I read with interest your June 25 story on recent scombroid poisoning cases on the East Coast.
Four years ago, in trying to understand what the incidence of scombroid poisoning was in this country, which fish were involved, what the causes are and how it could be prevented, I requested case history records going back 5 years from public health agencies in 15 states. (Comparing the record keeping by the various states is a whole other story.) Then I read everything I could find on the subject in the University of Washington medical library.
Scombroid poisoning, as you pointed out, is caused by storing and/or shipping certain fish at improper temperatures. When the fish gets warm, free histidine (present only in fish such as tuna, mackerel, mahi mahi, amberjack and bluefish) forms histamines. It was not clear to medical experts at the time whether histamine causes the poisoning or is only a reliable indicator of "scombrotoxins." There is much that is not understood. Distribution throughout a single piece of fish is uneven, and not everyone is susceptible.
Fundamental quality control practices for fish--"continuous icing and refrigeration"--as you pointed out, are the way to prevent scombroid poisoning, but I have to take issue with the Virginia Department of Health's conclusion that "the consumer is dependent on the fishing industry for protection against this illness." There are too many cases of histamine formation (which occurs rapidly above 70 degrees Fahrenheit) occurring while in restaurant or retail environments, and a large number of cases involve unrefrigerated sport-caught fish. As I recall, a majority of the cases on the East Coast are associated with sport-caught bluefish. Educating the public is the key, and articles like yours help accomplish that education.
The Virginia report says "fish containing high levels of histamine do not necessarily show any signs of spoilage." That is true, but temperature abuse can be detected visibly and is certainly a precondition to spoilage. Once again, the educated consumer and the educated recreational fisherman are ultimately the key to scombroid prevention.
On another minor point: "Scombrotoxins" do not cause decomposition. Bacteria cause decomposition. Hypothetically you could have completely decomposed fish with no histamines if the fish was adequately refrigerated throughout, yes?
\o7 Rowley is the owner of the consulting firm Fish Works and a recognized fish expert.