United States Department of Agriculture-Agricultural Research Service, Cattle Fever Tick Research Laboratory, Moore Air Base, Building 6419, 22675 N. Moorefield Road, Edinburg, TX 78541, USA.
J Med Entomol. 2011 Mar;48(2):314-21. doi: 10.1603/me10154.
The therapeutic and persistent efficacy of a single subcutaneous injection of a long-acting formulation of moxidectin at a concentration of 1 mg/kg body weight was determined against Rhipicephalus (Boophilus) microplus (Canestrini), along with the concentration-time blood sera profile in treated cattle. The therapeutic efficacy against ticks of all parasitic stages on cattle at the time of treatment was >99.9%, and the mean tick number, index of fecundity, engorgement weight, and egg mass weight of ticks recovered from treated animals were all significantly lower than ticks from untreated animals. The index of fecundity, engorgement weight of females, and egg mass weight of ticks recovered from treated animals infested at weekly (7-d) intervals between 14 and 63 d posttreatment were significantly lower than for ticks on untreated animals, whereas the number of ticks per animal recovered from treated cattle remained lower than that of untreated cattle for up to 49 d posttreatment. The percentage control remained >99% at weekly intervals between 14 and 49 d posttreatment, which is the minimum level of efficacy considered acceptable for use in the United States Cattle Fever Tick Eradication Program. The serum concentration of moxidectin in treated cattle increased to 25.6 ppb (parts per billion) within 1 d after treatment, and peaked at 47.3 ppb at 8 d posttreatment. Moxidectin sera levels remained above the estimated 100% threshold level for elimination of feeding ticks (5-8 ppb) for 44-53 d after treatment. The label claim of 50 d of prevention against reinfestation for the long-acting moxidectin formulation used in the study was supported by the efficacy and sera concentration data obtained. Based on these results, cattle could be treated at 63-d intervals with minimal risk of viable ticks detaching from treated animals. This treatment interval would be 4.5-fold longer than the presently required treatment interval of 14 d, thus leading to approximately 75% reduction in gathering and handling costs of cattle incurred by producers.
对 1 毫克/千克体重的长效型莫昔克丁进行单剂皮下注射，评估其对（硬蜱属）璃眼蜱（Canestrini）的治疗效果和持久性，同时检测牛血清中的浓度-时间曲线。在治疗时，对牛的所有寄生阶段的 ticks 的治疗效果>99.9%，并且从处理过的动物中回收的 tick 的平均数量、繁殖指数、饱食体重和卵质量都显著低于未处理过的动物。从处理过的动物中回收的 tick 的繁殖指数、雌性饱食体重和卵质量在治疗后 14 至 63 天内每 7 天（1 周）感染一次时显著低于未处理过的动物，而从处理过的牛中回收的 tick 数量在 49 天内仍低于未处理过的牛。在治疗后 14 至 49 天内，每周的控制率仍>99%，这是美国牛热病蜱根除计划可接受的最低疗效水平。治疗后 1 天内，牛血清中的莫昔克丁浓度增加到 25.6 ppb（十亿分之几），在治疗后 8 天达到 47.3 ppb 的峰值。在治疗后 44-53 天内，莫昔克丁血清水平仍保持在高于估计的 100%消除喂食 tick 的阈值水平（5-8 ppb）。研究中使用的长效莫昔克丁制剂的标签声称可预防再感染 50 天，该说法得到了疗效和血清浓度数据的支持。基于这些结果，牛可以每 63 天间隔处理一次，并且几乎没有来自处理过的动物身上存活的 tick 脱落的风险。这一处理间隔是目前要求的 14 天间隔的 4.5 倍，因此可以将生产商承担的牛的采集和处理成本降低约 75%。
