title: 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 degrees C or -80 degrees 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 degrees C or 22 degrees C for 7 d and when held at 4 degrees C or 10 degrees C d for 2 months. In contrast, no TAMs were produced from T. tubifex cultures inoculated with myxospores held at 20 degrees 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 replicate T. tubifex culture at 240 mJ/cm2 and in one replicate culture at 480 mJ/cm2. Treatments of myxospores with chlorine bleach at active concentrations of at least 500 mg/L for 15 min largely inactivated myxospore infectivity for T. tubifex. Likewise, there was no evidence of TAMs produced by T. tubifex inoculated with myxospores treated with alkyl dimethyl benzyl ammonium chloride (ADBAC) at 1,500 mg/L for 10 min. Treatments of myxospores with 1,000-mg/L ADBAC for 10 min reduced TAM production in T. tubifex cultures sevenfold relative to that in cultures inoculated with an equal number of untreated myxospores. These results indicate that myxospores of M. cerebralis demonstrate a selective rather than broad resistance to selected physical and chemical treatments, and this selective resistance is consistent with conditions that myxospores are likely to experience in nature.
authors.affiliation: Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, One Shields Avenue, Davis, California 95616, USA. rphedrick@ucdavis.edu
authors.forename: Ronald P
authors.initials: RP
authors.lastname: Hedrick
authors.forename: Terry S
authors.initials: TS
authors.lastname: McDowell
authors.forename: Kaveramma
authors.initials: K
authors.lastname: Mukkatira
authors.forename: Elizabeth
authors.initials: E
authors.lastname: MacConnell
authors.forename: Brian
authors.initials: B
authors.lastname: Petri
mesh_terms: D000818:Animals; D003063:Cnidaria / Q000187:drug effects / Q000472:pathogenicity / Q000502:physiology / Q000528:radiation effects; D003890:Desiccation; D004202:Disinfectants / Q000494:pharmacology*; D005615:Freezing; D009835:Oligochaeta / Q000469:parasitology*; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D012973:Sodium Hypochlorite / Q000494:pharmacology; D013170:Spores / Q000187:drug effects / Q000472:pathogenicity / Q000502:physiology / Q000528:radiation effects; D014466:Ultraviolet Rays; D014774:Virulence / Q000187:drug effects / Q000502:physiology
chemical_list: D004202:Disinfectants; D000644:Quaternary Ammonium Compounds; D012973:Sodium Hypochlorite