Resistance to Ivermectin and the Effect of Topical Eprinomectin on Faecal Egg Counts in St Croix White Hair Sheep

Veterinary Research Communications -     

国产表阿佛菌素在绵羊体内的药代动力学研究

用反相高效液相色谱结合荧光检测法,对试验绵羊经静脉、皮下单剂量注射0 2 mg/kg表阿佛菌素的药代动力学进行了研究。血样提取物通过C18小柱富集、洗脱,甲醇洗提部分经加入1 甲基咪唑和三氟乙酸酐的乙腈液衍生化后进行色谱分析。血药浓度在 2. 5 ~ 200 ng/mL 范围呈良好线性关系(R= 0 996 8),方法平均回收率96 65%±3.84%,血药最低检测限 2.5 ng/mL,日内、日间变异系数分别小于 10%、12%。2 种途径给药后体内药物运转分别符合二室和一室开放模型。主要药代参数如下,静脉注射:消除半衰期(T1/2β)12.66±2.05 h,药时曲线下面积(AUC0~74)1.02±0 30 (mg/L)·h,fc=0 13±0 05; 皮下注射:吸收半衰期(T1/2ka )4.42±1.04 h,峰浓度(Cmax)0 02±0 01 μg/mL,峰时(Tmax ) 15. 36±2. 91 h,消除半衰期(t1/2k ) 26. 22±9. 04 h,药时曲线下面积(AUC0~122)1.19±0 37 (mg/L)·h。上述结果表明,绵羊静脉注射表阿佛菌素后体内药物分布广泛,消除较慢。皮下注射吸收好,消除比静脉注射更为缓慢,体内药物平均滞留时间长。     

Eprinomectin 'pour-on' and the shedding of Haemonchus contortus eggs in experimentally infected goats

The effect of eprinomectin on goats experimentally infected with the nematode Haemonchus contortus was investigated. Faecal analysis showed that a single dose of eprinomectin 'pour-on' delayed the onset of shedding of eggs for 10 to 17 days.     

乙酰氨基阿维菌素国家对照品的研制

以乙酰氨基阿维菌素为原料研制首批乙酰氨基阿维菌素国家对照品,并进行质量评价。采用高效液相色谱法和质谱法对原料进行结构确证,分装后的乙酰氨基阿维菌素对照品采用质量平衡法定值,同时采用高效液相色谱外标法加以佐证。结果显示,以质量平衡法计算乙酰氨基阿维菌素(B_1a+B_1b)含量为97.79%,液相色谱外标法测定含量为98.18%,两种方法测定结果基本一致。本次研制的乙酰氨基阿维菌素对照品可用于乙酰氨基阿维菌素及其制剂的鉴别与含量测定。     

Perinatal development of lymphoid tissue and its associated epithelium in the ovine pharyngeal tonsil: A morphological study

The perinatal development of lymphoid tissue and its associated epithelium in the pharyngeal tonsil of sheep was investigated by light and electron microscopy. The lymphoid cells first appeared in the subepithelium in a scattered form at about 92 days gestation. These cells proliferated rapidly during the last trimester of gestation, and had formed many dense aggregates at the time of parturition. At birth, the epithelium overlying the aggregates was extensively infiltrated with lymphocytes and showed early transformation of follicle-associated epithelium. The lymphoid tissue and its associated epithelium did not, however., fully develop until after birth, when well-differentiated follicle-associated epithelium and lymphoid follicles with vigorous lymphopoiesis were present. In l–2 week old lambs, these structures were ultrastructurally similar to those seen in adult sheep although their size was smaller. The results of this study suggest that the lymphoid tissue of the ovine pharyngeal tonsil and its associated epithelium are morphologically ready to cope with antigens in the extra-uterine environment at birth, but that their full development and maturation are dependent on postnatal antigen stimulation.     

Corneal sequestrum in the cat. Repair using a tarso-conjunctival pedicle flap

Corneal sequestrum was diagnosed upon clinical examination of 12 cats. The cornea of seven were examined histologically and had focal necrosis and inflammation of the stroma and epithelium. As the simple excision of the corneal lesions had been unsuccessful in two of the cats, repair of these was effected by construction of a tarso-conjunctival pedicle flap after the excision of the sequestrum.     

牛肝中阿维菌素类药物残留的高效液相色谱荧光检测方法的研究

采用高效液相色谱分离,荧光检测器检测,建立了固相萃取分析牛组织中埃普利诺菌素、阿维菌素、多拉菌素和伊维菌素残留的方法.样品用乙腈提取,碱性氧化铝和C18SPE柱净化,用乙酸酐和1-甲基咪唑的乙腈溶液作衍生化试剂,在96℃条件下,完全衍生化需要100min.4种药物的平均回收率为70.02%～88.75%,日内变异系数小于8.52%,日间变异系数小于7.13%.埃普利诺菌素、阿维菌素、多拉菌素和伊维菌素的检出限为0.4～0.5μg/kg,定量限为2ug/kg.该方法可靠、灵敏,可用于常规残留分析.     

3种固相萃取柱在测定牛血清样品中乙酰氨基阿维菌素前处理中的比较研究

初步评价在乙酰氨基阿维菌素药动学前处理中3种固相萃取柱对乙酰氨基阿维菌素的净化、萃取效果。首先在空白胎牛血清中加入一定量的乙酰氨基阿维菌素标准溶液,经色谱甲醇提取后,分别经Agilent公司、Waters公司和Agela Technologies公司的C₁₈SPE柱进行萃取(分别简称A固相萃取柱、W固相萃取柱、AT固相萃取柱),再经N-甲基咪唑和三氟乙酸酐衍生化,最后用超高效液相色谱-荧光检测器进行测定。与此同时,将等量的乙酰氨基阿维菌素标准溶液进行衍生化,用超高效液相色谱-荧光检测器进行测定,其结果作为对照。以绝对回收率作为评价3种SPE柱净化、萃取EPR效果的标准。结果显示,含有EPR的胎牛血清经A固相萃取柱萃取后,EPR峰形尖锐对称且无明显杂质峰,其绝对回收率为80.79%;经W固相萃取柱萃取后,乙酰氨基阿维菌素峰形尖锐对称且无明显杂质峰,其绝对回收率为83.61%;经AT固相萃取柱萃取后,乙酰氨基阿维菌素峰形尖锐对称且无明显杂质峰,其绝对回收率仅为64.20%。相对于A与AT固相萃取柱,Waters公司的C₁₈SPE柱萃取EPR的效果更好。研究结果为后期乙酰氨基阿维菌素的药物代谢动力学试验奠定了基础。     

HPLC法同时测定复方吡喹酮浇泼剂中有效成分的含量

本试验旨在建立一种同时测定复方吡喹酮浇泼剂中吡喹酮和乙酰氨基阿维菌素含量的HPLC方法.色谱条件为 C18柱(250 mm×4.6 mm,5 μm),柱温30 ℃,流动相为乙腈-水-三氟乙酸(70:30:0.01),流速1.0 mL/min,进样量20 μL,检测波长245 nm.吡喹酮在0.7506~7.5063 mg/mL范围内,乙酰氨基阿维菌素在31.266~312.660 μg/mL范围内线性关系均良好,相关系数(r)均为0.9999,平均回收率分别为99.0%、98.1%,RSD分别为1.02%、0.32%.本试验所建立的HPLC法快速简便、准确可靠,可用于复方吡喹酮浇泼剂中吡喹酮和乙酰氨基阿维菌素含量的测定.     

Efficacy of macrocyclic lactones for the control of larvae of the Old World screw-worm fly (Chrysomya bezziana)

OBJECTIVE: To assess the efficacy of four macrocyclic lactones for the control of larvae of the Old World Screw-worm Fly (OWS), Chrysomya bezziana, and to examine the effects of excreted residues on the dung fauna. ANIMALS: 100 heifers were divided into five groups of 20 animals. One group remained untreated, whereas the other groups were treated respectively with pour-on formulations of moxidectin, eprinomectin or doramectin, or a sustained-release bolus of ivermectin. PROCEDURES: At intervals of 1 to 15 weeks after treatment, five cattle from each group were challenged with newly-laid eggs of OWS. The efficacy of each treatment was determined 48 h later by comparing the number of myiases in the treated and untreated groups. Abundance of fly larvae in naturally-voided dung pads and the survival of a species of dung beetle, Onthophagus sagittarius, were used to assess the effects of drug residues on the dung fauna. RESULTS AND CONCLUSIONS: Moxidectin showed no activity against larvae of OWS during the first 14 days after treatment. Eprinomectin provided protection for 3 days after dosing, but failed at days 7 and 14, whereas doramectin was effective at day 7, but not at days 14 or 21. In contrast, no myiases were established on bolus-treated cattle from 14 to 102 days after treatment. Faecal residues of moxidectin had no effect on the survival of larvae of dung-feeding flies, whereas those of eprinomectin and doramectin reduced survival for 1 to 2 weeks. Dung voided by bolus-treated cattle inhibited fly breeding and had adverse effects on the development and survival of O sagittarius for up to 15 weeks after treatment.