Therapeutic potential of intraperitoneal miconazole nitrate against Saprolegnia parasitica in Labeo rohita under feeding refusal conditions.

Fungal infections caused by Saprolegnia parasitica are a major concern in freshwater aquaculture, particularly during advanced stages of disease when affected fish often exhibit feeding refusal, rendering oral medication ineffective. This study investigates the therapeutic potential of intraperitoneally administered miconazole nitrate (MCZ) in Labeo rohita fingerlings under such critical conditions. The 96-h LD50 of MCZ was determined to be 0.20 ± 0.13 mg kg-1 body weight (BW). Three sub-lethal doses (0.01, 0.02, and 0.04 mg MCZ kg-1 BW) were evaluated alongside a DMSO control over eight time points (0-240 h), analyzing haematological and immuno-biochemical parameters including erythrocyte and leukocyte counts, hemoglobin, hematocrit, Mean Corpuscular Volume (MCV), Mean Corpuscular Haemoglobin (MCH), Alanine Aminotransferase (ALT), Aspartate Aminotransferase (AST), glucose, plasma ion concentrations, lysozyme activity, total protein, and respiratory burst activity. A dose-dependent physiological response was observed, with lower doses (especially 0.01 mg MCZ kg-1 BW) exhibiting minimal adverse effects while enhancing immune indicators such as lysozyme and respiratory burst activity. Challenge trials with S. parasitica zoospores further confirmed higher survival and recovery in the low-dose group. These findings highlight the efficacy of injectable MCZ as a vital therapeutic alternative during feeding suppression, offering a targeted strategy for managing saprolegniasis in aquaculture.