The information provided here is for
educational purposes only. You should seek the advice of medical
professionals if you believe you have been exposed to Mycobacterium
marinum. Only your doctor can correctly diagnose this condition
and recommend an appropriate course of treatment. It is only
my intention to make you aware of the dangers, suggest a few
simple protective measures, and to encourage you to seek medical
attention with this disease in mind if you suffer from any
suspect skin conditions.
Brooklynella. You are all probably familiar with these
fish diseases, but are you aware of the dangers that Mycobacterium
marinum poses to your fish and, more importantly, you?
Never heard of it? How about fish tuberculosis, piscine TB,
fish tank granuloma, or possibly swimming pool nodules? These
are all common names for somewhat uncommon ailments caused
by Mycobacterium marinum. You might recognize from
the genus, that Mycobacterium marinum is a distant
relative to the organism that causes tuberculosis in humans.
Fish Infections of Mycobacterium marinum
Mycobacterium marinum causes a chronic
progressive fish disease found in freshwater, saltwater, and
brackish environments. Weight loss, non-healing open ulcers,
a distended abdomen, loss of appetite, fin erosion, unusual
coloration, pop-eye, spinal deformities, and listless behavior
are all possible signs of infection. Unfortunately, it is
also possible an infected fish will show no external signs
and may die mysteriously. A post-mortem examination will reveal
the telltale nodules on and in the internal organs; in particular,
the kidney, spleen, and liver.
Closed aquatic systems with a high density
of fish and warm waters (Hint, hint; this is another way of
saying your average everyday home aquarium) appear to be conditions
particularly favorable to this infectious agent. Poor overall
water quality and various nutritional deficiencies have also
been implicated as possible contributing factors to the onset
of this pathogen. Good husbandry practices such as strict
quarantine protocols, a high-quality and varied diet, as well
as regular cleanings can help to keep your aquarium free of
this bacterium, but unfortunately it is no guarantee. Mycobacterium
can be found in soil samples and frankly just about any puddle
of water, including swimming pools that are improperly sanitized.
Consequently, it would be wise to assume it is always present
in your aquarium and appropriate protective measures should
Sterilizing a tank is not usually effective
since re-infection is so likely. It is also unpractical for
our reef aquaria. To properly sterilize a tank, you must treat
everything with bleach: aquarium, plumbing, pumps, filters,
live rock, sand, corals, etc. I doubt this is a measure that
many reef aquarists would want to undertake. There was even
one documented case
of a group of Egyptian spiny-tailed lizards, Uromastyx
aegyptius, contracting Mycobacterium marinum because
they were housed in an enclosure that was once used for fish
(Morales, Dunker 2001). The tank was stored completely dry,
but un-sterilized, for some time, and this bacterium managed
to survive and infect the reptiles. This goes to show how
truly resilient this pathogen is, and how extreme sterilization
methods must be undertaken to be effective. The best protection
for your fish against this disease is to keep them as healthy
as possible and, therefore, keep their immune system operating
in peak condition. As alluded to above, regular water changes
with removal of dirt and detritus, closely monitoring the
specifics as well as general trends in water quality parameters,
and nutritious foods can all be helpful in prevention.
Obviously, sick or dying fish should be
removed from the display tank and placed in a proper isolated
quarantine tank or euthanized. Healthy fish feeding off of
diseased ones is a primary means of transmitting the infection.
Carbon dioxide poisoning and freezing are two commonly used,
allegedly humane methods to put a fish down, but neither will
kill this bacteria. If you choose to euthanize the fish, please
dispose of the carcasses safely. Treating the bodies with
bleach and subsequently disposing of them in the trash minimizes
the risk of spreading a particularly virulent or antibiotic
resistant strain as compared to flushing.
If you don't want to give up on a particular
specimen, there are a few treatments that can be attempted,
although none have been proven effective. Rifampicin, erythromycin,
streptomycin, kanamycin, and minocycline have all been reported
with varying degrees of success to combat this disease. These
antibiotics need to be administered daily in the food for
a minimum of one month, perhaps for as long as three months.
At the same time, the use of ozone and/or ultraviolet sterilization
may aid in controlling the spread of this disease. If you
are serious, you should consult with a veterinarian trained
in treating fish to come up with a specific course of treatment.
Keeping your fishes disease-free is one
thing, but I am more concerned that you keep yourself disease
free. Having had this infection once myself, I can tell you
it is absolutely no fun, and one should try to avoid it at
all costs. The simplest, most effective thing you can do is
to keep your hands out of the tank as much as possible. Far
too many hobbyists are in their tanks too often monkeying
around with things; moving live rock around because the aquascaping
does not look quite right, rebuilding because of avalanches,
or adjusting the positioning of your corals because the polyp
extension or coloration is not what was expected or desired.
It is, quite simply, good aquarium practice to minimize having
your hands in the tank. Magnet cleaners, long-handled algae
scrapers, aquarium tongs, and various other grabbing devices
are quite useful in minimizing human contact with the water.
Even when using all the tools available,
occasionally it is still necessary to put your hands in the
aquarium. For these instances, I strongly urge using a good
pair of gloves. I have tried several different models marketed
for aquarium use, as well as a few I picked up from veterinarian
supply places and cleaning goods distributors, yet I keep
coming back to a pair sold by Coralife. They are shoulder
length, so they keep your entire arm dry and are thick enough
so they don't tear easily, yet have a reasonable sense of
feel. The only problem that I have found with them is they
have a seam at the wrist, which seems to eventually leak.
I own an aquarium maintenance business. On average I will
service two to four different tanks per day five days per
week. The Coralife gloves last me anywhere from three to six
months before needing to be replaced. Given that will likely
be used less often, I would imagine they would last a casual
hobbyist considerably longer.
The last preventative measure is one you
should all know well from Kindergarten: wash your hands!
Washing with warm water and an antibiotic soap for 30-60 seconds
can be especially helpful in keeping the aquarist from becoming
infected. I recommend washing your hands immediately after
coming into contact with any aquarium water and even when
wearing gloves, just in case there was a small leak that went
Human Infections of Mycobacterium marinum
In humans, the two most common manifestations
of this infection are a single large granuloma or an ascending
lymphangitic granuloma (a series of smaller nodules usually
starting on the dominant hand and progressing in a line up
the arm). Less commonly seen is an infection in the joints,
which will cause arthritis-type symptoms. This latter type
of deep infection is associated with a puncture, like that
from the spiny ray of a catfish or from a deep, open wound
that becomes infected. Lastly, there is a rare case of a disseminating
disease seen in immuno-compromised individuals that can be
fatal. People diagnosed with HIV or AIDS, cancer patients
undergoing chemotherapy, or any other person with a known
immune system problem should be particularly careful. If you
fall into any one of these categories, you may want to consider
hiring a service company to take care of your tank. Also note
that symptoms can wait to present themselves from two weeks
to four months after initial exposure, due to the slow growth
rate of this bacterium. Keep a close eye on any open cuts
for that same time frame to ensure they heal properly and
are not subject to infection.
A Couple of Case Studies
My good friend Don Tuttle, who is an accomplished
aquarist with over 50 tanks in his house, incurred a minor
cut on his right middle finger. He did not think anything
of it and cared for it like any minor scrape. He washed it
and applied a bandage. Several weeks later he noticed some
swelling in the area, so he went to his doctor. This is the
scariest part of this disease. So often it is misdiagnosed.
Most physicians rarely see Mycobacterium marinum. It
also cultures poorly, taking 4-6 weeks for a definitive test.
Nothing specific will show up on either an X-Ray or blood
work, except perhaps a weakly positive test for Tuberculosis.
Poor Don went through several doctors and specialists. All
of which were unable to figure out what was wrong with him.
All the while his finger continued to swell to the point of
discomfort. His doctors were seriously considering amputation
when during a little bit of small talk Don mentioned something
about his fish tanks. It was this little bit of information
that triggered a correct diagnosis and saved Don's finger.
He still had to go through surgery to remove the single large
granuloma of Mycobacterium marinum that had formed
as well as continue the subsequent antibiotic treatments.
The pictures of his finger after his procedure showing the
incisions that were made, how enlarged his finger still was,
and the mass of nodules that were removed, are seen below.
About a year after Don went through his
bout, I noticed a small bump on my right pinky finger knuckle.
It looked somewhat like an ingrown hair at first. I covered
it with a bandage and used an antibiotic ointment for one
week and it seemed to disappear. However, it reappeared later,
this time slightly larger and more dry and scaly. Because
I remembered what Don went through, when it came back, I went
straight to my Primary Care Physician and told him I was concerned
that I had a Mycobacterium marinum infection. He referred
me to a Dermatologist for treatment. Some time had passed
between getting an appointment with my own doctor, having
the referral clear the HMO, and then finally getting to see
the specialist. By the time I saw the Dermatologist, my single
bump had become an ascending lymphangitic granuloma, with
a second bump at mid-forearm and a third just short of my
elbow. The doctor confirmed my suspicions and prescribed an
antibiotic. I ended up going through three different prescriptions
before we found one my body could tolerate. I was prescribed
a large dose of a strong
antibiotic twice a day for three months. This cured me of
the Mycobacterium marinum infection, but caused a whole
new problem. While my actual encounter with Mycobacterium
marinum was relatively harmless, I am still getting over
the long-term effects of the cure. The long course of strong
antibiotics absolutely wrecked my digestive system, and I
am still suffering with minor difficulties to this day.
Please be careful. This disease is sort
of the "dirty little secret" of the ornamental fish
industry. It is not often discussed with the casual aquarist
when getting their first 10-gallon starter tank, but it is
a real danger, although admittedly rare. They are many other
dangers in our aquariums that I did not cover in this article,
too; envenomation from fish like Lionfish and Foxfaces, anaphylactive
shock from repeated contact with Cnidarians, Vibrio
infections, stings from Fireworms, getting stuck by a Sea
Urchin, etc. The good news is that all of these can be combated
with the same simple precautions mentioned previously in this
article. If you follow these guidelines, you can remain relatively
safe from harm and continue to enjoy the beauty of this hobby.