Efficacy of albendazole, levamisole and fenbendazole against gastrointestinal nematodes of cattle, with emphasis on inhibited early fourth stage Ostertagia ostertagi larvae

Abstract

An experiment was conducted to compare the anthelmintic efficacy of albendazole (ABZ), levamisole (LEV) and fenbendazole (FBZ) against inhibited early fourth stage larvae (EL 4) of Ostertagia ostertagi during April in Louisiana. Forty cross-bred beef heifers (average weight 165 kg) were acquired during winter and grazed on pastures contaminated with O. ostertagi and other nematodes until early April. The cattle were weighed and randomly allotted into four groups of ten animals on 6 April and treatments were administered on 7 April. Experimental groupings were: Group 1, non-treated controls; Group 2, ABZ by oral drench at 10 mg kg −1; Group 3, LEV by topical, pour-on administration to back midline at 10 mg kg −1; Group 4, FBZ by oral drench at 10 mg kg −. Equal numbers of cattle from each group were slaughtered daily between 10 and 13 days after treatment. Mean numbers of O. ostertagi developmental stages present in untreated controls were: adults, 13 714; developing L 4 (DL 4), 6487; inhibited EL 4, 21 719. The mean percentage of inhibited EL 4 was 51.8. Smaller numbers of Haemonchus placei, Trichostrongylus axei and Cooperia spp. were recovered uniformly in control cattle. Percentage reduction values for the three compounds against O. ostertagi adults, DL 4 and EL 4, respectively, were: ABZ, 99.0, 95.3, 84.9; LEV, 1.0, 21.8, 32.1; FBZ, 99.2, 97.2, 97.5. Differences between ABZ and LEV EL 4 counts were not significant, but in all other cases worm counts in ABZ and FBZ-treated cattle were significantly lower ( P ≤ 0.05) than in LEV-treated and control cattle. Both ABZ and FBZ were 98–100% effective against Haemonchus adults and L 4, T. axei adults, and Cooperia spp. adults and L 4. LEV was 100% effective against Haemonchus adults and L 4, 85.6% against T. axei, and 94.6% and 89.59% effective against Cooperia spp. adults and L 4, respectively.