title: Efficacy of ivermectin administered via sustained-release bolus against gastrointestinal nematodes in cattle.
abstract: Twelve calves (mean weight, 175.5 kg) were used to confirm efficacy of ivermectin delivered from a prototype sustained-release bolus against naturally acquired gastrointestinal nematodes including early fourth-stage (inhibited) larvae of Ostertagia ostertagi. The calves were allocated by restricted randomization on weight to 1 of 2 groups: controls, to which a placebo bolus was given orally, and treated calves, to which a sustained-release bolus designed to deliver 8 mg of ivermectin/day at a steady rate was given orally. After treatment, the 2 groups were housed in separate pens with concrete flooring. Twenty-eight days after treatment, all calves were euthanatized and necropsied. The ivermectin-treated calves had no larval or adult Ostertagia spp and significantly (P less than 0.01) fewer adult Trichostrongylus axei and adult Cooperia (C oncophora, C punctata and C surnabada) than control calves. Efficacy of ivermectin was greater than 99% for Cooperia spp, and 100% for other parasites. Drug-related adverse reactions were not observed.
authors.affiliation: College of Veterinary Medicine, Oregon State University, Corvallis 97331.
authors.forename: G L
authors.initials: GL
authors.lastname: Zimmerman
authors.forename: D M
authors.initials: DM
authors.lastname: Mulrooney
authors.forename: D H
authors.initials: DH
authors.lastname: Wallace
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy* / Q000469:parasitology; D003692:Delayed-Action Preparations; D007559:Ivermectin / Q000008:administration & dosage / Q000627:therapeutic use*; D007814:Larva / Q000187:drug effects; D009348:Nematoda / Q000187:drug effects; D009349:Nematode Infections / Q000188:drug therapy / Q000469:parasitology / Q000662:veterinary*; D010028:Ostertagia / Q000187:drug effects; D014254:Trichostrongylus / Q000187:drug effects
chemical_list: D003692:Delayed-Action Preparations; D007559:Ivermectin