Norwegian University of Life Sciences, Faculty of Veterinary Medicine, Department of Production Animal Clinical Sciences, Kyrkjevegen 332/334, 4325 Sandnes, Norway.
Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark.
Int J Parasitol Drugs Drug Resist. 2018 Aug;8(2):304-311. doi: 10.1016/j.ijpddr.2018.05.002. Epub 2018 May 16.
Ovine Eimeria spp. infections cause reduced welfare, increased mortality, and substantial economic losses, and anticoccidials are crucial for their control. Recent reports of toltrazuril resistance in pigs, and anecdotal reports of reduced anticoccidial efficacy in lambs, necessitate evaluation of anticoccidial efficacy. Due to the substantial lifecycle differences between nematodes and coccidia, current WAAVP methods for assessing anthelmintic efficacy are not suitable for such evaluations. Faecal samples were collected from 8 pairs of twin lambs from 36 Norwegian sheep farms 6-8 days after turnout. One twin of each pair was then treated with 20 mg/kg toltrazuril and a second faecal sample from all lambs was collected 7-11 days later. Oocyst excretion rate in all samples was determined using McMasters. Suitability of treatment timing was investigated by evaluating the increase in mean log oocyst excretion in untreated lambs. Based on comparisons between groups, a threshold of ≥0.75 (13 farms) was used to identify farms where drug efficacy could be assessed with confidence, drug efficacy on farms with increases of ≥0.5 but <0.75 (7 farms) were evaluated with caution, and drug efficacy on farms with increases of <0.5 (16 farms) was not estimated. Reduction in oocyst excretion between samples from treated lambs compared with controls from the 20 farms with a threshold of ≥0.5 were then analysed using a generalised linear mixed model. The results were classified based on 95% CI obtained using parametric bootstrapping. Among these 20 farms, two exhibited reduced drug efficacy (upper 95% CI < 95%), 13 had good efficacy (lower 95% CI > 90%), and for 5 the results were inconclusive. This is the first evidence-based report of reduced anticoccidial efficacy in ovine Eimeria spp. Additionally, we highlight the problem of sub-optimal timing of treatment (16/36 farms), which could potentially result in incorrect conclusions being reached regarding lack of drug efficacy.
绵羊艾美耳球虫感染会导致福利下降、死亡率增加和巨大的经济损失，而抗球虫药对于控制球虫病至关重要。最近有报道称猪对甲苯达唑产生了耐药性，并且有传闻称羔羊的抗球虫药效果降低，因此有必要评估抗球虫药的疗效。由于线虫和球虫的生命周期有很大的差异，目前 WAAVP 评估驱虫药疗效的方法并不适用于此类评估。在 36 个挪威绵羊养殖场中，从 8 对双胞胎羔羊中采集粪便样本，在放牧后 6-8 天进行。每对中的一只羔羊用 20mg/kg 甲苯达唑进行治疗，然后在所有羔羊的粪便中采集第二个样本，时间为 7-11 天。使用 McMasters 确定所有样本中的卵囊排出率。通过评估未处理羔羊的平均卵囊排出量增加来研究治疗时间的适宜性。根据组间比较，使用≥0.75（13 个农场）作为阈值，以确定可以有信心评估药物疗效的农场；对于卵囊排出量增加≥0.5 但<0.75（7 个农场）的农场，则谨慎评估药物疗效；而卵囊排出量增加<0.5（16 个农场）的农场则不进行药物疗效评估。然后使用广义线性混合模型分析来自用 20 个有≥0.5 阈值的农场处理过的羔羊的样本与对照样本之间的卵囊排出量减少情况。基于使用参数引导获得的 95%CI 对结果进行分类。在这 20 个农场中，有两个农场的药物疗效降低（上限 95%CI<95%），13 个农场的药物疗效良好（下限 95%CI>90%），而对于 5 个农场的结果则不确定。这是首次报道绵羊艾美耳球虫抗球虫药疗效降低的循证报告。此外，我们还强调了治疗时机不理想的问题（36 个农场中的 16 个），这可能会导致对药物疗效缺乏的错误结论。
