Effects of sub-lethal doses of miconazole nitrate on Labeo rohita and its curing efficacy against Saprolegniasis

Miconazole nitrate (MCZ) is an imidazole derivative antifungal drug used as therapeutic and prophylactic agent against fungal outbreak in human and veterinary animals. However, its use in aquaculture industry has not been reported yet. The aim of this study was to evaluate the acute toxicity of MCZ in fish and the effects of sub-lethal doses of MCZ on the haematological and biochemical parameters in Labeo rohita. Different haematological parameters like total blood cell counts, haemoglobin content along with mean corpuscular haemoglobin, mean corpuscular volume and mean corpuscular haemoglobin concentration values were observed. Biochemical parameters like plasma glucose level, plasma glutamic oxaloacetic transaminase and plasma glutamic pyruvic transaminase activity, alkaline phosphatase activity, plasma Na+ and K+ levels were also determined. In this experiment, 32 treatments (4 dose × 8 exposure times) of four MCZ doses (control- 0.0 mgMCZ kgBW−1, T1–6.30 mgMCZ kgBW−1, T2–12.61 mgMCZ kgBW−1 and T3–25.22 mgMCZ kgBW−1) with eight exposure times were set up in triplicates. In the second experiment, fish infected with Saprolegnia parasitica were fed with MCZ based feeds @ 1% BW daily for 21 days and their relative percent survival were recorded. The study revealed that the sublethal doses of MCZ have the significant (p < 0.05) effect on the haematological and biochemical parameters of the fish and also lowered (p < 0.05) the mortalities of saprolegnia infected fish. Fish fed with diet T3 (25.2 mgMCZ kg−BW−1) had maximum survivability with highest curing efficacy without any observable harmful effect on the physiology of fish. Thus, MCZ has an effective role in maintaining the health status of fish and providing protection against oomycetes, S. parasitica infection.