" in fish and the fact that stress influences hormone production may serve to exacerbate the situation. When stress is chronic it negatively impacts immune function. Chronic stress in fish can lead to a generalized melanosis and the loss of tissue between fin rays. Could it also cause tissue loss in the lateral line sensory system?

What Fish are Susceptible?

Neither HLLE nor AD appears to be contagious. Genetics plays an established role in human autoimmune disease. Certain autoimmune diseases occur frequently among family members. Taking this a bit further, could we surmise that certain families or species of fish would also be more susceptible to autoimmune disease? HLLE is frequently seen in tangs (Acanthuridae) and angels (Pomacanthidae). Groupers, lionfish, damsels and clownfish and other species suffer from the condition less often. There appears to be a strong correlation between the incidence of this syndrome and the species of fish involved. Larger, older (long-term aquarium inhabitants) fish appear to be more frequently stricken with HLLE. This may be due to the fact that they have been fed an inadequate diet long enough to exhibit the clinical signs of HLLE. Perhaps the immune systems of these older fish simply do not function as well as those of fish that have been in captivity a shorter period of time.

Stress and Autoimmune Disease

It is a well-documented fact that stress suppresses immune function. Since stress does inhibit some aspects of immune function it is not a stretch to assume that it may cause the immune system to malfunction in other ways. This may be what happens in Head and Lateral Line Erosion. While stress may inhibit some aspects of immune function it may also over-stimulate still other aspects of immune system function. Could stress also cause the overproduction of reactive oxygen intermediate molecules that are made by macrophages and neutrophils in the immune system? This would lead to the destruction of normal tissue surrounding these immune system components. Could stress in fish cause T cells in the immune system to overproduce chemokines and cytokine molecules that attract destructive macrophages (white blood cells)? Is it possible that stress can cause B cells to mistakenly make antibodies against the body's own tissues? All of these suppositions are apparently true in human autoimmune disease.

The second installment in this three-part series will include my hypothesis of what causes Head and Lateral Line Erosion. I will also cover autoimmune disease, treatment and how to eliminate or reduce stress in fish. Part three will include sections on how immune function and nutrition is related, how we can enhance immune function, the treatment of diseases secondary to HLLE and the prognosis for recovery.