Department of Biomedical Sciences and Veterinary Public Health, Section for Parasitology, Swedish University of Agricultural Sciences, SE-751 89 Uppsala, Sweden.
Vet Parasitol. 2012 Dec 21;190(3-4):482-8. doi: 10.1016/j.vetpar.2012.07.011. Epub 2012 Jul 20.
An experiment was carried out to study the possible interaction between dexamethasone (DXM) treatment and the efficacy of ivermectin (IVM) treatment in young cattle. Two groups, each of seven calves, were experimentally inoculated with an equal mixture containing 15,000 third stage larvae of Cooperia oncophora and Ostertagia ostertagi each, and with no history of being resistant to any anthelmintics. However, in this study C. oncophora was unexpectedly classified as IVM-resistant according to the outcome from the faecal egg count reduction test (FECRT). Blood parameters and faecal egg counts (FEC) were monitored from 0 to 35 days post infection (d.p.i.). The calves in one group received intramuscular injections of short and long-term acting DXM at 22 and 24 d.p.i., respectively. The other group remained as a control. Three days post patency (24 d.p.i.) both groups were injected subcutaneously with IVM (Merial) at the recommended dose (0.2mg/kg). A significant difference (p<0.001) in FEC patterns was observed between groups. Although both groups still excreted eggs (100-200 eggs per gram faeces) 11 days post anthelmintic treatment, the control group had a significantly higher reduction between 23 and 35 d.p.i. (p=0.025). After 35 days, four animals per group were euthanized, and worms in the gastrointestinal tract were counted. No O. ostertagi were found in the abomasums, but low to high numbers (800-6200) of C. oncophora remained in the small intestines in both groups. Overall, these findings indicated that there was an interaction between the efficacy of IVM and DXM treatment. As significantly lower plasma levels of IVM were observed in the DXM group, we conclude that the impaired efficacy of ivermectin was most likely due to the altered pharmacokinetics.
进行了一项实验，以研究地塞米松（DXM）治疗与伊维菌素（IVM）治疗在小牛中的疗效之间可能存在的相互作用。两组，每组 7 头小牛，通过含有 15000 个第三期幼虫的混合感染实验接种，其中包含无抗驱虫药史的无齿食道口线虫和奥斯特利希绦虫，然而，根据粪便卵减少计数试验（FECRT）的结果，无齿食道口线虫出乎意料地被归类为 IVM 耐药。从感染后 0 至 35 天（d.p.i.）监测血液参数和粪便卵计数（FEC）。一组小牛在 22 和 24 d.p.i.时分别接受肌肉注射短效和长效 DXM。另一组作为对照。两组在孵化后 3 天（24 d.p.i.），均按推荐剂量（0.2mg/kg）皮下注射 IVM（梅里亚）。两组之间的 FEC 模式存在显著差异（p<0.001）。尽管两组在驱虫后 11 天仍排出卵（每克粪便 100-200 个卵），但对照组在 23 至 35 天之间的下降具有显著差异（p=0.025）。35 天后，每组处死 4 头动物，计算胃肠道中的蠕虫数量。在皱胃中未发现奥斯特利希绦虫，但在两组小肠中仍发现低至高数量（800-6200）的无齿食道口线虫。总体而言，这些发现表明 IVM 和 DXM 治疗的疗效之间存在相互作用。由于在 DXM 组中观察到 IVM 的血浆水平显著降低，我们得出结论，伊维菌素疗效降低很可能是由于药代动力学改变所致。
