| Summary: | Yersinia ruckeri is a pathogen which causes yersiniosis and significant losses in farmed Atlanticsalmon ( Salmo salar ) in the Southern Hemisphere. Currently, Yersinivac-B, a commercial bacterin-basedvaccine manufactured by MSD Animal Health and prepared from formalin killed whole-cells,is used for immersion vaccination against Y. ruckeri for most Tasmanian Atlantic salmon. Untilrecently, these fish were vaccinated once by bath immersion at 5g. However, half a millionvaccinated juvenile Atlantic salmon died of yersiniosis in a single Tasmanian hatchery in 2007. Inthis PhD study, we evaluated different inactivation methods of Y. ruckeri on the efficacy of singledip vaccines including formalin inactivation, ammonium sulphate inactivation, and pH-lysed thenformalin inactivation. Additionally, hyperosmotic infiltration was combined with an ammoniumsulphate inactivated bacterin in immersion vaccination to assess the protection of these vaccines.The relative percent survival (RPS) afforded was 93.4% for the fish vaccinated with ammoniumsulphate inactivated vaccine, 85.4% for fish vaccinated with formalin inactivated vaccine and81.3% for fish vaccinated with pH-lysed then formalin inactivated vaccine. The results of this studyhave shown that ammonium sulphate can be used to inactivate Y. ruckeri and can replace formalininactivation.
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