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United States Department of Agriculture

Agricultural Research Service


Location: Food Safety and Intervention Technologies Research

Title: Enteric virus and vibrio contamination of shellfish: intervention strategies)

item Richards, Gary

Submitted to: Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 11/13/2013
Publication Date: 11/15/2013
Citation: Richards, G.P. 2013. Enteric virus and vibrio contamination of shellfish: intervention strategies. Symposium Proceedings. In: Proceedings of the Korean Society of Food Science and Nutrition.Food Safety for the Food Industry, Gwangju, South Kore, November 13-15,2013.pp.57-58

Interpretive Summary:

Technical Abstract: INTRODUCTION. Molluscan shellfish include oysters, clams, mussels, and cockles, which can cause illnesses from a variety of human pathogens. Enteric viruses, like norovirus and hepatitis A virus, are generally transmitted to shellfish through fecal contamination of shellfish harvesting areas, although post-harvest processing contamination can also lead to illnesses. Noroviruses are the most common cause of foodborne illness throughout much of the world. In addition to enteric viruses, naturally occurring Vibrio vulnificus and Vibrio parahaemolyticus are bacteria that threaten the safety of molluscan shellfish. Vibrio vulnificus has a high mortality rate (around 50%) for the infected consumer, while V. parahaemolyticus seldom causes death but is a common source of infection in many countries. Virus- and Vibrio-contaminated products lead to: a) outbreaks of illness among shellfish consumers, b) loss of consumer confidence in the safety of shellfish, c) increased need for regulatory intervention, d) product recalls, and e) substantial financial loss to the industry, consumer, and regulatory agencies. VIRUS MONITORING OF SHELLFISH. The inactivation of enteric viruses within shellfish tissues is difficult to achieve. Currently, the best management practice to prevent norovirus infection is to make certain the shellfish are obtained from clean waters and are handled in a sanitary manner. Thorough cooking is effective for the inactivation of viral contaminants; however, many consumers like shellfish raw or only lightly cooked. Methods to extract and test for viruses in shellfish have been developed and should be implemented in regular monitoring programs. Molecular biological methods are available for the detection of norovirus, hepatitis A virus, and other enteric viruses in shellfish and should be used for general screening purposes and in outbreak investigations, but their limitations must also be recognized. Once contaminated, shellfish can maintain high virus levels, especially if they are stored in an environment that is cold, dark, and wet. Unlike many bacteria, human norovirus and hepatitis A virus do not replicate outside the human host, thus they do not increase in numbers during shellfish storage. VIBRIO-CONTAMINATED SHELLFISH. Vibrio parahaemolyticus is the major source of seafood-borne illness in the United States and in some parts of Asia. Some serotypes are more virulent than others. The pandemic O3:K6 serotype has been the focus of attention in recent years. We characterized the persistence of V. parahaemolyticus O3:K6 in United States coastal waters as well as factors that affect its colonization of the intestinal tract of an adult mouse model. Our findings and their significance will be discussed. Another Vibrio, namely Vibrio vulnificus, can cause serious illness and death in individuals who have compromised immune systems, especially in people with liver disease. Factors associated with V. vulnificus levels in seawater will be discussed. Both V. parahaemolyticus and V. vulnificus are naturally present in marine waters during summer months when seawater temperatures are high; therefore, monitoring for vibrios in seawater or shellfish should be performed, especially during the summer. Health authorities should also monitor for possible Vibrio outbreaks and trace back to their origin shellfish that were known to cause illness. During periods of outbreaks, products already in the market place should be recalled and harvesting should be suspended until levels of vibrios in the shellfish or seawater drop to acceptable levels. PROCESSING INTERVENTIONS FOR VIRUSES AND VIBRIOS. Vibrios are more easily controlled in shellfish than enteric viruses. Controls include: a) bacteriological monitoring for Vibrio levels in harvesting areas, b) restriction in harvesting based on the levels of vibrios

Last Modified: 8/24/2016
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