Miller J E, Morrison D G
Department of Epidemiology and Community Health, School of Veterinary Medicine, Louisiana State University, Baton Rouge 70803.
Vet Parasitol. 1992 Jul;43(3-4):265-70. doi: 10.1016/0304-4017(92)90168-9.
Thirty-nine weaned steer calves (mean weight 284 kg) were maintained under dry-lot conditions and assigned (based on fecal nematode egg count) to one of three treatment groups of 13 animals each as follows: control (no treatment), fenbendazole (5 mg kg-1), and ivermectin (0.2 mg kg-1). Fecal samples were collected 12 h before treatment, at treatment, and 12, 24, 48 and 72 h after treatment for determination of nematode eggs per gram, and (after culture) infective larvae per gram and population distribution. The effect of treatment on egg development was observed in feces collected 12 and 24 h after treatment. There was essentially no difference in efficacy, based on egg counts, of fenbendazole and ivermectin. Egg count was reduced 100% by both anthelmintics at 72 h after treatment. Viability, based on percent of eggs reaching the infective larval stage, of developing stages at 12, 24, and 48 h after fenbendazole treatment was 0.1%, 1.1%, and 0%; after ivermectin treatment the corresponding values were 23.7%, 30.1%, and 28.6%, respectively. Fenbendazole treatment resulted in little or no development of eggs and/or larvae in feces deposited 12 and 24 h after treatment, whereas development proceeded normally (compared with the control group) in ivermectin treated feces. Population distribution of infective larvae was predominantly Haemonchus and Cooperia with some Ostertagia and Oesophagostomum.
39头断奶小公牛犊（平均体重284千克）在舍饲条件下饲养，并（根据粪便线虫卵计数）分为三个处理组，每组13头动物，具体如下：对照组（不处理）、芬苯达唑（5毫克/千克）和伊维菌素（0.2毫克/千克）。在处理前12小时、处理时以及处理后12、24、48和72小时采集粪便样本，以测定每克粪便中的线虫卵数量，以及（培养后）每克粪便中的感染性幼虫数量和种群分布。在处理后12和24小时采集的粪便中观察处理对虫卵发育的影响。基于虫卵计数，芬苯达唑和伊维菌素的疗效基本没有差异。在处理后72小时，两种驱虫药均使虫卵计数降低了100%。基于达到感染性幼虫阶段的虫卵百分比，芬苯达唑处理后12、24和48小时发育阶段的存活率分别为0.1%、1.1%和0%；伊维菌素处理后的相应值分别为23.7%、30.1%和28.6%。芬苯达唑处理导致处理后12和24小时排出的粪便中虫卵和/或幼虫几乎没有发育，而伊维菌素处理的粪便中发育正常（与对照组相比）。感染性幼虫的种群分布主要是血矛线虫和古柏线虫，还有一些奥斯特他线虫和食道口线虫。
