Aquarium sued over child's infection
The Tennessee Aquarium in Chattanooga is being sued for $2.4 million by the parents of a child who allegedly acquired an infection after petting stingrays and sharks. The news report contains very little information, but the reference to "fish-handler's bacteria" means the infection was presumably caused by the bacterium Erysipelothrix rhusiopathiae. This bacterium can be found in various animal species, particularly pigs, and can be spread to people. The risk of infection is greatest in people with pre-existing skin lesions, since these allow the bacterium to bypass the normal skin barrier. It can also be found in/on fish, and infections in fish handlers tend to occur because they have close contact with fish and they often have skin lesions from fish, knives or other sharp objects, hence the name fish-handler's disease. When infection occurs, it is usually limited to a local skin infection, but more invasive infections involving deeper tissues or infections that spread to other parts of the body can rarely occur. In this case, the child must have had a deeper infection since according to the report he's had to undergo multiple surgeries.
Aquarium officials (unsurprisingly) refute the suggestion that the aquarium was the source, pointing to five negative water tests after the child's visit to the facility. Unfortunately, water tests taken after the suspected time of exposure don't really tell you much. It's going to be hard to prove anything, but it's reasonable to suspect that the aquarium was the source. This is a rare infection that can be associated with contact with fish and their environment, and the child had that kind of contact. Looking at other potential sources of exposure like pig contact is also necessary.
Even if no other potential sources of exposure are identified, it's still not definitive that the child acquired the infection at the aquarium, nor does it necessarily mean that the aquarium is at fault. Every contact with an animal or its environment (just like any contact with a person) carries some degree of infectious disease risk. The key issue is whether the facility took reasonable precautions to reduce that risk. In particular, this would include providing easy access to a handwashing or hand sanitizer station immediately after the contact occurred, and clear signs indicating the need for hand hygiene. Any animal contact event, be it a traditional petting zoo, pony rides or aquatic contact exhibits like this one, need to take those basic precautions. If proper measures are used, infections can still occur, but that's a fact of life. We cannot prevent 100% of infectious diseases. What we try to do is reduce the risk as much as possible, while maintaining the benefits of activities that involve animal contact. It's a balancing act and it's never perfect, but that's all we can do and what we need to expect from animal contact events.
Serious infection from a fish tank
A California teen has been battling a chronic and severe infection acquired from a fish tank. Five years ago, Hannele Cox cut her hand when she pulled it out of an aquarium. It sounds like it was a pretty minor scratch, but it doesn't take much to cause an infection under the right circumstances.
A while after the injury, infection was apparent. A round of antibiotics didn't fix it (no word on whether any bacterial cultures were performed at that point). Eventually, a dermatologist diagnosed the problem: Mycobacterium marinum infection. One problem with infections like this is that they are sometimes not diagnosed until they are quite advanced. If the patient doesn't mention the aquarium exposure and/or the physician doesn't ask about pets, an infection like M. marinum might not be considered.
Mycobacterium marinum infection is sometimes called "fish tank granuloma" in testament to its common association with fish tanks. It can be found in both freshwater and marine fish (and the water in their tanks), and most often infected fish don't have any signs of disease. Therefore, you have to assume that any fish and any aquarium could be infected, and therefore a potential source of human infection.
Infections with M. marinum usually develop a couple of weeks after exposure and are characterized by small bumps (papules) on the skin that progress to shallow ulcers. Typically, infection is not very invasive and responds to treatment, although months of treatment may be required. Sometimes, the infection can spread to deeper tissues, making it much harder to treat. Unfortunately, that's what happened to Hannele Cox. Her infection has not responded well to treatment and has spread to deeper tissues, including bone. She's had two surgeries to try to save her hand, and at least one more is planned. Amputation isn't outside of the realm of possibility, but will hopefully be avoided.
Fish owners should be aware of the risk of M. marinum infection. While fish are often ignored as a potential causes of infection and the overall risk is low, there are simple measures that can be undertaken to reduce the risk of acquiring an infection from fish tanks. These mainly involve limiting contact with fish tank water and the use of good general hygiene practices:
- Contact with aquarium water should be minimized
- Never dump aquarium water into kitchen or bathroom sinks.
- Promptly clean up any aquarium water spills.
- Take care when putting your hands in the aquarium, especially if there are sharp surfaces (e.g. rock, coral) that might result in cuts or abrasions.
- Hands should be washed thoroughly after contact with aquarium water.
- People with compromised immune systems should not have contact with aquarium water. They should have someone else clean their fish tank.
Antagonzing piranha... Maybe not a good idea
Pet bites are a big p
roblem. Dogs bites in particular are far too common and can result in serious injury or even death in a small percentage of cases. Bites from other pet species also happen, but the extent of the problem is not clear. A good general rule is if it has a mouth, it can bite.
Another good general rule is if it has numerous sharp teeth, is a carnivore and your as upsetting it, you should get your hand out of the way. Pet store owner Dave Brown found this out the hard way, although in this situation he has the dubious distinction of having been bitten by a fish.
It seems that Mr. Brown was trying to catch a piranha that he was selling. I would have thought the standard way of catching a fish, not to mention a six-inch-long carnivorous fish, would be to use a net. Apparently not. Mr. Brown used 
his bare hands, and after a couple unsuccessful attempts to catch the fish, the piranha fought back, sinking his teeth into the store owner's thumb. The bite was severe enough that stitches were needed. According to Mr. Brown "There was blood everywhere. Every time I had him in a plastic bag the fish would bite through it. He was quite a feisty one." Personally, I think if a carnivorous fish was repeatedly trying to attack me through the bag, I'd probably change my approach to catching it.
According to a local fish expert, "[Mr. Brown] was very unlucky as these fish normally just attack when they're hungry. It may have been a bit peckish."
Fortunately, apart from a sore thumb, it sounds like the biggest problem Mr. Brown will face is the harassment that I assume he's going to take from friends after being bitten by a fish.
...but pet fish are absolutely safe... aren't they???
Fish are very popular pets. It has been estimated that freshwater fish are owned by over 14 million people in the US, and saltwater fish are owned by approximately 800 000 people. Fish can be interesting, low maintenance pets, and the risks of disease transmission to people are low. However, low does not mean zero, and there are some diseases than can be spread from fish to people.
The most common (but still quite rare) disease that can be transmitted from fish to humans is infection with Mycobacterium marinum. This microorganism can be found in both freshwater and saltwater. It can cause skin infections, usually in areas where the skin is already broken, such as pre-existing scrapes and cuts, or skin that is damaged while cleaning an aquarium. Serious or long-term problems are rare in otherwise healthy people, but infection can be fatal in individuals with a weakened immune system.
Various other bacteria found on fish and in aquariums can cause infection in people as well. These are usually also "opportunistic infections" that tend to occur in people with weakened immune systems or infected wounds.
While fish are low risk pets, you can still minimize the risks that do exist by following a few simple precautions:
- Wash your hands after contact with aquarium water or items in the aquarium. Gloves should be worn to prevent skin damage if you need to touch rough or sharp surfaces.
- Do not clean an aquarium in the kitchen.
- Do not dump aquarium water down the kitchen sink.
- Prevent contact of aquarium water or contents with open wounds on your skin.
- Keep aquariums covered. This helps keep other pets (e.g. cats) from drinking or playing in the water. (It also prevents escape attempts by the fish, which never end well!)
