VACCINATION TRIALS ON GILTHEAD SEABREAM (SPARUS-AURATA) AGAINST PASTEURELLA-PISCICIDA

A comparative study of the efficacy of two vaccine formulations, a who le-cell bacterin (WCB) and a toxoid-enriched whole-cell vaccine (WCEB) , against Pasteurella piscicida was conducted by bath immersion in gil thead seabream in order to evaluate the role of the extracellular prod ucts (ECP) as protective antigens against this pathogen. With this aim , two strains showing differences in their ECP composition were used t o prepare both vaccines. Only the toxoid-enriched vaccine conferred pr otection apinst P. piscicida within a 4-week period. The relative perc ent survival (RPS) acheived with this type of vaccine ranged between 3 7 and 41 depending on the bacterial strain and dose used in the challe nge. Although this protection level is not very high, we consider that it is valuable considering the economic importance of the fish suscep tible to pasteurellosis throughout the world. The booster immunization with the WCEB P. piscicida formulation did not increase the protectio n levels of gilthead seabream. The antibody response in the sera of bo th immunized fish groups was very low with no correlation between the level of agglutinating antibodies and the protection. In addition, thi s vaccine did not confer cross-protection apinst serotypes 01 and 02 o f Vibrio anguillarum.