The control of gastrointestinal nematodes (GIN) of cattle in pasture-based production systems such as Ireland is highly dependent on the availability of efficacious anthelmintics. There is very little information available on the efficacy of the broad-spectrum anthelmintics against GIN of cattle in Ireland and the aim of this study was to determine the prevalence of anthelmintic resistance on dairy calf to beef farms. GIN burden was monitored on thirty-six recruited farms by performing herd level faecal egg counts (FEC) every 2 weeks. Of these, nine farms were lost from the study as calves were treated with an anthelmintic for Dictyocaulus viviparus, two were lost as they treated for GIN, one dropped out of the study and on one the herd FEC did not reach the threshold for carrying out the Faecal Egg Count Reduction Test (FECRT). On the remaining 23 farms, once the herd FEC reached 100 eggs per gram, a FECRT was carried out. Pre and post-treatment larval cultures were also performed to identify the GIN to genus level. The efficacy of fenbendazole, levamisole, ivermectin and moxidectin was evaluated on 15, 11, 16 and 11 farms respectively. Resistance to fenbendazole was identified on 9 farms (60%) with resistance suspected on a further farm. Resistance to levamisole, ivermectin and moxidectin was detected on 2 (18%), 16 (100%) and 8 (73%) farms respectively. The predominant genera detected pre and post-treatment were Cooperia and Ostertagia with both genera detected post-treatment with fenbendazole and ivermectin. Due to the low proportion of Ostertagia spp. pre-treatment, the efficacy of levamisole or moxidectin against this genus could not be reliably established. Anthelmintic resistance was widespread on the sampled dairy calf to beef farms in Ireland with resistance to benzimidazole, levamisole, ivermectin and moxidectin detected.

中文翻译：

---

爱尔兰奶牛场牛的胃肠道线虫对驱虫的抗性。

在爱尔兰等以牧场为基础的生产系统中，牛的胃肠道线虫 (GIN) 的控制高度依赖于有效驱虫剂的可用性。关于广谱驱虫药对爱尔兰牛 GIN 的功效的信息很少，本研究的目的是确定奶牛对肉牛场的驱虫药抗性的流行情况。通过每 2 周进行一次畜群水平的粪便卵子计数 (FEC) 来监测 36 个招募的农场的 GIN 负担。其中，有 9 个农场因小牛接受了盘尾藻的驱虫剂治疗而失去研究，2 个农场因接受 GIN 治疗而失去，1 个农场退出研究，还有一个农场的 FEC 未达到实施的阈值粪便卵计数减少测试 (FECRT)。在剩余的 23 个农场中，一旦牛群 FEC 达到每克 100 个鸡蛋，就会进行 FECRT。还进行了处理前和处理后的幼虫培养，以将 GIN 鉴定到属水平。芬苯达唑、左旋咪唑、伊维菌素和莫昔克丁的疗效分别在 15、11、16 和 11 个农场进行了评估。在 9 个农场（60%）中发现了对芬苯达唑的耐药性，另外一个农场怀疑存在耐药性。分别在 2 个（18%）、16 个（100%）和 8 个（73%）农场检测到对左旋咪唑、伊维菌素和莫昔克丁的耐药性。处理前和处理后检测到的主要属是Cooperia 和Ostertagia，在用芬苯达唑和伊维菌素处理后检测到这两个属。由于 Ostertagia spp 的比例低。治疗前，左旋咪唑或莫昔克丁对该属的疗效无法可靠确定。