Eddi C, Muniz R A, Caracostantogolo J, Errecalde J O, Rew R S, Michener S L, McKenzie M E
Instituto de Patabiologia, CICV-INTA, Moron, Argentina.
Vet Parasitol. 1997 Sep;72(1):33-41. doi: 10.1016/s0304-4017(97)00076-9.
A study was conducted in Argentina, to investigate the period of protection of a single injection of doramectin administered subcutaneously (s.c.) at 200 micrograms kg-1 (1 ml/50 kg) compared with single treatments of ivermectin (200 micrograms kg-1 s.c.) and fenbendazole (5 mg kg-1 p.o.), against field infections of gastrointestinal parasites of cattle. Eighty-three animals were selected and ranked on the basis of serial fecal egg counts (e.p.g.'s). From this group, three animals were slaughtered before treatment and their lungs, abomasum, small and large intestines, were processed for parasite counts and identification. The remaining 80 animals were allocated in ranked groups of four to a control or one of three treated groups. Animals of the four groups were grazed together in the same pasture for the duration of the study. Treatments were administered on Day 0. Individual fecal samples were collected at weekly intervals for the first 49 days post-treatment and twice a week from Day 52 to Day 84 (end of study). At each collection day fecal samples were pooled for coprocultures. On Day 28 and 56, two animals from each group, previously identified on Day 0, were killed and their parasite burdens determined. The duration of protection of a single injection of doramectin was longer than ivermectin or fenbendazole treatment. On Day 56, the total number of parasites found in doramectin-treated animals was significantly (P < 0.05) lower than parasite burdens found in either ivermectin- or fenbendazole-treated animals. The longer persistent activity of doramectin was expressed by the lower number of adults and L4 stages of Ostertagia ostertagi. Data from this experiment demonstrated the limitations of using fecal egg counts to evaluate the persistent efficacy of anthelmintics. The duration of activity of doramectin was demonstrated more accurately by parasite counts in cattle from each group since decreasing e.p.g.'s were seen in non-medicated animals without changes in total parasite burdens.
在阿根廷进行了一项研究，以调查皮下注射（s.c.）200微克/千克（1毫升/50千克）多拉菌素单次注射的保护期，与伊维菌素（200微克/千克，皮下注射）和芬苯达唑（5毫克/千克，口服）单次治疗相比，对牛胃肠道寄生虫野外感染的保护期。选择了83只动物，并根据连续粪便虫卵计数（每克粪便虫卵数，e.p.g.）进行排名。从该组中，三只动物在治疗前被屠宰，其肺、皱胃、小肠和大肠被处理用于寄生虫计数和鉴定。其余80只动物按排名分成每组四只，分为一个对照组或三个治疗组之一。在研究期间，四组动物在同一牧场一起放牧。在第0天进行治疗。在治疗后的前49天，每周收集一次个体粪便样本，从第52天到第84天（研究结束）每周收集两次。在每个收集日，将粪便样本合并进行粪便培养。在第28天和第56天，每组中两只在第0天预先确定的动物被处死，并确定其寄生虫负荷。多拉菌素单次注射的保护期比伊维菌素或芬苯达唑治疗的保护期长。在第56天，多拉菌素治疗的动物中发现的寄生虫总数显著低于（P<0.05）伊维菌素或芬苯达唑治疗的动物中的寄生虫负荷。多拉菌素较长的持续活性表现为奥斯特他加线虫成虫和L4期数量较少。该实验的数据表明了使用粪便虫卵计数评估驱虫药持续疗效的局限性。由于在未用药的动物中粪便虫卵数下降而总寄生虫负荷没有变化，通过每组牛的寄生虫计数更准确地证明了多拉菌素的活性持续时间。
