Bacterial Gill Disease
Time to re-visit an "old friend"..
or fiend.. bacterial gill
disease/BGD. Bacterial gill disease
(BGD) is exactly as it sounds.. a
nasty bacterial infection of the gills. The bad news is that getting affected
gills to heal after physical damage is very difficult and even after we stop
the infection, there is no guarantee that the fish will thrive because of the
damage to the gills and we can still expect long-term breathing problems.
So, how does it start?? First, one of the really key points to understand about
gills is that they are the ONLY direct and most intimate contact that the fish
has the water that is not protected by a layer of tissue. This makes the gills susceptible
to everything in the water. In the vast majority of the cases we see of BGD,
the proximate cause is a parasite or fluke attack on the gills. The signs that
parasites are attacking the gills are flashing, flared gills, gasping for air
at the surface (especially in the early morning hours), rapid gill movements
and parking in a high-O2 concentration area of the pond, like a waterfall or
water return area. In the latter stages, the fish will clamp its fins and
remain lethargic on the bottom as it loses its energy levels caused by among
other things, low O2 levels.
Oddly, though not unheard of, chemical damage to the gills does not support BGD
yet it poses its own set of problems as the gills loose their
"mechanical" ability to function properly.
Anytime a fish exhibits this behavior, a physical exam is always advised. Since
most of us will handle a fish either for a scrape and scope or a bath or to
move to a q-tank when we see these types of problems, I suggest that ANYTIME
you handle a fish, take the time to exam the gills as this is often the very
first evidence of a less than obvious problem (i.e., ulcers, etc). And we all
know what healthy gills look like.. bright
meat red and with crisp edges to the gill filaments. If you don't know what
healthy gills look like, take the time to learn.
A fish's gills affected by parasites and/or flukes will exhibit some easy signs
to read. First, you will see tattered edges to the gill filaments and they will
lose their crispness. Again, commit to memory what healthy gills look like and
you will immediately know when something else is wrong. It is that obvious. Also,
damaged gills tend to stick together a little more than healthy gills. Gills
also have a natural mucous covering on them.. but it is a very slight covering and easy to miss. This
mucous covering is designed to do the same the body slime does: protects the
gills from parasite attacks and makes the water pass over the gills more
easily. If you see an excessive slime build-up on the gills, this is evidence
that something is irritating the gills... just like the body. Now it is time to
dig deeper. Is it parasites? flukes? maybe a chemical irritation (ammonia will do this..)?
In advanced labs, we teach koi owners how to scrape
the gills and even do gill snips for scope exams. These are fairly easy to do
but practice is needed (as is a GOOD grip on the fish), but well worth the
effort as you can easily the form of the gill structures and any parasites
living in it. If done properly, minimum damage will be done to the gills and
the fish won't be affected at all and will heal nicely.
Once the parasites and/or flukes have attacked the gills and because of the
gill's vulnerability to everything in the water, it is not uncommon for
bacteria in the water to step and cause the BGD. Since the gills are intimate
with the blood stream, usually the fish can ward off the bacteria until the
gills heal as the immune system manages the problem. If everything else is
healthy in the pond and the fish is not further stressed, the fish should heal
nicely all by itself once the parasite/fluke attack is repulsed. It is when something
else is wrong in the pond or with the fish and the immune system is suppressed
that we see the greatest incidence of BGD. Does this sound like how ulcers take
over?? It should, it is the same concept. Remove the stressors, remove the
proximate cause and the fish will heal.
The "B" in BGD can be any of the pathogenic bacteria in the pond,
including the most common - aeromonas, pseudomonas,
and flexobacter-c. For practical purposes, we don't
care which one it is (as they are all gram-negative), and our treatment options
are consistent with ulcer disease. So when treating BGD, consider that you are
treating an ulcer problem on gills... sort of..
Once the bacteria infection has taken hold on the gills, we see a rapid
deterioration of the gill structure. The bacteria feeding on
the gills easily creates a large volume of necrotic tissue and this
appears as white/gray and sometimes green slime on the gills. In some cases we
will also see saprolegnia or another mold attach
itself to the wound site and this just compounds the problem and if left
untreated, will hasten the fish's demise.
Often times, and as I believe happened with Karen's fish, the right things were
done but bad things still happened. Karen recognized a fluke problem a couple
of weeks ago or so and she treated her pond with Prazi.
This was the right thing to do and she can rest assured that she probably
killed off the proximate cause. And frankly, this is what most of us would do.
But what we may not realize is that if the gills are damaged, there is a good
chance that a bacterial infection will follow. As I stated, usually a fish will
fight this off, but if added stressors are not relieved and let me included the
massive rains we have had in the East, the fish may not be strong enough to
fight off the bacteria. So, while the parasites/flukes are gone or greatly
diminished, the bacteria still has a hold and begins rapidly to destroy the
gills. Once this happens, the fish looses much of its ability to process O2
effectively and so problems associated with low O2 start and this adds stress which suppresses the immune system and the fish
is in no-win situation. See the cycle??
To treat fish affected with BGD is not an easy process as remember we are
dealing with the gills and a fish that is severely impacted by the problem.
Every treatment option we consider MUST be weighed against its impact on the
gills. Do not forget this point. Obviously the first thing we need to do is
isolate the fish in well salted water (.3%) with lots of aeration and
comfortable place to rest. Do not use Melafix, Stress
Zyme, or any other med designed to relieve the fish
of other problems. Stick to the basics of managing a nasty bacterial infection.
If you confirm flukes, go with the Prazi, not
formalin or PP. Formalin and PP are oxidizers and while may kill off the
flukes, tey may also cause more damage to the already
affected gill tissue.
If you confirm parasites, starting at .3%, step up your salt baths .1% at a
time until you have killed the parasites. Do not exceed .6% as above that you
are adding to stress, not reducing it.
Let's assume now that we have defeated the parasites/flukes. Next we need to
attack the bacteria and here is where it gets tricky. For those who read
Karen's thread, you might have noticed where I advised Tricide-Neo
and not Baytril injections and here is why. While Baytril, amikacin, or other injectables can be life-savers in advanced bacterial
infections and provide us with the best chance of saving a fish, they do not
perform well when the gills are infected. The gills are a
complicated, 3-D structure that are designed to move blood effectively
so that the "pump" cells can exchange gases and minerals. However,
when they are affected by bacteria, they tend to "shut-down" at the
affected areas and this prohibits the blood to get to the affected site efficiently.
This is why the general consensus is to treat gill infections
"externally" with in-water treatments and with a medication that the
gills can take up easily. For this, I recommend two different meds. DO NOT USE
THESE TOGETHER.
The first is Tricide-Neo. As a bath treatment, Tricide-Neo will attack the bacteria directly and because
of its killing ability, will effectively kill all the bacteria in one
application. This application requires a bath (I recommend using a bag to do
this) and should be repeated two or three times. The downside is that the fish
has to be handled and this adds to stress. The up-side is that it is HIGHLY
effective.
The second is Chloramine-T or BGDX (commercial
version). This is an in-water anti-bacterial that works very well against BGD
and it is also taken up well enough by the gills to give the fish a better than
even fighting chance. It does not work as rapidly as Tricide-Neo
but does not require that you handle the fish (less stress). I recommend using
BGDX in a q-tank and it WILL affect your filter so you will need to manage
water quality closely using Amquel, etc. KOIVET has a
nice write up on how to use BGDX/Chloramine-T.
So, let's now assume that we have knocked out the parasites and the bacterial
infection as been suppressed or even knocked out. Now comes
the important healing process. And here is where doing more can be the wrong
thing to do. Rich now has a fish recovering from BGD and I recommended to him
to add nothing to the tank except salt to .3% to ease breathing and fresh, well
aerated water. The fish really needs time to heal and I know of no technique to
speed or assist this process other than to support the immune system and
overall health of the fish. If he will eat, look for vitamin C sources. In body
and tissue wounds, we often recommend Melafix to
assist in tissue regeneration. Personally I think this is a bad choice for BGD
as Melafix is oil based and there is ample evidence
that it can be an irritant. The only thing I would consider in the water is Chloramine-T as a deterrent to re-infection. But then
again, I am a fan of letting the fish heal itself assuming we properly support
his environment.
The healing process with gills can be extensive and I would in no hurry to get
the affected fish back to the pond, so plan on a long term q-process.
In dealing with BGD we need to be realistic with the prognosis. In Karen's
case, the damage to the gills was extensive and since this was a large fish,
the chance for recovery was very remote. But Karen wanted to try heroic steps
to save the fish and I applaud her for that. But the reality is that most fish
affected with BGD do not recover as the gills do not re-grow effectively and so
we can expect long-term problems. Moreover, the extent of the damage can most
often cause irreversible damage to the point where there is no hope and the
fish should be euthanized. Without adequate gill material, the fish is subject
to O2 deprivation and this causes, among other things,
a shut-down of the organs. Post-morts have shown us
the extent of the damage that started with BGD or other gill-related problems.
I am sure others have techniques that worked for them and I would like to hear
what anyone else has done to fight this rather nasty problem.