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Validation of a Triplex Test for Saxitoxin, Domoic Acid, and Okadaic Acid Measured in Shellfish Tissue from New England and the Pacific Northwest

Primary Contact(s): maggie.broadwater@noaa.gov
This project began in September 2020 and ends in August 2023.

We will evaluate an assay that simultaneously detects paralytic shellfish poisoning, amnesic shellfish poisoning, and diarrhetic shellfish poisoning toxins in mussels. 

Why We Care
Shellfish aquaculture is a large and growing U.S. industry due to customer demand and because shellfish are environmentally friendly, easy to seed, and immobile, making them an ideal aquaculture product. U.S. sales exceed $260M annually, and this number is expected to rise due to the significant advantages of expanding this economic sector. However, to ensure public safety and confidence in the aquaculture industry, shellfish must be tested for toxins produced by harmful algal blooms (HABs). Shellfish are filter feeders and can accumulate HAB toxins, making them unsafe for human consumption. When toxin levels are detected in shellfish at levels exceeding regulatory thresholds, harvesting is prohibited until the toxin is cleared or depurated and products are safe for consumption. Such delays can cause significant economic losses for the aquaculture industry, so reopening shellfish beds is a high priority for local and regional economies. The three toxin classes targeted most commonly for testing include the paralytic shellfish poisoning (PSP) toxins, domoic acid (DA), which causes amnesic shellfish poisoning (ASP), and the diarrhetic shellfish poisoning (DSP) toxins. A simple, low-cost detection method to simultaneously determine these three toxins in a single sample will greatly reduce the testing burden on the aquaculture industry, while improving the safety of the nation’s food supply and contributing to NOAA’s targeted enhancement of the American Blue Economy.

Currently, testing for PSP, ASP, and DSP toxins in shellfish is burdensome, which is why the Interstate Shellfish Sanitation Conference (ISSC) has prioritized “the development of field-deployable, rapid, inexpensive screening methods for all toxins and for each commercially-harvested bivalve species.” The ISSC is the federal/state/industry cooperative body in the U.S. tasked with fostering and improving the sanitation of shellfish through interstate cooperation and uniformity of state shellfish programs. ISSC-approved methods become a part of the National Shellfish Sanitation Program (NSSP). Current ISSC-approved testing methods for PSP, ASP, and DSP are expensive, time-consuming, and must be performed by expert staff in a laboratory, causing delays in obtaining actionable test results. Screening tests are often used to determine when testing with ISSC-approved methods are necessary. This project will provide a commercial toxin screening test that will determine all three toxin classes from one shellfish sample.

What We Are Doing
Simple, rapid, cost-effective screening methods will make toxin detection capabilities widely available to the aquaculture industry and state resource managers. Multiplexed testing will contribute to the safety of the U.S. shellfish supply by enabling effective and efficient monitoring of multiple toxins across more regions. The multiplexed LightDeck PSP/ASP/DSP shellfish test kit is designed to meet these needs as a rapid, field portable, quantitative, and robust product accessible to a wide range of end users in the aquaculture and management communities.

The project team will seek ISSC approval for LightDeck’s triplex assay for the simultaneous detection of PSP, ASP, and DSP toxins in mussels. The LightDeck triplex assay has demonstrated simultaneous measurement of all three of these toxins with sensitivity sufficient for regulatory applications. The ISSC Single Laboratory Validation (SLV) protocol will be performed with mussels sourced from two geographically distinct regions that have historically measured all three of these toxins in shellfish, Maine and Washington state.

Dr. Sarah Bickman of LightDeck Diagnostics leads this project. Co-investigators are Drs. Stephen Archer (Bigelow Laboratory for Ocean Sciences) and Gregory Doucette (NOAA NCCOS). The project is funded through the NCCOS Prevention, Control, and Mitigation of Harmful Algal Bloom (PCMHAB) Program.

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