Comparison of Oral and Intraperitoneal Toxicity of Yessotoxin Towards Mice

Currently, yessotoxin is regulated among the toxins in the diarrhetic shellfish poisoning (DSP) complex. Yessotoxin is equally acutely toxic towards mice upon intraperitoneal injections as those algal toxins giving diarrhea, but is not diarrheagenic. Its presence in mussels may therefore lead to overestimation of risk of DSP in consumers when the standard mouse bioassay is used. Arguments are presented for the use of analytical methods instead of the mouse bioassay for the diarrheagenic DSP toxins and yessotoxin. Yessotoxin was found to be more than ten times less toxic to mice via the oral route, compared with intraperitoneal injections. Even at 10mg/kg body weight, the highest dose ever tested orally, yessotoxin did not kill the mice. By means of light microscopy of several organs, moderate changes were only observed in the heart. Ultrastructural studies revealed swelling of heart muscle cells leading to separation of the organelles. Effects were most pronounced close to the capillaries. The pathological changes were clearly dose dependent, and the lowest oral dose where any effects were seen was 2.5mg yessotoxin per kg.