Screening Tests for the Rapid Detection of Diarrhetic Shellfish Toxins in Washington State

Bich-Thuy Eberhart,Neil Harrington,Jerry Borchert,Nicolaus Adams,Vera Trainer,Leslie Moore

doi:10.3390/md11103718

Abstract

The illness of three people due to diarrhetic shellfish poisoning (DSP) following their ingestion of recreationally harvested mussels from Sequim Bay State Park in the summer of 2011, resulted in intensified monitoring for diarrhetic shellfish toxins (DSTs) in Washington State. Rapid testing at remote sites was proposed as a means to provide early warning of DST events in order to protect human health and allow growers to test “pre-harvest” shellfish samples, thereby preventing harvest of toxic product that would later be destroyed or recalled. Tissue homogenates from several shellfish species collected from two sites in Sequim Bay, WA in the summer 2012, as well as other sites throughout Puget Sound, were analyzed using three rapid screening methods: a lateral flow antibody-based test strip (Jellett Rapid Test), an enzyme-linked immunosorbent assay (ELISA) and a protein phosphatase 2A inhibition assay (PP2A). The results were compared to the standard regulatory method of liquid chromatography coupled with tandem mass spectroscopy (LC-MS/MS). The Jellett Rapid Test for DSP gave an unacceptable number of false negatives due to incomplete extraction of DSTs using the manufacturer’s recommended method while the ELISA antibody had low cross-reactivity with dinophysistoxin-1, the major toxin isomer in shellfish from the region. The PP2A test showed the greatest promise as a screening tool for Washington State shellfish harvesters.

Highlights

Diarrhetic shellfish poisoning (DSP) is an illness in humans caused by the ingestion of shellfish contaminated by diarrhetic shellfish toxins (DSTs), including okadaic acid (OA) and the dinophysis toxins (DTXs), which are lipophilic toxins produced by dinoflagellates in the genera Dinophysis and Prorocentrum [1,2,3]
Our findings confirmed previous survey of Puget Sound showing DTX-1 to be the primary toxin found in shellfish from Puget Sound and the coast of Washington state [15]
We found that when used as recommended by the manufacturer, the Jellett Rapid Test for diarrhetic shellfish poisoning (DSP) gave a high number of false negatives (Table 2), most likely due to incomplete extraction of DSTs by the Jellett extraction method compared to the standard European Union (EU) method (Table 2)

Summary

Introduction

Diarrhetic shellfish poisoning (DSP) is an illness in humans caused by the ingestion of shellfish contaminated by diarrhetic shellfish toxins (DSTs), including okadaic acid (OA) and the dinophysis toxins (DTXs), which are lipophilic toxins produced by dinoflagellates in the genera Dinophysis and Prorocentrum [1,2,3]. OA and its analogs (DTX-1, DTX-2 and DTX-3) are acid polyethers that inhibit serine/threonine protein phosphatase activity by binding to its receptor site, resulting in a rapid increase of phosphorylated proteins [4,5,6]. They are the only toxins of the DSP complex with diarrheagenic effects in mammals [7]. DSP events had been suspected, but not confirmed in the U.S

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Discussion

Conclusion