IDENTIFICATION OF A MICROCYSTIN IN BENTHIC CYANOBACTERIA LINKED TO CATTLE DEATHS ON ALPINE PASTURES IN SWITZERLAND

During the last two decades, more than 100 cattle deaths have been rep orted from II alpine sites in south-eastern Switzerland. pathological findings and the histological examination of their organs strongly ind icated acute hepatotoxicosis. Clinical symptoms suggestive of neurotox icity were also observed in some cases. To elucidate the etiology of t hese poisonings, different water bodies in one of the affected alpine pastures were investigated for cyanobacterial toxins. The waters were highly oligotrophic, cold and turbid, and the ice-free period was limi ted to 3-4 months. The algal community in these waters consisted mostl y of benthic cyanobacteria forming dense mats on the surface of sedime nts and on submerged rocks. Oscillatoria limosa and Phormidium konstan tinosum (= Oscillatoria tenuis) dominated these populations, but occas ionally other species of Oscillatoria, Phormidium, Tychonema and Pseud anabaena also occurred in the mars. Samples from the cyanobacterial ma rs yielded positive results in a protein phosphatase inhibition assay, reacted with antibodies against microcystins in an enzyme-linked immu nosorbent assay and were hepatotoxic in a mouse bioassay. The same cya nobacterial material also included neurological effects in mice. High- performance liquid chromatography was used to identify a microcystin, in these cyanobacterial samples as well as in the corresponding lake w ater. To our knowledge, this is the first documented example of hepato toxicity associated with benthic cyanobacteria, and the first report o f toxic cyanobacteria from the remote, oligotrophic alpine environment .