Westers T, Jones-Bitton A, Menzies P, VanLeeuwen J, Poljak Z, Peregrine A S
Department of Population Medicine, Ontario Veterinary College, University of Guelph, 50 Stone Road E, Guelph, Ontario N1G 2W1, Canada.
Department of Population Medicine, Ontario Veterinary College, University of Guelph, 50 Stone Road E, Guelph, Ontario N1G 2W1, Canada.
Prev Vet Med. 2016 Nov 1;134:49-57. doi: 10.1016/j.prevetmed.2016.09.021. Epub 2016 Sep 24.
Haemonchosis is often associated with late gestation and parturition in ewes in Canada. Due to widespread concerns about development of anthelmintic resistance (AR), targeted selective treatment (TST), where individual animals are treated with an anthelmintic rather than the entire flock, is a possible strategy to control clinical signs in recently lambed ewes while still maintaining parasite refugia. Performing fecal egg counts (FEC) on individual animals is often cost-prohibitive, so indicators that identify ewes with high FEC are essential for TST programs. The study objectives were to: a) evaluate the ability of four TST indicators to identify periparturient ewes with high Haemonchus sp. FEC and b) determine appropriate treatment thresholds for statistically-significant indicators. A field study was conducted during the 2013 and 2014 lambing seasons (February-May) on three client-owned farms in Ontario with documented AR and problems with haemonchosis in ewes. Ewes were examined within three days of lambing and selected for treatment with oral closantel (10mg/kg body weight), a novel anthelmintic to Canada, if they met at least one of four criteria: a) the last grazing season was their first grazing season; b) body condition score ≤2; c) Faffa Malan Chart (FAMACHA) score ≥3; and/or d) three or more nursing lambs. Fecal samples were collected per rectum on the treatment day from each of 20 randomly selected treated and untreated ewes on each farm. Haemonchus sp. percentages on each farm, as determined by coproculture, ranged from 53% to 92% of total fecal trichostrongyle-type egg counts. Mean Haemonchus sp. FECs were significantly higher in treated ewes (n=136) than in untreated ewes (n=103) on the day of treatment in both years (p=0.001), suggesting the indicators were suitable for identifying animals with high Haemonchus sp. FEC. A linear mixed model was fit with logarithmic-transformed Haemonchus sp. FEC as the outcome variable, the four indicators and year as fixed effects, and farm as a random effect. FAMACHA score was the sole indicator to remain significantly associated with FEC (p=0.002). A receiver-operator curve determined that test sensitivity was maximized (92.4%) with FAMACHA score ≥3 as the sole indicator. FAMACHA score should therefore be included in TST programs to identify ewes requiring treatment at lambing due to Haemonchus sp.
在加拿大，血矛线虫病常与母羊妊娠后期和分娩有关。由于人们广泛关注抗蠕虫药耐药性（AR）的发展，针对性选择性治疗（TST），即对个体动物而非整个羊群进行驱虫治疗，是一种在控制近期产羔母羊临床症状的同时仍维持寄生虫避难所的可行策略。对个体动物进行粪便虫卵计数（FEC）通常成本过高，因此识别高FEC母羊的指标对于TST计划至关重要。本研究的目的是：a）评估四种TST指标识别围产期血矛线虫属FEC高的母羊的能力；b）确定具有统计学意义指标的适当治疗阈值。在2013年和2014年产羔季节（2月至5月），在安大略省的三个客户所有的农场进行了一项实地研究，这些农场有记录的AR以及母羊血矛线虫病问题。在产羔后三天内对母羊进行检查，如果它们符合以下四个标准中的至少一个，则选择用口服氯氰碘柳胺（10mg/kg体重，一种在加拿大新出现的驱虫药）进行治疗：a）上一个放牧季节是它们的第一个放牧季节；b）体况评分≤2；c）Faffa Malan图表（FAMACHA）评分≥3；和/或d）三只或更多哺乳羔羊。在治疗当天，从每个农场随机选择的20只经治疗和未经治疗的母羊中，每只母羊经直肠采集粪便样本。通过粪便培养确定，每个农场血矛线虫属的百分比占粪便毛圆线虫型虫卵总数的53%至92%。在这两年的治疗当天，经治疗母羊（n = 136）的平均血矛线虫属FEC显著高于未经治疗的母羊（n = 103）（p = 0.001），这表明这些指标适用于识别血矛线虫属FEC高的动物。以对数转换后的血矛线虫属FEC作为结果变量，四个指标和年份作为固定效应，农场作为随机效应，拟合了一个线性混合模型（linear mixed model）。FAMACHA评分是唯一与FEC仍有显著关联的指标（p = 0.002）。一条接受者操作特征曲线（receiver-operator curve）确定，以FAMACHA评分≥3作为唯一指标时，测试灵敏度最高（92.4%）。因此，FAMACHA评分应纳入TST计划，以识别因血矛线虫属在产羔时需要治疗的母羊。
