Identification of a benthic microcystin-producing filamentous cyanobacterium (Oscillatoriales) associated with a dog poisoning in New Zealand.

In November 2008 a dog died soon after ingesting benthic "algal" mat material from the Waitaki River, New Zealand. Based on a morphological examination of environmental material, the causative organism was putatively identified as the filamentous cyanobacterium Phormidium sp. Two strains (VUW25 and CYN61) were isolated and cultured to enable further taxonomic and cyanotoxin characterisation. Phylogenetic analyses based on a region of the 16S rRNA gene sequence, intergenic spacer (ITS) region and the mcyE gene demonstrated that the species was likely to be a new Planktothrix species that is either benthic or has a biphasic life cycle. Using liquid chromatography-mass spectrometry (LC-MS), microcystin-LR, [D-Asp(3), Dha(7)] microcystin-LR, [D-Asp(3)] microcystin-LR, and minor proportions of [D-Asp(3), ADMAdda(5)] microcystin-LhR were identified. This is the first report of [D-Asp(3)] microcystin-LR, [D-Asp(3), Dha(7)] microcystin-LR and an ADMAadda variant in New Zealand. No cylindrospermopsins, saxitoxins or anatoxins were detected. Dog deaths caused by the consumption of cyanobacterial mats containing anatoxins have previously been reported in New Zealand. To our knowledge, however, this is the first instance of a benthic microcystin-producing species causing an animal death in New Zealand.