Better give up fish for Lent
From the CDC’s current issue of Morbidity and Mortality Weekly Report comes a story about an outbreak of ciguatera toxemia (CTX) attributable to eating tainted fish. During the summer of 2010, several individuals in New York City were admitted to the emergency room with complaints of diarrhea, lightheadedness, and tingling on the face and extremities. Between August 2010 and July 2011, almost 3 dozen people were associated with this outbreak of food toxemia, a larger number than had been reported in the previous ten years in New York. Samples of fish from a market were found to have levels of CTX at 10 times the levels allowed by the Food and Drug Administration, leading to an embargo on the sale of barracuda from that market.
Ciguatera toxin is produced by several species of marine dinoflagellates (algae) associated with coral reefs. The toxin producing algae are eaten by small herbivorous fish, and move through the food chain to large predatory fish, which may be eaten by humans. Fish such as snapper, grouper, and barracuda are particularly potent accumulators of the toxin. The toxin is odorless, tasteless, and heat stable, so that cooking tainted fish does not protect one against poisoning. The toxin can produce a variety of symptoms in patients, depending on the amount of toxin ingested, the weight of the individual, as well as their overall health, but symptoms may persist for many months after exposure. Treatments for patients are mainly supportive in nature to maintain fluids during diarrhea and vomiting, and to alleviate pain.
The Wikipedia entry for ciguatera toxin notes that some cases of poisoning may ultimately be misdiagnosed as multiple sclerosis, due to the long term neurological defects that may occur. This CDC report concurs that CTX toxemia is likely a significantly underreported disease, with potentially only 10% of the cases properly being diagnosed. Editorial comments in the CDC alert argue that timely diagnosis and trackback to contamination sources are critical to fully gauge the extent of the problem, and to reduce the number of cases. Unfortunately, detection of contamination requires specialized testing not available outside of many diagnostic labs. The case study linked to by the graphic above suggests that ciguatera poisoning will become a more significant problem in the years to come, as dinoflagellate blooms are promoted by warmer ocean waters and coral reef die offs.