The Palm Island mystery disease 20 years on: a review of research on the cyanotoxin cylindrospermopsin

Poisoning of humans resulting from consumption of water affected by the toxic cyanobacterium Cylindrospermopsis raciborskii was first reported almost 20 years ago from Palm Island, northern Queensland, Australia. Since that time a great deal has been learned about this organism and cylindrospermopsin (CYN), the toxin it produces. This article reviews the information now available to us. It summarizes aspects of the chemistry of the toxin-now known to be produced by some cyanobacterial species other than C. raciborskii-and its biosynthesis and chemical synthesis in vitro, as well as its detection and measurement by chemical and biological assay. Some of the factors affecting toxin production by cultured isolates of C. raciborskii are reviewed and the conditions that cause its release from the cells described. The occurrence of CYN in water bodies and the management strategies used to minimize the harmful effects of the toxin are outlined. These include a range of water-treatment practices now in place to remove CYN-producing organisms and/or to neutralize the toxin together with some management procedures that have been tried, with varying degrees of success, to prevent buildup of blooms of the offending organisms. Some of the public-health considerations arising from exposure to water supplies affected by CYN are summarized along with the risk factors and guidance values as they are currently applied. Among the more recent developments described are those that come from the application of molecular techniques for characterizing toxic and nontoxic strains and for exploring the genetic aspects of CYN production