PARALYTIC SHELLFISH POISONING - USA: (ALASKA)
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Date: Fri 18 Nov 2011
Source: CDC. MMWR Morb Mortal Wkly Rep 2011; 60(45): 1554-6 [edited] <http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6045a3.htm?s_cid=mm6045a3_w>
Paralytic shellfish poisoning - southeast Alaska, May-June 2011
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On 6 Jun 2011, the Section of Epidemiology (SOE) of the Alaska Division of Public Health was notified of a case of paralytic shellfish poisoning (PSP) in southeast Alaska. In collaboration with local partners, SOE investigated and identified a total of 8 confirmed and 13 probable PSP cases that occurred during May-June 2011. Warnings to avoid noncommercially harvested shellfish were broadcast on local radio and television and displayed at beaches and in post offices, government offices, and businesses throughout the region. Commercially harvested shellfish, which are tested for the presence of PSP-causing toxins, were safe. Because the risk for PSP is unpredictable, persons who consume noncommercially harvested Alaskan shellfish should know that they are at risk for PSP, and suspected cases should be reported promptly to SOE to initiate control measures in the affected area.
On 3 Jun 2011, a man aged 52 years residing in Metlakatla, on Annette Island in southeast Alaska, awoke from a nap with numbness around his mouth, tingling in his hands, and slight dyspnea. He was taken to the Annette Island Service Unit, the community's health center, where a clinician inquired about recent seafood consumption. After the man reported eating a meal of steamed cockles shortly before his nap, the clinician diagnosed PSP. The man was transported to Ketchikan where, having become weak and unable to sit up in bed without assistance, he was admitted to the intensive-care unit.
PSP primarily results from ingestion of saxitoxins, toxins produced by marine dinoflagellate algae that accumulate in bivalve mollusks (such as, butter clams, cockles, geoducks, and mussels) (1). PSP is a potentially fatal neuroparalytic condition. Signs and symptoms of PSP range from mild, short-lived paresthesias of the mouth or extremities to severe, life-threatening paralysis (1). Because PSP is such a serious condition and because a case indicates widespread risk to the shellfish-consuming population of the affected area, immediate reporting of PSP cases to SOE by health-care providers is mandatory in Alaska.
When SOE was notified of the probable case of PSP (in patient A) (Table - for table, see source URL above. - Mod.LL) on 6 Jun 2011, they also were informed by a nurse in Metlakatla that other community members had eaten cockles and had experienced PSP symptoms. That afternoon, 2 SOE epidemiologists traveled to Metlakatla (population:
1460 persons) to investigate. The epidemiologists met with a visiting public health nurse onsite and conducted active case finding by broadcasting messages on local television and radio and through word-of-mouth among community members.
For this investigation, a probable case of PSP was defined as a compatible illness, including paresthesias, in a person shortly after consumption of noncommercially harvested shellfish from Alaska waters during spring 2011. A confirmed case also met this case definition and had detectable saxitoxins in urine or levels 80 or more microg saxitoxins/100 g of meat (the level at which product is considered
unsafe) in the shellfish that had been consumed before illness onset.
SOE identified an additional 12 probable cases in Metlakatla and used a structured questionnaire for patient interviews. The team collected shellfish from 2 beaches where shellfish associated with PSP had been harvested. They also collected frozen cockles from a community member who harvested them with the index patient (patient A) before that patient became ill.
While conducting the investigation in Metlakatla, SOE was notified of
2 men working in Ketchikan (population: 8050 persons) who had been examined in the hospital's emergency department on 8 Jun 2011 and subsequently were admitted with symptoms consistent with PSP, including paresthesias (patients F and G). Both patients were severely ill; one had required intubation and assisted ventilation and was admitted to the intensive-care unit. The men had shared a meal of boiled, noncommercially harvested mussels. The hospital shipped leftover mussels brought in by the men to the Alaska Department of Environmental Conservation's Environmental Health Laboratory. Urine specimens from the 2 hospitalized men and 2 persons who had accompanied them to the hospital and had eaten the same meal of mussels, but who had no symptoms themselves, were sent to CDC for analysis (2). SOE requests that clinicians collect the 1st available urine, freeze it immediately, and ship as soon as possible.
On 9 Jun 2011, the 2 SOE epidemiologists in Metlakatla traveled to Ketchikan to interview patients F and G and conduct additional case finding. While at the hospital in Ketchikan, the epidemiologists were informed of 2 additional patients who had been examined in the emergency department in May 2011 and who had been diagnosed with shellfish allergies but who had symptoms consistent with PSP hours after consuming a clam and cockle chowder. Active case finding in Ketchikan identified 3 additional probable cases.
Overall, 8 probable and 5 confirmed PSP cases were identified in Metlakatla, and 5 probable and 2 confirmed cases of PSP were identified in Ketchikan during this outbreak. Another confirmed case of PSP (in patient H) in Ketchikan had been reported to SOE in May 2011, for a total of 8 confirmed cases. In all, 21 cases of PSP were identified in southeast Alaska during May-June 2011. All 21 patients reported experiencing paresthesias, with incubation periods for all cases ranging from 0 to 3.75 hours (median: 30 minutes). 4 of the 21
(19 percent) patients were hospitalized; none died. Of the 21 patients, 15 (71 percent) had consumed cockles; 4 (19 percent) had consumed blue mussels; 1 (5 percent) had consumed butter clams and cockles; and 1 (5 percent) had consumed clams that were otherwise unspecified. 4 of the cases were reported to SOE, one after a delay of
3 days.
The cockles collected from the community member in Metlakatla and the mussels collected from the hospital in Ketchikan tested positive for high levels of saxitoxins (Table). Mussels collected from implicated beaches in Metlakatla also tested positive for saxitoxin (range:
4602-5429 microg/100 g of meat).
[Reported by: McLaughlin JB, Fearey DA, Esposito TA, Porter KA]
MMWR Editorial note
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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 or less cases annually in Alaska since 1998).
However, this was not the 1st 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 (such as, 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.
References
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1. RaLonde R: Paralytic shellfish poisoning: the Alaska problem.
Alaska's Marine Resources 1996; 8(2): 1-7 [available at <http://seagrant.uaf.edu/features/PSP/PSP.pdf>].
2. Johnson RC, Zhou Y, Statler K, et al: Quantification of saxitoxin and neosaxitoxin in human urine utilizing isotope dilution tandem mass spectrometry. J Anal Toxicol 2009; 33(1): 8-14 [abstract available at <http://www.ncbi.nlm.nih.gov/pubmed/19161664>].
3. State of Alaska Section of Epidemiology; Alaska roulette -- paralytic shellfish poisoning, Ketchikan. State of Alaska Epidemiol Bull 1982; 10 [available at <http://www.epi.alaska.gov/bulletins/docs/b1982_10.htm>].
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[Metlakatla and Ketchikan in southeast Alaska can be located in the HealthMap/ProMED-mail interactive map at <http://healthmap.org/r/1rAZ>. - Sr.Tech.Ed.MJ]
[Paralytic shellfish poisoning (PSP)
(<http://aquaticpath.umd.edu/toxalg/psp.html>) is a significant problem on both the east and west coasts of the USA. Caused by several closely related species in the genus _Alexandrium_, PSP toxins are responsible for persistent problems due to their accumulation in filter feeding shellfish, but they also move through the food chain, affecting zooplankton, fish larvae, adult fish, and even birds and marine mammals. On the east coast, PSP is a serious and recurrent problem from Maine to Massachusetts. Connecticut, Long Island (New York), and New Jersey occasionally experience the toxin at low levels, but these areas seem to define the southern extreme of this organism's geographic distribution. On the west coast, PSP is a recurrent annual problem along the coasts of northern California, Oregon, Washington, and Alaska. Overall, PSP affects more coastline than any other harmful algal bloom problem.
It is likely that seasonally recurring outbreaks of PSP are linked to the existence of a dormant cyst stage in the _Alexandrium_ life history. This strategy allows the species to deposit dormant cells in sediments where they survive through harsh winter conditions and then germinate to initiate new outbreaks in subsequent years. Prior to 1972, for example, PSP was restricted to the far eastern sections of Maine ("down east") near the Canadian border. That year, however, a massive red tide causing high levels of toxicity in those areas for the 1st time recorded in history. Virtually every year since that event, this region has experienced PSP outbreaks, a result of the successful colonization of the area by _Alexandrium_ spp. A similar expansion, with subsequent recurring outbreaks of _Alexandrium_, occurred in the Puget Sound region of Washington in the late 1970's an area with no prior history of shellfish poisoning. Long-term climatic variability, which affects temperature, upwelling, and currents or allows cysts to survive in areas where they did not before, may be factors in such range extensions.
Shellfish that have caused this disease include mussels, cockles, clams, scallops, oysters, crabs, and lobsters. Symptoms begin anywhere from 15 minutes to 10 hours after eating the contaminated shellfish, although usually within 2 hours. Symptoms are generally mild, and begin with numbness or tingling of the face, arms, and legs. This is followed by headache, dizziness, nausea, and muscular incoordination.
Patients sometimes describe a floating sensation. In cases of severe poisoning, muscle paralysis and respiratory failure occur, and in these cases death may occur in 2 to 25 hours. - Mod.LL]
[see also:
2010
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Paralytic shellfish poisoning - Canada: (BC) warning 20101008.3665 Paralytic shellfish poisoning - USA: (ME) warning 20100714.2353 Paralytic shellfish poisoning - China (03): (GD) scallops
20100524.1718
Paralytic shellfish poisoning - China (02): (HK,MC) scallops, alert
20100519.1653
Paralytic shellfish poisoning - China: (HK) scallops, alert
20100518.1627
2008
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Paralytic shellfish poisoning - South Africa: alert 20080409.1309
2007
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Paralytic shellfish poisoning, human - USA (ME) 20070802.2508 Paralytic shellfish poisoning - South Africa (W. Cape): red tide
20070325.1039
2006
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Paralytic shellfish poisoning, human - Viet Nam (02): correction
20060622.1728
Paralytic shellfish poisoning, human - Viet Nam 20060621.1717
2005
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Paralytic shellfish poisoning - El Salvador 20051205.3512
2004
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Paralytic shellfish poisoning - Canada (NB) 20040809.2202 Paralytic shellfish poisoning - Venezuela (Sucre) 20040626.1709
2003
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Paralytic shellfish poisoning - New Zealand 20030604.1371
2002
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Paralytic shellfish poisoning - Australia (VIC):alert 20021226.6131 Paralytic shellfish poisoning - Canada (NB) 20020914.5303] .................................................ll/mj/mpp
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