Greer A W, Kenyon F, Bartley D J, Jackson E B, Gordon Y, Donnan A A, McBean D W, Jackson F
Moredun Research Institute, Pentlands Science Park, Bush Loan, Edinburgh EH26 0PZ, Scotland, United Kingdom.
Vet Parasitol. 2009 Sep 16;164(1):12-20. doi: 10.1016/j.vetpar.2009.04.017. Epub 2009 Apr 15.
The recent focus of strategies to slow the rate of development of anthelmintic resistance in gastro-intestinal parasites has centred on the need to better manage the parasite population that is unexposed to the drug, i.e. in refugia. One strategy involves the use of targeted selective treatments (TST) where anthelmintics are only administered to those individuals that are likely to benefit from it, rather than to the whole flock. However, there are few TST indicators currently available for farmers in temperate environments. Here we describe the development and field evaluation of a performance-based decision support model to identify individual animals whose performance is suffering from nematodoses, and thus, likely to benefit from an anthelmintic treatment. One hundred and ninety two twin-suckled lambs were separated into eight groups and each grazed on a one-hectare paddock and exposed to one of four anthelmintic treatment regimes. Groups of lambs received either: a whole flock anthelmintic treatment either every four weeks (neo-suppressive treatment, NST); when clinical signs of disease were evident (metaphylactic/therapeutic treatment, MT); at pre-determined times throughout the grazing season (strategic treatment, SPT) or treatment on an individual animal basis as determined by a performance-based decision support model that relied on a calculation of the efficiency of nutrient utilization (targeted selective treatment, TST). Animal performance and parasitological data were recorded every two weeks. Mean faecal egg counts were low throughout the season for the NST group and moderate for the MT, SPT and TST groups. During the entire grazing season the NST, MT, SPT and TST animals each received on average 5.0, 2.0, 3.0 and 2.6 anthelmintic treatments, respectively. Compared to the NST animals, cumulative weight gains were 11% lower at the end of the grazing season in MT animals, whereas no reduction was observed in either the SPT or TST groups. The proposed decision support system appeared to be successful in discriminating between animals which were likely to respond favourably to anthelmintic treatment and those that were not and provided a quantitative estimate of the likely response. Furthermore, 87% of animals that had a pre-treatment efficiency of nutrient utilization value lower than the suggested threshold of the model responded positively to treatment. The potential benefits of using the decision support model as a TST indicator for managing the parasite population in refugia in temperate environments are discussed.
减缓胃肠道寄生虫抗蠕虫药耐药性发展速度的策略，近期重点集中在更好地管理未接触药物的寄生虫种群，即避难所中的种群。一种策略是采用靶向选择性治疗（TST），仅对可能从中受益的个体施用抗蠕虫药，而不是对整个羊群用药。然而，在温带环境下，目前可供农民使用的TST指标很少。在此，我们描述了一种基于性能的决策支持模型的开发和田间评估，以识别那些因线虫病而生长性能受影响、因此可能从抗蠕虫药治疗中受益的个体动物。192只双羔羔羊被分成八组，每组在一公顷的围场中放牧，并接受四种抗蠕虫药治疗方案之一。羔羊组分别接受以下处理：每四周进行一次全群抗蠕虫药治疗（新抑制性治疗，NST）；在疾病临床症状明显时进行治疗（应急/治疗性治疗，MT）；在整个放牧季节的预定时间进行治疗（策略性治疗，SPT）；或根据基于性能的决策支持模型进行个体动物治疗，该模型依赖于养分利用效率的计算（靶向选择性治疗，TST）。每两周记录一次动物生长性能和寄生虫学数据。NST组整个季节的平均粪便虫卵计数较低，MT、SPT和TST组的平均粪便虫卵计数中等。在整个放牧季节，NST、MT、SPT和TST组的动物平均分别接受了5.0、2.0、3.0和2.6次抗蠕虫药治疗。与NST组动物相比，MT组动物在放牧季节结束时的累积体重增加低11%，而SPT组和TST组均未观察到体重下降。所提出的决策支持系统似乎成功地区分了可能对抗蠕虫药治疗有良好反应的动物和无良好反应的动物，并提供了可能反应的定量估计。此外，治疗前养分利用效率值低于模型建议阈值的动物中，87%对治疗有积极反应。文中讨论了将决策支持模型用作TST指标以管理温带环境中避难所寄生虫种群的潜在益处。
