Paralytic Shellfish Poisoning

Southeast Alaska, May-June 2011

Joseph B. McLaughlin, MD; Donna A. Fearey, MS; Tari A. Esposito

Disclosures

Morbidity and Mortality Weekly Report. 2011;60(45):1554-1556. 

In This Article

Editorial Note

The 21 cases of PSP identified in southeast Alaska during May–June 2011 represent a considerable increase in the numbers reported in recent years (≤10 cases annually in Alaska since 1998). However, this was not the first time an increase occurred in the annual number of PSP cases in Alaska.[3] Active case finding during this outbreak enabled epidemiologists to identify persons with PSP symptoms who had not sought care and thus would never have been reported. This demonstrates that the overall burden of PSP in Alaska likely is underestimated through standard reporting. However, saxitoxin levels were reported to have been higher in shellfish in the region during spring 2011 than in previous years (Kate Sullivan, University of Alaska Southeast, personal communication, 2011), indicating that the increase in the number of cases might not have been a surveillance artifact.

PSP is a preventable condition. Avoidance of noncommercially harvested Alaskan shellfish not tested for saxitoxins is the best way to prevent PSP. Commercially harvested shellfish are tested for saxitoxin in Alaska* and considered safe for human consumption but shellfish collected by persons for their own use are not. Because shellfish harvesting is an important cultural tradition and shellfish are an important subsistence food source for many Alaska Natives and other Alaska residents, not everyone follows the public health recommendation to avoid eating shellfish from noncommercial sources. Furthermore, transient fish-processing workers in Alaska might be unaware of the potential danger of eating untested Alaskan shellfish because they are unfamiliar with PSP and might have limited English literacy.

During the investigation, SOE epidemiologists posted signs at beaches on Metlakatla and within the community to warn residents about the PSP risks associated with consuming noncommercially harvested shellfish. The warnings were printed in English, Tagalog, Russian, Spanish, and Korean. The Ketchikan Public Health Center and the Alaska Department of Fish and Game posted similar signs throughout Ketchikan and surrounding areas. Additionally, the Alaska Department of Health and Social Services issued press releases and conducted media interviews to inform the public about the outbreak and the need to avoid noncommercial harvesting of shellfish. No additional cases of PSP have been reported in Alaska since this investigation.

Because Alaskan shellfish can have high levels of PSP saxitoxins at any time of year and neither cooking nor freezing destroys the toxin, development of a widely available, inexpensive, and easy-to-use test kit to measure toxin concentrations in noncommercial shellfish would be beneficial. Symptoms of PSP occur within minutes to hours of shellfish consumption,[1] and because the course of the illness is unpredictable, immediate medical assessment is strongly recommended. The roles of state and local governments, clinicians, and community leaders include 1) identifying cases so that investigations and control measures (e.g., posting warning signs) can be initiated promptly, 2) educating persons who choose to continue to consume noncommercially harvested shellfish about the signs and symptoms of PSP, and 3) recommending that medical care be sought immediately if symptoms develop. Clinicians should report suspected cases of PSP to local health authorities immediately and promptly collect and freeze samples of patient urine and any uneaten shellfish for PSP toxin testing.

*Food safety requirements for commercial harvesting of shellfish in Alaska are available at https://www.dec.alaska.gov/eh/fss/seafood/shellfish_home.html.

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