| Abstract: |
The state of Washington routinely experiences seasonal restrictions on commercial and recreational shellfish harvest due to two toxic phytoplankton syndromes, Paralytic Shellfish Poisoning (PSP) and Amnesic Shellfish Poisoning (ASP), which is often referred to as Domoic Acid Poisoning (DAP). The biotoxin that causes PSP temporarily interferes with the transmission of nerve impulses in warm-blooded animals, causing symptoms in humans such as, numbness and tingling of the lips, tongue, face and extra difficulty talking, breathing, swallowing and muscle incoordinations. Symptoms develop quickly (within 1-2 hours of consumption) and can result in death. The species that causes PSP in Washington state marine waters is Alexandrium catenella. Alexandrium is usually present in small numbers; however, when environmental conditions are optimum, rapid reproduction occurs. Filter-feeding shellfish can accumulate the toxins to dangerous levels during these "blooms". Domoic acid poisoning is caused by eating fish, shellfish or crab containing the toxin. Symptoms include vomiting, nausea, diarrhea and abdominal cramps within 24 hours of digestion. In severe cases, neurological symptoms develop within 48 hours and include headache, dizziness, confusion, disorientation, loss of short-term memory, motor weakness, seizures, profuse respiratory secretions, cardiac arrhythmias, coma and possibly death. Domoic acid produced by marine diatoms of the genus Pseudo-nitzschia, was first detected on the Pacific coast in 1991 when several pelican and cormorant deaths were link to domoic acid in anchovies. The Washington State Department of Health routinely monitors for PSP and ASP in shellfish from areas throughout the state. Areas are closed for harvest of molluscan shellfish when PSP toxin levels are equal to or exceed 80 ug toxin/100 grams shellfish tissue. Molluscan shellfish areas are closed when domoic acid (DA) levels reach 15 ppm in a composite sample of six shellfish (this level was changed to 20 ppm in 2001), whereas Dungeness crab areas are closed when DA levels reach 30 ppm in three of six individual crab viscera. |