We are seeking Interstate Shellfish Sanitation Conference approval for a quick test to replace the mouse bioassay in some regulatory instances as the method for monitoring brevetoxins in shellfish. These toxins, acquired through exposure to Florida red tide, can cause Neurotoxic Shellfish Poisoning in people who consume tainted shellfish. We will also expand the list of species for which the test is used, provide training in its use, and evaluate other sample preparation and analysis methods. 

Why We Care
Blooms of the dinoflagellate Karenia brevis (red tide) threaten the productive Gulf of Mexico shellfish industry. Brevetoxins produced by K. brevis are toxic to humans and can result in Neurotoxic Shellfish Poisoning (NSP) if contaminated shellfish are eaten. To prevent NSP, shellfish harvesting areas are closed when K. brevis concentrations exceed 5,000 cells per liter and are re-opened once K. brevis levels decrease and mouse bioassay testing demonstrates that shellfish are no longer toxic. This protocol successfully prevents occurrences of NSP from lawfully harvested shellfish, but NSP closures come at a steep economic cost to the shellfish industry.

The American Public Health Association’s mouse bioassay—the only approved method for regulatory NSP testing—has many drawbacks, and the delays caused by the time required to analyze samples (two days) and low sample throughput compound economic losses. To mitigate economic harm to the shellfish industry and ensure the continued protection of public health, rapid alternative methods for NSP testing are needed.

What We Are Doing
In the U.S., the Interstate Shellfish Sanitation Conference (ISSC) and the Food and Drug Administration (FDA) establish methods of toxin analysis to regulate shellfish, and the National Shellfish Sanitation Program (NSSP) adopts these methods. Our project goals are to:

1. implement the Marbionic, Inc. enzyme-linked immunosorbent assay (MARBIONC ELISA) as the first non-mouse based NSP testing method within the U.S. shellfish sanitation regulatory framework;
2. expand the list of species for which the method can be used;
3. transfer this technology to appropriate end users; and
4. evaluate other methods of sample preparation and analysis for potential use in monitoring and managing harmful algal bloom (HAB) toxins in shellfish.

We will work to meet ISSC requirements for approval of the new method. Following ISSC approval, rapid NSP ELISA testing will be integrated with Florida’s NSP monitoring and management program. This includes analyzing all regulatory NSP samples by both ELISA and mouse bioassay while the ISSC proposal is in process, and increasing shellfish testing in key shellfish harvesting areas, both during K. brevis blooms and in the absence of blooms.

In the second year of the project, we plan to expand NSP testing capabilities in affected states through training workshops conducted in Texas, Louisiana, Mississippi, and Alabama. We will also validate the ELISA method for use with Southern hard clams (Mercenaria campechiensis), a native species gaining renewed interest among Florida clam farmers.

In the third year of the project, we will evaluate another widely used NSP ELISA kit (manufactured by Abraxis) for comparability with the MARBIONC ELISA and its potential for use in NSP management. We will develop methods to extract multiple HAB toxins simultaneously from shellfish to enable shellfish management programs to incorporate more proactive screening for HAB toxins of concern.

Dr. Leanne Flewelling (Florida Fish and Wildlife Conservation Commission) leads this project, along with co-lead Dr. Ann Abraham (U.S. FDA). The project is funded through the NCCOS Prevention, Control, and Mitigation of HABs (PCMHAB) Program.