Weatherley A J, Hong C, Harris T J, Smith D G, Hammet N C
Pfizer Central Research, Sandwich, UK.
Vet Parasitol. 1993 Jul;49(1):45-50. doi: 10.1016/0304-4017(93)90222-9.
Three studies were conducted involving cattle exposed to experimental nematode infections. These studies were designed to investigate the prophylactic activity of a single subcutaneous treatment of doramectin at 200 micrograms kg-1 body weight against infections of Ostertagia ostertagi, Cooperia oncophora and Dictyocaulus viviparus. For each study, parasite-naive calves were randomly allocated to either a treated or a matched control group. One group received doramectin and the other received doramectin and the other received either no treatment or an injection of saline at 1 ml per 50 kg body weight by the subcutaneous route. Thereafter, all calves received a daily oral challenge of infective larvae of the particular parasite species on test in each study. Challenge of each pair of treatment/control groups continued for periods of 14, 21 or 28 days. An interval of 14-21 days was then allowed to permit the parasites which had established to mature, after which all animals were slaughtered and their worm burdens determined using standard techniques. Geometric mean worm burdens were calculated from the log worm counts and used to estimate percentage efficacy. Accumulated burdens of C. oncophora in doramectin-treated cattle resulting from a daily challenge infection for 14 or 21 days were reduced by 99.2% and 90.7% respectively, in comparison with those of non-treated control animals. For D. viviparus, burdens were reduced by 100% and 99.9% after a 21 or 28 day challenge, respectively. The corresponding figures for O. ostertagi were 99.9% after a 21 day challenge and 93.7% after a 28 day challenge.
开展了三项涉及牛的实验性线虫感染研究。这些研究旨在调查皮下注射一次多拉菌素（剂量为每千克体重200微克）对牛奥斯特线虫、牛古柏线虫和胎生网尾线虫感染的预防活性。每项研究中，未接触过寄生虫的犊牛被随机分配到治疗组或匹配的对照组。一组接受多拉菌素治疗，另一组不接受治疗或通过皮下途径按每50千克体重注射1毫升生理盐水。此后，在每项研究中，所有犊牛每天口服特定寄生虫种类的感染性幼虫进行攻毒。每对治疗/对照组的攻毒持续14、21或28天。然后间隔14 - 21天，以使已定植的寄生虫成熟，之后所有动物被屠宰，并使用标准技术确定其蠕虫负荷。根据对数蠕虫计数计算几何平均蠕虫负荷，并用于估计疗效百分比。与未治疗的对照动物相比，多拉菌素治疗的牛在每天攻毒感染持续14天或21天后，牛古柏线虫的累积负荷分别降低了99.2%和90.7%。对于胎生网尾线虫，在攻毒21天或28天后，负荷分别降低了100%和99.9%。对于牛奥斯特线虫，在攻毒21天后相应数字为99.9%，攻毒28天后为93.7%。
