Understanding Ostreid herpesvirus type 1 risk: alternative hosts and in situ hybridisation
SCRC: RTG: Visit to the laboratory of Professor Douglas Tocher (Institute of Aquaculture, University of Stirling, Scotland) to undertake collaborative research into the lipid and polyunsaturated fatty acid (PUFA) metabolism of Southern Bluefin Tuna
Final report
The purpose of this grant was to undertake collaborative research into the lipid and polyunsaturated fatty acid (PUFA) metabolism of Southern Bluefin Tuna (SBT) using a SBT cell line that was recently produced. This project followed an international trend towards increasing fish oil replacement in feeds for farmed fish to improve the sustainability of the target industry.
Very little is known about dietary fish oil replacement in Bluefin tuna species so the purpose of this research was to obtain data which may be used to predict the impacts of fish oil replacement in future manufactured feeds for farmed SBT. Since it was logistically difficult and expensive to obtain such data from traditional feeding trials with SBT, the approach using the SBT cell lines offered a more rapid and cost-effective alternative.
SCRC: PhD Extension : RNA interference (RNAi) as a means to control Neoparamoeba perurans, the causative agent of amoebic gill disease (AGD). (Student: Paula Lima)
Paula Lima began her PhD within project 2007/750 ‘AGD Vaccine Phase III: Sea-based trials, refinement and commercialisation’. Paula began in 2009 and her full stipend, travel and operating funds were paid out of this project. Paula was adopted into the Seafood CRC in late 2009, with no further financial support for her stipend or operating expenses. In 2010 at a meeting of the project’s Management Advisory Committee (MAC), a decision was made to redirect research as it was apparent that the vaccine was not a commercial reality. This occurred one full year into her PhD. This had an effect on Paula’s PhD which was subsequently changed to investigating the use of RNAi as either a research tool and/or a control strategy for AGD. This meant that the entire 1st year’s work was made redundant and Paula had to effectively ‘start over’. Paula has effectively been working in her new area for almost two years. However, the project which funded her stipend is no longer operating. Therefore, Paula still has effectively one year of her PhD left to run. For this reason we sought support from the Seafood CRC to enable Paula to complete her research. This application has the full support of Adam Main, the CEO of the Tasmanian Salmonid Growers' Association (TSGA).
Final report
RNA interference has emerged as a powerful tool for rapid analysis of gene function in non-model organisms and has the potential to identify candidate targets for interventions against diseases of economic importance to aquaculture. The main purpose of the study was to use functional and comparative genomics approaches to investigate whether the RNAi mechanism has been retained or lost in species from the Neoparamoeba genus.
The results provide strong evidence that both infective and non-infective species from Neoparamoeba spp. have evolutionarily retained key genes involved not only in the canonical RNAi mechanism, but also in the mirNA and PiRNA pathways. Despite being promising, these findings are still preliminary and the reality of applying RNAi technology to develop new treatment strategies against AGD still needs further effort.
SCRC: PDRS: Use of next generation DNA technologies for revealing the genetic impact of fisheries restocking and ranching
SCRC: Developing efficient diagnostic tools for assessing resistance to viral infection in abalone and oysters
The molluscan fisheries and aquaculture industries in Australia are threatened by herpesviruses. AbHV caused mass mortalities on Victorian farms from 2005-07 and is endemic off Victorian and possibly Tasmanian coasts. Herpesviruses are known to reactivate under stress conditions, threatening future productivity in the abalone industry and limiting movement of broodstock. Recently, OsHV-1 has been detected in Pacific Oysters in NSW, where it caused mass mortality and threatens the entire Australian oyster industry.
Research in France, where OsHV-1 is endemic, indicates that it is possible to select for higher resistance to this virus in oysters (ie. there is a strong genetic effect on resistance). Work by CSIRO and NSWI&I confirms that resistance to OsHV-1 is under strong genetic control. Screening of resistance level in the context of survivors within selected families is now being incorporated as a component of CRC project 2009/743.
Because molluscs lack acquired immunity, they cannot be vaccinated. The only feasible way to counter the threat of these viruses is to identify and develop resistant populations. As part of our current CRC PhD project (2008/739), we have developed an assay for screening antiviral activity in abalone haemolymph. The next step is to identify antiviral agents in abalone and oysters so they can be used as efficient diagnostic tools for identifying virus-resistant stocks. Biological and chemical screening assays, using antiviral activity and antiviral agent respectively, will be applied to different genetic breeding lines of abalone and oysters. We need to know if these assays could be used to improve resistance and whether genetic improvement of other traits such as growth rate might be compromised. Genetic analysis will determine whether haemolymph antiviral activity is under genetic control, is positively correlated with survival after challenge, and whether there are any undesirable associated effects.
Final report
The project examined the genetic basis of antiviral resistance in oysters and abalone in response to the significant disease threats posed by oyster and abalone herpesviruses. Laboratory-based systems for the growth and assay of such viruses are problematic. The project undertook to measure the antiviral activity of different breeding lines of oysters and abalone using as a proxy measure the antiviral activity against the human herpesvirus HSV-1. We demonstrated that oysters and abalone have antiviral activity against HSV-1, and that this trait is heritable. We identified a hemolymph compound providing antiviral activity. Our analysis of the oyster genome identified what is likely to be a key role for the protein viperin in resistance to viral infection. The project has provided outstanding value in three important areas. First, in adding to the knowledge base directing mollusc breeding programs. Second, in enhancing knowledge of molluscan immunity to viral infections. Third, in building research and development capacity in the Australian seafood industry.