Moeller Robert B, Puschner Birgit, Walker Richard L, Rocke Tonie, Galey Frank D, Cullor James S, Ardans Alex A
California Animal Health and Food Safety Laboratory System, Tulare Laboratory, University of California, 18830 Road 112, Tulare, CA 93274, USA.
J Vet Diagn Invest. 2003 Nov;15(6):523-6. doi: 10.1177/104063870301500603.
Because of the difficulty in identifying botulinum toxin in cattle, it is hypothesized that cattle are sensitive to levels of toxin below the detection limits of current diagnostic techniques (the mouse protection bioassay and the immunostick enzyme-linked immunosorbent assay [ELISA] for type C botulinum toxin). Using an up-down method for toxicologic testing, the median toxic dose (MTD50) for cattle was determined. Four lactating Holstein cows were dosed at 0.125 or 0.25 ng/kg with Clostridium botulinum type C toxin and failed to develop clinical signs of botulism during the 7-day observation period. Three cows given 0.50 ng/kg of toxin developed clinical signs of botulism. From these results, the MTD50 was calculated at 0.388 ng/kg (3.88 mouse lethal doses/kg) using the trim-logit method. These results suggest that cattle are 12.88 times more sensitive to type C botulinum toxin than a mouse on a per kilogram weight basis. The mouse protection bioassay and the immunostick ELISA for type C botulinum toxin failed to identify the presence of the toxin in the serum, blood, and milk samples taken from all 7 animals.
由于在牛体内鉴定肉毒杆菌毒素存在困难，因此推测牛对低于当前诊断技术（用于C型肉毒杆菌毒素的小鼠保护生物测定法和免疫棒酶联免疫吸附测定法[ELISA]）检测限的毒素水平敏感。采用上下法进行毒理学测试，确定了牛的半数致死剂量（MTD50）。四头泌乳的荷斯坦奶牛分别以0.125或0.25 ng/kg的剂量注射C型肉毒杆菌毒素，在7天的观察期内未出现肉毒中毒的临床症状。三头给予0.50 ng/kg毒素的奶牛出现了肉毒中毒的临床症状。根据这些结果，使用trim-logit方法计算出MTD50为0.388 ng/kg（3.88小鼠致死剂量/kg）。这些结果表明，以每千克体重计算，牛对C型肉毒杆菌毒素的敏感性比小鼠高12.88倍。用于C型肉毒杆菌毒素的小鼠保护生物测定法和免疫棒ELISA未能在从所有7只动物采集的血清、血液和牛奶样本中鉴定出毒素的存在。
