Effects of adjuvanted AEROMONAS SALMONICIDA vaccines on growth, oxygen consumption, and selected haematological and immunological variables in juvenile rainbow trout (ONCORHYNCHUS MYKISS)

Seven injectible vaccines against Aeromonas salmonicida were tested to determine the various effects they might have on selected variables of the physiology, swimming performance and immune functions of juvenile rainbow trout (Oncorhynchus mykiss). The study involved three trials of consecutively longer times, 5, 12, and 24 weeks in duration, at the beginning of which fish were injected with a variety of adjuvanted and non-adjuvanted vaccines. The array of vaccine preparations was based on a simple, formalin killed, Aeromonas salmonicida bacterin. They were: bacterin only, bacterin adjuvanted with levamisole, bacterin in oil emulsion, microencapsulated- bacterin, microencapsulated bacterin with the addition of muramyl dipeptide, microencapsulated bacterin with P-1,3 glucan added, and microencapsulated bacterin with the addition of Vibrio anguillarum lipopolysaccharide (LPS). Midway through each of the three trials, oxygen consumption was determined in whole fish as an indicator of metabolic rate. At the termination of each study, fish weights and lengths were determined and specific growth rates were calculated. Fish were sacrificed and blood was collected for determination of haematocrit, leucocrit, differential white blood cell count, agglutinating antibody titre, and haemolytic activity in the plasma. Somatic organs were dissected from the animals, and the somatic indices for total kidney, head kidney and spleen were determined. Finally, kidney lysozyme activity was determined from tissue homogenates. The highest level and broadest range of positive responses were gained from the A. salmonicida bacterin which was microencapsulated with V. anguillarum LPS as an immunostimulant. This preparation proved to increase the metabolic and specific growth rates of fish over a short period of time. Such effects may have potential long term positive impacts on the size of fish at harvest. The LPS treatment also caused a high plasma antibody titre, and high levels of kidney lysozyme activity for a substantially longer period of time than other immunizations.Land and Food Systems, Faculty ofGraduat