(Also known as: Swimming pool granuloma, fish tank granuloma,
fish-handlers’ nodules, surfers’ nodules)
Mycobacterium Marinum (M. marinum) is a slowly
growing bacteria that may cause disease in fish and people.
This bacteria occurs in bodies of fresh or salt water
in various parts of the world. It has also been found
in fish from the Chesapeake Bay and other waters. Other
types of mycobacteria, such as M. chelonae and M. chesapeaki,
may also be present in water.
While they can sometimes cause disease in fish, they
rarely do in people. Human infections by M. marinum are
rare. However, people who have breaks in the skin such
as cuts and scrapes may be at risk when in contact with
water from an aquarium or fish tank
- when handling, cleaning, or processing fish, or
- while swimming or working in fresh or salt water.
One form of the infection, known as “swimming pool
granuloma”, can be due to the ineffective chlorination
of swimming pools.
In the United States, most human infections due to this
bacteria had been associated with exposures to fish
tanks. M. marinum infection is not spread from person
to person. After exposure, symptoms usually appear within
2 to 4 weeks. Some reported cases have developed symptoms
after 2 to 4 months or longer due to the slow-growing
nature of this bacterium.
The most frequent symptom is a slowly developing nodule
(raised bump) at the site the bacteria entered the body.
Frequently, the nodule is noticed on the hand or upper
arm. Later the nodule can become an enlarging sore (ulcer).
Swelling of nearby lymph nodes occurs. This infection
can also involve the joints and bones.
Infections with this bacterium can be treated with antibiotics.
Antibiotics may need to be taken for as long as 6 months
or more.
A health care provider should be consulted if a skin
nodule or reddened sore (ulcer) develops following direct
skin contact with fresh or salt water or after handling
or processing fish.
For people with immune system problems, M. marinum infection
can become severe. If an infection is suspected in such
persons, a health care provider should be promptly consulted.
When fish are infected with M. marinum, they may have
skin nodules and/or ulcers. Although there are no documented
health problems in people that eat cooked infected fish,
as a general rule it is recommended to not eat any fish
that looks diseased.
There is no evidence that human infections of M. marinum
occur if fresh or salt water is swallowed.
Steps to reduce risk of infections with M. marinum:
- Avoid fresh or salt water activities if there are
open cuts, scrapes, or sores on your skin, especially
in
bodies of water where this bacterium is known to exist.
- Persons with weakened immune systems can reduce risk
of infection by carefully covering cuts, scrapes,
or sores during fresh or salt water activities and while
cleaning fish tanks or handling, cleaning or processing
fish.
- Wear heavy gloves (leather or heavy cotton) while
cleaning or processing fish, especially fish with sharp
spines that may cause cuts, scratches, or sores to the
hands and skin. Wash hands thoroughly with soap
and water after fish processing or use a waterless cleanser.
- Wear waterproof gloves when cleaning home aquariums
or fish tanks. Wash hands and forearms
thoroughly with soap and running water after cleaning
the tank, even if gloves were worn.
- Ensure regular and adequate chlorination of swimming
pools to kill any bacteria that may be present.
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Maryland Department of Health & Mental
Hygiene
Office of Epidemiology and Disease Control Programs
September 2002 |
are PDF. Download