title: Prophylactic efficacy of an ivermectin sustained-release bolus against challenge exposure with gastrointestinal and pulmonary nematode infective larvae in calves.
abstract: Twelve Holstein calves were used to determine the prophylactic efficacy of ivermectin against challenge exposure with gastrointestinal and pulmonary nematodes. Two groups of 6 calves (mean body weight, 205 kg) each were formed by restricted randomization according to body weight. Group-1 calves served as nonmedicated controls. Each calf of group 2 was orally given one prototype sustained-release bolus designed to deliver ivermectin at a continuous daily dose of 8 mg. Third-stage nematode infective larvae were given to the calves on posttreatment days 28 and 42. The calves were euthanatized 77 or 78 days after treatment. Ivermectin was 100% effective (P less than 0.05) in preventing the establishment of infection by Haemonchus placei, Ostertagia ostertagi, Cooperia spp (C punctata, C oncophora, C surnabada), Nematodirus helvetianus, Oesophagostomum radiatum, and Dictyocaulus viviparus and was greater than 99% effective against Trichostrongylus axei. Incidental infection by Trichuris spp was reduced by 94% (P = 0.08).
authors.affiliation: Animal Science Research, Merck Sharp & Dohme Research Laboratories, Rahway, NJ 07065.
authors.forename: R
authors.initials: R
authors.lastname: Alva-Valdes
authors.forename: D H
authors.initials: DH
authors.lastname: Wallace
authors.forename: J R
authors.initials: JR
authors.lastname: Egerton
authors.forename: G W
authors.initials: GW
authors.lastname: Benz
authors.forename: S J
authors.initials: SJ
authors.lastname: Gross
authors.forename: J W
authors.initials: JW
authors.lastname: Wooden
authors.forename: V E
authors.initials: VE
authors.lastname: Reuter
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000517:prevention & control*; D003692:Delayed-Action Preparations; D007411:Intestinal Diseases, Parasitic / Q000517:prevention & control / Q000662:veterinary*; D007559:Ivermectin / Q000008:administration & dosage / Q000627:therapeutic use*; D008174:Lung Diseases, Parasitic / Q000517:prevention & control / Q000662:veterinary*; D008297:Male; D009349:Nematode Infections / Q000517:prevention & control / Q000662:veterinary*
chemical_list: D003692:Delayed-Action Preparations; D007559:Ivermectin