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.