Comparing Two Seawater Temperatures For Human Norovirus Depuration From Oysters

• Published in: Journal of food protection 2025-01, Vol.88 (1), p.100406, Article 100406
• Main Authors: Le Guyader, Françoise S., Ollivier, Joanna, Parnaudeau, Sylvain, Gauffriau, Mathias, Papin, Mathias, Stavrakakis, Christophe, François, Virginie, Vincent-Hubert, Françoise, Garry, Pascal
• Format: Article
• Language: English
• Subjects: Animals; Depuration; Field-contaminated oysters; Food Contamination - analysis; Food Handling; Food Microbiology; food safety; gastroenteritis; Gastroenteritis - virology; genome; genomics; Human norovirus; Humans; microbiological quality; Norovirus; Ostreidae - virology; Oysters; seawater; Seawater - virology; sewage; Shellfish; Shellfish - virology; T90; Temperature; Water-temperature
• ISSN: 0362-028X; 1944-9097; 1944-9097
• DOI: 10.1016/j.jfp.2024.100406

•No difference of norovirus depuration was observed when oysters were contaminated through occasional or repeated exposure.•When purified in seawater at 8 °C, the time needed to achieve a one-log decrease in norovirus concentration is around 41 days.•When purified in seawater at 18 °C, the time needed to achieve a one-log decrease in norovirus concentration is around 24 days.•Warm seawater favors norovirus elimination from oysters, but may increase the risk of bacterial pathogen growth. Despite regulations set up to monitor the microbiological quality of shellfish in producing areas, shellfish-borne gastroenteritis outbreaks still occur. Indeed, oyster depuration practices that are efficient to eliminate bacteria, fail to eliminate human norovirus from oyster flesh. In order to evaluate the impact of seawater temperature on the elimination of norovirus particles from oysters, large batches of oysters were contaminated using raw sewage containing norovirus and subjected to depuration at 8 °C or 18 °C. Over the experiment, quantitative RT-qPCR showed a one-log decrease of norovirus (both genogroups combined) genome copies per gram of digestive tissue after 41 days for oysters depurated at 8 °C and 24 days at 18 °C. The decrease of norovirus (both genogroups combined) in two batches of field-contaminated oysters depurated for two weeks at 18 °C was in the same range (21 and 23 days, respectively). All experiments showed a difference in genomic decay between the two norovirus genogroups, with norovirus genogroup I being more persistent in March/April compared to April/May.