The effect of sea bream (Sparus aurata) broodstock and larval vaccination on the susceptibility by Photobacterium damsela subsp. piscicida and on the humoral immune parameters

Sea bream broodstock were immunised 1 or 2 months before spawning with a novel photobacteriosis vaccine. Sixty-seven-day-old larvae (mean weight 22.3 mg) originating from immunised and non-immunised parents were experimentally infected with the Photobacterium damsela subsp. piscicida (Phdp). Larvae from immunised fish showed delayed onset and lower mortality (66.67%) compared with larvae from control fish (80%). Eighty-nine-day-old larvae (mean weight 162.2 mg) from both groups were bath vaccinated with Phdp and Escherichia coli lipopolysaccharides (LPS) and larval samples were collected for measurement of humoral parameters. Larvae vaccinated with Phdp and LPS showed significantly higher anti-protease activity, lysozyme activity and total immunoglobulin compared to the controls. One-hundred-and-twenty-day-old larvae (mean weight 297.85 mg) from both parental groups were challenged with (LD70) virulent Phdp bacterial cells. Vaccinated larvae from both groups showed significantly less mortality compared to the respective controls. The RPS values of larvae from immunised parents vaccinated with Phdp and LPS was 95.83% and 72.22%, respectively. The RPS values of larvae from non-immunised parents vaccinated with Phdp and LPS was 62.5% and 70.83%, respectively. Results are discussed with respect to the beneficial effect of broodstock immunisation prior to spawning and the immunisation of larvae on their survival against photobacteriosis.