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VOL. 72 (3), 391-408, 2006 HARMFUL ALGAL BLOOMS, RED TIDES AND HUMAN...

high percentage of DSP toxins present in some seafood products (25-
26). Ingestion of contaminated shellfish or fish results in a wide
variety of human symptoms, depending upon the toxins present,
their concentrations and the amount of contaminated shellfish
consumed. Diagnosis is based on observed symptomatology and
recent dietary history. The principal target for the effects of the DSP
toxins is the gastro-intestinal tract and the clinical profile of DSP is
characterised by nausea, vomiting, diarrhoea, abdominal pain,
shivering, headaches and fever. Depending on the dose of toxin
ingested, the onset may vary from 30 minutes to 12 hours after
ingestion. Complete recovery is even in severe cases 2-3 days with or
without medical treatment (23, 27).

The DSP toxins comprise a group of high molecular weight
polyethers (Okadaic acid and dinophysistoxins, pectenotoxins,
yessotoxins, and azaspiracids) (28). The main toxin responsible of
DSP is okadaic acid (OA), a cyclic C38 polyether fatty that is
concentrated by shellfish in their digestive glands (29-30). Detection
of DSP toxins is performed by HPLC or mouse bioassay,
concentration is expressed in okadaic acid equivalents (µg OA/g
meat).

MONITORING, REGULATION AND PREVENTION
OF DSP TOXINS

Shellfish is one of the main commercial productions in
aquaculture industry. Shellfish associated with human outbreaks of
DSP are mainly mussels, oysters, clams and scallops (26, 31).
European legislation allows up to 0,16 µg Okadaic acid equivalent
per gram of meat (Decision 2002/225/CE) (28).

The principal measures to avoid DSP outbreaks are the
monitoring of shellfish harvesting areas and analysis for toxins. A
major constraint to monitoring programs for HABs and marine
biotoxins is the need to identify the microalgal species responsible
for toxicity. The identification and enumeration of cells of potentially
dangerous species within a mixed plankton assemblage is a serious
problem. If the toxic alga is unknown, a lot of work is necessary to
see whether toxin presence and algal occurrence are related. In

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