A Few Comments on Mycobacterium marinum, by Dr. Adrian Lawler

A Few Comments on Mycobacterium marinum

by Adrian Lawler, Ph.D.
(retired) Aquarium Supervisor (l984-l998) J. L. Scott Aquarium Biloxi, MS 39530
Original to Aquarticles

Mycobacterium marinum infection in fish and humans has been called fish TB in the past. Some other names used are: swimming pool granuloma, fish tank granuloma, surfer's nodules, fish tuberculosis, fish handler's disease, fish mycobacteriosis. Mycobacterium marinum is in the same genus as human TB and leprosy. Fish TB and human TB are different species of the same genus of bacteria. Human TB has multiplied in carp; fish TB can infect humans.

The term "tuberculosis" had been used with diseases of fishes when an acid-fast bacillus was involved. In 1960 fish mycobacteriosis was suggested by some as a more appropriate name.

Many parasitologists and microbiologists study bacteria, and are qualified to speak about various bacteria. Anyone can discuss a disease; however, only medical doctors can prescribe drugs and/or supervise/direct treatment of said disease in humans.

I've found few medical doctors familiar with Mycobacterium marinum. Dermatologists and military doctors (who have been in various places, or treated patients who have been all over the world) have been most familiar with the infection.

In September 06 I assisted a mother whose young daughter had gotten a presumed Mycobacterium marinum infection on her right hand after brushing against a fish tank. The infection had been going for about 2 months and she had also apparently infected her eyes via rubbing them with her infected right hand. Previous eye infections by Mycobacterium marinum and other species of Mycobacterium have been reported in the literature.

For some information on infections and some past treatments see Lawler, A.R. 1994. Human Mycobacterium marinum Aronson infections. Journal of Aquariculture and Aquatic Sciences 6, (4), 93-94. And for ways to avoid infection and other information see the various articles by Lawler and others at Aquarticles.com.

In order to avoid much pain, spread of infection, and long-time antibiotic use, one must recognize and treat this bacterial infection as soon as possible. One does not want it to get into joints or last up to 17 years as it has in extreme cases with some people.

The percentage of people that get Mycobacterium marinum infections out of ALL human bacterial infections is low. But don't tell that to the man in severe pain because it got into a joint, or to a young girl with it in her eyes, or to anyone who has had to take antibiotics for a year or more. To them it is not rare, and it is a very personal, trying struggle. As one grows older, and has his immune system weakened (by any of a number of ways), he becomes more susceptible to infections by Mycobacterium marinum and other organisms. Those that scoff at the disease now, and do not practice safe procedures around fish and tanks, etc, may themselves get infected at a later date. Those that belittle a concern of infection at a young age, will find themselves eventually apprehensive about getting infected if they live long enough and are still exposing themselves to infections by this bacterium. I had no problems with Mycobacterium during about 50 years of fish tank work, then suddenly found myself infected on my right thumb. My immune system apparently was down due to advancing age. Unfortunately, presently there is no easy way to measure the strength of one's immune system.

For human infections, the number for disease incidence given by some on the internet is reported to be about 0.27 cases per 100,000 (0.0000027) people per year (or 0.00027 %), which is lower than the chance of being killed in a car wreck (50,000 of 300,000,000 = 0.0167 % per year). So you are 0.0167 divided by 0.00027 or about 62 times as likely to get killed in a car wreck as to get a Mycobacterium marinum infection. Due to the inability of many doctors to recognize the infection, especially when it is first starting, due to the difficulty of growing and culturing, and due to the difficulty of getting a positive identification, Mycobacterium marinum infections are generally under-recognized and under-reported. I would expect the true number of cases to be higher than that reported above.

A more interesting and realistic figure for understanding the incidence of the disease would be the number of Mycobacterium marinum infections per 100,000 people who are associated with fish and fishing, fish tanks, natural waters, etc., i.e., those that could be potentially exposed and are taking the risk of being infected (A comparable example would be the number of football players killed during play out of the total number of people actually playing football.). Not all people of the total population are subjected to situations whereby they could become potentially exposed and infected. This number would reflect those infected per those that could be potentially exposed and would be considerably higher than 0.27 per 100,000, probably (estimate) on the order of 100-250 per 100,000, or 1-2.5 per 1000, or a 0.1 % to 0.25 %, or higher, infection rate (of those that are doing things which could expose them to a Mycobacterium marinum infection). We will probably never see this number because it would be difficult to count the people who put themselves at risk (swimmers, fishermen, fish tank keepers, etc.).

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