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H2020

VIVALDI Report Summary

Project ID: 678589
Funded under: H2020-EU.3.2.

Periodic Reporting for period 1 - VIVALDI (Preventing and mitigating farmed bivalve diseases)

Reporting period: 2016-03-01 to 2017-08-31

Summary of the context and overall objectives of the project

The European shellfish industry is a major contributor to global production of marine bivalves. Its social impact is significant, employing about 40000 people in 8500 companies. European shellfish production focuses on a limited number of species, including oysters, mussels and clams which are produced at industrial levels.
Over the recent years, this sector has grown more slowly than other fish farming sectors, notably because its success depends on high environmental quality and susceptibility to mortality events, often linked to pathogenic organisms such as viruses, bacteria and parasites.
Since 2008, massive mortality outbreaks in Pacific oyster Crassostrea gigas spat have been reported in Europe. They were attributed to the presence of oyster herpesvirus, OsHV-1 in combination with adverse environmental factors. More recently, increased mortality has been reported in France and Ireland in adult Pacific oysters associated with bacterial infections Vibrio aestuarianus and among blue mussels with the detection of V. splendidus. In Galicia, the parasite Marteilia cochillia has contributed to the collapse of cockle Cerastoderma edule fishery since 2012. These mortality events cause serious economic losses throughout the concerned European countries.
The European project VIVALDI aims at increasing the sustainability and competitiveness of the shellfish industry in Europe.
VIVALDI will bring new knowledge on the complex interactions between shellfish, environment and pathogens and will develop practical tools and approaches aiming at better preventing and controlling diseases in the main European farmed shellfish species. These species include oysters (Crassostrea gigas and Ostrea edulis), mussels (Mytilus edulis and M. galloprovincialis), clams (Ruditapes philippinarum) and scallops (Pecten maximus). The project addresses the most harmful pathogens affecting these species: the virus Ostreid herpesvirus 1 (OsHV-1), Vibrio species including V. aestuarianus, V. splendidus and V. tapetis, as well as micro- eukaryotes such as the parasites Perkinsus olseni and Bonamia ostreae.
VIVALDI investigates:
- the pathogen diversity and life cycle ;
- the interactions between bivalves, pathogens and environmental parameters;
VIVALDI develops:
- genetic selection strategies
- practical methods for disease control;
-a strategic approach to inform stakeholders

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The sampling effort is well underway, especially in key sites (Dungarvan bay in Ireland, Rade of Brest in France, Ría de Vigo and Delta del Ebro in Spain). Bivalves, micro-invertebrates, sediment, water have been sampled and are due to be analysed and serve in various studies. In order to make it possible to compare the results, harmonised sampling and process procedures have been established. The diversity of some oyster pathogens, particularly the virus OsHV-1 and the bacteria Vibrio aestuarianus, are being investigated by different VIVALDI partners. Passive sensors were successfully tested in laboratory, allowing for the detection of aquatic viruses. These will now be tested in the field near oyster farms.
Both responses of host and pathogen have been investigated by sequencing transcriptomes in different infection models including oysters, mussels and clams. These data sets allow the researchers to identify important pathways involved in the bivalves’ response against some pathogens. For example, autophagy is an intracellular degradation system that allows degradation and recycling of cellular components. This mechanism seems to be activated in oysters infected with OsHV-1, hence suggesting that autophagy is involved in the defence mechanisms against the virus. Interestingly, mussels show an extremely high basal expression of antimicrobial peptides that might be very effective against bacteria, viruses and fungi.
Several oyster families were produced in hatchery from animals showing better survival after an infection with OsHV-1 in order to understand resistance behaviour. Complementarily, the impact of the diet on the resistance to a viral infection is investigated at different ages. Several intraspecific and interspecific crossings of cupped oysters were carried out and animals were tested for their survival against several pathogens. Clam families (Ruditapes philippinarum) were also produced for laboratory and field challenges with Vibrio tapetis and the parasite Perkinsus olseni. First simulation studies carried out to help designing breeding programs are very promising. A new specific quantitative method to rapidly phenotype clams regarding the presence of P. olseni has been set up and is in a validation stage.
Microbial communities (i.e. microbiota) play a key role in the interactions between host and pathogens. In order to characterise microbiota and pathogen organisms in bivalves during mortality outbreaks and under environmental modulations, harmonised protocols have been established and used in laboratory experiments and field studies. Some first sequence data sets have been obtained and are under analysis. Pathogen dissemination models have been developed. Once validated, these hydrodynamic models will be used to simulate disease dissemination in key sites.
A review on strategies to avoid OsHV-1 in hatcheries/nurseries has been done: it describes existing management control measures to reduce mortalities caused by the virus. Field experiments aiming at identifying husbandry practices to reduce oyster mortalities started in Ireland, South of France and Delta del Ebro. Experimental tests demonstrated the efficacy of UV-based technology to treat oyster active stages. A model has been developed for risk-ranking shellfish farms and farming. Case studies to examine how the models for risk ranking and disease transmission are ongoing key sites.
A stakeholder analysis and mapping was carried out in Ireland, France, Italy and Spain to investigate the interest and influence of key stakeholders on disease management issues and improve communication flows.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

First results obtained on pathogen diversity and life-cycles and identification of key mechanisms involved in the response of bivalves during a viral or bacterial infection increase our knowledge of pathogen biology and host-pathogen interactions.
The identification of several modulated genes in oysters and mussels after experimental infections with pathogens like OsHV-1 or V. splendidus may help to identify potential markers related with resistance against diseases.
Tests carried out in laboratory conditions demonstrated the efficiency of passive sensors to detect aquatic viruses. Such tools should demonstrate their usefulness for pathogen surveillance in the open environment and development of early warning systems in terms of disease detection.
Strategies to avoid OsHV-1 in hatchery/nursery were identified from the literature and are completed by field studies to identify best husbandry practices to reduce mortality. UV treatment showed efficacy to treat oyster active stages in water. These results improve our knowledge regarding water treatment and decontamination.
The development of a risk ranking shellfish farm model and the stakeholder network analysis will not only improve risk based surveillance but will also enable decision making by identifying the best dissemination strategy regarding bivalve disease management.

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