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FDA Fact Sheet
February 8, 1993
Advice on Consumption of Raw Molluscan Shellfish
FDA has received inquiries about the safety of eating raw
molluscan shellfish such as oysters, clams and mussels. The
following can be used to answer such questions:
Any animal protein consumed raw or partially cooked carries a
higher potential for causing illness than food that is thoroughly
cooked. Most illnesses that result in the general population from
eating raw or partially cooked molluscan shellfish are not
life-threatening and commonly range from mild intestinal disorders to
acute gastroenteritis. Although more serious illnesses can occur,
they are rare in otherwise healthy individuals. The main sources
of all of these illnesses are bacteria and viruses that are present
in water due to human pollution.
On the other hand, individuals who immune systems are compromised
should not eat raw or partially cooked molluscan shellfish at all.
These people are susceptible to far more serious illnesses that are
caused by naturally occurring marine bacteria from the Vibrio
species, particularly Vibrio vulnificus. These bacteria are
unrelated to human pollution. In susceptible people, they can
cause serious illness and even death.
Immune compromised individuals include those with liver disease,
including cirrhosis, hemochromatosis and disease caused by chronic
alcohol abuse; diabetes mellitus; immune disorders, including
advanced stages of infection with the AIDS virus, cancer and
reduced immunity due to steroid or immunosuppressant therapy; and
gastrointestinal disorders, including previous gastric surgery and
low gastric acid (for example, from antacid use or achlorhydria).
People unsure of their medical status should consult their
physician before consuming raw or partially cooked shellfish.
FDA has developed brochures for these individuals that provide
advice about raw shellfish and related matters. They are available
through the FDA Seafood Hotline, at 1-800-FDA-4010 (202-205-4314,
in the Washington, D. C., area), or from public affairs specialists
in FDA district offices throughout the United States.
Vibrio vulnificus and other kinds of Vibrio bacteria are often
found in estuaries. FDA is conducting research to discover more
about them and how to control their presence in molluscan
shellfish.
Potential sources of illnesses related to human pollution are
better understood. FDA cooperates with federal and state public
health officials and the shellfish industry in the National
Shellfish Sanitation Program (NSSP) to maintain and improve
shellfish safety. Among other activities, NSSP establishes
procedures for monitoring bodies of water for signs of pollution
and closing them to shellfish harvesting when appropriate.
FDA Fact Sheet
T93-8
February 8, 1993