Vercruysse J, Dorny P, Claerebout E, Weatherley A
Faculty of Veterinary Medicine, University of Gent, Department of Virology, Parasitology and Immunology, Merelbeke, Belgium.
Vet Parasitol. 1998 Feb 28;75(2-3):169-79. doi: 10.1016/s0304-4017(97)00210-0.
A study was conducted to evaluate the efficacy of two topical treatments with doramectin on the season-long control of lungworm and gastrointestinal infections in first grazing season (FGS) calves. At the start of the study, 20 FGS calves were randomly allocated into two treatment groups of 10 animals each. Calves in the D-group were treated with doramectin pour-on on days 0 and 56, at a dosage of 500 microg kg(-1) BW: calves in the C-group were designated as controls. A permanent pasture was divided in two blocks and these were randomly allocated to the treatment groups. Throughout the study, tracers (n = 32) were grazed on each paddock at 3-week intervals. Clinical signs of parasitic bronchitis (PB) were observed in the C-group in July and this necessitated two salvage treatments with levamisole. From day 28, post-turnout lungworm larvae were recovered from faeces of the C-calves until housing. No signs of PB were observed in the D-group during the entire grazing season. Shedding of lungworm larvae in the principals of the D-group did not occur until 112 days post-turnout. From the data obtained from the tracer calves. it appeared that larvae had overwintered on both pastures. On the C-pasture, the number of lungworms recovered from the tracer calves gradually increased to a peak in September, whereas on the D-pasture, the increase was observed only at the end of the pasture season. Both strongyle faecal egg counts and pepsinogen levels were relatively low in both groups throughout the present study. At the end of the grazing period (day 161). the principals were housed and treated with oxfendazole. During the housing period, all principal animals (D- and C-groups) and a third group of four helminth free animals (N-group) received a challenge infection with Dictyocaulus viviparus. It appeared that the different exposure to the parasite during the grazing season resulted in different establishment rates, i.e.. group C < group D < group N. The present results show that overwintering of lungworm larvae occurs in Belgium and that in such conditions, doramectin pour-on given at turnout and at 8 weeks controls PB in calves during the first grazing season.
开展了一项研究，以评估两种多拉菌素局部治疗方法对首个放牧季节（FGS）犊牛整个季节的肺线虫和胃肠道感染的控制效果。在研究开始时，将20头FGS犊牛随机分为两个治疗组，每组10头动物。D组犊牛在第0天和第56天接受多拉菌素浇泼剂治疗，剂量为500微克/千克体重；C组犊牛被指定为对照组。一片永久性牧场被分成两个区，随机分配给治疗组。在整个研究过程中，每隔3周在每个围场放牧一批示踪动物（n = 32）。7月在C组观察到寄生性支气管炎（PB）的临床症状，这使得必须用左旋咪唑进行两次挽救性治疗。从第28天起，直到犊牛入舍，从C组犊牛的粪便中回收出栏后肺线虫幼虫。在整个放牧季节，D组未观察到PB的迹象。D组犊牛直到出栏后112天才出现肺线虫幼虫排出。从示踪犊牛获得的数据来看，似乎幼虫在两个牧场上都越冬了。在C区牧场上，从示踪犊牛回收的肺线虫数量逐渐增加，在9月达到峰值，而在D区牧场上，仅在放牧季节结束时才观察到增加。在本研究过程中，两组的圆线虫粪便虫卵计数和胃蛋白酶原水平都相对较低。在放牧期结束时（第161天），将犊牛入舍并用奥芬达唑进行治疗。在入舍期间，所有主要动物（D组和C组）以及第三组4头无蠕虫动物（N组）接受了胎生网尾线虫的攻击感染。结果表明，在放牧季节不同的寄生虫暴露导致了不同的定植率，即C组 < D组 < N组。目前的结果表明，在比利时存在肺线虫幼虫越冬的情况，在这种情况下，在出栏时和8周时给予多拉菌素浇泼剂可在首个放牧季节控制犊牛的PB。
