Saxitoxin and Other Paralytic Toxins: Toxicological Profile

Abstract

Toxic microalgal blooms that produce paralytic shellfish poison (PSP) have increased worldwide in frequency, duration, and extension of affected areas, with severe impacts on human health, local economies, and exports. PSP is a variable mixture of tetrahydropurine marine biotoxins collectively named as saxitoxins (STXs) that are produced by dinoflagellates from the genera Alexandrium, Pyrodinium, and Gymnodinium. Harmful algal blooms of these species (named “red tides”) produce accumulation of saxitoxins in shellfish, fishes, and other organisms. Ingestion of contaminated tissues may lead to paralytic shellfish poison intoxications in humans and deaths by muscle paralysis and cardiorespiratory failure. Tetrodotoxins (TTXs) are compounds chemically different from STXs, synthesized by cyanobacteria present in freshwater ecosystems that produce a similar paralytic syndrome in cattle, birds, and fishes. TTXs (and STXs) are also present in puffer fishes and cause also human intoxications. In addition, saxitoxins and tetrodotoxins are produced by a number of other species that may represent additional health risks. The severe public health and economic impacts of PSP intoxications brought the attention of researchers almost 80 years ago. Since then a large body of scientific studies on PSP shellfish toxins has accumulated. In recent years an international regulatory effort has been developed to assess, manage, and control health risks caused by PSP toxins and other marine toxins. However, in many countries of the developing world, monitoring and management programs for marine biotoxins in products destined for domestic consumption are limited in scope, geographical extension, frequency, and methodologies. Evidence from physiological, toxicological, and risk management studies is examined that may indicate that current approaches to manage risk and to protect consumers may be still insufficient, especially for underdeveloped countries. Strategies for future work are suggested.