Sources of viral contamination can be varied and include both human and agricultural input. Where contaminated shellfish are consumed raw or lightly cooked, this represents a significant health risk for consumers.
Contamination with viruses from human sources, in particular sewage outfalls, is probably the most significant of these risks. Despite extensive controls outbreaks of gastroenteritis and hepatitis A have both been associated with shellfish consumption. The REDRISK project is increasing the knowledge of factors responsible for virus contamination and leading research into procedures for controlling the risk.
During the project a number of environmental factors have been monitored to establish their viral impact on shellfisheries in four European countries.
Using state of the art virus testing methods, results have shown clear links with viral contamination in shellfish and changes in environmental conditions in one of the areas investigated. Two high rainfall events in the region showed significant correlation with the appearance of virus in oysters in an harvest area which was otherwise shown to be largely free of virus throughout the study. Virus levels appeared to be very low and the real significance of the associated risk thus remains unclear.
Despite this, the ability to identify site-specific environmental risk factors may pave the way forward for using sophisticated programmes for continuous monitoring of environmental factors such as salinity or rainfall to trigger real-time management action in shellfisheries. This could include temporary suspension of harvesting or increased treatment practices.