Newer quinolones offer hope for the future although some as yet unpublished

Newer quinolones offer hope for the future although

This preview shows page 399 - 401 out of 594 pages.

extensive use of oxoHnic acid and flumequine in Europe. Newer quinolones offer hope for the future, although some as yet unpublished evidence points to possible problems with this class of molecules. Whatever the range of compounds available, their effectiveness is a function of the method of administration to fish (and in the way in which it is carried out). We have listed seven basic approaches to the administration of antimicrobial compounds to fish (Table 10.4). These are the oral route via medicated food and bioencapsula- tion, bath, dip and flush treatments, injection, and topical application. With the oral method drugs are mixed with food and then fed to the fish. Usually, the treatment regime leads to the administration of a unit weight of drug to a standard weight of fish per day for a predetermined period. Examples of commonly used antimicrobial compounds have been included in Table 10.5. Fortunately, medicated food appears to be quite stable (McCracken and Fidgeon, 1977). Moreover, this method is advan- tageous insofar as the quantities of compound fed to the fish are carefully controlled, and if sensible feeding regimes are adopted, only minimal quantities would reach the waterways. Three provisos exist, namely that: the fish are capable of feeding; the drug is palatable; the drug is capable of absorption intact through the gut.
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Control 381 Table 10.4. Methods for application of antimicrobial compounds to fish Method of appHcation Comments Oral route (on food) Need palatable components; minimal risk of environmental pollution Bioencapsulation Need palatable compounds; minimal risk of environmental pollution Bath Need for fairly lengthy exposure to compound, which must be soluble or capable of being adequately dispersed; problem of disposal of spent drug Dip Brief immersion in compound, which must be soluble or cap- able of being adequately dispersed; problem of disposal of dilute compound Flush Compound added to fish holding facihty for brief exposure to fish; must be soluble or capable of being adequately dis- persed; poses problem of environmental pollution Injection Feasible for only large and/or valuable fish; usually requires prior anaesthesia; slow; neghgible risk of environmental pol- lution Topical appHcation Feasible for treatment of ulcers on valuable/pet fish A more recent approach has involved bioencapsulation, principally of quinolones (Duis et al, 1995). This theme was expanded with some excellent work which examined the potential for Artemia nauplii to serve as carriers to sulphamethoxazole and trimethoprim for the chemotherapy of diseased marine fish fry (Touraki et ai, 1996). Both these compounds accumulated in the nauplii, with maximal levels recorded after 8h. In a trial with sea bass larvae challenged with V. anguillarum, an improvement in survival followed use of the medicated nauplii (Touraki et al, 1996). Whether or not the fish will feed is largely a function of the nature and severity of the disease. Often in advanced cases of disease the fish will not feed. Therefore, it
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