Cyanobacterial (blue-green algae) poisoning of livestock in the western Cape Province of South Africa.

: Three outbreaks of cyanobacterial (blue-green algae) poisoning involving cattle and sheep are described. In 2 of these acute mortality was followed by photodermatitis in some of the surviving animals. In all 3 outbreaks the hepatotoxicity of the water collected from the dams where the animals had been drinking was confirmed following the intraperitoneal administration to mice. Nodularia spumigena was the dominant cyanobacterium in the first 2 outbreaks, and Microcystis aeruginosa in the third. The presence of the heptapeptide toxin microcystin-LR in the third outbreak was demonstrated by high pressure liquid chromatography.