Microcystin toxicosis in nursery pigs

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This case report documents a clinical case of blue-green algae toxicosis, caused by microcystin toxins, in 5-week-old pigs. Mortality during the investigation was elevated by approximately 7.5% in three affected groups, with a final mortality of 11.4%, and 50% of the population demonstrating clinical signs of various degrees. Affected pigs grew slowly and had distended abdomens. Histological examination of tissue samples revealed hepatic centrilobular necrosis with chronic-active periacinar individual hepatocyte necrosis and regeneration or centrilobular hepatocyte necrosis with hemorrhage. Additional testing of the feed revealed no toxicity concerns. Algae were present on the surface of a small area of standing water near the pond that had a waterway to the main water supply. There was a small waterway that connected the standing water to the main pond. Water sampled from that small area tested positive for microcystin. On the basis of these findings, it was determined that the toxicity was caused by algae growth in that area. The affected area was removed to prevent further exposure, and no clinical signs have been present since the standing water area was drained. To the knowledge of the authors, this report describes the first documented case of microcystin toxicosis in nursery pigs.