Both under-yearling and post-yearling Atlantic salmon parr produced high agglutinating antibody titres in response to a single intraperitoneal injection of killed bacterial kidney disease (BKD) cells emulsified in Freund's complete adjuvant (FCA), Low or no response was observed in animals injected with BKD cells in saline or in animals vaccinated by hyperosmotic immersion. Immunological duration was insufficient in fish vaccinated as under-yearling parr to provide protective immunity 2 years later when the fish had become smolts. Atlantic salmon post-yearling parr injected with BKD cells in FCA demonstrated a reduced prevalence of BKD lesions compared to control animals when both were observed as smolts 1 year after vaccination.

Serological analyses of typical and atypical Aeromonas salmonicida divided the representative strains into two distinguishable groups based on their antigenic composition. However, the serological groupings do not coincide with divisions constructed on the basis of physiological reactions. All of the A. salmonicida strains and the two A. hydrophila strains examined share at least one antigen and are sensitive to A. salmonicida bacteriophage 40 RR2.8t. These data reinforce the reasons for placing these two species in the genus Aeromonas. Haemophilus piscium, the causative agent of ulcer disease, was serologically indistinguishable from A. salmonicida and sensitive to A. salmonicida bacteriophages. This information, in addition to published H. piscium DNA studies, suggests this organism is actually an atypical A. salmonicida; more H. piscium isolates should be characterized to confirm this identification.

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and identification of an atypical Aeromonus sul~~~eriicidu strain causing epizootic Bosses among Atlaimtic salmon (Sulmo salar) reared in a Nova Scotian hatchery. Gin. J. Fish. Aquat. Sci. 37: 2236-2241.The bacterium causing 50:>;l cumallative mortality among postyearling parr (pyp) Atlantic salmon (Sabtno sulur) reared at a Nova Scotian hatchery was icientified to be an atypical, achronlogenic Aeromonus sultnor~ic.irifa strain. This srganism~, although differing in several biochemical reactions from typical A. sulrnotiicicicr, was sensitive to A. .sulnro,ijcidu bacteriophages. Aratigenically, the Kejirnkujik A. salrnotlr'cir/a was indistinguishable from typical A . sulmonbcid~~ strains when the serological relatedness was examined using cross-adsorbed rabbit antisera. Analysis of DNA from the atypical A. sulrnot~icir/o yielded a (,I; GC value of 57.85, a value within the range expected for A. sulmonicidu.

The survival of infectious pancreatic necrosis (IPN) virus under conditions of practical import and its susceptibility to destruction by two common disinfecting agents were examined. An indigenous strain of virus, shed to trough water at a concentration of 105 TCID50 per milliliter during an epizootic, lost 99% of its infectivity in fresh water at 4 C in 10–12 wk. There was residual infectivity after 24 wk. Survival was prolonged in sea water where loss of activity of an ATCC strain after 10 wk incubation at either 4 or 10 C was negligible. The loss in 5–6 mo was under 99%.IPN virus (107 TCID50/ml) survived drying in air at laboratory temperature and humidity for 5 but not for 6 wk. Under reduced humidity, residual infectivity was still evident after 8 wk.At a titer of 105.0 TCID50/ml, IPN virus was completely inactivated by exposure to 25 ppm available chlorine in 30 min. A concentration of 40 ppm available chlorine was required to inactivate 107.5 TCID50 of virus/ml in the same period of time. IPN virus, at a titer of 105.5 TCID50/ml, was totally destroyed by 30 ppm active iodine (Wescodyne) in 5 min. An increase in virus concentration, to 106.6 TCID50/ml increased the iodine requirement to 35 ppm to achieve the same result.The implications for salmonid culture of the persistence of IPN virus in an aqueous environment and its resistance to destructive agents are discussed.