Clinical and pathological changes in sheep experimentally poisoned by the blue-green alga Microcystis aeruginosa.

Fifteen young sheep were inoculated intraruminally with various doses of an algal bloom of Microcystis aeruginosa. Lethally poisoned sheep died between 18 and 48 hours after inoculation. Findings included marked elevation of serum concentrations of certain enzymes and bilirubin, mild elevations of blood urea nitrogen and serum inorganic phosphorus with marked reduction in blood glucose, a mild neutrophilia with a marked left shift and marked changes in coagulation parameters. Necropsy findings included pale swollen, sometimes hemorrhagic, livers, edema involving the body cavities and widespread small hemorrhages. The primary site of toxicity was the liver which had centrilobular to near massive hepatocyte necrosis. Electron microscopic lesions were aggregation of endoplasmic reticulum with displacement of subcellular organelles towards the periphery of the hepatocyte, and vacuolation of the contents of more severely affected cells.