title: Efficacy of avermectin B1a for treatment of experimentally induced nematode infections in cattle.
abstract: Two formulations of avermectin B1a, C-076 and MK-933, were examined for anthelmintic activity in two trials, each using 20 calves with experimentally produced nematode infections. In one trial, C-076 was given orally, and in the other trial, MK-933 was given by injection at dosages of 50, 100, and 200 micrograms/kg of body weight. Treated calves were held for 7 to 8 days and then, together with nontreated controls, were euthanatized and were examined for nematodes in their gastrointestinal tracts and lungs. Efficacy of C-076 approached 100% for Dictyocaulus viviparus, Ostertagia ostertagi, Trichostrongylus axei, T colubriformis, and Oesophagostomum radiatum at 50 micrograms/kg. A dosage level of 100 micrograms/kg was required to achieve 97% efficacy against Cooperia punctata. Efficacy of MK-933 at 50 micrograms/kg was variable, but at 100 micrograms/kg, it approached 100% for D viviparus, O ostertagi, Haemonchus placei, T axei, and T longispicularis. Activity against C oncophora was less, reaching 80% efficacy at 200 micrograms/kg.
mesh_terms: D000818:Animals; D000871:Anthelmintics / Q000627:therapeutic use*; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy*; D004022:Dictyocaulus Infections / Q000188:drug therapy; D007559:Ivermectin / Q000031:analogs & derivatives*; D007783:Lactones / Q000627:therapeutic use*; D009349:Nematode Infections / Q000188:drug therapy / Q000662:veterinary*; D009814:Oesophagostomiasis / Q000188:drug therapy / Q000662:veterinary; D014253:Trichostrongylosis / Q000188:drug therapy / Q000662:veterinary
chemical_list: D000871:Anthelmintics; D007783:Lactones; C022120:avermectin B(1)a; D007559:Ivermectin