title: The residual effect of treatment with ivermectin after experimental reinfection with nematodes in calves.
abstract: The residual effect of treatment with ivermectin after experimental reinfection in calves was tested. Twenty-four calves were divided into 6 groups of 4 calves each. All calves received a primary infection of 50,000 larvae of both Ostertagia ostertagi and Cooperia oncophora and 1000 Dictyocaulus viviparus larvae. Calves of group 1 remained untreated, and all other calves were treated 21 days after primary infection (0.2 mg/kg injected subcutaneously). Calves of groups 1 and 2 were slaughtered 7 days later. Calves of groups 3-6 were reinfected with the same number of larvae 3 days, 1, 3 and 6 weeks after treatment respectively. Slaughter was 21 days after reinfection. Based on post-mortem worm counts the efficacy of ivermectin after primary infection was 99.7% for O. ostertagi, 95.1% for C. oncophora and 100% for D. viviparus. A residual effect was present for at least one week, but could not be observed 3 weeks after treatment.
mesh_terms: D000818:Animals; D000969:Antinematodal Agents / Q000627:therapeutic use*; D002417:Cattle; D002418:Cattle Diseases / Q000097:blood / Q000188:drug therapy* / Q000469:parasitology; D004022:Dictyocaulus Infections / Q000097:blood / Q000188:drug therapy; D004804:Eosinophils; D005243:Feces / Q000469:parasitology; D007559:Ivermectin; D007783:Lactones / Q000627:therapeutic use*; D007958:Leukocyte Count / Q000662:veterinary; D008297:Male; D009349:Nematode Infections / Q000097:blood / Q000188:drug therapy* / Q000662:veterinary; D010029:Ostertagiasis / Q000097:blood / Q000188:drug therapy / Q000662:veterinary; D010435:Pepsinogens / Q000097:blood
chemical_list: D000969:Antinematodal Agents; D007783:Lactones; D010435:Pepsinogens; D007559:Ivermectin