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Title: Norovirus contamination of Mytilus edulis shellfisheries : assessing the threat to human health
Author: Winterbourn, J. Ben
ISNI:       0000 0004 5350 1634
Awarding Body: Prifysgol Bangor University
Current Institution: Bangor University
Date of Award: 2014
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Contamination of bivalve molluscan shellfish (BMS) with enteric viruses from human faecal sources is recognised as an important human health risk. Norovirus (NoV) is the principal agent of acute nonbacterial gastroenteritis worldwide and infection with NoV is the most common health risk associated with the consumption of faecally contaminated BMS. Advances in molecular methods provide new opportunities for assessment and management of this risk. Previous research has clearly demonstrated that oysters are a vector in NoV disease outbreaks. However, mussels (e.g. Mytilus edulis) have also been implicated in transmission of viral illness. There is a need for more information on the practical application of molecular methods to establish robust sampling strategies for M. edulis end-product testing and production area surveillance. The aim of my PhD was to reduce knowledge gaps associated with NoV accumulation and elimination in Mytilus edulis, and to provide mitigation recommendations to the industrial partner. My research determined that Mytilus edulis are efficient accumulators of NoV but variability in bioaccumulation can be detected between individual animals. However, composite samples (pool of 10 animals - as prescribed by ISO TS 15216) will effectively reduce the effect of animal-to-animal variation and provide a good sampling model for surveillance and monitoring purposes. NoV concentrations in M. edulis show high spatial variability within production areas. However, the spatial distribution of contamination can be effectively predicted using advection-dispersion modelling of effluent plumes, with implications for future risk assessment and management. Offshore cultivation or relaying represent options for avoidance or elimination of viral contamination of BMS but production efficiency may be compromised. It was shown that traditional commercial BMS depuration systems, optimised for elimination of pathogenic bacteria, are ineffective for elimination of NoV from M. edulis. NoV is currently regarded as non-culturable, with complications for the direct determination of infectivity. However, The T90 value for infectious FRNA bacteriophage, a morphologically similar, non-enveloped RNA virus, in mussel digestive tissue at 90°C was determined to be 42 s. Experiments showed that domestic cooking of whole animals at temperatures >90°C reduced infectious concentrations of FRNA Bacteriophage to undetectable levels within 3 minutes. The results of this thesis support the argument that control of harvesting area pollution is likely to represent a more effective strategy for controlling the risk of viral illness associated with consumption of BMS than currently available post-harvest processing strategies. However, the health risks associated with consumption of Mytilus edulis when thoroughly cooked are far less than for any BMS consumed raw.
Supervisor: Jones, Davey Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available