Effects of Freezing, Drying, Ultraviolet Irradiation, Chlorine, and Quaternary Ammonium Treatments on the Infectivity of Myxospores of Myxobolus cerebralis for Tubifex tubifex

Abstract The effects of freezing, drying, ultraviolet irradiation (UV), chlorine, and a quaternary ammonium compound on the infectivity of the myxospore stage of Myxobolus cerebralis (the causative agent of whirling disease) for Tubifex tubifex were examined in a series of laboratory trials. Freezing at either −20°C or −80°C for a period of 7 d or 2 months eliminated infectivity as assessed by the absence of production of the actinospore stage (triactinomyxons (TAMs)) from T. tubifex cultures inoculated with treated myxospores over a 4–5-month period. Myxospores retained infectivity when held in well water at 5°C or 22°C for 7 d and when held at 4°C or 10°C d for 2 months. In contrast, no TAMs were produced from T. tubifex cultures inoculated with myxospores held at 20°C for 2 months. Drying of myxospores eliminated any evidence of infectivity for T. tubifex. Doses of UV from 40 to 480 mJ/cm2 were all effective for inactivating myxospores of M. cerebralis, although a few TAMs were detected in one replicat...