Davey Ronald B, Miller J Allen, George John E, Klavons Jerome A
USDA-ARS, Southern Plains Area, Cattle Fever Tick Research Laboratory, Moore Air Base, Bldg. 6419, 22675 North Moorefield Rd., Edinburg, TX 78541, USA.
J Med Entomol. 2007 Mar;44(2):277-82.
The efficacy of injectable doramectin applied at 200 microg/kg was evaluated against adult female Boophilus microplus (Canestrini) (Acari: Ixodidae) in the later stages of engorgement before detachment. Lethal levels of doramectin in the serum of treated cattle (9.7-36.6 ppb) were reached and sustained within 24 h after treatment. However, treatment at 19 or 20 d postinfestation allowed greater tick survival and reproductive capability (IF) than at 18 d postinfestation, indicating that a significant portion of the ticks were able to engorge and detach before obtaining a lethal dose of doramectin. Thus, treatment at 18 d after infestation provided significantly higher overall control (99.5%) than treatment at 19 or 20 d postinfestation (95.8 and 89.1%, respectively). Analysis of control on a daily basis demonstrated that treatment at 18 d postinfestation provided > 99% on each day of the evaluation. Conversely, treatment at 19 or 20 d postinfestation produced levels of control ranging from 22.6 to 85.6% during the first 2 d of female detachment, and > or = 99% control was not achieved until after the fourth day of female detachment, where it remained throughout the study. Therefore, application of injectable doramectin at < or = 18 d after tick infestation was the only treatment regime considered acceptable for use in the U.S. Boophilus Eradication Program. Treatment intervals > 18 d postinfestation could pose a substantial risk of dispersing viable ticks to tick-free areas outside the permanent quarantine zone that has been established along the Texas-Mexico border.
评估了以200微克/千克剂量注射多拉菌素对饱血后期、即将脱落的成年雌性微小牛蜱（Canestrini）（蜱螨目：硬蜱科）的效果。处理后的牛血清中多拉菌素达到致死水平（9.7 - 36.6 ppb），并在处理后24小时内维持该水平。然而，在侵染后19或20天进行处理时，蜱的存活和繁殖能力（IF）比侵染后18天更高，这表明相当一部分蜱在获得致死剂量的多拉菌素之前就已饱血并脱落。因此，侵染后18天进行处理的总体防治效果（99.5%）显著高于侵染后19或20天进行处理的效果（分别为95.8%和89.1%）。每日防治效果分析表明，侵染后18天进行处理在评估的每一天防治效果均> 99%。相反，侵染后19或20天进行处理在雌性蜱开始脱落的前2天防治效果为22.6%至85.6%，直到雌性蜱开始脱落的第四天之后才达到≥ 99%的防治效果，且在整个研究过程中保持该水平。因此，在蜱侵染后≤ 18天注射多拉菌素是美国消灭牛蜱计划中唯一被认为可接受的处理方案。侵染后处理间隔> 18天可能会带来将存活蜱传播到沿得克萨斯州 - 墨西哥边境设立的永久检疫区外无蜱区域的重大风险。
