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.     

利用Moxidectin对放牧初期牛毛圆科线虫感染的控制

本文报道了在放牧初期利用Ｍｏｘｉｄｅｃｔｉｎ药物对牛毛圆科线虫感染的控制策略。研究结果表明：Ｍｏｘｉｄｅｃｔｉｎ与伊维菌素相比，具有较长的残效期：在放牧开始和８周时进行预防性给药，可以在很大程度上减轻对草场的污染，降低毛圆科线虫对牛的感染。给药组与对照组相比动物增重快，饲料报酬率高。而且从二组胃蛋白酶原水平来看，差异较明显，反映出药物预防对避免机体的病理性损伤发生起到了很好的作用。此外，试验也显示出Ｍｏｘｉｄｅｃｔｉｎ对奥斯特线虫的作用优于对古柏线虫。建议在驱杀后者时，应该提高药物剂量。本研究还证实动物体针对细颈线虫感染的免疫力产生最快；其次是古柏线虫、奥斯特线虫，Ｍｏｘｉｄｅｃｔｉｎ同其它某些抗蠕虫药一样，可以推迟一些线虫免疫力的建立。     

Toxicity in three dogs from accidental oral administration of a topical endectocide containing moxidectin and imidacloprid

Three dogs were presented with a history of oral administration of a topical endectocide containing imidacloprid and moxidectin. They were diagnosed with imidacloprid and moxidectin intoxication, having ingested doses ranging from 7.5 to 1.4 mg/kg of imidacloprid and 1.9 to 2.8 mg/kg of moxidectin. The three dogs were affected to different degrees of severity, but all displayed signs of ataxia, generalised muscle tremors, paresis, hypersalivation and disorientation. Temporary blindness occurred in two cases. The three dogs were tested for the presence of the multi-drug resistance 1 gene deletion, which can cause an increased sensitivity to the toxic effects of moxidectin, and were found to be negative. Treatment included gastrointestinal decontamination, intravenous fluid therapy and benzodiazepines to control muscle tremors. All three dogs made a complete recovery within 48 h of ingestion.