Freshwater Blue-Green Algae (Cyanobacteria) Toxins — A Review

Abstract

Exotoxins are known to be produced by strains of at least three species of freshwater Cyanobacteria. These are Anabaena flos-aquae, Microcystis aeruginosa and Aphanizomenon flos-aquae. Of about 12 toxins produced by these species only one has been identified, synthesized and its toxinology determined. When water-blooms of these toxic species are present in a reservoir, lake, pond or slough, the cells and toxins can become concentrated enough to cause illness or death in almost any mammal, bird or fish which ingests enough of the toxic cells, or extracellular toxin. Major losses to animals include mainly cattle, sheep, hogs, birds (domestic and wild) and fishes while minor losses are reported for dogs, horses, small wild mammals, amphibians and invertebrates. Acute oral toxicity to humans has not been documented but there is increasing evidence that the toxins cause gastroenteritis and contact irritations in users of certain recreational and municipal water supplies. Lipopolysaccharide endotoxin is also produced by certain Cyanobacteria including Schizothrix calcicola and Anabaena flos-aquae and has been implicated in certain water-borne outbreaks of gastroenteritis among humans.