Davey Ronald B, Miller J Allen, Miller Robert J, George John E
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. 2009 Jan;46(1):93-9. doi: 10.1603/033.046.0112.
Efficacy of a single dip treatment in coumaphos at 0.182% active ingredient was determined against all parasitic stages of Rhipicephalus (Boophilus) microplus (Canestrini) on infested cattle exposed to various levels of rainfall immediately after treatment. One group of calves remained untreated with no exposure to rainfall to serve as a negative control. A second group of cattle treated with coumaphos, but not exposed to rainfall, acted as a positive treated control. Three additional groups of coumaphos-treated cattle were exposed to 14.3, 28.6, and 42.9 mm of rainfall, respectively. In the coumaphos-treated group not exposed to a rainfall, overall mean control (99.2%) was greater and mean female engorgement weight (200 mg), egg mass weight (43 mg), and index of fecundity (IF; 2.90) were all less than any group exposed to rainfall. Although exposure to the lowest level of rainfall (14.3 mm) resulted in substantially greater control (83.7%) with lower mean egg mass weight (65 mg) and IF (62.26) than ticks exposed to 28.6 or 42.9 mm of rainfall, differences were seldom significant (P > 0.05). This suggested that higher levels of rainfall exposure adversely impacted coumaphos efficacy somewhat more than lower levels of rainfall exposure. Control remained >97% against larval ticks regardless of rainfall exposure level; however, against nymphs or adults, dramatic declines in control occurred as a result of exposure to any rainfall. Thus, the movement of coumaphos treated cattle exposed to any level of rainfall would pose a high risk of dispersing viable ticks into uninfested areas.
测定了活性成分含量为0.182%的蝇毒磷单次浸浴处理对感染微小牛蜱（Canestrini）各寄生阶段的效果，处理后的牛立即暴露于不同降雨水平下。一组小牛未进行处理且未接触降雨，作为阴性对照。第二组牛用蝇毒磷处理，但未接触降雨，作为阳性处理对照。另外三组用蝇毒磷处理的牛分别暴露于14.3、28.6和42.9毫米的降雨中。在未接触降雨的蝇毒磷处理组中，总体平均防治率（99.2%）更高，雌蜱饱血体重（200毫克）、卵块重量（43毫克）和繁殖力指数（IF；2.90）均低于任何接触降雨的组。尽管接触最低降雨水平（14.3毫米）导致防治率大幅提高（83.7%），平均卵块重量（65毫克）和IF（62.26）低于接触28.6或42.9毫米降雨的蜱，但差异很少显著（P>0.05）。这表明，较高的降雨暴露水平对蝇毒磷效果的不利影响比低降雨暴露水平略大。无论降雨暴露水平如何，对幼虫蜱的防治率仍>97%；然而，对于若虫或成虫，由于接触任何降雨，防治率都会急剧下降。因此，接触任何降雨水平的经蝇毒磷处理的牛移动，都有将存活蜱传播到未感染地区的高风险。
