Molecular Tracing of viral pathogens in Aquaculture (EMIDA)

The focus of the MOLTRAQ project has been to collect virus isolates from several different host-pathogen systems from all over Europe, and utilise these to increase knowledge on transmission, prevention and control of viral diseases in aquaculture and develop a generic approach to viral disease control. The uniqueness of the MOLTRAQ project was that the focus was on identifying generic properties of viral aquatic pathogens. This could be achieved because the joined project group had a large collection of different virus isolates sampled from many different species of fish and molluscs in many different countries over a considerable timespan. The background for the project was the compromised efficiency of preventive interventions, that are a result of control strategies for diseases in aquaculture that have been designed based on general knowledge on biosecurity, and only to a very limited degree take into account disease-specific transmission patterns, since the understanding of these are poor. An overview of achievements Essential for the project has been the access to high quality data on samples of representative isolates belonging to various fish and shellfish viruses including part- and whole genome sequences together with epidemiological data. This has allowed for phylogenetic comparisons of differences and similarities between virus isolates over a wide span in time and space. Specifically, the intraspecific phylogeny and evolution of one of the most serious aquatic viral diseases, viral haemorrhagic septicaemia virus (VHS), on a European base has been elucidated. The genetic diversity of the ostreid herpesvirus 1 that has been ravaging the Pacific oyster industry in later years has also been disentangled. The webbased platform www.fishpathogens.eu has been extended with a database on Betanodavirus, and work on one on Salmonid Alphaviruses has been initiated. The platform ensures worldwide access for professionals and researchers within the field of aquatic viruses, to quality-controlled collections of molecular- and epidemiological data on virus specimens. Molecular tracing of outbreaks of VHS, Infectious Heamatopoietic Necrosis virus (IHNV) and betanodaviruses has been performed and manuscripts for publication of the findings are currently under preparation. A model that has been successfully used to trace the outbreaks of Infectious Salmon Aneamia virus in Norway to infections with the low-pathogenic variant HPR0, has been adapted to trace the sources of outbreak of VHS in Denmark, thus demonstrating that the model can be used on several different host-pathogen systems. In order to gain knowledge into the factors that control viral spread at the molecular level, the project has been investigating the effect of temperature on viral expression for the Carp virus, Cyprinid herpesvirus-3. For this, high-throughput next-generation sequencing of viral genomes from virus isolates collected at different temperatures has been performed, thus using this method for identifying potential virulence factors. Finally, a stochastic model using spatio-temporal data on infected and non-infected populations of Atlantic Salmon in Norway, simulating the spread of Pancreas Disease (PD) has been developed. This model is now being used to investigate the economic consequences of using screening for virus to forecast disease-outbreaks and perform coordinated early harvest to avoid outbreaks in defined zones. During MOLTRAQ, we have explored the possibility to adapt scenario simulation models and models for molecular tracing for spread of viral diseases in aquaculture to different viral-pathogen systems. It has been proven feasible to use the same models to different settings, and also for testing different intervention strategies. This will be explored further in the future, and we expect this can be an important tool for advising how to control viral diseases in aquaculture. Thanks to MOLTRAQ the repository of sequences from Viral haemorrhagic septicaemia virus (VHSV) and infectious hematopoietic necrosis (IHNV) is very significant and will be used in future tracing of new outbreaks in Europe. The increasing number of full genome sequences will as well be a tool for assessing virulence markers, and designing vaccine components. All project results have been presented at a stakeholder meeting in Montpellier, France at the end of January 2015, where project partners was also hosting and teaching a workshop on how to use molecular tracing for diseases in aquaculture. Finally, a workshop discussing the implications and perspectives of the project findings took place at the 17th International conference on Diseases in Fish and Shellfish in September 2015. You can read more about the project results at the webpage: www.moltraq.wordpress.com

This project will i)generate and use spatio-temporal epidemiological data, phylogeographic data and gene expression data for important host-viral pathogen systems to identify important factors affecting the spread of diseases in aquaculture, and ii)integr ate these in scenario simulation models to assess effects of various control strategies for selected host-pathogen systems. The purpose of the project is to increase knowledge on transmission, prevention and control of viral diseases in aquaculture and d evelop a generic approach to viral disease control by using information on epidemiological and physiogenetical attributes from several important aquatic animal viruses. The specific objectives are: 1)Collection of isolates of specific important aquatic an imal viruses and their respective epidemiological data (from as wide host ranges, broad geographic distributions and variable pathogenicities as possible), 2)Characterisation of the isolates by phylogenetic and expression analyses and 3)Constructing scena rio simulation models to assess effects of different control strategies. (Se også prosjektbeskrivelse i vedlegg)