Comparing Two Seawater Temperatures For Human Norovirus Depuration From Oysters

Area of Science:

• Marine microbiology
• Food safety
• Virology

Background:

• Shellfish consumption is a common source of gastroenteritis outbreaks.
• Current depuration methods effectively remove bacteria but not human norovirus.
• Norovirus contamination in oysters poses a significant public health risk.

Purpose of the Study:

• To determine the effect of seawater temperature on norovirus elimination from oysters.
• To compare the depuration efficiency at 8°C and 18°C.
• To assess the persistence of different norovirus genogroups during depuration.

Main Methods:

• Oysters were contaminated with norovirus-containing raw sewage.
• Depuration was performed at controlled seawater temperatures (8°C and 18°C).
• Quantitative RT-qPCR was used to quantify norovirus genome copies in oyster tissues.

Main Results:

• A one-log decrease in norovirus genome copies required 41 days at 8°C and 24 days at 18°C.
• Field-contaminated oysters showed similar depuration times at 18°C (21-23 days).
• Norovirus genogroup I exhibited greater persistence than genogroup II, particularly in earlier season samples.

Conclusions:

• Elevated seawater temperatures significantly enhance norovirus elimination from oysters.
• Warmer depuration conditions reduce the time required for norovirus reduction.
• Norovirus genogroup and seasonal variations influence elimination rates, highlighting the complexity of shellfish safety.