Environmental Public Health Division

“Make that a dozen oysters on the half shell, please.”

For oyster aficionados and those who serve them, the darker side of the passion for eating this mollusk in its raw state frequently graces summertime headlines.  Vibrio vulnificus, a bacterium found naturally in warm, coastal waters, is often the culprit in oyster-related deaths.  The Food and Drug Administration (FDA) estimates that nationwide about 12 shellfish related V. vulnificus deaths occur annually.  All of the deaths have occurred in high-risk individuals, individuals with pre-existing health conditions such as liver disease, diabetes, or cancer.  The chances of healthy individuals even being infected with V. vulnificus are less than .6 per cent per 1 million persons.  So, even though the chances are remote for such a tragedy to occur at your restaurant, what precautions can you take when you serve raw shellfish?

Buy your oysters (and all shell stock) from an approved source.  Even though V. vulnificus is not attributed to polluted waters, insure that your supplies are harvested in approved bays and are handled by certified dealers.  There are other bacteria and viruses (Vibrio parahemolyticus, Norwalk virus) that can be carried by oysters that, while rarely fatal, can cause consumers discomfort.  Never use oysters that are caught for recreational fishing.  All shell stock must be obtained in containers that bear id tags and labels affixed by the harvester and each dealer that ships or reships the shell stock.

Inspect shell stock. 
When shell stock arrives, it should be relatively free of mud, be alive, and have unbroken shells.  Reject or discard dead shell stock or shell stock with badly broken shells.

Post the consumer advisory. 
The Texas Food Establishment Rules require that you inform consumers of the risk of eating raw shellfish.  This advisory must be available through brochures, placards, table tents, the menu or other written means wherever shellfish is served or sold for raw consumption.  If you serve raw shellfish in different locations in your establishment (bar, dining room), insure that the advisory is available in each area.

Keep accurate records. 
The Texas Food Establishment Rules require that if shell stock are removed from the container, only one labeled or tagged container can be used at a time.  Do not commingle shell stock from one container with another unless the tag information is identical.  Keep shell stock tags attached to the container in which the shell stock is received until the container is empty.    Keep the tags for 90 calendar days from the date the container is emptied.  Use a record keeping system (not thrown in a shoebox or drawer) that keeps the tags in chronological order according to the date when the shell stock are served or sold.

And finally, there is a post-harvesting process, the Instant Quick Frozen (IQF) process, that will reduce the V. vulnificus bacteria in oysters to non-detectable levels.  IQF-treated oysters are a much safer alternative for your immunocompromised and high-risk patrons who absolutely insist on eating raw oysters.

Unfortunately, although oyster aficionados would love to hear otherwise, eating raw oysters with hot sauce or while drinking alcohol does not kill the bacteria.  But by keeping your customers informed of the risks of consuming raw oysters and following the requirements of the Texas Food Establishment Rules, you can minimize, but not completely eliminate, the possibility of an oyster-borne illness occurring at your restaurant.

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