Contents
Identifying columnaris
Preventing columnaris
Columnaris outbreak - an
example
Discus Salt Dip Methodology
Potassium Permanganate
Methodology
Antibiotics
Columnaris disease is a problem that has had a long and
often confusing history. What follows is broadly divided
into three main sections. Firstly, ‘classic columnaris’ is
briefly outlined (see
1 for further information on
columnaris disease; and
2 for further information on
the Flavobacteriaceae). Secondly, recent
developments, specific to tropical fish are reviewed.
Finally, what all this may mean to the discus hobbyist is
discussed - along with a ‘real life’ example and potentially
useful treatments.
Columnaris disease is a bacterial disease of freshwater
fish. It is the second highest killer of farmed catfish in
the
USA
3,
and it is widely accepted that most species of fish are
susceptible to columnaris disease
4.
The aetiological agent of columnaris disease is the gram
negative rod bacteria, Flexibacter columnare (ex
Herbert Spencer Davis 1922) Bernardet and Grimont 1989
(Synonyms: "Bacillus columnaris; Chondrococcus
columnaris; Cytophaga columnaris; Flexibacter
columnaris. It is often referred to as "fin rot",
"cotton wool disease", "cotton mouth disease", or
"saddleback disease"
3,
4.
Outbreaks tend to occur following environmental stress and
clinical signs or symptoms may include yellowish brown or
white lesions on the gills, skin, or fins. The bacteria
attach themselves to the fish where they release protein and
cartilage degrading enzymes. It may be argued that the most
important site of attachment is that of the gills. The
bacteria attach to the gills where they multiply, and
eventually cover and destroy the entire gill filament - if
untreated, substantial damage can occur, subsequently
leading to the death of the fish
3.
In
the early stages of the disease, the lesions may simply
appear as an area that is ‘less glossy’ than the surrounding
scales. Advance lesions may be round or oval in shape, and
can if untreated, progress to an open ulcer. In some fish
the lesion may appear as a pale band, encircling the body of
the fish – hence the name saddleback disease
3.
Prior
to 1998, the majority of published works on columnaris
disease primarily focused on temperate farmed fish
5.
During 1998, Decostere, Haesebrouck and colleagues
4,
5,
6,
7,
became the first to publicly correct this problem by
isolating and studying Flavobacterium columnare
directly from tropical aquarium fish. The fish species
studied included black mollies Poecilia sphenops,
platies Xiphophorus maculatus, guppies Poecilia
reticulata, and tetras Cheirodon axelrod.
Decostere
et al. 5
isolated four strains of F. columnare. Each of these
strains were compared to the F. columnare reference
strain, NCMB 2248, and or the 5 F. columnare strains
that had previously been isolated from temperate fish.
Whilst there were similarities e.g. all were gram negative
‘flexing’ filamentous bacteria between 0.2-0.5mm
x 5-8mm
in size; all had an optimum growth rate at between 25oC
and 30oC – there were also significant
differences amongst the strains.
Importantly, the tropical strains continued to grow at 37oC;
they demonstrated a notable difference in virulence; and
none were able to grow in-vitro, when immersed in a 1% NaCl
(Salt) solution. In tanks where mortality occurred, the
time to death following infection ranged from between 8
hours and 6 days. It was also noted, that the strains were
able to enter the blood system and cause septicaemia.
The 4
‘type strains’, which were isolated, are listed in order of
virulence:
1.
AJS1 was extracted from a fish with bleached and ulcerated
skin, and from a tank in which daily mortality occurred.
2.
AJS2 was extracted from a discoloured fish, which displayed
fin rot, especially in the caudal region; in addition, there
was chronic mortality in its aquarium.
3.
AJS3 was extracted from a fish that displayed small white
patches around mouth, opercula, and from tanks that had no
significant mortality.
4.
AJS4 was extracted from a discoloured fish, with pale
patches on the skin and fins, especially in the dorsal
region, and again from a tank that had no significant
mortality.
In
fish that were infected with F. columnare, the
sequence of visible physical symptoms included slight
swellings at the site of infection (infection was achieved
by intramuscular injection of simple contact infection),
which subsequently developed into a white/blanched patch.
As the infection progressed, in the more virulent strains,
the fish began swimming at the water surface. Shortly
before death, the fish lost their ability to remain at the
surface and became motionless, lying on their sides on the
floor of the aquarium. AJS1 was the most virulent strain
with acute mortality occurring 10 hours post-infection.
Further studies 5,
7
on tropical columnaris note that the development, progress,
and ultimate pathogenicity of the disease, is highly
associated with the ability of F. columnare to adhere
to gill tissue. AJS-1 has a high adherence ability and
AJS-4 has a low ability. Therefore, as AJS-1 is the more
virulent and deadly strain, the mechanism and conditions
that favour attachment are of prime importance.
Factors that affect the gill adherence capability of F.
columnare include: temperature, over-crowding, excessive
organic loads, ionic composition of the water, excessive or
poor handling, and slow movement of water. The mechanisms
hypothesised to explain these occurrences are not fully
understood – some suggestions include:
· The
slow movement of water allows the bacteria to withstand the
water-flow, and turnover of the mucus cells/epithelium -
thus allowing the bacteria to remain in an area where there
is a high concentration of nutrients, that are efficiently
obtained via ‘slime layer’ localisation of dergradative
enzymes.
· Ionic
composition of water affects adhesion. MG++ and
CA++ play a part in adhesion by reducing surface
potential and repulsive forces.
· High
levels of nitrites and organic matter enhance adhesion; the
underlying mechanism involving nitrites is not known and it
is suspected that high levels of organic matter may result
in debris being trapped within the
mucus layer at gills thus resulting in an ‘ideal
target site’ for the bacteria.
· In
regards to the cellular binding mechanism involved between
gills and the cells, a capsule incorporated, lectin-like
carbohydrate has been suggested
6.
There
can be no doubt that columnaris disease can occur in
virtually all aquarium environments. It may be present even
when there are no obvious external signs. When external
signs are present, they may take the form of: yellowish
brown lesions, ‘cotton wool’ tufts, the fish may simply look
‘dull’ or ‘dark’, or the fish may have small white patches
on its fins or body. In addition to these external signs of
infection, it should be noted that, one study found that in
40 % of all diagnosed cases of columnaris, the internal
organs were also affected (see
3 for references).
Stress
is a major factor in columnaris disease and may involve any
one, or combination of stressors e.g. low oxygen levels,
high nitrite levels, comparatively high (or low) water
temperatures, rough handling, mechanical injury,
overcrowding, water of inappropriate hardness etc (See
8,
9 for
further details on stress, fish, its management and fish
health).
In
discus as with other tropical fish, many of theses stressors
occur during catching, bagging, transporting and subsequent
reintroduction into the new aquarium. The closed
re-circulating system of the aquarium is an ideal habitat
for columnaris to spread and to result in high mortality
rates. In addition, it is not unusual for discus to be kept
in overcrowded tanks with inappropriate water parameters; or
to be placed in tanks that have immature filters.
For
the discus hobbyist the external signs of columnaris to the
naked eye can closely resemble the signs presented by range
of other parasites. It is unlikely that the average
hobbyist will have the necessary equipment, time, experience
and access to the drugs that are required to be able to
identify specific strains of F. columnare; however if
they do, I suggest they start with references
4,
5,
6,
7 and
follow up their original methodology used by the authors as
a guide. However, gross identification of F. columnare
is certainly achievable using a reasonable microscope, a
high powered lens, appropriate accessories, and comparative
slides, images, videos.
Rather
than repeat information that is commonly available, I
suggest that, if you are new to microscopes and the gross
identification of F. columnare, that you pay a visit
to the
DPH Articles Page – there, you will find a collection of
excellent information, images and videos.
Aside:
I often meet people who moan that microscopes and vets are
expensive and a waste of time in regards tropical fish. In
my experience an adequate ‘scoping’ kit cost less than a
decent pair of discus (certainly in the UK) and with a
little practice becomes a phenomenal diagnostic tool, and
may well aid the survival of your complete stock.
Secondly, if one takes along suffering stock to a vet/aqua
culture specialist who has the experience and equipment to
identify specific pathogenic bacteria – this again can cost
less than the price of a breeding pair. Be prepared to ask
the individual if they have the necessary equipment for
accurate identification on the premises. In saying this, I
accept that you are not going to be able to use your local
dog and cat vet (unless you are very lucky) – Contact your
local fisheries advisory board; they often keep a list which
can be issued to the public of the laboratories that they
use, e.g. I have used the Ministry of Agriculture, Fisheries
and Food ([MAFF]; which are now the Department for
Environment, Food and Rural Affairs [DEFRA] to track down
the appropriate specialists in various regions of the UK for
friends and colleagues. Remember your stock is potentially
worth thousands – it is not good sense to rely on guess work
and chance when confronted by any potentially virulent
disease.
The
first step in managing columnaris is to prevent its
occurrence. To do this, it is important to minimise the
amount of stress our fish are subjected to e.g.:
· Proper
handling - use soft nets and careful netting techniques to
avoid mechanical injury
· Ensure
that there is adequate oxygen in shipping bags and tanks
o
salt
or other additives may be used to minimise the effect of
shipping
· Allow
a sufficient run-in period for the maturation of new tanks
o
coupled with regular partial water changes appropriate to
stocking density and feeding regime
· Do
not overstock or keep discus in water of inappropriate
hardness and pH
· When
receiving new fish - ACCEPT
that they have just undergone a journey that is likely to
have placed them under a phenomenal amount of stress –
therefore, the risk of columnaris (amongst other infections)
is considerably higher than ‘normal’.
o
It is
all to easy to blame the breeder or wholesaler when fish
arrive worse for the wear and an epidemic of columnaris
breaks out almost immediately the fish hits the tanks. In
the main, breeders or wholesalers will take every precaution
possible to ship their stock correctly - once the shipment
leaves their premises though – a lot can happen, from
plunging pH levels, increasing carbon dioxide
levels/decreases in the available oxygen, chilling of water,
boxes being thrown through the air and dropped from heights.
Hopefully the above is indicative of how important it is to
quarantine new stock correctly, and to take steps to reduce
any population increases of ecto- and endo-parasites, that
may have occurred during the relocation process. With this
in mind I would like to draw attention to several points re:
quarantining discus.
· A
quarantine tank (qt) is not necessarily a hospital tank
(although it may become one).
·
It
should contain a mature filter and conditioned water, prior
to the new fish being added. The qt tank’s water should
match the water in which the discus will ultimately be
placed.
· A
record of observations are essential in preventing,
diagnosing and treating problems e.g. temp, pH, GH, KH,
behaviour, physical appearance, feeding practices, the
appearance of waste etc. . . Don’t forget, during the qt
period you are not only making observations for visible
signs of disease, you are also looking for signs of stress -
the most common pre-cursor to disease outbreaks.
· Many
different quarantine periods have been suggested from 1 week
to 6 weeks. In my opinion the minimum for discus is 4 weeks
with the preferred time being 6 weeks.
· If
a 6 week quarantine period has been chosen – between weeks 4
& 5 add a discus from the main tank into the qt tank, in
case the newly acquired discus are unaffected carriers of,
as yet, unidentified pathogens etc.
Whilst
the best ‘cure’ for columnaris is prevention; F.
columnare is such a ubiquitous organism, that there is a
high probability that at some point in our fish keeping
lives, our stock will suffer from an outbreak. The example
that follows is based on a factual occurrence and the text
was provided by Davis Gailitis.
‘One day I looked into my tank and noticed that one of my
discus looked different’ . . . ‘she had a spot on her left
side just below the beginning of her dorsal fin. It looked
like a scale had come up a bit. I now know looking back that
I should have looked closer at it. I just did a casual
glance and assumed that was what it was. I didn't think
anything of it, except to look at it again later that day’
‘Things stayed the same for several days and I was not
overly concerned.’
‘On the fourth day I noticed the scale that was turned up,
now looked like a small pimple, all white, around 3ml in
diameter and about the same in distance protruding from the
body.’
‘The next morning I looked at her when she was facing
sideways to me all of a sudden I could see, in her slime
coat, this white opaque haze, circular in form, about the
size of an American dime.’
‘Later that evening the opaque circle had grown t the size
of an American Quarter. Up until this point, my fish had
behaved normally and was eating with the rest. Tonight, she
was at the back of the tank, facing the corner, and getting
progressively darker.’
Following discussion with Fred Goodall and further
investigation - several days of treatment were performed
with the result of . . . ‘She is fine now and is horny as
hell, she has also found a mate in the tank and is on a four
day cycle with laying of eggs!’
Davis Gailitis
In my
experience Davis’ example is very common. It is important
to mention here that this is only one manifestation of
columnaris. In many cases columnaris has been known to
effectively wipe-out several hundred discus in a matter of
weeks; with the first deaths occurring within hours of a new
shipment arriving at the retailers.
Should
you be unfortunate enough to experience columnaris, the
disease must be brought under control as soon as practically
possible.
In
Davis’ example, the treatment referred to, was the
application of a series of salt dips, coupled with in tank
temperatures of 35oC, large daily water changes
using fresh conditioned water, and scrupulous tank hygiene.
Below, I list a couple of methods that I have used and that
have worked for me and others I have visited. If you choose
to use the examples – do so with great care – remember, the
onus is on you to make judgements regarding appropriate
treatment and the current condition and status of your fish
and tanks – if you are unsure, nervous or need help, please
ask, or seek professional advice.
Type of salt to
use:
The
type of salt used should be non-iodized and contain no ‘free
flow’ or other additives (e.g. no iodine or sodium
ferrocyanide etc. I have used ‘Freshwater Aquarium Salt’,
rock salt and sea salt. If purchasing non-aquarium salt
please read the packaging carefully as current trends show
an increase in the use of additives even in natural products
such as rock salt (UK).
If new to Salt
Dipping
If new
to dipping fish a good place to start would be with a 1.5-2%
salt solution; for more experienced users I would suggest
you start with a 3% solution immediately. The solution
should be made up in a clean bucket or spare (fishless)
tank. Whilst it is preferable to weigh out the correct
amount of salt e.g. for a 2% solution one would use 20g of
salt per litre of water, the following approximate measure
are given for the sake of simplicity.
1
TABLESPOON of salt approximates to 15grams.
Therefore 1 TABLESPOON of salt per litre of water equates
to a 1.5% solution
Worked examples (See Table 1 for other
strengths):
· If
your bucket/tank contains 10 litres of water you
would add 13 tablespoons of salt to get an
approximate 2% salt solution
· Or - If you place 3 US gallons of water in a
5 gallon bucket you would add 14½ tablespoons of salt -
to get an approximate 2% solution.
And so
on
· It
is important to ensure that the salt is fully dissolved
before placing the fish in the bucket/tank and that the
water temperature matches the tank from which the fish are
taken.
As you
will need to multi-dip throughout the day, place a heater in
the tank, if you do not want to have to remake new salt
solution each time; personally I make a fresh solution for
each dip.
Before
you place the fish in the solution please remember that:
· The
length of time that you can leave discus in the solution
varies greatly from a few seconds to 30 minutes
o
5
minutes would be a reasonable average
· The
time they tolerate the dip DECREASES with the
number of dips performed in a 24 hour period
· The
fish MUST NOT
be left unattended
· During
the treatment your fish may show some interesting
discolouration, do not worry this is short term.
Place
the fish into the solution as quickly and as carefully as
possible - then observe closely.
Initially, the respiration of the fish will increase
substantially, 120 gill beats per minute is not uncommon.
At some point, the fish will keel over on its side
- and it is at this point that
the novice should remove the fish
and return it to its tank. If you are confident and
experienced in dipping you may want to extend the time that
the fish is exposed to the saline solution - I have found it
effective to leave the fish in the solution until the gill
beats have slowed to around 20 bpm - irrespective of whether
the fish has keeled over or not.
Once
the fish are returned to their tank they should within a few
minutes regain their composure. If they appear to be in
difficulty, the fish can be supported using your hands and
then gently pulled backwards through the water at a slow
pace - so that water is forced over the gills.
I have
dipped 5 times a day for up to 7 days and there has been no
lasting negative effect. It is important that
the dips continue until all visible
signs of infection are gone.
|
|
|
Salt Solution |
|
|
|
|
0.1% |
0.2% |
0.3% |
1% |
2% |
3% |
|
|
10 |
Litres |
1 |
2 |
3 |
100 |
200 |
300 |
salt
in grams |
|
10 |
US Gallons |
3.8 |
7.6 |
11.4 |
379 |
757 |
1136 |
|
10 |
Imperial Gallons |
4.6 |
9.1 |
13.6 |
455 |
909 |
1364 |
TABLE 1A
|
|
|
Salt Solution |
|
|
|
|
0.1% |
0.2% |
0.3% |
1% |
2% |
3% |
|
|
10 |
Litres |
0.07 |
0.13 |
0.2 |
6.7 |
13 |
20 |
salt
in table-spoons |
|
10 |
US Gallons |
0.25 |
0.5 |
0.76 |
25 |
50 |
75.7 |
|
10 |
Imperial Gallons |
0.3 |
0.61 |
0.91 |
30 |
61 |
90.9 |
TABLE 1B
Tables 1 A & B give approximate figures for various salt solution concentrations.
It must be remembered that Table B are coarse approximations only.
Important Note:
In regards to salt dipping it may be argued that returning
the dipped fish to the tank from which it came is pointless
– this is not the case. Ideally we would want to return the
fish to a tank which had been sterilised and which contained
100% fresh (but conditioned) water, with a matured filter.
It is important to remember here, that all we are doing is
‘knocking back’ the population of a ubiquitous
organism and promoting the production of copious amounts of
slime layer in order that the fish immune system can regain
control and management of the problem. If we must return
the fish to the same tank etc. then large water changes with
conditioned water, scrupulous tank hygiene and the addition
of salt at a rate of 2 table spoons per 10 gallons (assuming
that the tank does not contain delicate plants or salt
intolerant species) can work wonders – in conjunction with
correct salt dipping.
Whilst
I personally prefer the use of salt - it should not be
forgotten that there are several alternatives. In relation
to discus, various combinations of: potassium permanganate,
formalin, temperature, hydrogen peroxide, acetic acid, large
water changes, and so on, have been used to help CONTROL
the external infection - with the likelihood of success
being dependent on the virulence of the strain involved.
For the sake of balance I will summarise the use of
potassium permanganate (as an insitu bath [not a dip]).
Important Notes:
1.
Potassium permanganate and formalin must never be
used in the same water, nor should they be stored together.
When combined, their vapours are highly explosive.
2.
I only use PP in BB tanks.
3.
Wear rubber gloves, eye protection and old clothes –
the aim is to treat fish – not to become blind, to have
sun-tanned hands or to stain your best outfit. PP is a
powerful oxidising agent and shows no discrimination between
human skin, fish gill filaments, mucous layers etc – it will
start with the top layer and continue to oxidise, until
exhausted – therefore, it must be handled and used with
appropriate respect. If you do get PP on your clothes or
work surfaces, the resulting brown stains of manganese
dioxide can be removed by using a solution composed of 1
parts 9% hydrogen peroxide, 4 parts white vinegar, and 3
parts tap water. If you end up having to use this solution
to remove the stain from your skin, wash off the excess once
the stain is gone. Do not use: if the skin becomes
red or irritated, or on open wounds, or burns etc.
4.
When working with PP in aquariums, it is probable
that you will be working with very small amounts e.g. 1g and
dilutions of . . .
A 1g spoon can be purchased from some of the ‘older’ style
chemists which can be used for making up 2l of stock
solution at a time; however, many chemists will weigh out
the necessary amount for you, if you tell them what you are
using the substance for. If you are new to the use of PP,
I strongly recommend you let the chemist weigh the
necessary amounts for you, so that you can see
precisely what you are supposed to be working with – you may
be surprised at how small the amounts are.
5.
Never expose discus that have open wounds to PP
treatment.
Potassium permanganate (PP) can be used to treat external
columnaris. It is added to the aquarium water, where it
oxidises all organic matter, until it reaches a point of
exhaustion. Commonly, 2 mg/l of PP is added to the aquarium
water, and the tank is then monitored to ensure that the
water retains the resulting ‘purple/red’ for at least 4
hours. If the colour begins to fade, then more PP will have
to be added.
In my
opinion, it is all to easy to overdose and kill you fish
when you simply rely on subtle changes in colour; therefore
a 15 minute PP demand test should be performed. By
performing this test you will be able to calculate the
correct amount of PP to use, in respect to the organic
loading of the aquarium water in which the fish are to be
treated.
Methodology to
perform a 15 minute PP demand test on aquaria and ponds that
have a high organic load
Note: If you have a bare bottom tank and perform regular
water changes, siphoning off any debris each day – you may
find that even at 1mg/l the water will retain a degree of
pink colouration – if this is the case I suggest that you
use the standard treatment dose of 2mg/l PP and maintain the
colouration for four hours – Perform the test first, though
– Don’t guess!
Step 1
Prepare a 500mg/l water ‘stock solution’. This is achieved
by adding 0.5g of PP to 1 litre of distilled water.
Step 2
Label
four, 1 litre, transparent containers (e.g. 1, 2, 3, 4)
Step 3
To
each container add 500 ml of water taken from the tank that
is to be treated.
Step 4
Then
add the following:
Container 1 - add 1ml of stock solution (results in a 1mg/l
solution of PP)
Container 2 - " 3ml " "
" 3mg/l
Container 3 - " 5ml " "
" 5mg/l
Container 4 - " 7ml " "
" 7mg/l
Step 5
After
15 minutes note the colour of the solution
Step
6
Calculate the quantity of PP to use in the aquarium to be
treated
A.
You will find that the solution in one container will be
slightly pink, and in another the solution will be clear.
The
concentration you use is the concentration that falls
between the two
