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The use of drugs in aquaculture is necessary to combat pathogens responsible for causing the high rate of mortality in fish farming, such as infection by ectoparasites. The aim of this research was to evaluate the efficacy: (A) of toltrazuril (TOL) treatment against Ichthyophthirius multifiliis, Trichodina heterodentata and Anacanthorus penilabiatus; (B) of thiamethoxam (TH), in treating fish infected by A. penilabiatus and (C) of enrofloxacin (ENR) and florfenicol (FFC) against Aeromonas sp. and Streptococcus sp. The drugs TOL and TH were administered in therapeutic baths while ENR and FFC were mixed with the fish food. The drug concentrations were adjusted according to the experimental conditions (laboratory, microcosm or mesocosm). The drug TOL presented a treatment efficacy rate of 100% against I. multifiliis in microcosm and T. heterodentata in mesocosm. Moreover, ENR presented an efficacy rate of 100% in treating fish infected by Aeromonas sp. and Streptococcus sp. in mesocosm. Finally, TH efficacy rate in controlling A. penilabiatus infection was 81.86% in mesocosm and FFC decreased the overall bacterial load in infected fish. Aeromonas sp. and Streptococcus sp. strains were found in the samples collected for microbiological analysis. In conclusion, TH presented a high efficacy in treating fish against A. penilabiatus infection while TOL was better in controlling T. heterodentata. The antibiotics used in mecoscosm condition presented potential to be used against bacterial infection in aquaculture. [ABSTRACT FROM AUTHOR]