Spironucleus

alias "Hex", HITH and HLLE

By: Fred Goodall & Dougall Stewart 

i.  Foreword
ii.   Abstract

1.  Introduction – Common Symptoms

2.  Erroneous identification

 

3.  Spironucleus
3.1     Where are flagellates found in discus

3.2     ‘Holes’, organ/systemic infection and jelly excreta

3.3     The transmission of Spironucleus.

 

4.  Treatments

4.1     Metronidazole

4.1.1  Safety rationale and the horror stories

4.1.2  Dosage

4.1.2.1     Dosage in water

4.1.2.2     Dosage in food

4.1.3  Additional notes on metronidazole

4.1.3.1     How the medication works

4.2     Secondary infections and stubborn cases

 

5.  Food and its role in ‘holes’ and other symptoms

5.1     Dietary vitamins, minerals and trace elements

5.1.1  Vitamins

5.1.2  ‘Vitamin, mineral and trace element’ – WARNING!

5.1.3  Red Wrigglers - Eisenia foetida

 

6.  Management and or avoidance of Spironucleus vortens ‘outbreaks’ – A holistic approach

 

7.  Other fun stuff – or ‘it’s a fact Jack’

 

8.  Conclusion

 

9.  Science and the fish hobbyist – a final word

 

10.  Acknowledgments

 

11.  References

 

12.  Endnotes:

i.  Foreword

The text that follows has been written as a ‘working document’ for those that are faced with a case of ‘Spironucleus’ or a gestalt of ‘Spiro-type’ symptoms.  The authors advise that it should not be considered in isolation, and that it is vital that the reader draws on a wealth of other high quality information. Only then, can the reader make an informed judgement on the symptoms experienced and follow an appropriate treatment regime that takes into account their specific localised parameters.

The use of ‘I’ in this document has occasionally been used for simplicity’s sake, and is indicative of a shared point of view unless otherwise indicated. 

ii.   Abstract

This article considers the correct identification of the pathogen said to be responsible for HITH, HLLE, Hex etc and considers the symptoms and treatments from a holistic point of view.  The identity of the organism involved is Spironucleus vortens and epizootic proportions of these flagellates results in an overworked immune system, severe dietary deficiency, jelly like excreta and a number of behavioural problems.  Attempted cures should avoid ‘misleading, over simplistic, single causation theories’ and focus on a regime of correct environmental parameters, healthy diet and appropriate medication.  Metronidazole is the current drug of choice and is comparatively safe to use in discus aquaria – dosages are suggested as guidance.  The role of diet in the occurrence of ‘holes’ and the recovery of this fish is also discussed – along with some popularly myths and misconceptions that are currently held.

1.  Introduction – Common Symptoms

The majority of us will have heard of, or in many cases, have had fish that have suffered from the following symptoms:

      a darkening in colours

      a tendency to ‘hang’ in corners,  or to remain in isolation from other fish, even at feeding

      a tendency to stare at food but without eating it, or if it does take a sample it immediately spits it out again

      the decline in food acceptance, is often accompanied or followed by lethargy, and a reduction in muscle tissue which gives the fish a ‘pinched’ appearance behind the head and the skin ‘texture’ may take on a roughened appearance

      white, jelly like excreta can often be seen trailing from the anal vent, on the floor of bare bottom aquaria, or sometimes white, stingy ‘rotted plant-like material’ is ‘adrift’ in the aquarium

      the wasted fish may develop a bloated stomach region

      skin lesions may start to appear, especially on the body and the head, in the region of the  lateralis system – these holes may eventually expand and connect to from considerable size ‘craters

Over the years there have been many names attributed with the above symptoms.  Some of these include: 

      Hole in the head disease - HITH

      Head and Lateral Line  Erosion - HLLE

      Hex

      Flagellate Infestation

      Holes disease

      Hexamitiasis

      Wasting Disease

      Spironucleus

      Malawi Bloat

      Dropsy

The list is almost as endless at the range of causative phenomena and cures that have been attributed to the above symptoms.  My aim in writing this paper is to introduce to the discus hobbyists some of the recent developments that have been made in the identification of the causative organism, for what I will refer to, from here on in, as ‘Spironucleus’; and also to consider some of the methods and implications for treating a Spironucleus infestation in Discus Symphysodon  species.

2.  Erroneous identification

Many species of marine and freshwater fish commonly host parasitic flagellates (see table 1 for some examples).  These flagellates tend to be found in the lumen of their digestive tract, systemically, and less frequently on the skin of their host.   In the past, where diplomonad flagellates involved, they were ascribed to the genera of: Hexamita, Octomitus and Spironucleus (Poynton, Sterud, 2002).  

Table 1

An example of several families of fish (and their common English names) that are affected by pathogenic diplomonads infestations. 

It is also suggested that the only genre involved is that of Spironucleus.

However, due to the limitations of light microscopy, the size and nature of the flagellates involved and the lack of high quality identification keys that used easily identifiable morphological differences - much of the earlier identifications appear to be erroneous. 

Evidence is mounting that suggests that all of the 15-20 species of diplomonads that have been found on fish, and described and stored in reference collections - need to be reconsidered.  This is exemplified by the fact that recent studies have neither found true Hexamita nor Octomitus species in/on ANY species of fish.  This statement is based on  work that involved the accurate description of the above genera and the employment of transmission electron microscopy (TEM) which allows the investigator to accurately identify internal ultrastructural features which can then be used as an aid to genera and species identification (see figures 1, 2, 3; also Poynton, Sterud, 2002 for full details). The cry for clarity is not new - it has been growing in vigour since Kulda & Lom’s work in the sixties and was catalysed by TEM work by Brugerolle and more recently by Poynton and Sterud; and Paull and Matthews. 

 3.  Spironucleus

In discus, the prime organism responsible for much of the woe described above has been identified as Spironucleus vortens (an organism that also affects other cichlids e.g. Angels, Pterophyllum scalare, P. Altum etc (Paull and Matthews, 2001).  S. vortens has an elongated body that is approximately 8 to 14 µm long & 3 to 6 µm wide.  It has 6 anterior and 2 posterior flagella and possesses 2 sigmoid shaped, elongated nuclei; TEM is required for accurate identification of the ultrastructural organelles (see figures 1-8).

Figures 4, 5, 6 Correctly identified SEM of Spironucleus vortens.  Extracted from head lesions on a discus.   Note shape of body and arrangement of the 8 flagella, each of which taper terminally culminating in a small bulb. (B) Note prominent lateral compound ridge (α) and peripheral ridge (β) extending the length of the body. (C) Posterior region of S. vortens. Note elaborate swirls of the peripheral ridge and papilla on the base of each terminal flagella (arrowed)   Source: Paull, G C; Matthews, R A, (2001), ‘Spironucleus vortens, a possible cause of hole-in-the-head disease in cichlids’, Diseases of Aquatic Organisms, 45: 3; 197-202 and reproduced with permission
Figures 7 & 8 Symphysodon discus. Photographs of a discus with moderate hole-in-the-head infection. (Left) Side view. Small regular-shaped holes around the eyes and mouth. (Right) Head-on view of the same fish. Note bilaterally symmetrical holes.|   Source: Paull, G C; Matthews, R A, (2001), ‘Spironucleus vortens, a possible cause of hole-in-the-head disease in cichlids’, Diseases of Aquatic Organisms, 45: 3; 197-202 and reproduced with permission

3.1     Where are flagellates found in discus

Paull and Matthews (2001) were able to isolate S. vortens from the intestine, kidney, liver, spleen, and head lesions of discus; and also from the intestine and head lesions of angelfish. In addition, studies by Somboon (2002) found S. vortens in the blood, stomach, intestine, spleen, gall bladder, and ovaries of angel fish.  Somboon also found S. vortens in apparently healthy fish.

Paull and Matthews (2001) note that S. vortens interacts with the gut wall of the discus, attaching itself to the intestinal mucosa. In addition, they suggest that there may well be some form of intracellular interaction within epithelial cells lining the intestine. If the flagellates reach epizootic proportions they suggest that it is via the invasion of the lamina propria (loose connective tissue/mucosa) that systemic entry, and infection of additional organs, especially the liver, may be achieved. Paull and Matthews (2001; and many others) suggest that it is at this point of dissemination that an infestation S. vortens becomes lethal. 

In simple terms, in ‘healthy discus’ S. vortens is commonly found in the flagellated stage in the lumen of the upper intestine, where it remains, controlled by the immune system of the fish.  In stressed discus, the immune system is placed under greater strain, and the organism, in theory, multiplies unchecked causing considerable localised damage. Once the damage is severe enough the intestinal lining is penetrated and the S. vortens enters the blood causing systemic and organ infections.  In regards to stress, I have stated elsewhere (Stewart, 2001) that stressors can include: low oxygen levels, high nitrite levels, comparatively high (or low) water temperatures, rough handling, mechanical injury, overcrowding, water of inappropriate hardness etc (see Francis-Floyd, 1997; Rottmann, Francis-Floyd, Durborow, 1992 for more information on stress and its effects and management).

3.2     ‘Holes’, organ/systemic infection and jelly excreta

As mentioned above, Paull & Matthews (2002) found S. vortens, to some degree, in all of the fish that they studied – including the controls.  In addition, S. vortens were isolated from the lateralis lesions of the fish studied, which supports Bassleer’s 1983 work.  It was suggested that the flagellates either caused the holes through ‘direct infection’ (least likely); or that, the ‘host tissue underneath the skin or indirectly by blocking the tiny blood vessels that supply the sensory system’ (most likely).  If one, takes into consideration the nutrient deficiencies that are said to occur during severe and systemic infections it is no wonder that the lateralis system begins to disintegrate.  Of the cases studied by Paull and Matthews (2001) where the external manifestations of S. vortens were severe, S. vortens had always progressed to the liver, spleen and kidney.   In the less severe cases the parasite had yet to progress to the aforementioned organs and ‘in these instances the infection appeared to be in a state of remission’.

In regards to the ‘jelly’ excreta found in aquaria, one often reads comments such as ‘it is only the stomach lining of the fish – and is perfectly harmless’.  This needs addressing. The stomach lining or for that matter, the whole of the epithelial cells of the digestive tract undergo constant replacement, day in day out.  For sufficient to be shed to be fully visible and of considerable dimensions, either the fish has been turned inside out, or there is a problem. At this point it should be noted that feeding meat-mixes based on gelatine can result in the discus passing ‘a sheet of membrane like whitish material’ and this should not be confused with what is being discussed.  Importantly, in discus the final protein uptake occurs in the intestine, not the stomach.  It is in the intestine that the ‘protein digesters’ of: trypsin, chymotrypsin and metalloproteases are found (Chong et al., 2002). Their location and the findings by Paull & Matthews (2001) is indicative that if, and this is a big if, the sheet of whitish material being passed is ‘lining’, it is intestinal lining ,and may well be the product of  protein digesters, and flagellate damage to the lumen and mucosa.  In addition, their evidence helps explain why ‘hole closure’ occurs post nutritional supplementation.

3.3     The transmission of Spironucleus.

Whilst there is little known at the moment on the complete lifecycle and transmission of Spironucleus vortens it is reasonable to expect that it is very similar to other Spironucleus species. One way that Spironucleus may be transmitted is via contaminated faecal material.  That is the adult trophozoite undergoes longitudinal binary fission in the intestine, the trophozoites are then passed in faeces.  It may also be possible that cysts are produced and evacuated in a similar manner, though this is yet to be demonstrated; however other diplomonads have reproduced in this manner under laboratory conditions (Poynton, Sterud, 2002).  In this way, discus ‘pecking’ at the base of the aquarium are likely to ingest S. vortens.  Post ingestion excystment would occur, if cysts are involved; and/or the newly ingested trophozoites would start to colonise the mucosal surface and mucus layer of the small intestinal lumen – and so the cycle continues.

4.  Treatments

Today the most common treatments propounded are ‘vitamins and minerals - that is all you need this will cure everything’, ‘heat treatment - crank the temps and kill all bugs’, ‘metronidazole the fish - chuck it in the tank and in 3 days your fish will be breeding babies by the millions and be laughing and smiling’, or ‘it’s a wire, it’s a wire, your fish has eaten halfway through the heater cable and is being blasted by stray voltage’, and finally I suspect that there are those that think S. vortens is in fact a killer bug devised by some discus super power (which happens to be the only person with a cure) and is simply one step in global discus domination.

Therefore I will try to treat this section fairly and rationally in the hope that people will see that 1 factor in isolation – does not a cure make and that the problem often needs a more holistic approach. 

4.1     Metronidazole

4.1.1  Safety rationale and the horror stories

When one recommends the use of metronidazole in the treatment of fish on many of the ‘popular’ forums - there is often a cry of ‘be warned it is mutagenic and carcinogenic and your fish will die a thousands deaths’.  Whilst I am firm believer in ‘warnings’ on the overuse of drugs, I do feel that at times their expedient use may well be appropriate and safe. 

In respect to the mutagenic and carcinogenic warnings, often those postings refer to information extracted from ‘clinical statistical results’ and quote the results as statistical certainties for ‘normal’ dosing levels of the drug involved.  The trouble with this is if you look in a Physician’s Desk Reference (PDR), what tends to catch the eye is the glaring warnings on ‘chronic, high dose’, and it often takes 20 minutes or more of detailed reading to realise that what is in fact being referred to is a dose that is taken orally at 5X the recommended dose, for 30 days or you IV the drug for 3 days at 3X the recommended dose.  It is this information that is the foundation of the ‘statistical’ results on mutagenic activity, and often takes the form of an ‘assay’ – i.e. not in a mammal, (in chemicals, as opposed to live animals).

Taking the above into account, current ‘recommended’ dosage, and the half life of metronidazole I consider the risk that our discus are going to develop three heads or become riddled with cancer a week later, reasonably minimal.

4.1.2  Dosage

4.1.2.1     Dosage in water

This is the option for non-eating discus.  Firstly it should be remembered that metronidazole in water is assumed to enter the fish like most antibiotics, across the gill membranes and directly into the blood stream - and many of the ‘older’ doses were calculated on just that.  However, it is our opinion that the delivered dose is considerably lower than the ‘older hobby science’ portrays.  The evidence to support this is that the medical literature states that metronidazole in IV solutions has a 6 - 8 hr half life, it is temperature sensitive either side of its optimum, and at temperatures under ~ 28^oC it can precipitate out of solution. Furthermore, it is light sensitive whilst in solution, and will begin breaking down on exposure.  Now none of us IV our discus, but we do expose the metronidazole to an illuminated aquatic environment, high temps, and for some considerable period of time.  Therefore, there is no way that a professional ‘standard’ dose can be calculated if the metro is going to be added to the water in this manner – there are simply to many individual random variables to take into consideration.  At best, one can come up with an ‘informed’ suggested dosage – that may need adapting according to individual parameters and needs.

Therefore the dosages we list below are based on our personal experience, informed reading and the results of application.

4.1.2.1.1     Dose 1  - The average case of ‘white poos’.

This is where the Spironucleus has been spotted early i.e. the discus has demonstrated a change in behaviour - indicative of an S. vortens infestation; white poo may have been seen on 1 or 2 occasions (at the most – it is believed that by the time this jelly excreta has developed the population of S. vortens is already at considerable levels); and preferably S. vortens has been grossly identified using a compound light microscope.

      A 30% water change prior to dosing

      A temperature of 30^oC

      250mg of metronidazole / 10gallons of aquarium water.

      After 8 hours 25% water change is performed followed by another 250mg of metronidazole / 10gallons of aquarium water.

      This cycle is repeated for three days 

      Note: mortar and pestle the tablet/s, add a drop of warm aquarium water and mix to thick paste; keep adding drops until you have a thinner paste; – you can then add more water, mix thoroughly and spread over the aquarium.

4.1.2.1.2     Dose 2 – Severe case or reoccurrence

This is where the Spironucleus has not been spotted early i.e. the discus has demonstrated a behavioural change indicative; white poo may have been seen on several occasions and the fish may in fact no longer be passing visible excreta; or this is a repetition of a previous case of S. vortens; again has been grossly identified using a compound light microscope.

      A 30% water change prior to dosing

      A temperature of 30^oC

      400mg of metronidazole / 10gallons of aquarium water.

      After 8 hours 25% water change is performed followed by another 400mg of metronidazole / 10gallons of aquarium water.

      This cycle is repeated for three days

      The dose of metronidazole can be increased further than this, I have a personal preference of 500mg but greater care must be taken and careful observations are a must.

Remember other factors play a role as to how much actually gets to where it is needed and as to how effective the dose will be, e.g. age, metabolism, temps, other medications, water, degree of infestation, immune system efficiency etc.

Please remember the doses are not meant to be a ‘be all and end all’ of cures - other factors must be taken into consideration.

4.1.2.2     Dosage in food

      Mixing

The mixing of medicated food is of vital importance - the preferred method is to mortar and pestle the tablet, ‘grind it with the end of a wooden rolling pin; then roll out the food, on some grease proof paper, so that it is thin and flat.  Then sprinkle the powder thinly and evenly over the food and knead it in. The mix is then rolled up and placed into mixing bowel where it is very carefully mixed so that an even distribution of the drug is assured.

      Dosage

      The preferred dose is (Francis-Floyd & Reed, 1994; Yeng, 2001) i.e. 1gm of metronidazole to 100gm of Fred’s beef heart mix or similar.

      Again I have increased this dose considerably where warranted  When preparing a medicated mix, it is important to use appropriate amounts as there is a life expectancy once the drug has been added to the food.

      The medicated food, if stored should be frozen

      Feeding the medicated food

      Some suggest that normal feeding 3x day for 3 days is the best way.  A recommended alternative is small portions throughout the day, ensuring that all of the food is eaten i.e. it should not remain on the bottom after a minute or two.  This can continue for up to 10 days

4.1.3  Additional notes on metronidazole

4.1.3.1     How the medication works

The normal tissues of our bodies require oxygen to survive and to function correctly

If an area occurs that is deprived of oxygen, for whatever reason, e.g. as is the case with abscessed tissues and or tumours, an anaerobic growth zone allows the development of anaerobic bacteria infections e.g. Spironucleus vortens (or facultative anaerobes e.g. the Vibrionaceae – Vibrio sp., Aeromonas sp.), and the necrotisation of soft tissue.

In anaerobic conditions, ‘the metronidazole molecule changes so as to inhibit the DNA repair enzymes that normally would repair cells. This means death for anaerobic bacteria’ but has no effect on aerobic tissues.   In addition, it ‘normalises’ excessive immune reactions, especially in the gut. The specific mechanisms underpinning this function are currently being investigated (Brooks, 2002, DVM, DABVP).

It is widely accepted that metronidazole is most effective when given with food

4.2     Secondary infections and stubborn cases

Evidence (Somboon & Smith, 1999) suggests that a 3 day treatment is only suitable for mild or early diagnosed cases of S. vortens and that once remission starts to occur in these cases, the immune systems continues with the recovery process.   If there are ‘complicating factors’, e.g. it is not in fact an early diagnosis, damage is severe, or the treatment has been ineffectually repeated as if often the case – then the likelihood that epizootic numbers will reappear is very considerable.  What’s more there is a real probability that a secondary infection may take hold e.g. competition within the anaerobic zone during non-treatment time or systemic gram-negative aerobic bacteria (during treatment or post treatment but not fully recovered).  In the more severe cases, it is our preference to treat for septicaemia - as a real precaution.

5.  Food and its role in ‘holes’ and other symptoms

In regards to healing the ‘holes’ that are present on a discus, or even ‘curing’ a flagellate infestation - it is often stated that all an individual needs to do is to increase the ‘dietary value’ of the food being fed to the fish.  The most common supplements include: vitamins C, D and B complex along with the minerals Calcium, Potassium and Phosphorus, plus additional trace elements.  This is pretty difficult and pointless if the fish is not eating in the first place - though it is a great preventive measure, and good practice, for all manner of woes.

5.1     Dietary vitamins, minerals and trace elements

5.1.1  Vitamins

The information here based on Untergasser (1991) and general reading.  I strongly suggest that for serious hobbyists, Untergasser’s book, although slightly dated, is well worth reading - even for the nutritional work alone

      Vitamin C - Ascorbic acid.

Mammals to some extent can produce this for D-Glucose; however fish cannot.  Therefore, they must obtain this essential vitamin from their food.  A lack of vitamin C leads to a degradation of normal connective tissue and an increase in the permeability of cell membranes.  This may result in tissue that is easily ruptured and haemorrhages under the skin, especially in the area of the lateralis system.  Self healing is retarded, the fish becomes more susceptible to pathogens and there is a risk of skeletal and nervous system deformities/problems

Importantly the degradation of vitamin C is accelerated in the presence of light, oxygen, heat, copper, a base ( pH over 7.2 ) solution and high nitrate levels.

      Vitamin D - the calciferols

It is stored in the liver and is essential for optimum calcium-phosphate (c/p) metabolism i.e. if it is absent then c/p cannot be absorbed by the intestinal mucosa.  Therefore c/p that would have been used for bone formation is used for general body maintenance.  It is important that if the diet is to be supplemented with vitamin D then calcium and phosphate should also be given.

It should be noted that it is possible to overdose vitamin D which can cause a demineralisation of the skeletal system.  The calcium is removed and deposited in the renal tubules and as result the body’s ability to excrete toxic metabolites decreases - often with fatal results.