Saprolegniasis is a detrimental fungal- like disease prevalent in the aquaculture industry, seriously causing damage to cultured fish populations and their eggs, leading to high mortality rates with subsequent economic losses. Unfortunately, many existing therapeutics for this disease prophylaxis have proven to be ineffective and have also raised concerns regarding their negative environmental impact. This study compared the efficacy of three medicinal plant extracts and a chemical compound readily available in Ghana to assess their potential as anti-fungal agents against Saprolegnia ferax.
The fungistatic and fungicidal properties of plant extracts i.e. Azadirachta indica (neem leaf), Vernonia amygdalina (bitter leaf), Terminalia catappa (Indian almond), and the chemical (potassium permanganate (KMnO4)), were investigated under in vitro conditions. This study was carried out within 96 hours at different concentrations ranging from 5 mg/ml to 20 mg/ml. Molten Sabouraud Dextrose Agar, maintained at 45⁰C, was combined with all treatments at different concentrations in six well-cultured plates. Following that, the mixture was allowed to solidify, and 0.4 mm agar plug was centrally positioned in each plate. Subsequently, the average radial growth of the fungi was assessed at 12, 24, 72, and 96 hours. A two-way ANOVA was used to test for the statistical differences between the treatments and exposure time on radial growth. There was a significant difference among all treatments with Terminalia catappa showing the least radial growth (0.02mm) at 96hrs (Fig 1). The results indicate that both Terminalia catappa and KMnO4 exhibited complete inhibitory effects on fungal growth compared to the other two plant extracts (Fig 1).
Therefore, in terms of affordability and availability to fish farmers in Ghana, Terminalia catappa is recommended as a valuable prophylactic treatment alternative for saprolegniasis under in vitro conditions, however, further studies are needed to confirm its safety for fish