Click here to print page

Are Raw Oysters Safe To Eat?

Marshalee Valentine

Thursday, August 15, 2019

While attending the yearly Denbigh Agricultural and Industrial Show this year, I walked by the resident oyster bar with a line longer than the one server could handle. Of course, a few random thoughts crossed my mind: Where is this from? Was it treated? Was it cooked? Do people know what they are eating? Was it really safe?

Raw oysters can become contaminated with Vibrio vulnificus — a bacteria naturally living in warm coastal waters — which causes a condition called vibriosis. People who become infected are those who consume raw or undercooked shellfish, particularly oysters. However, it can also be present in clams and mussels. Oysters' feeding mechanism involves constantly drawing in water and materials, which of course include harmful bacteria and viruses. These may become concentrated in an oyster's body and infect individuals who consume oysters raw or undercooked. The Centers for Disease Control and Prevention in the United States has reported that vibriosis can be life-threatening and possibly fatal when shellfish eaten by someone with liver disease, diabetes or a weakened immune system.

I know we have all heard quite a few myths on oysters which include:

“Eat it, man, the peppa wi kill all germs!”

“Di water weh we get it from clean-clean, so it good!”

“Two likkle oysters nah do you nuttn.”

“Raw oysters are an aphrodisiac so eat all you can.”

The reality is, however, the only thing that can kill bacteria in this case is prolonged exposure to heat. Additionally, one oyster can in fact spoil the whole bunch and make you ill and no one will know if the water is contaminated unless they test it.


How do I know if the oyster is good or bad?

The reality is, you can't really tell when raw oysters are contaminated as an oyster that contains harmful bacteria doesn't look, smell, or even taste different from any other oyster. The only way to be sure you are safe is to cook them properly, to kill any harmful bacteria present.


How to prepare and cook oysters?

Check your batch for any oyster with an open shell and throw it out.

Ensure you boil until the shell opens and boil for an additional 3-5 minutes after it opens

Do not eat oyster or any shellfish that does not open fully after cooking.

What are some symptoms of infection?

Diarrhoea and vomiting are minor initial symptoms. However, severe Vibrio vulnificus infection can lead to bloodstream infections, blistering skin lesions, and limb amputations.

If you have eaten oysters or any kind of shellfish and experience any of the above symptoms you should seek medical advice immediately.

Who is at risk?

Once you consume raw or undercooked oysters you are at risk. However, people with the following conditions are more susceptible:

• Liver disease

• Alcoholism

• Cancer

• Diabetes


Plus, recipients of immune-suppressing therapy for the treatment of any disease.


How can I stay safe?

The only way to be certain is to ensure you don't eat raw or undercooked oysters or other shellfish. Fully cook them before eating, and only order fully cooked oysters at restaurants — especially if you suffer from any of the above conditions. Pepper sauce and/or lemon juice do not kill the Vibrio bacteria and neither does alcohol.

Some oyster farms ensure the product undergoes some manner of treatment for safety after harvesting; however, this may not remove all the contaminants.

Ensure you separate cooked seafood from raw seafood and its juices to avoid cross-contamination.

Wash utensils and containers used to hold raw shellfish thoroughly before use and hands with soap and water after handling raw seafood.