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Distribution of Norwalk virus within shellfish following bioaccumulation and subsequent depuration by detection using
K J Schwab1, F H Neill, M K Estes
1Division of Molecular Virology, Baylor College of Medicine, Houston, Texas 77030, USA.
Journal of Food Protection
|January 5, 1999
Summary
Raw shellfish contaminated with Norwalk virus (NV) pose a health risk. This study found NV localizes in shellfish tissues and is poorly removed during depuration, even when bacteria are effectively cleared.
Area of Science:
- Food safety
- Environmental microbiology
- Virology
Background:
- Consumption of raw bivalve mollusks poses a human health risk due to pathogen contamination.
- Norwalk virus (NV) is a common cause of gastroenteritis transmitted through contaminated food and water.
Purpose of the Study:
- To investigate the uptake, tissue localization, and depuration of Norwalk virus (NV) in oysters and clams.
- To analyze the distribution of NV in various shellfish tissues after exposure and depuration periods.
Main Methods:
- Shellfish (oysters and clams) were exposed to different titers of NV for 4-24 hours.
- Tissues including stomach, digestive diverticula, adductor muscle, and hemolymph cells were analyzed for NV using reverse transcription polymerase chain reaction (RT-PCR).
- Depuration experiments were conducted for 24-48 hours to assess NV removal, alongside Escherichia coli bacteria removal.
Main Results:
- NV was detected in the alimentary tract (digestive diverticula and stomach) at all tested concentrations.
- NV was found in adductor muscle and hemolymph cells only after exposure to higher virus titers.
- While 48-hour depuration significantly reduced E. coli (95%), NV reduction in digestive diverticula was minimal (7%).
Conclusions:
- Norwalk virus can accumulate both within and outside the alimentary tract of shellfish.
- Standard depuration methods effective for bacteria are inefficient for removing NV from shellfish tissues.