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		Use of Antibiotics in Ornamental Fish Aquaculture
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		Optimal Approach to Fighting Bacterial Infections Most bacteria that cause diseases in fish are normal inhabitants of aquatic systems and, ordinarily, they do not cause a problem. However, fish that are stressed by one or more factors (such as temperature changes, poor water quality, recent transport or handling), may have compromised (less effective) immune systems, making them more susceptible to bacterial infections. In addition, stress factors which compromise the immune system of fish may actually favor bacterial growth, further increasing the risk of a disease outbreak. The ideal solution to bacterial diseases involves working with a fish health specialist to culture the organism and to run sensitivity tests. 'Culture' refers to growing the infective bacteria on a special type of media (or 'food'; usually agar or gelatin based), and 'sensitivity' refers to treating the bacteria with a series of antibiotics to determine which one will work best. Although culture and sensitivity tests generally take two or three days, they are, by far, the best methods for selecting an antibiotic that will successfully and economically treat an infection. A fish health specialist should be contacted during the initial stages of the disease and given a complete history of the problem. The specialist should provide instructions on submitting samples to a diagnostic laboratory (see UF/IFAS Fact Sheet FA-55 Submission of Fish for Diagnostic Evaluation). Affected fish should not be treated with any antibiotic until after a sample has been analyzed. The sample should include at least 3 to 5 fish showing typical symptoms of the disease. Fish that are submitted after they have been given antibiotics often provide poor culture results. While waiting for the culture results, the fish health specialist may suggest a broad-spectrum antibiotic that can be used until culture and sensitivity tests have been completed. Legalities must also be considered when selecting antibiotics. Producers of food fish have more limited options than producers working with ornamental fish because, according to the U.S. Food and Drug Administration (FDA), ornamental fish are a low regulatory priority. Your fish health specialist will be able to provide information on legal constraints for specific antibiotics, information for correct dosages, proper methods of administration, and concerns about effluent from ponds with treated fish. Proper Dosages and Treatment Regimens: Pharmacokinetics Although selecting the correct antibiotic is an important first step in controlling bacterial disease, proper administration of any antibiotic for the recommended number of days is equally important. Your fish health specialist should provide you with instructions on the amount of antibiotic to use (dose), the frequency (how often) and duration (how long) it should be given (administered), withdrawal time (if applicable - this is the length of time required, after the last dose of antibiotic has been given, that a producer must wait before selling the fish, and is usually more of a concern in food fish species) and any other relevant information. The technical term for the branch of medical science that determines all of these variables is 'pharmacokinetics'; defined as the study of how drugs are absorbed by, distributed within, chemically altered within, and eventually excreted by the body (in this case, the body of a fish). How are the pharmacokinetics of a specific antibiotic scientifically determined? Firstly, different concentrations of the selected antibiotic are tested against various bacteria in order to determine what concentration will work best against these bacteria. Next, the antibiotic is administered (given) in one of three ways: 1) by injection, 2) mixed in feed, or 3) in a bath treatment. Then, antibiotic levels in the body (usually in the blood) are measured at different time intervals after treatment. The purpose of these measurements is to determine how long the antibiotic stays active in the body of the fish and whether or not the concentration in the body is high enough to kill or inhibit bacteria. more ...

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