Efficacy of medicinal plants on microbial fish pathogens

Studies were conducted to examine the efficacy of fifteen medicinal plants against common microbial (bacterial and fungal) fish pathogens. Crude extracts were prepared from these medicinal plants and applied to the fresh culture of pre-isolated bacterial (Aeromonas hydrophila, Pseudomonas fluorescens and Edwardsiella tarda) and fungal pathogens (Aphanomyces invadans, Saprolegnia sp. and Achlya sp.) under in-vitro condition. A high dose was initially used to detect antimicrobial effects of these plants and garlic, turmeric, neem, shoti, akand etc. were screened out strong and moderate effective on the pathogens. In the case of bacterial pathogens, strong inhibitory response was exhibited by garlic and mixed extract of akand + neem; followed by turmeric and akand. Four different doses of plants extract were exposed under the in-vitro condition to determine minimum inhibitory dose (MID). However, garlic offered the best result with 93.33 ± 3.33% recovery of challenged fish (Barbonymus gonionotus) in aquarium trial. Akand + neem, turmeric and akand showed moderate to weak recovery rate with the same dose. In the case of fungi, in-vitro test on the individual culture was done at four pre-selected doses. Treatment trial was performed using the minimum inhibitory dose (MID) of the highly effective plants (viz., turmeric, shoti, neem + turmeric and neem shoti) on experimental infected of fish. Turmeric (80.00 ± 1.15% recovery rate) and neem + turmeric (80.00 ± 2.88% recovery rate) were found to be the most effective plants. These could be used as an effective, low-cost and alternative disease control measure in fish health management.