Effect of gamma irradiation on inactivation of Ichthyophthirius multifliis trophonts and its efcacy on host response in experimentally immunized rainbow trout (Oncorhynchus mykiss)

Abstract

The present study was conducted to investigate the effects of gamma irradiation on Ichthyophthirius multifliis trophontsand to determine the efects of exposure on inactivated parasites in rainbow trout. In the frst trial, fsh were treated with irradiatedIchthyophthirius multifliis trophonts for 21 days. Results showed that irradiation at doses of 150 Gy and higher was required to inactivateIchthyophthirius multifliis trophonts. The LD50 value obtained was 52.2 Gy. In the second trial, the effects of irradiated Ichthyophthiriusmultifliis trophonts on physiological and biochemical components of blood and mucus, as well as skin morphology, were studied for30 days. Results showed that total protein levels increased in fsh exposed to 100 and 150 Gy irradiated trophonts. Fish exposed to150 Gy treated parasites showed signifcant increases in serum lysozyme activity. Serum alkaline phosphatase levels were signifcantlylower in the treatment groups. In the skins of fsh exposed to 100 and 150 Gy irradiated trophonts, a higher percentage of goblet cellswas observed. Mucus protease and esterase levels were also higher in the treatment groups compared to the control group on days 20and 30. Tis suggests that rainbow trout appear to beneft from treatment with gamma-irradiated Ichthyophthirius multifliis trophonts,especially at 150 Gy.