Since 2016, VIVALDI project, supported by the European Union H2020 programme, has aimed to improve the sustainability and competitiveness of the European shellfish industry, which has been hit by a growing number of mortality cases over the recent years. To this end, tools and strategies to better prevent and mitigate the impact of bivalve diseases have been developed through 6 work packages:

• In the 1^st work package, the diversity and lifecycles of some bivalve pathogens have been investigated. Environmental-based approaches such as passive sensors or the use of magnetic beads and electrochemical biosensors could be useful for pathogen surveillance and the development of early warning systems.


• In the 2^nd work package, some key mechanisms involved in the response of bivalves during a pathogen infection have been identified. Several modulated genes were also found, which may help to identify potential markers related with resistance against diseases. VIVALDI has also demonstrated that stimulating bivalve immunity is possible.


• In the 3^rd work package, oyster and clam families have been produced and challenged regarding their susceptibility to pathogens. Panels of well-selected SNP markers are now available for oysters and clams and have allowed us to identify markers associated with resistance to some pathogens and will optimise breeding programmes.


• In the 4^th work package, the impact of environmental parameters on the development of bivalve diseases has been studied: for example biodiversity for infection with OsHV-1 and plankton for bacterial diseases. The characterisation of bivalve microbiota under different scenarios, including disease development or environmental perturbations, should contribute to the identification of bivalve health markers.


• In the 5^th work package, a literature review and field studies have been carried out to identify the best husbandry practices to reduce mortality. The efficiency of UV treatment to remove pathogens, oyster gametes and larvae from the wastewater has been confirmed. Finally, our risk ranking shellfish farm model could be used by competent authorities to implement risk-based surveillance of shellfish diseases.


• In the 6^th work package, aRecommendations to prevent mitigate and control bivalve diseases have been identified from the results of VIVALDI and will feed, together with existing guidelines, a manual for disease management and biosecurity, which is being co-constructed with a group of stakeholders.

Many studies have been carried out in VIVALDI and lay the foundations for future works notably on the impact of global change on bivalve diseases and also perspectives in the field of restoration of local bivalve species. Finally, VIVALDI has contributed to develop solutions, recommendations for a better implementation of the legislation. These outcomes will also bring helpful information for the evolution of this legislation.