Abstract
Various species of algae can produce marine toxins under certain circumstances. These toxins can then accumulate in shellfish such as mussels, oysters and scallops. When these contaminated shellfish species are consumed severe intoxication can occur. The different types of syndromes that can occur after consumption of contaminated shellfish, the corresponding toxins and relevant legislation are discussed in this review. Amnesic Shellfish Poisoning (ASP), Paralytic Shellfish Poisoning (PSP), Diarrheic Shellfish Poisoning (DSP) and Azaspiracid Shellfish Poisoning (AZP) occur worldwide, Neurologic Shellfish Poisoning (NSP) is mainly limited to the USA and New Zealand while the toxins causing DSP and AZP occur most frequently in Europe. The latter two toxin groups are fat-soluble and can therefore also be classified as lipophilic marine toxins. A detailed overview of the official analytical methods used in the EU (mouse or rat bioassay) and the recently developed alternative methods for the lipophilic marine toxins is given. These alternative methods are based on functional assays, biochemical assays and chemical methods. From the literature it is clear that chemical methods offer the best potential to replace the animal tests that are still legislated worldwide. Finally, an overview is given of the situation of marine toxins in The Netherlands. The rat bioassay has been used for monitoring DSP and AZP toxins in The Netherlands since the 1970s. Nowadays, a combination of a chemical method and the rat bioassay is often used. In The Netherlands toxic events are mainly caused by DSP toxins, which have been found in Dutch shellfish for the first time in 1961, and have reoccurred at irregular intervals and in varying concentrations. From this review it is clear that considerable effort is being undertaken by various research groups to phase out the animal tests that are still used for the official routine monitoring programs.
Highlights
Of the 5,000 phytoplankton species known to date under specific circumstances about 300 of them have a high proliferation rate, resulting in high density algae clouds called blooms
Toxins responsible for neurologic shellfish poisoning (NSP), diarrhetic shellfish poisoning (DSP), azaspiracid shellfish poisoning (AZP) and other toxins such as pectenotoxins, yessotoxins and cyclic imines all have as common denominator a molecular weight (MW) above 600 Da
In 2005 and 2007 the presence of D. acuminata in the Wadden Sea triggered the application of a monitoring program using liquid chromatography (LC) mass spectrometry (LC-MS)/MS. These analyses showed the presence of OA in mussels at levels well below the current regulatory limit, ranging from 18 till 68 μg OA equivalents/kg shellfish
Summary
Of the 5,000 phytoplankton species known to date under specific circumstances about 300 of them have a high proliferation rate, resulting in high density algae clouds called blooms. Of the 300 phytoplankton species mentioned above, more than 40 species belonging to the classes of dinoflagellates and diatoms are known to produce phycotoxins (marine toxins) [5]. The abundance of these toxic phytoplankton species can vary from thousand until a few million cells per liter. In Europe an estimated annual loss of 720 M€ for the recreation and tourism industry and 166 M€ for the shellfish industry is due to the occurrence of algae blooms [10,11]. Alternative methods are reviewed that have been developed to replace the animal bioassays that are currently used for the detection of lipophilic marine toxins
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