Determination of Effective Dose of Ultraviolet Irradiation to Influent Water for Prevention of Kudoa yasunagai Infection

Abstract

We determined the minimum ultraviolet (UV) irradiation dose to influent water to prevent Kudoa yasunagai infection, using microscopy and qPCR. The infection prevalence in Seriola lalandi reared in untreated water reached 45% while that in fish reared in UV-treated water at 5 mJ/cm² remained below 10%. Additionally, 5 mJ/cm² UV irradiation significantly reduced spore formation in the brain. No infection was detected when the water was treated with UV at the doses 15 and 30 mJ/cm². These results indicate that K. yasunagai actinospores are relatively vulnerable to UV irradiation and the minimum effective dose lies between 5 and 15 mJ/cm².