Fish, aquariums and skin infections: What is Mycobacterium marinum ?
A recent study by researchers at the Henry Ford Hospital in Detroit shows that a skin infection linked to exposure to contaminated water in home aquariums is frequently under-diagnosed due to the prolonged incubation time.
Cleaning fish tank
Image/Video Screen Shot
Researchers say diagnosing and managing Mycobacterium marinum infection is difficult because skin lesions don’t appear for two to four weeks after incubation, leading to delayed treatment and unnecessary and ineffective use of antifungal and antibacterial agents.
During the incubation period, patients also fail to remember the source of the exposure, which is often traced to them cleaning their aquarium. Infection results when bacteria in the non-chlorinated water attacks an open skin wound on the arm or hand.
“People just don’t know or think about their fish tank harboring this bacterial organism,” says George Alangaden, M.D., a Henry Ford Infectious Diseases physician and the study’s lead author.
“And unless they’re directly questioned about it by their physician, who may or may not have adequate knowledge of Mycobacterium marinum and its prolonged incubation period, appropriate treatment often gets delayed.”
What is Mycobacterium marinum ?
Human infection with Mycobacterium marinum was first recognized a pathogen of aquarium fish about nine decades ago.
It survives in both fresh and salt water in most parts of the world. It was once responsible for outbreaks of skin infection in swimming pools prior to the stricter pool disinfection we have now. M. marinum doesn’t survive in a well chlorinated swimming pool.
Today, exposure to aquariums is by far the most common risk factor for acquiring this infection. Certain other recreational activities are rarely implicated such as skin diving and boating activities. Occupational exposure is seen in oyster workers and marine animal handlers.
Human infection is typically associated with trauma, like cuts and abrasions from fish spines or crustaceans. The injury may be quite trivial and typically is confined to the arms and hands.
Mycobacterium marinum is a bacterium that doesn’t grow well at body temperature. This may explain why infections are localized to the extremities where body temperature is cooler.
The infection makes take a few months to manifest. The lesions may appear as groups of small papules or a nodule (granuloma). About half of those infected feel pain and it rarely goes systemic. It is more common in adults than children.
Dissemination in immunosuppressed people have been reported, again usually acquired from home aquariums.
How can you prevent infection with Mycobacterium marinum?
• Use rubber or plastic gloves when handling fish or cleaning aquariums.
• Stay out of fresh or salt water when you have open cuts or sores.
• If you are cleaning fish, wear heavy leather gloves to avoid cuts from sharp spines.
• Make sure your swimming pool is properly chlorinated and maintained.
• Special care should be taken if you have a depressed immune system.
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