Geerts S, Brandt J, Kumar V, Biesemans L
Vet Parasitol. 1987 Jan;23(1-2):77-82. doi: 10.1016/0304-4017(87)90026-4.
Observations on a beef cattle farm in Flanders led to the suspicion of resistance to levamisole in a strain of Ostertagia ostertagi. After treating a group of six animals with levamisole (5 mg kg-1 L.W., i.m.) the reduction in the number of trichostrongylid eggs per gram of faeces varied between 0 and 66.6%, whereas a similar group treated with fenbendazole (7.5 mg kg-1 L.W., p.o.) showed a reduction in worm burdens of 100%. Coproculture showed that the remaining eggs in the first treatment group were all Ostertagia sp. The suspected field strain was compared with a reference strain of O. ostertagi by means of the in vitro larval paralysis test. This test showed LC95 values of 9.12 micrograms ml-1 and of 99.04 micrograms ml-1 for the reference and the field strain respectively, which indicates a resistance factor for the latter of 10.9. These results were not unequivocally confirmed by the post mortem findings on a tracer calf necropsied 4 days after treatment with levamisole.
在佛兰德的一个肉牛养殖场进行的观察引发了对奥斯特他线虫（Ostertagia ostertagi）某一菌株对左旋咪唑产生抗性的怀疑。在用左旋咪唑（5毫克/千克体重，肌肉注射）治疗一组6只动物后，每克粪便中毛圆线虫卵数量的减少幅度在0至66.6%之间，而用芬苯达唑（7.5毫克/千克体重，口服）治疗的类似组蠕虫负荷减少了100%。粪便培养表明，第一个治疗组中剩余的卵均为奥斯特他属（Ostertagia sp.）。通过体外幼虫麻痹试验将疑似的田间菌株与奥斯特他线虫的参考菌株进行了比较。该试验显示，参考菌株和田间菌株的LC95值分别为9.12微克/毫升和99.04微克/毫升，这表明后者的抗性因子为10.9。在用左旋咪唑治疗4天后对一头追踪小牛进行尸检的结果并未明确证实这些结果。
