Fish, Aquariums and Skin Infections

There is a risk for skin infections for the fish aquarium enthusiast. 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 a well chlorinated swimming pool.

Today, exposure to aquariums is by far the most common risk factor (84%) 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.

There are typically over 100 cases in the United States annually so it is a relatively rare disease.

The infection can be diagnosed by laboratory culture, tissue biopsy or PCR. Even if cultures turn out to be negative, a history of past fish or aquarium exposure may warrant treatment. M. marinum is treatable with antibiotics.

How can you prevent infection with Mycobacterium marinum?

o Use rubber or plastic gloves when handling fish or cleaning aquariums.

o Stay out of fresh or salt water when you have open cuts or sores.

o If you are cleaning fish, wear heavy leather gloves to avoid cuts from sharp spines.

o Make sure your swimming pool is properly chlorinated and maintained.

o Special care should be taken if you have a depressed immune system.