Netzel Gabriele, Palmer Dieter G, Masters Anne M, Tai Samantha Y, Allen Jeremy G, Fletcher Mary T
Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Health and Food Sciences Precinct, Coopers Plains, 4108, QLD, Australia.
Department of Primary Industries and Regional Development, South Perth, 6151, WA, Australia.
Toxicon. 2019 May;163:48-58. doi: 10.1016/j.toxicon.2019.03.007. Epub 2019 Mar 14.
Indospicine is a natural toxin occurring only in Indigofera plant species, including the Australian native species I. linnaei. These perennial legumes are resistant to drought and palatable to grazing livestock including cattle. Indospicine accumulates in the tissues (including muscle) of animals grazing Indigofera and these residues persist for several months after exposure. Dogs are particularly sensitive to indospicine with reports in past decades of hepatotoxicosis and mortalities in dogs after dietary exposure to indospicine-contaminated horse and camel meat. The risk for human consumption is not known, and the current study was undertaken to assess indospicine levels in cattle going to slaughter from divergent regions of Western Australia, and to predict the likelihood of significant residues being present. Muscle and corresponding liver samples from 776 cattle originating from the Kimberley and Pilbara Regions in the tropical north of the state, where I. linnaei is prevalent, and 640 cattle from the South West and South Coast Regions in the temperate south west of the state, where the plant is not known to occur, were collected at abattoirs over four seasons in 2015-2017. Indospicine levels were measured by LC-MS/MS and ranged from below detection to 3.63 mg/kg. No indospicine residues were detected in any of the animals originating from the South West and South Coast Regions. Prevalence of indospicine residues in cattle from the Kimberley Region was as high as 33% in spring and 91% in autumn, with positive animals being present in most consignments and on most properties. The average prevalence of indospicine residues from the Kimberley and Pilbara Regions throughout the survey period was 63%. @Risk best fit probability distributions showed ninety-fifth percentile (P95) indospicine concentrations of 0.54 mg/kg for muscle and 0.77 mg/kg for liver in cattle originating from the Kimberley and Pilbara Regions during the survey period. When considered with average Australian meat consumption data, the estimated consumer exposure from this P95 muscle was 0.32 μg indospicine/kg bw/day, which compared favourably with our calculated provisional tolerable daily intake (PTDI) of 1.3 μg indospicine/kg bw/day. However canine exposure is of potential concern, with active working dog exposure calculated to exceed this PTDI by a factor of 25, based on a P95 indospicine concentration of 0.54 mg/kg in muscle.
吲哚西平是一种仅存在于豆科木蓝属植物中的天然毒素，包括澳大利亚本土物种林氏木蓝。这些多年生豆科植物耐旱，且受包括牛在内的放牧牲畜喜爱。吲哚西平会在放牧木蓝属植物的动物组织（包括肌肉）中蓄积，且这些残留物在接触后会持续数月。狗对吲哚西平特别敏感，在过去几十年中有报道称，狗在食用受吲哚西平污染的马肉和骆驼肉后会出现肝中毒和死亡。人类食用的风险尚不清楚，因此开展了本研究，以评估西澳大利亚不同地区待屠宰牛的吲哚西平水平，并预测是否存在显著残留的可能性。在2015年至2017年的四个季节里，从该州热带北部金伯利和皮尔巴拉地区（林氏木蓝普遍生长）的776头牛以及该州西南部温带地区西南和南海岸地区（未知该植物生长）的640头牛身上，在屠宰场采集了肌肉和相应的肝脏样本。通过液相色谱-串联质谱法测量吲哚西平水平，范围从低于检测限到3.63毫克/千克。在来自西南和南海岸地区的任何动物中均未检测到吲哚西平残留。金伯利地区牛的吲哚西平残留患病率在春季高达33%，秋季高达91%，大多数批次和大多数养殖场的牛都呈阳性。在整个调查期间，金伯利和皮尔巴拉地区牛的吲哚西平残留平均患病率为63%。@Risk最佳拟合概率分布显示，在调查期间，来自金伯利和皮尔巴拉地区的牛，肌肉中吲哚西平浓度的第95百分位数（P95）为0.54毫克/千克，肝脏中为0.77毫克/千克。结合澳大利亚平均肉类消费数据来看，估计消费者从这种P95肌肉中摄入的吲哚西平为0.32微克/千克体重/天，与我们计算的暂定每日可耐受摄入量（PTDI）1.3微克/千克体重/天相比更有利。然而，犬类接触情况值得关注，根据肌肉中P95吲哚西平浓度0.54毫克/千克计算，活跃工作犬的接触量预计超过该PTDI的25倍。
