The oral toxicity for mice of the tropical cyanobacterium Cylindrospermopsis raciborskii (Woloszynska)

Exposure of humans and domestic animals to Cylindrospermopsis raciborskii a nd its associated toxin cylindrospermopsin in their drinking water will nor mally be by ingestion. Studies of the cyanobacterium to date have involved dosing mice by the intraperitoneal route, which excludes the possible influ ence on its toxicity of the alimentary tract barrier. In the present study, outbred MF1 male mice were fasted overnight and then given a single oral d ose suspended in normal saline of freeze-dried C. raciborskii culture conta ining 0.2% cylindrospermopsin. The median lethal dose was in the range 4.4- 6.9 mg/kg alkaloid equivalent, Death occurred from 2 to 6 days after dosing , and pathological changes included marked fatty liver, often with periacin ar coagulative necrosis, acute renal tubular necrosis, atrophy of the thymi c cortex and the lymphoid follicles in the spleen, subepicardial and myocar dial hemorrhages, and multiple ulcerations of the esophageal part of the ga stric mucosa. The syndrome was consistent with that already reported for cy lindrospermopsin dosed parenterally. (C) 1999 by John Wiley & Sons, Inc.