Zoonotic Diseases: On the Usage & Dangers of Antibiotics
On May 1, 2012, 24-year old University of West Georgia graduate student Aimee Copeland was on a zip-lining adventure with friends on the Little Tallapoosa River in Georgia. When it was her turn, the homemade zip line snapped, causing her to fall into the river. The fall also caused a big gash in her calf, which required some 20+ stitches. As might be expected, there was pain, but this continued to worsen and resulted in another trip to the emergency room, where she was diagnosed with a condition called necrotizing fasciitis. Something, a bacterium, is eating away at her tissues, and this flesh-eating pathogen turned out to be Aeromonas hydrophila. Ms. Copeland had come into contact with Aeromonas when she fell into the river. Thankfully, her life was spared, but the infection necessitated the amputation of her leg, part of the abdomen, and some fingers.
Aeromonas should sound somewhat familiar to you, as the bacterium is found virtually in every freshwater aquarium setting. It normally doesn't cause (m)any problems, but according to Noga, it is one of the causative agents of ulcers, depression, exopthalmia (popeye), and dropsy/peritonitis. The bacterium only becomes an issue when tank conditions have deteriorated, such as can result with infrequent water changes, overcrowding, overfeeding and/or other circumstances where stress levels have increased in the aquarium inhabitants. Likewise, in humans with normal/healthy immune systems, Aeromonas usually doesn't pose any problems. However, in some circumstances, such as in immunocompromised individuals or some unfortunate few like Ms. Copeland, Aeromonas can wreak havoc on the human body.
Aeromonas is just one example of a zoonotic disease, where an infection of an animal (fish) can be naturally transmitted to human beings. As seen in the table below, there are a host of other zoonotic organisms, ranging from bacteria, to parasites, to viruses. Some require that you actually have to ingest the infected fish, although in other cases, infection can be established by either ingesting infected fish water, by touching infected fish, or simply by coming into contact with the infected fish water.
To put things in perspective, it should be noted that although these things can happen, they normally don't, especially when you are an otherwise healthy person. Additionally, practical safety measures that are easy adapt can be very effective in preventing the occurence of zoonotic infections. Wear gloves when you clean or come into contact with aquarium water, especially if you have a cut on your arm. If you have a particularly deep cut, then avoid exposing the cut to the aquarium water! Always take care to disinfect your quarantine tanks and other equipments. Disinfectants for equipments can range from salt, hydrogen peroxide, potassium permanganate, and/or bleach.
The other big safety precaution that should be noted and exercised at all times has to do with putting measures in place to avoid generating antibiotic resistant bacteria. This is an individual and a public health concern. In our fish keeping hobby, at times we will need to treat our fish with an antibiotic. However, when antibiotics are used inappropriately, such as underdosing, chronic exposure, or ineffective antibiotic treatment, you run the risk of raising bacteria that are resistant to the antibiotic(s) that you were using, and possibly others. Imagine what would happen if the Aeromonas strain Ms. Copeland had to face was a multi-drug resistant bug. To that end, these are some practical suggestions when it comes to antibiotics:
1. Consider other options prior to using antibiotics. Just because you can use it, or because it's available to you, does not mean you should use it. Try other alternatives, such as salt or some other mild treatment, which will be less damaging on the fish, and resistance to these substances is much harder to achieve.
2. When you think you have to use an antibiotic, seek a second or third opinion. Sometimes when we are worrying for our fish, we lose objectivity, and having other opinions can only help.
3. When you do have to use antibiotics, start with the least aggressive but still effective choice you have. Make sure that you are using an antibiotic that will actually be effective in your system. For example, if you have hard water with basic pH, then tetracyclines are not appropriate to use.
4. When you do have to use antibiotics, make sure you use the proper amount, and for the proper length of time. Don't cut the dose in half, or less, because you think your fish is too small or too weak to handle it. This is the surest way for you to raise resistant bugs, which can then plague your system for years later, and it can become a personal and public health concern. Cutting the dose won't necessarily be harmful, and if you think a regular dose of antibiotics is too strong for the fish, then that antibiotic is not appropriate to use. Consider other alternatives. In the same vein of thought, you should be not be cutting a course of antibiotics short. This is effectively cutting the dose.
5. When you do have to use antibiotics, always choose medicated feed and/or injections over adding the meds to the water. Waterborne antibiotics have very limited applications and effectiveness, and when used inappropriately is another setting which can promote antibiotic resistance.
6. The majority of antibiotics we are now using in the fish keeping hobby is no longer in wide usage for humans. Don't be tempted to try novel or more powerful antibiotics. This is extremely dangerous.
In conclusion, while zoonotic diseases is always a possibility, by taking some prudent measures, we can keep this hobby safe for ourselves and others.