A reader who loves oysters, raw on the half-shell or any way he can get them, has a thoughtful approach to minimizing risk from Vibrio infections from raw oysters. He has gone back to the old rule of only eating raw oysters in months which have an "r", i.e. September through April, the months which tend not to be as hot. He asks if that make sense.
Farmers, and 93% of oysters in the U.S. today are farmed rather than wild-harvested, use “triploid” oysters which have an extra chromosome, making them sterile. Without reproductive demands they are not using their energy spawning in the summer and thus don’t become watery, one of the old reasons for the “r” rule.
Modern refrigerated trucks for shipping oysters during the summer months negate a second old reason for the “r” rule.
However, warmer water conditions favor gastrointestinal distress-producing Vibrio bacteria and so are a reason to consider sticking with the “r” rule. Northern states like Massachusetts and Washington with their colder waters may be less conducive for Vibrio species than the South, but one study in Wellfleet and Duxbury in Cape Cod Bay found Vibrio was detectable in all its samples.
So if raw oysters are just too good not to eat, maybe aim for oysters grown in colder waters. Remember some medical conditions make eating raw shellfish and the inherent risk of vibriosis a no-no, so for any questions check with your doctor.
I feel like I learned about Snow and several epidemiologists in a causal inference statistics course I took in grad school. Something about the cause and effect of certain diseases and their treatments just makes it so easy to understand causality!
Thanks, Dee! I was very happy to be able to make the pilgrimage to Dr. John Snow's Broad Street pump and see the places Snow visited in his investigation, even though all the original buildings are gone. The scientific rigor of Snow's work was impressive.
A reader who loves oysters, raw on the half-shell or any way he can get them, has a thoughtful approach to minimizing risk from Vibrio infections from raw oysters. He has gone back to the old rule of only eating raw oysters in months which have an "r", i.e. September through April, the months which tend not to be as hot. He asks if that make sense.
Farmers, and 93% of oysters in the U.S. today are farmed rather than wild-harvested, use “triploid” oysters which have an extra chromosome, making them sterile. Without reproductive demands they are not using their energy spawning in the summer and thus don’t become watery, one of the old reasons for the “r” rule.
Modern refrigerated trucks for shipping oysters during the summer months negate a second old reason for the “r” rule.
However, warmer water conditions favor gastrointestinal distress-producing Vibrio bacteria and so are a reason to consider sticking with the “r” rule. Northern states like Massachusetts and Washington with their colder waters may be less conducive for Vibrio species than the South, but one study in Wellfleet and Duxbury in Cape Cod Bay found Vibrio was detectable in all its samples.
So if raw oysters are just too good not to eat, maybe aim for oysters grown in colder waters. Remember some medical conditions make eating raw shellfish and the inherent risk of vibriosis a no-no, so for any questions check with your doctor.
This was a really interesting post, thanks Ric!
I feel like I learned about Snow and several epidemiologists in a causal inference statistics course I took in grad school. Something about the cause and effect of certain diseases and their treatments just makes it so easy to understand causality!
I loved this backgrounder on our public health forebear and hero, John Snow!
Thanks, Dee! I was very happy to be able to make the pilgrimage to Dr. John Snow's Broad Street pump and see the places Snow visited in his investigation, even though all the original buildings are gone. The scientific rigor of Snow's work was impressive.