Human fatalities from cyanobacteria: Chemical and biological evidence for cyanotoxins

An outbreak of acute liver failure occurred at a dialysis center in Caruaru , Brazil (8 degrees 17 'S, 35 degrees 58 'W), 134 km from Recife, the state capital of Pernambuco. At the clinic, 116 (89%) of 131 patients experience d visual disturbances, nausea, and vomiting after routine hemodialysis trea tment on 13-20 February 1996. Subsequently, 100 patients developed acute li ver failure, and of these 76 died. As of December 1996, 52 of the deaths co uld be attributed to a common syndrome now called Caruaru syndrome. Examina tion of phytoplankton from the dialysis clinic's water source, analyses of the clinic's water treatment system, plus serum and liver tissue of clinic patients led to the identification of two groups of cyanobacterial toxins, the hepatotoxic cyclic peptide microcystins and the hepatotoxic alkaloid cy lindrospermopsin. Comparison of victims' symptoms and pathology using anima l studies of these two cyanotoxins leads us to conclude that the major cont ributing factor to death of the dialyses patients was intravenous exposure to microcystins, specifically microcystin-YR, -LR, and -AR. From liver conc entrations and exposure volumes, it was estimated that 19.5 mug/L microcyst in was in the water used for dialysis treatments. This is 19.5 times the le vel set as a guideline for safe drinking water supplies by the World. Healt h Organization.