The EC Council Directive 2006/88/EC has, for the first time, listed three crustacean diseases: White Spot Disease (WSD) caused by the White Spot Syndrome Virus (WSSV), Yellowhead disease (YHD) caused by Yellowhead Virus (YHV) and Taura syndrome (TS) caused by Taura syndrome virus (TSV). WSD is currently listed as a ‘non-exotic’ pathogen to the EU based upon its reported occurrence in penaeid shrimp farms in the Mediterranean while YHD and TS are listed as exotic due to their apparent absence from the EU. Their inclusion within the new Directive recognises the global importance of these three viral pathogens in causing massive economic losses in farming regions, the lack of control measures available to deal with disease outbreaks and the potential for them to occur in non-farmed hosts, either as passive, latent or disease causing agents.
To date, despite the relatively free transfer of these viral agents around the globe, either with the movement of live animals for farming (e.g. broodstock and larvae) or as contaminating agents in commodity products (e.g. frozen shrimps) and their demonstrable ability to establish in new hosts at point of destination, very little research has been carried out on the susceptibility of European species to these diseases. Furthermore, little information is available on the environmental tolerance of these viral agents or their ability to establish infection and disease in non-target hosts should they be introduced. Available data is especially lacking for European crustaceans, particularly those that exist at temperatures that may be considered outwith the normal range experienced by these viruses in endemic zones in Asia and South America.
Crustaceans are keystone elements of all aquatic systems. They are fundamental elements in the food chain and as such form a significant element of the diet of most fish species. In fisheries terms, their importance in European marine waters is amply demonstrated by a total crustacean fishery production of c.400 thousand tons per annum, with a large majority of this comprising the decapods, shrimp (c. 200kt), lobsters (c. 60kt) and crabs (c. 85kt) - a significant proportion of this concentrated in the shallow shelf seas around the UK. In UK freshwaters, the white claw crayfish (Austropotomobius pallipes), another decapod, is considered endangered and is protected under UK and European legislation (including the IUCN Red Data list, the Wildlife and Countryside Act 1981 and the EC Habitats Directive 1992). A significant feature of the viral disease WSSV is its potentially wide host suscpetibility range (listed as 'all decapods' by the OIE). When coupled to apparent environmental resiliance, the wide host range identified for WSSV identifies it as a significant potential threat to sustainability of UK crustacean stocks in freshwater and marine environments.
Fundamental work is now required to a. assess the susceptibility of key UK crustacean wildlife and fishery species, and b. assign environmental variables to a risk assessment for the potential for WSD, YHD and TS to establish in the UK aquatic environment following an introduction event. This proposal aims to gather this baseline data and to inform a risk and consequence assessment for these pathogens.