ASSESSMENT OF HYDROGEN PEROXIDE ON HISTOPATHOLOGY AND SURVIVAL RATE IN COMMON CARP, CYPRINUS CARPIO L. INFECTED WITH SAPROLEGNIASIS
The present study was carried out in order to understand and describe the histological alterations and survival rate in common carp, Cyprinus carpio L. treated with various concentrations of hydrogen peroxide following Saprolegniasis infection. One hundred fish infected with Saprolegnia spp. were collected from fish farms in Babylon/Iraq. Fungal isolation was done from different parts of the body using the routine technique. Pathogenicity of the isolated fungi was tested on host fish with a concentration of 2×104 zoospores L-1 and the fishes were got the infection. Hydrogen peroxide at different concentrations (1, 3, 6 ml/L for 30 min for 3 successive d and control group) was used to control the experimental fungal infection in fish. In addition, formalin (0.15 ml/l for 60 min for 3 successive d interval) was used as a reference treatment. Results showed various histomorphological changes in the gills of the infected and treated fish with H2O2 including degeneration of lamellae, epithelial proliferation, fusion of the secondary lamellae, aneurysm and cellular necrosis. Similar alterations were seen in fish infected groups and treated with H2O2 or formalin but are significantly decrease (P<0.05) compared to positive control group. The skin of the positive control revealed loss of epidermal layer, necrotizing of dermis and hypodermis with mononuclear infiltration also were seen. Treatment group at concentration of 1mg/L H2O2 offered the highest survival rate (90%) followed by 3 and 6 ml/L (75 and 65%) respectively. In conclusion, the present study approved the potency of the hydrogen peroxide in controlling Saprolegniasis in common carp.