Abstract EN:

Abalone aquaculture has only recently been developed in western Europe, and already it has had to face numerous pathologies. Since 1998, natural and farm stocks of Haliotis tuberculata have suffered high mortalities on a regular basis, mainly due to the pathogenic bacterium, Vibrio harveyi. The vibriosis ofthe European abalone, in particular its macroscopic signs, and the conditions necessary for its development have been studied in detail by field and laboratory experiments. We have been able to show the importance of the interplay between water temperature (>17°C), animaI physiology (reproduction period) and a pathogenic strain (harbouring the plasmid pVCR1) for the development of this abalone disease. A limited localisation study of the abalone target tissues (gills, muscle and haemolymph) has been performed and a 3 phase disease development model is hypothesized. A clear link between the reproduction period with its accompanying immune difficiency and the animals sensitivy to the pathogen has been established. Using a molecular, approach strains of virulent V. Harveyi were found to directly intervene with the animal’s immune system, probably through a partial inhibition of the MAP kinase pathway activation in the haemocyte. Finally, we were also able to show the utmost importance ofthe pVCR plasmids for the virulence phenotype of this pathogenic bacterium.