A biochemical profile for predicting the chronic exposure of sheep to Microcystis aeruginosa, an hepatotoxic species of blue-green alga.

Sheep which grazed on the shoreline of a fresh-water lake which had a toxic bloom of Microcystis aeruginosa were studied for evidence of chronic poisoning, and a serum biochemical profile was developed to indicate sub-lethal, chronic poisoning in the sheep which had been exposed to microcystins. The profile included measurements of glutamate dehydrogenase (GLDH), gamma-glutamyl transferase (gamma GT), bile acids, bilirubin and albumin. Of 18 sheep which were exposed to M aeruginosa for more than three months, 100 per cent had high serum concentrations of bile acids, 94 per cent had high activities of GLDH and gamma GT, 83 per cent had high bilirubin and 72 per cent had low albumin concentrations compared with the median values of unexposed animals. Other sheep which were exposed for shorter periods, showed evidence of hepatic injury after one week of exposure. The majority of the sheep showed no preference for an alternative, uncontaminated source of water.