Davey R B, George J E, Snyder D E
USDA, ARS, Cattle Fever Tick Research Lab., Rt. 3, Box 1010, Edinburg, TX 78539, USA.
Vet Parasitol. 2001 Jul 31;99(1):41-52. doi: 10.1016/s0304-4017(01)00456-3.
The efficacy of a single whole-body spray of spinosad, a naturally derived control agent, applied at three concentrations was evaluated against cattle infested three separate times prior to treatment and at four weekly intervals following treatment with Boophilus microplus (Canestrini). At 0.0167% active ingredient (AI) both tick numbers (1894 ticks per calf) and index of fecundity (IF) of females (258.3) were no different than that of the control group. However, spinosad treatment at both 0.05 and 0.15% AI resulted in fewer ticks per calf (600 and 935, respectively) with lower IF values for females (43.4 and 38.4, respectively). The percent control of ticks on the animals at the time of treatment (acute efficacy) was dramatically lower at 0.0167% AI (21.4%) than at 0.05 (86.3%) and 0.15% AI (87.9%). Spinosad treatments appeared to be more effective against immature stages (nymphs and larvae) than against adult ticks that were on the animals at the time of treatment. The mean weight of females that survived to repletion was similar (322-348 mg) in all groups. By contrast, the mean weight of egg masses produced by females was highest in the control group (155 mg), whereas each increase in spinosad concentration resulted in a substantial decrease in egg mass weight, with the 0.15% AI group averaging only 73 mg. The hatch rate of eggs derived from females ranged from 93.4% in control females down to 53.9% hatch for females treated at 0.15% AI spinosad. The residual efficacy of spinosad at 0.0167% AI was poor even at 1 week following treatment, resulting in 101 ticks per calf and a level of control of only 66.4%. At 0.05% AI, protection against successful reinfestation was high at 1-week post-treatment where only five ticks per calf reached repletion, and control of the IF of these females was 99.3%. The 0.15% AI treatment provided almost complete protection against reinfestation for 2 weeks following treatment (< or =5 ticks per calf), and control of the IF of these ticks was >99.9%. Thus, the use of spinosad at US ports-of-entry would be unacceptable because of the critical necessity of achieving 100% control with a single treatment to prevent the reintroduction of ticks. However, it is likely ticks could be eradicated using spinosad in tick infested areas of the US if repeated (systematic) treatments were applied to cattle maintained on the premises.
评估了三种浓度的多杀菌素（一种天然衍生的防治剂）单次全身喷雾对感染微小牛蜱（Canestrini）的牛的效果。在处理前，牛分别三次感染蜱虫，处理后每隔四周进行评估。活性成分（AI）含量为0.0167%时，蜱虫数量（每头小牛1894只蜱虫）和雌性蜱虫的繁殖力指数（IF）（258.3）与对照组无差异。然而，AI含量为0.05%和0.15%的多杀菌素处理使每头小牛身上的蜱虫数量减少（分别为600只和935只），雌性蜱虫的IF值降低（分别为43.4和38.4）。处理时动物身上蜱虫的防治百分比（急性效果）在AI含量为0.0167%时（21.4%）显著低于0.05%（86.3%）和0.15%（87.9%）。多杀菌素处理对未成熟阶段（若虫和幼虫）的效果似乎比对处理时动物身上的成年蜱虫更有效。所有组中饱血存活的雌性蜱虫平均体重相似（322 - 348毫克）。相比之下，对照组雌性蜱虫产生的卵块平均重量最高（155毫克），而多杀菌素浓度每增加一次，卵块重量就大幅下降，AI含量为0.15%的组平均仅为73毫克。雌性蜱虫所产的卵孵化率从对照组雌性的93.4%降至AI含量为0.15%的多杀菌素处理组雌性的53.9%。AI含量为0.0167%的多杀菌素即使在处理后1周残留效果也很差，每头小牛身上有101只蜱虫，并仅达到66.4%的防治水平。AI含量为0.05%时，处理后1周对再次感染的防护效果很高，每头小牛只有5只蜱虫饱血，这些雌性蜱虫的IF防治率为99.3%。AI含量为0.15%的处理在处理后2周内几乎完全防止再次感染（每头小牛≤5只蜱虫），这些蜱虫的IF防治率>99.9%。因此，由于单次处理必须达到100%防治以防止蜱虫再次传入，在美国入境口岸使用多杀菌素是不可接受的。然而，如果对饲养在场地内的牛进行重复（系统性）处理，在美国蜱虫感染地区使用多杀菌素可能根除蜱虫。
