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Researchers working in the U.K and the U.S. reported in the October issue of the Journal of Agricultural and Food Chemistry the results of their tests of the single-step lateral flow immunoassay designed to detect okadaic acid (OA) and dinophysis toxins (DTXs). The performance of the immunoassay was compared to other more established methods, such as liquid chromatography tandem mass spectrometry (LC-MS/MS) and/or a mouse biosassay (MBA), approaches that require samples be sent to and tested at a lab.
The device is designed as a reader-based assay to eliminate subjective analyses. There is a qualitative cutoff for noncompliant results at concentrations relevant to regulatory limits, the researchers say. Using the lateral flow immunoassay, samples of the shellfish homogenates were screened in 20 minutes, not including extraction and assay time, to identify the presence of free toxins, including OA, DTX1, and DTX2. The device uses an antibody that binds and reacts to the presence of the toxins, and is intended for shipboard use or in remote locations.
Investigator Wagass Jawaid, a scientist at Neogen Europe Limited and Queen’s University’s Institute for Global Food Security, and colleagues report that there were no false compliant results and no false noncompliant results at less than 50 percent of the maximum permitted level among the 72 naturally contaminated samples tested. Jawaid says that the device “maintained the rigorous testing standards of off-site labs.”
He and his colleagues suggest that the device could be “ideal” for laboratories in developing countries where purchasing and using LC-MS/MS or MBA are “not feasible or desirable to conduct routinely.”
The presence of OA and DTXs in shellfish can cause diarrhetic shellfish poisoning, or DSP. Symptoms include nausea, abdominal pain, vomiting, diarrhea, headaches, chills, and fever. Onset can occur 30 minutes to several hours after consumption of the contaminated shellfish and can last up to 72 hours.
The first recorded cases of DSP were in the Netherlands in the 1960s, with incidents occurring worldwide since that time, according to the World Health Organization. An outbreak of DSP occurred in the Pacific Northwest in 2011, leading to a recall of clams and oysters harvested near Sequim Bay State Park and closure of recreational and commercial areas. In August 2015, the Food Safety Authority of Ireland recalled fresh mussels harvested in County Cork that were found to contain harmful levels of DSP toxins, according to a report on barfblog.com.