Résumé
This paper describes a case of poisoning by blue-green algae growing in a fresh water pond in Goyena, Provincia de Buenos Aires. The predominating algae were identified as Microcystis aeruginosa. They show an intense growth when certain meteorologic condition prevail, in coincidence with certain chemical characteristics of the water. Once this growth has occurred, the direction of the wind has a decisive role, because it determines the accumulation on the shore, increasing their concentration and consequently, the risk of poisonous action. From a total of 170 cows, 72 died after ingestion of algae in a lapse of 24 hours. Death was very sudden so that symptoms could be observed in only 10 animals: diarrhea, incoordination, excitability, dyspnea and death. The gross lesions observed were: full stomachs showing the presence of algae; a serum-blood collection in the abdominal cavity and congestive intestines. Histopathology showed nephrosis and probable hepatic centrolobular necrosis. Water toxicity was tested on laboratory animals and gave positive results. The gross lesions, the histological changes and the laboratory tests, confirm the toxicity of the water in the pond. Toxin detection in the digestive content of the poisoned animals has not been previously mentioned in the literature; it is a very valuable diagnostic method.