Monitoring Diarrhetic Shellfish Poisoning (DSP) in Washington

Monitoring for diarrhetic shellfish toxins (DSTs) was initiated in the summer of 2011 when the first illness due to diarrhetic shellfish poisoning (DSP) was reported in the state of Washington. Monitoring strategy includes collection of whole seawater for identification and enumeration of Dinophysis and several shellfish species collected from two sites in Sequim Bay, WA as well as other sites throughout Puget Sound during the following summer (2012). Shellfish samples were analyzed for Okadaic acid toxin group including DTX-1, DTX-2 and DTX-3 using rapid screening methods based on the functional assays, i.e. the protein phosphatase 2A inhibition assay (PP2A); the anti OA antibody in an enzyme-linked immunosorbent assay (ELISA) and a lateral flow test strip (Jellett Rapid Test) and the chemical method, i.e. liquid chromatography coupled with tandem mass spectroscopy (LC-MS/MS). The application of a rapid screening method along with Dinophysis cell counts can provide quick assessment of toxin levels, and the results of this study suggest that PP2A is better at screening for OA group of DSTs. The reason for this is due to the fact that DSTs in Washington consist mostly as DTX-1; test kits with antibody-based application tend to under-estimate toxin levels present because the antibody used in these tests is specific to Okadaic acid (100% cross-reactivity) and only 50% to DTX-1.