Moya-Borja G E, Oliveira C M, Muniz R A, Goncalves L C
Universidade Federal Rural do Rio de Janeiro, Brazil.
Vet Parasitol. 1993 Jul;49(1):95-105. doi: 10.1016/0304-4017(93)90228-f.
Two prophylactic studies and one persistent efficacy study were conducted in Brazil to evaluate one injection of doramectin at a dose rate of 200 micrograms kg-1 against induced infestations of the New World screwworm, Cochliomyia hominivorax. In each prophylactic study, 12 calves were allocated to two groups of six animals. Six calves were treated with doramectin and six with saline. Two hours after treatment, animals were anesthetized and received two incisions, one in the shoulder and one in the rump. Each incision was then infested with 50 first instar larvae. In the persistent efficacy study, 24 calves were allocated to six groups (T1-T6) of four animals each. On the day of treatment, three groups (T1, T3 and T5) were treated with saline and three groups (T2, T4 and T6) with doramectin. All animals were anesthetized and received four incisions, one in the shoulder and one in the rump of each side. Each incision was then infested with 30 first instar larvae of C. hominivorax with the following schedule: T1 and T2 at Day 3, T3 and T4 at Day 7, and T5 and T6 at Day 14 post-treatment. Calves were observed daily and incisions evaluated for 8 days post-infection. Larvae that completed development and exited the wounds were collected and incubated to evaluate viability. In all experiments, doramectin was 100% efficacious in preventing screwworm infestation caused by field isolates of C. hominivorax. First instar larvae were eliminated from the incisions of doramectin-treated calves between 24 and 48 h post-treatment, and no third instar were recovered at any time. As a consequence, healing started at 24 h and was completed at 96-120 h post-infection. Screwworm infestations and viable third-instar larvae developed in all the incisions in non-treated calves, and healing did not begin until larvae had completed their normal life cycle and exited the wounds. The persistent efficacy of a single injection of doramectin extended beyond 14 days.
在巴西进行了两项预防性研究和一项持续有效性研究，以评估以200微克/千克的剂量率注射一次多拉菌素，对新大陆螺旋蝇（嗜人锥蝇，Cochliomyia hominivorax）诱发感染的防治效果。在每项预防性研究中，12头小牛被分配到两组，每组6头动物。6头小牛用多拉菌素治疗，6头用生理盐水治疗。治疗后两小时，动物被麻醉并接受两处切口，一处在肩部，一处在臀部。然后在每个切口中接种50条一龄幼虫。在持续有效性研究中，24头小牛被分配到六组（T1 - T6），每组4头动物。在治疗当天，三组（T1、T3和T5）用生理盐水治疗，三组（T2、T4和T6）用多拉菌素治疗。所有动物均被麻醉并接受四处切口，分别在肩部和两侧臀部各一处。然后按照以下时间表在每个切口中接种30条嗜人锥蝇一龄幼虫：治疗后第3天接种给T1和T2组，第7天接种给T3和T4组，第14天接种给T5和T6组。每天观察小牛，并在感染后8天对切口进行评估。收集完成发育并离开伤口的幼虫并进行孵化，以评估其活力。在所有实验中，多拉菌素在预防由嗜人锥蝇野外分离株引起的螺旋蝇感染方面具有100%的有效性。在多拉菌素治疗的小牛切口中，一龄幼虫在治疗后24至48小时内被清除，且在任何时候都未发现三龄幼虫。因此，感染后24小时开始愈合，并在96 - 120小时完成。未治疗的小牛所有切口中均出现螺旋蝇感染和存活的三龄幼虫，直到幼虫完成其正常生命周期并离开伤口后才开始愈合。单次注射多拉菌素的持续有效性超过14天。
